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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Expression studies in the embryo and in the micropylar endosperm of germinating coffee (Coffea arabica cv. Rubi) seeds
Farias, E.T. de; Amaral da Silva, E.A. ; Toorop, P.E. ; Bewley, J.D. ; Hilhorst, H.W.M. - \ 2015
Plant Growth Regulation 75 (2015)2. - ISSN 0167-6903 - p. 575 - 581.
beta-mannanase - growth - purification - cloning
Germination of coffee (Coffea arabica L.) seed is slow and uneven. Its germination is the net result of events that occur simultaneously in the embryo and endosperm and which are controlled by abscisic acid (ABA). The aim of the study was to monitor the expression of genes related to the cell cycle and to cell wall modifications, including an actin (ACT), a cyclin-dependent kinase (CDK2a) and a-expansin (a-EXP) in the embryo, and a-galactosidase (a-GAL), ß-mannosidase (LeMSIDE2), endo-ß-mannanase (MANA) in the micropylar endosperm. The first seed germinated after 5 days of imbibition and 50 % germination was reached after 10 days. The embryo grew inside the seed prior to radicle protrusion and ABA inhibited both embryo growth and radicle protrusion. The expression of the genes associated with the embryo growth increased during germination and ABA partially inhibited expression. The expression of ß-mannosidase and endo-ß-mannanase increased during imbibition and ABA completely inhibited expression of these genes. However, a-galactosidase displayed a more constitutive expression and was less affected by ABA. ABA plays a dual role in the regulation of coffee seed germination; it concomitantly controls both endosperm weakening and embryo growth.
Dormancy cycling in seeds: mechanisms and regulation
Claessens, S.M.C. - \ 2012
University. Promotor(en): Linus van der Plas, co-promotor(en): Henk Hilhorst; P.E. Toorop. - S.l. : s.n. - ISBN 9789461731906 - 161
sisymbrium officinale - arabidopsis thaliana - kiemrust - zaden - genen - levenscyclus - slaaptoestand - membranen - metabolisme - seed dormancy - seeds - genes - life cycle - dormancy - membranes - metabolism

The life cycle of most plants starts, and ends, at the seed stage. In most species mature seeds are shed and dispersed on the ground. At this stage of its life cycle the seed may be dormant and will, by definition, not germinate under favourable conditions (Bewley, 1997).

Seasonal dormancy cycling is a characteristic found in plant seeds. Being able to cycle in and out of dormancy allows the seed to survive decades or even centuries, allowing germination to be spread over time, but only when optimal conditions are available, not only for germination but especially for seedling establishment. In this thesis we have attempted to further elucidate the mechanisms behind dormancy, germination and dormancy cycling.

Sisymbrium officinale seeds need nitrate and light to start germination (Chapter 2, 3, 4, 6). Nitrate acts in part by reducing the abscisic acid (ABA) levels (a plant hormone that elevates dormancy levels). The action of light and nitrate can also be reached by applying gibberellins (GAs) to the seeds (Chapter 2, 3, 4, 6). GAs are capable of inducing enzymes that hydrolyze the ensdosperm walls (Debeaujon and Koornneef, 2000; Chen and Bradford, 2000; Nonogaki et al., 2000; Manz et al., 2005) In this way GAs could be involved in lowering the physical restrictions imposed by the resistance of the seed coat and the endosperm. On the other hand, GAs may also increase the embryo growth potential.

For successful survival of the dormant seed, metabolic activity is reduced to avoid rapid depletion of reserves. The metabolic activity of the seed was measured using electron paramagnetic resonance (EPR), with TEMPONE as a spin probe, and the respiratory activity was measured with the Q2-test (Chapter 2).We showed that primary dormancy was accompanied by hardly any metabolic or respiratory activity, and this increased considerably when dormancy was broken by nitrate. However, when the light pulse was not given and the seeds had become secondary dormant the metabolic activity slowed down.

