Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Immunogenetics in dairy cattle : somatic cell count and natural antibody levels
    Wijga, S. - \ 2013
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Henk Bovenhuis; John Bastiaansen. - S.l. : s.n. - ISBN 9789461737274 - 178
    melkvee - melkkoeien - immunogenetica - celgetal - natuurlijke antilichamen - genomica - immunologie - genetica - dairy cattle - dairy cows - immunogenetics - somatic cell count - natural antibodies - genomics - immunology - genetics

    There remains is a lot to be learned about the interpretation of genetic parameters and the biology of disease resistance and SCS. This PhD thesis aimed to obtain additional insight in disease resistance and SCS by: 1) quantifying the impact of genetics on innate immunity, represented by natural antibodies (NAb), through estimation of heritabilities and genetic correlations; 2) identifying the genomic regions involved in SCS and NAb levels; 3) quantifying the impact of genetics on environmental sensitivity for SCS.

    Natural antibody levels are heritable with heritabilities ranging from 0.06 to 0.55 and in general, heritabilities for NAb isotypes were higher than heritabilities for total NAb levels, the latter making no distinction between isotypes. Genetic correlations suggest that isotypes IgA and IgM have a common genetic basis, but that the genetic basis for IgG1 differs from that for IgA or IgM. An additional genome-wide association study for NAb levels showed that information can be gained when total NAb levels are further subdivided into isotype levels. A region on chromosome 23 was significantly associated with genetic variation in isotype IgM levels. The bovine major histocompatibility complex (MHC) is located near this region, making this a region of candidate gene(s) involved in NAb expression in dairy cows both from a functional and positional perspective. Results from the study on genetic parameters and the genome-wide association study suggest that NAb isotypes may provide a better characterization of different elements of the immune response or immune competence and enable more effective decisions when breeding programs start to include innate immune parameters. A genome-wide association study was not only performed for NAb levels, but also for SCS. Relatively few associations, however, were found, which suggests that SCS is controlled by multiple loci, each with a relatively small effect, distributed across the genome.

    Somatic cell score is partly under genetic control, but is also affected by the environment. Sensitivity to respond to environmental factors, however, can have a genetic origin.

    Environmental factors can be divided into known and unknown factors, referred to as macro- and micro environment, respectively. Macro-environmental sensitivity can be expressed as genetic variation in the slope of a reaction norm, whereas micro-environmental sensitivity can be expressed as differences in residual variance that have a genetic origin. Both macro- and micro-environmental sensitivity were found for SCS and these sensitivities were positively correlated. Knowledge on both forms of sensitivity can aid in optimization of selection as correlations between the additive genetic variance in intercept, slope and environmental variance were all away from unity. Selection for reduced environmental sensitivity has the potential to reduce variability in animal performance due to environmental factors and herewith increase predictability of performance across and within environments.

    Knowledge on disease biology is important to fully understand the processes involved when selecting for increased disease resistance, as a better understanding enables a better prediction of the consequences. In this context, the general discussion involved the phenotype definition and statistical modeling, influence of maternal effects and genetic variation in the MHC region. The discussion contained three conclusions: 1) analyses of cell types (detailed phenotypes) rather than SCS can provide further insight in the genetic control of SCS and mastitis; 2) no evidence was found for maternal genetic effects on NAb levels in milk. Maternal environmental effects, however, could play a role in NAb levels; 3) genetic diversity in the MHC region is maintained by natural selection. Selective breeding and farm management practices may affect this genetic diversity, which could bring about negative effects on animal fitness, such as fertility problems. Selective breeding for specific MHC haplotypes may therefore impose a risk for negative effects on animal health.

    Immunogenetic analysis of natural antibody isotypes in laying hens
    Sun, Y. - \ 2013
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Jan van der Poel; Henk Parmentier. - S.l. : s.n. - ISBN 9789461736796 - 192
    hennen - pluimvee - immunogenetica - genetische analyse - antilichamen - isotopen - overleving - genetische parameters - verenpikken - dierveredeling - hens - poultry - immunogenetics - genetic analysis - antibodies - isotopes - survival - genetic parameters - feather pecking - animal breeding

    Worldwide, especially in Europe, poultry industry is undergoing important changes including ban of the battery housing system and prohibition of beak trimming. The former can facilitate more spread of infectious diseases, and the latter will contribute to higher mortality because of severe feather pecking. Furthermore, given the growing social concern about food safety and human health, abundant use of antibiotics will either be prohibited or restricted. These changes further emphasize the importance of implementing general disease resistance in layers breeding goals next to maintaining high production. The aim of this thesis was to find proper traits which are associated with laying hens survival, and reveal genetic architecture and background underlying the traits. Natural antibody (NAb), which are the antibodies present in normal healthy animals in the absence of a deliberate antigen exposure are an important humoral part of innate immunity. The relationships between survival and NAb isotype titers were firstly investigated by the logistic regression analysis in a population of laying hens from 12 purebred lines. The results indicated that NAb, especially the IgM isotype titers at young age was predictive for survival of a laying period. Genetic parameters of NAb isotypes IgM and IgG titers were estimated in the same population. The estimation showed that both NAb isotypes are moderate to high heritable traits which were possible to breed for. An association study revealed different QTL or SNP markers for NAb isotypes titers. The majority of the commercial laying hens are crossbred. Therefore, the relationships between NAb isotype titers and survival were further investigated in crossbred laying hens. However, a consistent relationship as in the purebred was not found. This confirmed the speculation that non-health-related causes of mortality (severe feather pecking) overruled the anticipated relationships between NAb isotype titers and survival in birds with intact beaks. Overall, the present studies indicate that it is possible to implement NAb especially the IgM isotype titers into the breeding goals of laying hens to improve the health-related survival.

    Sustained effects of early-life oral colistin treatment on immune reactivity to intratracheally administered LPS and HuSA in chicken
    Lammers, A. ; Zutphen, L.J.W. van; Vries Reilingh, G. de; Parmentier, H.K. - \ 2010
    In: Proceeding of the 11th Avian Immunology Research Group Conference, Budapest, Hungary, 7-10 October 2010. - Budapest, Hungary : Diamond Congress LTd. - ISBN 9789638801920 - p. 51 - 51.
    vogels - immunologie - immuniteit - b lymfocyten - interferon - receptoren - aviaire influenzavirussen - cytokinen - vaccinatie - immunogenetica - birds - immunology - immunity - b lymphocytes - interferon - receptors - avian influenza viruses - cytokines - vaccination - immunogenetics
    Evolution of major histocompatibility genes in cyprinid fish : molecular analyses and phylogenies
    Kruiswijk, C.P. - \ 2002
    Wageningen University. Promotor(en): H.F.J. Savelkoul; R.J.M. Stet. - S.l. : S.n. - ISBN 9789058087355 - 183
    cyprinidae - histocompatibiliteit - major histocompatibility complex - genen - nucleotidenvolgordes - pathogenen - evolutie - fylogenie - immunogenetica - cyprinidae - histocompatibility - major histocompatibility complex - genes - nucleotide sequences - pathogens - evolution - phylogeny - immunogenetics
    Plant domestication and evolution : a monovular twin or not?
    Raamsdonk, L.W.D. van - \ 1996
    Wageningen : CPRO-DLO - 101
    oorsprong - distributie - vestiging - wilde planten - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - fylogenie - fylogenetica - relaties - gewassen - acclimatisatie - domesticatie - plantkunde - nieuwe cultuurgewassen - economische botanie - origin - distribution - establishment - wild plants - genetics - genetic variation - evolution - speciation - immunogenetics - phylogeny - phylogenetics - relationships - crops - acclimatization - domestication - botany - new crops - economic botany
    Major histocompatibility complex genes in the common carp, Cyprinus carpio L.
    Erp, S.H.M. van - \ 1996
    Agricultural University. Promotor(en): W.B. van Muiswinkel; R.J.M. Stet. - S.l. : Van Erp - ISBN 9789054855095 - 159
    immunogenetica - reticulo-endotheliaal systeem - antilichamen - immunoglobulinen - cyprinidae - karper - immunogenetics - reticuloendothelial system - antibodies - immunoglobulins - cyprinidae - carp
    This thesis describes a study of the major histocompatibility complex (Mhc) genes of the common carp (Cyprinus carpio L.). The molecules encoded by Mhc genes play an essential role in the specific immune response, by presenting antigens to T lymphocytes. Knowledge of the Mhc of carp, therefore, contributes to our understanding of the immune response mechanisms in this species. In addition, it may give important insights in the phylogenetic development of these genes. The common carp was found to contain several distinct lineages of Mhc class I genes, denoted as Cyca-U, Cyca-Z, Cyca- TC16 and Cyca- C4. The Cyca-U sequences probably represent classical Mhc class I genes, of which most likely only a single locus is expressed in each individual. Cyca-Z genes are present in multiple polymorphic copies in the genome, but it is not clear whether these genes are expressed. The sequence of Cyca- TC16 is most similar to the class I genes of the coelacanth, a fish which is thought to be a representative of the evolutionary lineage leading to the tetrapods. It is, however, not clear whether Cyca -TC16 is expressed. In addition, the sequence encoding carp β 2 -microglobulin was isolated. Although two B2m genes were detected in each individual, apparently only one of these is expressed. In contrast, at least four class II B genes may be expressed in a single animal. These genes are linked in two pairs, which, however, segregate independently. In addition, two expressed class II A sequences were identified, most likely derived from two separate loci. Both the class II A and B genes are likely to encode bona fide class II chains, the components of the cell-surface class II α-βheterodimer. Although carp thus possess a complete set of class I and class II genes, it is not yet clear whether these genes reside in a single genetic Mhc region.
    Immunogenetics of disease resistance in fish
    Wiegertjes, G.F. - \ 1995
    Agricultural University. Promotor(en): W.B. van Muiswinkel; C.J.J. Richter; R.J.M. Stet. - S.l. : Wiegertjes - ISBN 9789054854630 - 141
    diergeneeskunde - karper - immunogenetica - immuniteit - immunologie - immuunsysteem - veterinary science - carp - immunogenetics - immunity - immunology - immune system

    The aim of the work described in this thesis is to investigate the possibility to select for immune responsiveness, and subsequently produce isogenic carp ( Cyprinus carpio L.) lines, via gynogenesis, that express the trait under selection. If possible, this would allow the repeated production of numerous isogenic fish lines, all selected for different immune parameters, that can be used for immunogenetic studies on disease resistance. As a model, we chose a defined antigenic determinant (dinitrophenyl: DNP), coupled to a carrier molecule (keyhole limpet haemocyanin: KLH) in combination with a reliable read-out system (enzymelinked immunosorbent assay: ELISA), to divergently select carp for the magnitude of their primary antibody response. The possibility to reproduce both homozygous gynogenetic females and functional males with a high or a low antibody response, resulted in the establishment of a number of F 1 hybrid crosses with high or low immune responsiveness to DNP-KLH. Typically, these isogenic lines showed no within-line genetic variation. Between-line genetic variation in susceptibility to infection with Trypanoplasma borreli, a haemoflagellate parasite of carp, was dependent upon the immune response type of the carp lines. Major histocompatibility complex (Mhc) class II β-chain polymorphism could be associated with the immune response types described and, in retrospect, may have contributed to the observed differences in magnitude of immune responsiveness to DNP-KLH, and possibly T.borreli.