Regulation of dormancy is tightly linked with abiotic stress factors from the environment. The regulation and survival of the seed under stress conditions is largely dependent on the composition of the cytoplasm. We tested this by EPR, using carboxyl-proxyl (CP) spin probe (Chapter 4). The primary dormant and sub-dormant seeds possessed a higher viscosity than the germinating seeds. The viscosity of secondary dormant seeds appeared intermediate; however, the ease at which the vitrified water melted was similar to that of primary dormant seeds. As a result of the differences in viscosity, the temperature of vitrified water melting differed between the different dormancy states. The changes in cytoplasmic viscosity and vitrified water melting may be linked to changes in metabolism and the content of high molecular weight compounds.

As membranes are the primary target for temperature perception, they are often implicated in regulating dormancy. Therefore, Hilhorst (1998) put forward a hypothesis in which changes in responsiveness to dormancy breaking factors like nitrate and light was a function of cellular membrane fluidity. In Chapter 3 we indeed showed that dormancy is a function of membrane fluidity. Primary dormant seeds of Sisymbrium officinale appeared to have very rigid membranes, whereas breaking dormancy increased membrane fluidity considerably. However, when sub-dormant seeds became secondary dormant membrane fluidity decreased again, but not to the rigidity seen in primary dormant seeds. One of the most common ways in which cells control membrane fluidity is by homeoviscous adaptation with the help of desaturases. Desaturase involvement in changes in membrane fluidity due to changes in dormancy was tested in Chapter 3 (using Sisymbrium officinale) and Chapter 5 (using Arabidopsis thaliana). Here we found that although desaturase activity may change the membrane fluidity or influence the germination/dormancy phenotype, the two are not linked, unless the effects of these enzymes are very local within the seed. Finally, in Chapter 7, we presented a new model in which a membrane anchored dormancy related protein/transcription factor is activated by changes in membrane fluidity. The activated form is transported to the nucleus, where it starts the germination process, which includes changes in metabolism and mobilization of storage reserves.