    Het inbrengen van genen coderend voor antibacteriele eiwitten bij wilg ter bescherming tegen de watermerkziekte
    Roest, S. ; Dam, B.C. van; Evers, P.W. - \ 1994
    Wageningen : IBN (IBN - rapport 082)
    bosbouw - genetische modificatie - immunisatie - immunogenetica - geïnduceerde resistentie - plantenziekten - plantenziekteverwekkende bacteriën - planten - recombinant dna - bomen - salix alba - brenneria salicis - forestry - genetic engineering - immunization - immunogenetics - induced resistance - plant diseases - plant pathogenic bacteria - plants - trees
    Genetica: de kern van de plantenwetenschappen.
    Koornneef, M. - \ 1993
    Wageningen : Landbouwuniversiteit Wageningen - 25
    genetica - genetische variatie - evolutie - soortvorming - immunogenetica - plantkunde - colleges (hoorcolleges) - genetics - genetic variation - evolution - speciation - immunogenetics - botany - lectures
    Engineering resistance against potato virus Y
    Vlugt, R.A.A. van der - \ 1993
    Agricultural University. Promotor(en): R.W. Goldbach; H. Huttinga. - S.l. : Van der Vlugt - ISBN 9789054850847 - 111
    plantenziekten - plantenvirussen - solanum tuberosum - aardappelen - potyvirus - planten - immunisatie - geïnduceerde resistentie - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - genetische modificatie - recombinant dna - plant diseases - plant viruses - solanum tuberosum - potatoes - potyvirus - plants - immunization - induced resistance - genetics - genetic variation - evolution - speciation - immunogenetics - genetic engineering - recombinant dna

    Potato virus Y is the type species of the potyvirus genus, the largest genus of the plant virus family Potyviridae. The virus causes serious problems in the cultivation of several Solanaceous crops and although certain poly- and monogenic resistances are available, these can not always be employed, e.g. R y genes in potato cv. 'Bintje'. The aim of the research described in this thesis was to establish new forms of resistance against PVY by genetic modification of host plants. One such form of genetic engineered resistance is 'coat protein-mediated resistance', whereby expression of a viral coat protein (CP) in a transgenic plant may confer resistance against infection with the homologous virus, and some closely related viruses.

    At the start of this investigation no sequence data on the RNA genome of PVY were available, therefore cDNA synthesis and subsequent sequence determination was performed to obtain the necessary PVY CP gene sequence as well as additional sequences from the 3'-terminal region of the viral genome (Chapter 2 and Van der VIugt et al., 1989). This enabled the determination of the exact taxonomic position of the PVY N('tobacco veinal necrosis strain') isolate used in these experiments, among other PVY isolates from at least two different strains. Detailed comparisons of the PVY NCP and 3'-non translated (3'-NTR) sequences with those from a large number of geographically distinct PVY isolates that became available during the course of this investigation, showed that these sequences, in addition to distinguish between different potyvirus species (Ward and Shukla, 1991; Frenkel et al., 1989), can also be used for the distinction between strains of one potyvirus (Chapter 3, Van der VIugt et al., 1992a). Several strain specific amino acid sequences in the CPs and nucleotide sequences in the 3'-NTRs could be discerned, that are possibly involved in virulence and/or symptom expression. Further experiments are required to elucidate the precise biological significance of these sequence motifs. Interestingly the sequence comparisons as complied in Chapter 3 also confirmed the high levels of CP and 3'-NTR sequence identity between the PVY isolates at one hand and one putative isolate of pepper mottle virus (PepMoV, Dougherty et al., 1985) at the other, as described previously (Van der VIugt et al., 1989; Van der Vlugt, 1992). Initially described as an atypical strain of PVY (PVY-S, Zitter, 1972) PepMoV was later found to be serologically and biologically distinct from PVY (Purcifull et al., 1973, 1975; Zitter and Cook, 1973). Recent determination of the complete genomic RNA sequence of a Californian isolate of pepper mottle virus (PepMoV-C; Bowman-Vance et al, 1992a,b) and comparisons between a Florida isolate of PepMoV and PVY (Hiebert and Purcifull, 1992) however, suggest that PepMoV represents a distinct potyvirus though more closely related to PVY than to any other potyvirus. Additional sequence information of other, biologically well characterized, isolates of PepMoV, like a virus isolate apparently intermediate between PepMoV and PVY (Nelson and Wheeler, 1978), will hopefully aid in establishing the exact taxonomic position of this pepper infecting virus in the genus Potyvirus. Generally it is to be recommended that of all virus isolates whose (partial) sequences are under investigation, precise origin and other relevant biological characteristics are also accurately documented.
    In contrast to all other viruses for which 'CP-mediated resistance' has been described sofar, potyviruses do not express their CPs from a distinct, separate gene but through proteolytic cleavage of a polyprotein precursor. This necessitated the
    addition of translational start signals, directly upstream of the CP encoding sequence, in order to enable expression of the PVY NCP in transgenic potato and tobacco plants. Potato tuber disc and tobacco leaf disc transformations with these constructs resulted in large numbers of transgenic plants (Chapters 4 and 5). Despite the fact that a large number of transgenic plants was tested for CP expression, using a highly sensitive enzyme-amplification based ELISA format, in none of the plants significant amounts of viral CP could be detected. Whether this is caused by the extra N-terminal methionine residue, or improper folding of the CP, resulting in decreased stability of the protein, or by inefficient protein extractions, possibly resulting from protein insolubility, is not known. It remains to be tested whether transformation of plants with a construct in which a functional protease domain is coupled to a potyviral CP with an intact protein processing sequence, will result in high levels of expression of the CP. For more practical purposes however, PVY CP expression levels appear not to be of significant importance since the protection against PVY, observed in the transgenic tobacco plants (Chapter 5 and 6), is apparently RNA-mediated, i.e. prima rily based on the presence of the CP encoding RNA rather than on the coat protein itself. Transgenic tobacco lines expressing PVY CP transcripts devoid of a translational start signal (CP -ATG), possess equal levels of protection against both mechanically inoculated virus and virus transmitted by the natural aphid vector Myzuspersicae (Chapter 5 and 6). It seems highly unlikely that the protection in these CP -ATGplants is based on minute amounts (i.e. less then 0.0001 % of the total soluble protein) of a truncated viral polypeptide since the presence of six translational stopcodons preceding the first in-frame AUG startcodon, 162 nucleotides down stream the 5'-end of the CP encoding sequence, will prevent expression of such a polypeptide.

    Analysis of the transgenic potato lines (Chapter 4) showed that most lines, as the transgenic tobacco lines, expressed CP specific RNA transcripts. Under the given greenhouse conditions, however, in none of the transgenic plants protection to PVY could be determined. In view of the results obtained with the transgenic tobacco lines, it may be anticipated that virus challenging of additional transgenic potato lines, under more optimal greenhouse conditions, will reveal similar levels of RNA-mediated virus resistance as observed in tobacco. For all practical purposes genetically engineered resistance based on the presence of RNA molecules is to be preferred over forms of resistance that are based on the expression of a (foreign) protein. Apart from being energetically more favourable for the plant, it is likely to aid in the acceptance of genetically modified crop plants by both politicians and the public, something which might, in the next few years, turn out to be the major obstacle in the successful application of plant transformation techniques.

    At this stage one can only speculate on the mechanism(s) on which this RNAmediated resistance is based. Transformation of plants with partial CP or other PVY Ngenomic sequences will help in identifying the protection mechanism(s) involved and show whether regions other than the CP-encoding domain can be equally effective in conferring virus resistance. If the resistance is based on a 'sense-RNA' effect, i.e. hybridization of the positive sense transgenic RNA to negative-sense viral RNA replication intermediates, thereby blocking further virus replication, the ribozyme technology might prove an efficient expansion of this genetically engineered type of resistance. Ribozymes, RNA sequences capable of specific and catalytic cleavage of other RNA-sequences, are able to cleave target RNAs efficiently and catalytically in vitro . The antiviral application of ribozymes in transgenic plants however has sofar demonstrated not to be very successful and reported protection levels are not yet exceeding those obtained with antisense RNAs (Edington and Nelson, 1992). Chapter 7 describes the design and synthesis of hammerhead ribozymes capable to cleave a highly conserved region from the PVY RNA dependent RNA-polymerase cistron. It was shown that the correct formation of the hammerhead cleavage complex, determined at least in part by the lengths of the antisense arms of the ribozyme, forms an important factor in the efficiency of cleavage. Cellular and full-length viral RNA molecules generally posses extended, unknown secondary structures which are likely to hamper precise formation of hammerhead structures, which requires bimolecular basepairing. Correct hammerhead formation and efficient cleavage of these RNAs will therefore require ribozymes with rather long basepairing arms. These long antisense arms however will make catalytic cleavage rather unlikely since complex dissociation will probably become the rate limiting factor. For this reason one can assume that ribozymes will only be successful when introduced into specific antisense RNA molecules, directed against the less abundant viral complementary strands, rather than as highly efficient RNA cleaving "enzymes".

    Early nodulins in root nodule development
    Scheres, B. - \ 1990
    Agricultural University. Promotor(en): A. van Kammen; T. Bisseling. - S.l. : Scheres - 155
    wortelknolletjes - knobbelvorming - rhizobiaceae - rhizobium - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - root nodules - nodulation - rhizobiaceae - rhizobium - genetics - genetic variation - evolution - speciation - immunogenetics

    The symbiotic interaction between bacteria of the genus Rhizobium and leguminous plants leads to the formation of root nodules, which are specific nitrogen-fixing organs on the roots of plants. Bacteria enter the root by infection threads, and concomitantly cell divisons are induced in the root cortex, which lead to the formation of a meristern. From this meristern the different tissues of the root nodule originate. In the nodule bacteria are released in plant cells and then differentiate into the endosymbiotic bacteroids. These bacteroids are capable of nitrogen fixation.

    The formation of root nodules involves expression of both bacterial and plant genes. Rhizobium genes involved in nodule formation are the nodulation ( nod ) genes. Nodulespecific plant genes are termed nodulin genes. According to their timing of expression they can be divided into early and late nodulin genes. Early nodulin genes are expressed well before the onset of nitrogen fixation, at the time that the nodule tissue is formed and the roots become infected by bacteria, while expression of late nodulin genes starts shortly before the onset of nitrogen fixation, when the nodule structure has been formed. Therefore only early nodulins can be involved in the infection process and in nodule development. Early nodulin genes expressed during the pea ( Pisum sativum L.) - Rhizobium leguminosarum bv. viciae interaction are the subject of this thesis. Several cDNA clones representing pea early nodulin genes have been isolated and they have been used to study root nodule development and the communication between bacteria and host plant.

    In chapter 2 we review general aspects of plant development. Recent progresses in understanding the molecular mechanisms underlying animal development are listed, and the possible significance of such mechanisms for plant development is discussed. The features of the root nodule formation system that make it suitable to study particular questions on the molecular basis of plant development are put forward.

    In chapter 3 the pea early nodulin cDNA clone pPsENOD2 is characterized. The nature of the encoded polypeptide is compared with that of the soybean early nodulin described before. ENOD2 transcripts are localized both in pea and soybean root nodules throughout successive stages of development by in situ hybridization. Data on the primary structure of the ENOD2 protein and localization data are then combined to hypothesise that the function of this early nodulin is to create an oxygen barrier in the root nodule.

    In chapter 4 the early nodulin ENOD12 is described. The spatial distribution of the corresponding transcript throughout root nodule development is depicted to demonstrate the involvement of ENOD12 in the infection process. We describe the primary structure of the ENOD12 protein and we examine whether ENOD12 gene expression is related to a defense respons. Using a sensitive detection method based on the polymerase chain reaction (PCR) we demonstrate that ENOD12 gene expression is induced by excreted Rhizobium factors and that bacterial nod genes are involved. ENOD12 transcripts found in flower and stem tissue are compared to the ENOD12 mRNAs in nodules using, among other techniques, a novel adaptation of RNase mapping to determine whether the same genes are expressed in these different tissues or not.