Assessing the potential value for an automated dairy cattle body condition scoring system through stochastic simulation
Bewley, J.M. ; Boehlje, M.D. ; Gray, A.W. ; Hogeveen, H. ; Kenyon, S.J. ; Eicher, S.D. ; Schutz, M.M. - \ 2010
Agricultural Finance Review 70 (2010)1. - ISSN 0002-1466 - p. 126 - 150.
Purpose – The purpose of this paper is to develop a dynamic, stochastic, mechanistic simulation model of a dairy business to evaluate the cost and benefit streams coinciding with technology investments. The model was constructed to embody the biological and economical complexities of a dairy farm system within a partial budgeting framework. A primary objective was to establish a flexible, user-friendly, farm-specific, decision-making tool for dairy producers or their advisers and technology manufacturers. Design/methodology/approach – The basic deterministic model was created in Microsoft Excel (Microsoft, Seattle, Washington). The @Risk add-in (Palisade Corporation, Ithaca, New York) for Excel was employed to account for the stochastic nature of key variables within a Monte Carlo simulation. Net present value was the primary metric used to assess the economic profitability of investments. The model was composed of a series of modules, which synergistically provide the necessary inputs for profitability analysis. Estimates of biological relationships within the model were obtained from the literature in an attempt to represent an average or typical US dairy. Technology benefits were appraised from the resulting impact on disease incidence, disease impact, and reproductive performance. In this paper, the model structure and methodology were described in detail. Findings – Examples of the utility of examining the influence of stochastic input and output prices on the costs of culling, days open, and disease were examined. Each of these parameters was highly sensitive to stochastic prices and deterministic inputs. Originality/value – Decision support tools, such as this one, that are designed to investigate dairy business decisions may benefit dairy producers.
Stochastic simulation using @Risk for dairy business investment decisions
Bewley, J.D. ; Boehlje, M.D. ; Gray, A.W. ; Hogeveen, H. ; Kenyon, S.J. ; Eicher, S.D. ; Schutz, M.M. - \ 2010
Agricultural Finance Review 70 (2010). - ISSN 0002-1466 - p. 97 - 125.
Purpose – The purpose of this paper is to develop a dynamic, stochastic, mechanistic simulation model of a dairy business to evaluate the cost and benefit streams coinciding with technology investments. The model was constructed to embody the biological and economical complexities of a dairy farm system within a partial budgeting framework. A primary objective was to establish a flexible, user-friendly, farm-specific, decision-making tool for dairy producers or their advisers and technology manufacturers. Design/methodology/approach – The basic deterministic model was created in Microsoft Excel (Microsoft, Seattle, Washington). The @Risk add-in (Palisade Corporation, Ithaca, New York) for Excel was employed to account for the stochastic nature of key variables within a Monte Carlo simulation. Net present value was the primary metric used to assess the economic profitability of investments. The model was composed of a series of modules, which synergistically provide the necessary inputs for profitability analysis. Estimates of biological relationships within the model were obtained from the literature in an attempt to represent an average or typical US dairy. Technology benefits were appraised from the resulting impact on disease incidence, disease impact, and reproductive performance. In this paper, the model structure and methodology were described in detail. Findings – Examples of the utility of examining the influence of stochastic input and output prices on the costs of culling, days open, and disease were examined. Each of these parameters was highly sensitive to stochastic prices and deterministic inputs. Originality/value – Decision support tools, such as this one, that are designed to investigate dairy business decisions may benefit dairy producers.
Modeling precision dairy farming technology investment decisions
Bewley, J.M. ; Boehlje, M.D. ; Gray, A.W. ; Hogeveen, H. - \ 2009
In: Precision Livestock Farming ‘09 / Bregt, A., Wolfert, S., Wien, J.E., Lokhorst, C., Wageningen : Wageningen Academic Publishers - ISBN 9789086861125 - p. 107 - 14.
Tomato
Heuvelink, E. ; Costa, J.M. - \ 2006
In: Encyclopedia of Seeds: Science Technology and uses / Black, M., Bewley, J.D., Wallingford, UK : CABI - ISBN 9780851997230 - p. 705 - 708.
Dormancy: acquisition, function, ecophysiology, genes
Hilhorst, H.W.M. - \ 2006
In: The Encyclopedia of Seeds: Science, Technology and Uses / Bewley, J.D., Black, M., Halmer, P., Wallingford : CABI Publishing - ISBN 0851997236 - p. 181 - 295.
Coffee seed physiology
Eira, M.T.S. ; Silva, E.A.A. da; Castro, R.D. de; Dussert, S. ; Walters, C. ; Bewley, J.D. ; Hilhorst, H.W.M. - \ 2006
Brazilian Journal of Plant Physiology 18 (2006)1. - ISSN 1677-0420 - p. 149 - 163.