    In chapter 5 it is demonstrated that the accumulation pattern of the transcripts corresponding to the pPsENOD5, pPsENOD3 and pPsENOD14 cDNA clones differs from that of ENOD2 and ENOD12 mRNA. The distribution of the former three transcripts is compared with the distribution of ENOD12 mRNA and the late nodulin leghemoglobin transcript. It is shown that the different transcripts are present at successive stages of development of the infected cell type. The primary structure of the ENOD5, ENOD3 and ENOD14 early nodulins is determined and these data are combined with the localization data of the transcripts to speculate on functions of these proteins, The involvement of different factors to induce expression of different early and late nodulin genes is discussed.

    In chapter 6 the results described in the previous three chapters are summarized and some additional data on early nodulins are presented. The significance of the availability of early nodulin gene probes to elucidate the mechanisms of communication between rhizobia and legumes, which underly the process of root nodule formation, is discussed. Finally, in chapter 7, the value of the obtained information on early nodulins for studying both specific and general aspects of root nodule development is discussed.

    Nodulins in root nodule development
    Nap, J.P. - \ 1988
    Agricultural University. Promotor(en): A. van Kammen, co-promotor(en): T. Bisseling. - S.l. : Nap - 113
    wortelknolletjes - knobbelvorming - rhizobiaceae - rhizobium - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - root nodules - nodulation - rhizobiaceae - rhizobium - genetics - genetic variation - evolution - speciation - immunogenetics

    In de bodem zijn Rhizobium bacteriën in staat de wortels van vlinderbloemige planten (erwt, boon, klaver) te infecteren en aan te zetten tot de vorming van knolletjes. In die wortelknolletjes zijn de bacteriën in staat om stikstof uit de lucht te binden en om te zetten in ammonia. Met de ammonia kan de plant zich in belangrijke mate voorzien in haar stikstofbehoefte. Op hun beurt krijgen de bacteriën voedingsstoffen van de plant, zodat beide partners profiteren van deze symbiose.

    Een stikstofbindende wortelknol is een uiterst gespecialiseerd plante-orgaan, dat gevormd wordt in een aantal opeenvolgende stappen, waarin rhizobia de plant binnendringen, en deze aanzetten tot de vorming van een wortelknolstructuur. Uiteindelijk vullen de Rhizobium bacteriën ongeveer de helft van de cellen in de wortelknol, veranderen van vorm en beginnen vervolgens met de stikstofbinding. Gedurende dit proces wisselen plant en bacterie waarschijnlijk voortdurend signalen uit om het goede verloop van het proces te bewerkstelligen.

    Het onderzoek naar het mechanisme van wortelknolvorming en stikstofbinding op moleculair niveau heeft een hoge vlucht genomen. Zowel in de bacterie als in de plant zijn genen geïdentificeerd, die alleen in de wortelknol tot expressie komen. Rhizobium bacteriën bezitten naast hun chromosoom een zogenaamd sym plasmide, waarop de genen liggen die betrokken zijn bij de symbiose. Geïdentificeerd zijn de genen voor wortelknolvorming ( nod genen) en stikstofbinding ( nif en fix genen). Over de functie van de genproducten en de regulatie van de expressie van deze genen is veel bekend, maar wat met name de ( nod genen precies teweegbrengen is nog onduidelijk.

    Een twintig- tot dertigtal genen van de plant komen uitsluitend in de wortelknol tot expressie; dit zijn de zogenaamde noduline genen. Onderzoek naar de expressie van noduline genen in relatie tot de ontwikkeling van de wortelknol heeft laten zien dat er tenminste twee klassen noduline genen onderscheiden kunnen worden: vroege en late noduline genen. De vroege noduline genen komen ruim voor de stikstof-binding tot expressie, als het orgaan de wortelknol wordt aangelegd. Vroege nodulines spelen daarom waarschijnlijk een rol bij het vormen van de structuur van de wortelknol. Late noduline genen komen tot expressie rond het tijdstip dat de wortelknol met stikstofbinding begint. Het is dan ook aannemelijk dat late nodulines betrokken zijn bij het functioneren van de wortelknol. Mogelijk scheppen zij de voorwaarden voor stikstofbinding en het transport van gebonden stikstof. Omdat de late noduline genen min of meer tegelijkertijd tot expressie komen, is het waarschijnlijk dat deze genen op één en dezelfde wijze worden gereguleerd.

    Het merendeel van de noduline genen die tot nu toe geïdentificeerd zijn, behoort tot de klasse van late noduline genen. Het best bestudeerde late noduline is leghemoglobine, een myoglobine- achtig eiwit dat de zuurstofhuishouding in de wortelknol regelt. Van slechts een gering aantal van de overige nodulines is de functie in de wortelknol bekend. Ook over de manier waarop de plant ervoor zorgt dat noduline genen op het juiste moment en op de juiste plaats, dus alleen in de wortelknol, tot expressie komen, en over de rol van de Rhizobium bacteriën bij dit proces, is de kennis nog gering.

    Dit proefschrift beoogt een bijdrage te leveren aan de kennis over nodulines en noduline genexpressie. De beschreven experimenten hebben tot doel inzicht te krijgen in het mechanisme van de regulatie van noduline genexpressie. Vooral de rol van Rhizobium genen bij de inductie van noduline genexpressie staat daarbij centraal. Anderzijds komt ook de functie van vroege nodulines tijdens de vorming van een wortelknol ter sprake.

    Na een korte algemene inleiding over wortelknolvorming (hoofdstuk een) wordt in hoofdstuk twee een cDNA kloon beschreven die een vroeg noduline gen representeert. Deze cDNA kloon, pGmENOD2, is geïsoleerd uit een cDNA bank gemaakt tegen wortelknoIRNA van soja. Het ENOD2 DNA blijkt te coderen voor een noduline met een molecuulgewicht van 75.000, aangeduid met Ngm-75. De aminozuurvolgorde van dit noduline, afgeleid uit de DNA sequentie, laat zien dat Ngm-75 een zeer proline-rijk eiwit is, met een repeterend motief in zijn primaire structuur. Dit duidt erop dat Ngm-75 een structureel eiwit zou kunnen zijn. Het gen dat codeert voor Ngm-75 komt tot expressie in wortelknol-achtige structuren, die weliswaar door Rhizobium bacteriën geïnduceerd zijn, maar waarin geen bacteriën aangetroffen worden, zogenaamde 'lege' knollen. Ngm-75 lijkt daarom geen functie te hebben in het proces waarbij de Rhizobium bacteriën de plant binnendringen, maar eerder lijkt dit vroege noduline een bijdrage te leveren aan de vorming van de wortelknolstructuur.

    In hoofdstuk drie wordt de regulatie van de expressie van late noduline genen op het niveau van het DNA onder de loep genomen. Leghemoglobine cDNA kloons, geïsoleerd uit een cDNA bank gemaakt van wortelknoIRNA van de erwt, zijn gebruikt om een leghemoglobine gen te isoleren uit een genomische bank gemaakt van erwteDNA. Van dit leghemoglobine gen van de erwt is de DNA sequentie bepaald. Uit de analyse van deze sequentie blijkt dat het geïsoleerde gen volledig is en alle kenmerken bezit van een actief gen. De vergelijking van de promotergebied van het uit de erwt geïsoleerde leghemoglobine gen met de promotergebieden van soja leghemoglobine genen laat zien dat er overeenkomstige sequenties voorkomen. Omdat de overeenkomstige sequenties ook worden aangetroffen in de promotergebieden van andere late noduline genen, zijn deze sequenties wellicht betrokken bij de wortelknolspecifieke expressie van alle late noduline genen.

    In de hoofdstukken vier en vijf staat de communicatie tussen plant en bacterie centraal. Gepoogd wordt te achterhalen welke genen van Rhizobium betrokken zijn bij het aanschakelen van noduline genen. Hierbij is gebruik gemaakt van de mogelijkheden die de bacteriële genetica biedt om bacteriën te construeren die weliswaar een gedefiniëerd deel van het totale Rhizobium genoom missen, maar toch nog wortelknollen kunnen induceren. Deze studies zijn uitgevoerd met wikke ( Vicia sativa subsp. nigra ), omdat dit kleine vlinderbloemige plantje snel reageert op inoculatie met (genetisch veranderde) Rhizobium bacteriën. In hoofdstuk vier is de basis gelegd voor de analyse door het identificeren van de noduline genen van wikke. Uit wortelknollen werd RNA geïsoleerd, en in vitro vertaald in eiwitten, welke werden gescheiden op tweedimensionale polyacrylamide gels. Door het vergelijken van het aldus verkregen eiwitpatroon met dat van worteIRNA zijn vijftien noduline mRNAs geïdentificeerd, waaronder één vroeg noduline mRNA. Een tweede vroeg noduline mRNA van wikke is geïdentificeerd op Northern blots met behulp van de in hoofdstuk twee beschreven soja cDNA kloon pGmENOD2.

    De expressie van de noduline genen van wikke is vervolgens bestudeerd in wortelknollen geïnduceerd door een Rhizobium stam waarin het sym plasmide is vervangen door een plasmide met alleen 12 kb van het nod gebied. Alle noduline genen bleken tot expressie te komen. Kennelijk speelt de informatie op het sym plasmide buiten deze 12 kb nod gebied geen enkele rol bij de inductie van noduline genexpressie. In wortelknollen geïnduceerd door een Agrobacterium transconjugant, waarin het Ti plasmide is vervangen door dezelfde 12 kb van het nod gebied, bleken alleen de twee vroege noduline genen tot expressie te komen. Het nod gebied is dus het enige Rhizobium DNA dat betrokken lijkt te zijn bij de inductie van vroege noduline genexpressie. Hoewel dit resultaat tegelijkertijd suggereert dat het Rhizobium c hromosoom betrokken moet zijn bij de inductie van late noduline gen expressie, mag die conclusie niet zomaar getrokken worden, want cytologisch onderzoek laat zien dat de Agrobacterium transconjugant een afweerreactie van de plant oproept. Het is dus mogelijk dat de genen op het nod gebied weliswaar in staat zijn om late noduline genen aan te schakelen, maar dat de verdere ontwikkeling van de wortelknol al gestopt is door de tussenkomst van het afweermechanisme, vóórdat die late noduline genen aangeschakeld konden worden. Agrobacterium transconjuganten zijn dus niet bruikbaar om de rol van de nod genen bij de inductie van late noduline genexpressie te onderzoeken.

    In hoofdstuk vijf worden experimenten besproken die, zij het indirect, laten zien dat de nod genen inderdaad betrokken zijn bij de expressie van late noduline genen. Gezien het fenotype van mutaties in de diverse nod genen aanwezig in de 12 kb van het nod gebied zijn het waarschijnlijk de nodA , B en C genen, die één of meer signalen aan de plant geven, waardoor de expressie wordt geïnduceerd van de vroege en vervolgens mogelijk ook van de late noduline genen.

    Uit bovenstaande experimenten bleek dat er een correlatie bestaat tussen de ontwikkeling van een wortelknol, zoals die op microscopisch niveau gevolgd kan worden, en de expressie van noduline genen. De correlatie tussen de expressie van een bepaald noduline gen en het bereiken van een bepaald ontwikkelingsstadium biedt de mogelijkheid om te speculeren over de functie die dat noduline zou kunnen hebben. Op grond van de experimenten beschreven in de hoofdstukken vier en vijf kunnen vroege zowel als late noduline genen verder onderverdeeld worden in subklassen, die ieder correleren met een stap in de ontwikkeling van een wortelknol. Hoofdstuk zes, tenslotte, is een overzicht van de huidige kennis over nodulines, noduline genen en de regulatie van noduline genexpressie. De resultaten gepresenteerd in de hoofdstukken twee tot en met vi# worden in dit laatste hoofdstuk met deze kennis geïntegreerd.

    Genetic control of immune responsiveness in the chicken
    Zijpp, A.J. van der - \ 1982
    Landbouwhogeschool Wageningen. Promotor(en): C.C. Oosterlee. - Wageningen : van der Zijpp - 100
    verbetering - weerstand - dierveredeling - pluimvee - kippen - immunogenetica - improvement - resistance - animal breeding - poultry - fowls - immunogenetics
    Disease can be combated by medication, vaccination, hygienic measures, eradication and genetic resistance. Genetic resistance to infectious diseases is advantageous because of its permanent character in contrast with the aforementioned procedures. In the chicken genetic resistance to specific diseases like Marek's disease and lymphoid leukosis is well known. Despite this knowledge improvement of genetic resistance to specific diseases is not included extensively in breeding programmes yet. The need for infection of populations, the lack of knowledge of correlations with resistance to other diseases and production traits and the rare understanding of defence mechanisms are major drawbacks for application.

    A different approach to genetic improvement of disease resistance is the composition of a series of defence traits, defining general resistance to disease. The major histocompatibility complex, the B-locus in the chicken, may be such a valuable marker especially for resistance to viral oncogenesis. The capacity to produce antibodies to a multideterminant antigen, like sheep red blood cells (SRBC) is another possible marker trait. Selective breeding for this trait in mice has shown, that the effects are non-specific. In this thesis genetic and environmental aspects of the agglutinin antibody response to SRBC in poultry are discussed.

    The agglutinin antibody response to SRBC was polygenically determined. Heritability estimates for total antibody titre and 2-mercapto-ethanol (2-ME) resistant and sensitive antibody titres varied from non-significant to, usually. levels around .2 to .3 for the primary response in White Leghorn (WL), White Plymouth Rock (WPR) and ISA Warren populations. The heritabilities of a secondary response, measured in WPR and ISA Warren populations, were somewhat lower. The size of these heritability estimates offers a good perspective for mass selection as already shown in the first selection generation for high and low antibody production in our ISA Warren population. Moreover the repeatibility of this trait is very high, above .9.

    Phenotypic correlations between primary and secondary total antibody titres were not significant in a OR population. This result was explained by a positive relationship between primary 2-ME sensitive antibody titres and secondary 2-ME resistant antibody titres and a negative relationship between primary and secondary 2-ME sensitive antibody titres. Additive genetic correlations between total antibody titres of primary and secondary response were quite negative. If these negative genetic correlations will be confirmed by other research workers, then the choice of the primary antibody response to SRBC as a selection criterion for general disease resistance becomes a major concern.

    Differences between three stocks: WL, WPR and ISA Warren were found for antibody response to three doses of SRBC and for the cell-mediated response, the swelling of the wingweb post phytohaemagglutinin (PHA) injection. Genetic origin by dose of SRBC interactions were absent. However the response curve was different for each stock, indicating genetic origin by testday post injection interactions. Phenotypic correlations between total antibody titres to SRBC and PHA wingweb swelling were absent, overall and within stocks.

    The antibody response to SRBC is influenced by many non-genetic factors. Important non-genetic effects were dose of SRBC, age of the chick, primary versus secondary response, vaccination programme, interval between SRBC injection and titre determination. Desirable traits of the defence system in combating infectious diseases are immune competence at an early age, responsiveness to low doses of infectious agents. a quick response post infection and development of memory. The selection criterion, therefore, has to be clearly defined and the effects of selection upon these desired characteristics will have to be evaluated.

    Considering the heritabilities, the repeatibility and the manifestation at an early age, the haemagglutinin antibody response to SRBC offers a perspective for selection. The value of this trait for general disease resistance will have to be proven in the near future, when our selection lines for high and low antibody responsiveness have been established.

    Studies on the expression of the genes for the third and fourth components of the complement system
    Odink, K.G. - \ 1981
    Landbouwhogeschool Wageningen. Promotor(en): A. van Kammen. - Wageningen : Odink - 48
    immunogenetica - immunogenetics
    The mayor part of the work reported in this thesis, aimed at the generation and isolation of DNA probes complementary to the messenger RNA for the complement components C3 and C4. Indeed for the complement component C3 the isolation of a complementary DNA probe has been successful and therefore it has become possible to perform detailed studies on the gene(s) and the RNA transcripts for this component.

    Recent results revealed that among the clones harboring recombinant plasmids (310, see chapter 3) eleven (3%) contained C3-specific sequences. Nine of these contained different plasmids with partially overlapping C3-cDNA inserts, covering in total 4700 nucleotides (90/1) of the C3-mMA.

    The C3-cDNA probes are now used for a variety of experiments in different lines of investigation. a) Further characterization of C3-mMA. In chapter 3 the C3-mRNA was estimated to contain 7500 nucleotides. This value was obtained by electrophoresis of mRNA in presence of the denaturing agent methyl mercury hydroxide. In chapter 4, using glyoxal for the denaturation of the RNA, C3- mRNA was found to contain only 5300 nucleotides. several independent experiments i.e. primer extended reverse transcription and digestion of C3- mRNA with RNase H after hybridization to C3-cDNA fragments, indicate that the value of 5300 probably is correct. Also the length of the mRNA for vitellogenin, which has a similar size as C3-mRNA, has been overestimated, using the methyl mercury hydroxide method (Dr. G. Ryffel, personal communication). b) Gene expression. Several aspects of the regulation of the expression of the gene for the complement component C3 have been studied in chapter 4. Sofar no convenient model system for the modulation of the expression of the C3-gene has been found, in which it will be possible to study the mechanism of control of gene expression. The continuous presence of complement component C3 might be so essential that its gene is expressed constitutively in the producer tissues and that major regulation never takes place. In any case, if in future regulatory stimuli will be found which have a strong effect on the expression of the C3-gene, tools for a detailed study of the mechanism are available. c) Gene structure. The mouse and human C3-genes have been analysed by digestion with several restriction enzymes, followed by size fractionation and detection of the C3-specific fragments by hybridization to radioactively labeled C3-cDNA. Fragments of the C3-gene, comprising at least 90% of the sequences coding for C3-mRNA, have been isolated from a mouse gene library. Results from several experiments are to be expected soon : the determination of the number of C3-genes in the mouse and human genome; the location of the human gene(s) on a chromosome(s), with the use of human-mouse hybrids cells; sequence analysis of parts of the C3-cDNA, which will possibly reveal the amino acid sequence of the C3a polypeptide and of the portion of C3b which contains the binding site for cells and particles (see 1.3.4 and 1.3.5).

    All these examples show that a new approach has become available to answer questions about the expression, genetic aspects and structural aspects of the gene for the complement component C3.

    For the complement component C4 the isolation of a complementary DNA probe has not been successful so far. The serum level of C4-protein is approximately three fold lower than for C3-protein. This might reflect a lower abundancy of the C4-mRNA in the liver. Indeed, after invitro translation of liver mRNA and immunoprecipitations using anti-C3 and anti- C4 sera, much less (at least ten fold) pro-C4 was found than pro-C3 (chapter 3). But low efficiency of the immunoprecipitation with anti-C4 could also explain these results. However, if macrophage mRNA is used for invitro translation, the immunoprecipitations with anti-C4 and anti-C3 are equally efficient. Therefore it is likely that part of the polypeptides, obtained after invitro translation of liver mRNA, which have a molecular weight of 190'000 is not related to pro-C4 and that indeed C4-mRNA appears approximately ten fold less abundant than C3-mRNA in liver. This in turn could explain why no recombinant plasmids were found which contained cDNA inserts for C4-mRNA. A larger collection of clones containing recombinant plasmids should be made in order to increase the chance of isolating a C4-cDNA probe. A C4-DNA probe would provide an entrance into the major histocompatibility complex and could help to elucidate whether there is a relation between this complex and the complement system, other than the location of some of the complement genes within the major histocompatibility complex.

    It is conceivable that in the future, apart from the complement components C3 (and C4?), for the other components of the complement system cDNA clones will be isolated. However, serious problems might be encountered due to low abundancies of their mRNA. If these isolations will be succesfull, the coherance in the regulation of the biosynthesis of the complement components might become understood.

    Van molecule tot populatie
    Veen, J.H. van der - \ 1970
    Wageningen : Veenman - 17
    genetica - genetische variatie - evolutie - soortvorming - immunogenetica - genetics - genetic variation - evolution - speciation - immunogenetics
    Rede Wageningen, 19 november 1970
    Verslag van een bezoek aan het Institut fuer Angewandte Genetik te Hannover op 22 en 23 september 1969
    Sparnaay, L.D. ; Eyk, J.P. van - \ 1969
    Wageningen : [s.n.] (Rapport / Instituut voor de Veredeling van Tuinbouwgewassen no. 72) - 7
    teelt - cultuurmethoden - evolutie - proefstations - genetische variatie - genetica - duitsland - immunogenetica - sierplanten - plantenveredeling - onderzoeksinstituten - soortvorming - cultivation - cultural methods - evolution - experimental stations - genetic variation - genetics - germany - immunogenetics - ornamental plants - plant breeding - research institutes - speciation
    Vijftig jaar genetica : afscheidscollege Landbouwhogeschool 21 oktober 1969
    Prakken, R. - \ 1969
    Wageningen : Veenman - 18
    genetica - genetische variatie - evolutie - soortvorming - immunogenetica - hogere agrarische scholen - universiteiten - nederland - veluwe - gelderland - genetics - genetic variation - evolution - speciation - immunogenetics - agricultural colleges - universities - netherlands - veluwe - gelderland
    Rede Wageningen
    Cytoplasmatische erfelijkheid
    Anonymous, - \ 1966
    Wageningen : [s.n.] (Literatuurlijst / Centrum voor landbouwpublikaties en landbouwdocumentatie no. 2702)
    bibliografieën - cytoplasma - evolutie - genetische variatie - genetica - immunogenetica - soortvorming - bibliographies - cytoplasm - evolution - genetic variation - genetics - immunogenetics - speciation
    Analyse van aardappelpopulaties ten dienste van de veredeling
    Maris, B. - \ 1962
    Wageningen University. Promotor(en): J.C. Dorst. - Wageningen : Pudoc - ISBN 9789022000762 - 208
    plantenveredeling - solanum tuberosum - aardappelen - plantenziekteverwekkende schimmels - plantkunde - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - plant breeding - solanum tuberosum - potatoes - plant pathogenic fungi - botany - genetics - genetic variation - evolution - speciation - immunogenetics
    A method was worked out for roughly predicting time of ripening of seedlings a few weeks after sowing. The method was tested by growing seedlings for several consecutive years and the clonal generations were studied and analysed for many other characters. Descriptions included both specific characters and general impression of the whole clones at various stages in successive years. The data were used to evaluate the practice of breeders of maintaining selection only on material which visually conforms to most of their objectives.

    To avoid or diminish the risk that many valuable clones would be lost the author suggested as a more rational procedure to raise fewer first-year seedlings, to classify these seedlings according to foliage length as a means of estimating approximate maturity in an early stage and to discard only the poor clones instead of retaining only the 'good' ones, until a sufficient number of tubers is available for trials which are statistically sound.

    Erfelijkheid en samenleving
    Honing, J.A. - \ 1934
    Wageningen : Veenman - 16
    evolutie - genetische variatie - genetica - immunogenetica - colleges (hoorcolleges) - populatiegenetica - sociale wetenschappen - soortvorming - evolution - genetic variation - genetics - immunogenetics - lectures - population genetics - social sciences - speciation
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