Coffee is a member of the Rubiaceae family and the genus Coffea. There are more than 70 species of coffee but only two are economically important: Coffea arabica L. and Coffea canephora Pierre; 70 % of the coffee traded in the world is arabica and 30 % is robusta (C. canephora). Other species such as C. congensis, C. dewevrei and C. racemosa have some interesting genetic characteristics, including resistance to pests and diseases and are used in breeding programs. To satisfy the demand for coffee within Brazil and around the world, intensive breeding programs have been undertaken to create new cultivars which are resistant to diseases and insects, and to incorporate new traits of value. In addition, new production and processing technologies are introduced every year, which have led to an enormous improvement in coffee production. Although progress has been made, not many studies have been devoted to the improvement of coffee seed quality for propagation. The purpose of this paper is to review our understanding of coffee seed physiology. Most of the work published in the literature and reported in this paper is on C. arabica seeds, although some aspects of C. canephora seed physiology are also included. Knowledge of seed physiology of other Coffea species is poor, with the exception of storage physiology, which is mostly related to germplasm conservation. Although this review will discuss some aspects of seed development and morphology, germination and storage physiology, the focus will be on germinability, and desiccation tolerance, with emphasis on the conservation of genetic resources
Exogenous gibberellins inhibit coffee (Coffea arabica cv. Rubi) seed germination and cause cell death in the embryo
Silva, E.A.A. Da; Toorop, P.E. ; Nijsse, J. ; Bewley, J.D. ; Hilhorst, H.W.M. - \ 2005
Journal of Experimental Botany 56 (2005)413. - ISSN 0022-0957 - p. 1029 - 1038.
abscisic-acid - endosperm - arabidopsis - mutants - tomato - elongation - metabolism - induction - viability - aleurone
The mechanism of inhibition of coffee (Coffea arabica cv. Rubi) seed germination by exogenous gibberellins (GAs) and the requirement of germination for endogenous GA were studied. Exogenous GA4+7 inhibited coffee seed germination. The response to GA4+7 showed two sensitivity thresholds: a lower one between 0 and 1 µM and a higher one between 10 and 100 µM. However, radicle protrusion in coffee seed depended on the de novo synthesis of GAs. Endogenous GAs were required for embryo cell elongation and endosperm cap weakening. Incubation of coffee seed in exogenous GA4+7 led to loss of embryo viability and dead cells were observed by low temperature scanning microscopy only when the endosperm was surrounding the embryo. The results described here indicate that the inhibition of germination by exogenous GAs is caused by factors that are released from the endosperm during or after its weakening, causing cell death in the embryo and leading to inhibition of radicle protrusion.
In vivo characterization of the effects of abscisic acid and drying protocols associated with the acquisition of desiccation tolerance in alfalfa (Medicago sativa L.) somatic embryos
Sreedhar, L. ; Wolkers, W.F. ; Hoekstra, F.A. ; Bewley, J.D. - \ 2002
Annals of Botany 89 (2002). - ISSN 0305-7364 - p. 391 - 400.
Although somatic embryos of alfalfa (Medicago sativa L.) had acquired some tolerance to desiccation at the cotyledonary stage of development (22 d after plating), additional culturing in 20 ?M abscisic acid (ABA) for 8 d induced greater desiccation tolerance, as determined by increased germination. Compared with fast drying, slow drying of the ABA-treated embryos improved desiccation tolerance. However, slow drying of non-ABA-treated embryos led to the complete loss of germination capacity, while some fast-dried embryos survived. An electron paramagnetic resonance spin probe technique and in vivo Fourier transform infrared microspectroscopy revealed that cellular membrane integrity and -helical protein secondary structure were maintained during drying in embryos cultured in media enriched with 20 ?M ABA, but not in embryos cultured in the absence of ABA. Slow-dried, non-ABA-treated embryos had low oligosaccharide to sucrose ratios, an increased proportion of ß-sheet protein secondary structures and broad membrane phase transitions extending over a temperature range of more than 60 °C, suggestive of irreversible phase separations. The spin probe study showed evidence of imbibitional damage, which could be alleviated by prehydration in humid air. These observations emphasize the importance of appropriate drying and prehydration protocols for the survival and storage of somatic embryos. It is suggested that ABA also plays a role in suppressing metabolism, thus increasing the level of desiccation tolerance; this is particularly evident under stressful conditions such as slow drying.
Cell-wall-associated endo-B-mannanase increases in the skin and outer pericarp of tomato fruits during ripening
Bewley, J.D. ; Banik, M. ; Bourgault, R. ; Fuertado, A. ; Toorop, P. ; Hilhorst, H.W.M. - \ 2000
Journal of Experimental Botany 51 (2000). - ISSN 0022-0957 - p. 529 - 538.
Activity of endo-ß-mannanase increases during ripening of tomato (Lycopersicon esculentum Mill.) fruit of the cultivar Trust. ß-Mannoside mannohydrolase is also present during ripening, but its pattern of activity is different from that of endo-ß-mannanase. The increase in endo-ß-mannanase activity is greatest in the skin, and less in the outer and inner pericarp regions. This enzyme is probably bound to the walls of the outermost cell layers of the fruit during ripening, and it requires a high-salt buffer for effective extraction. The enzyme protein, as detected immunologically on Western blots, is present during the early stages of ripening, before any enzyme activity is detectable. The mRNA for the enzyme is also present at these stages; endo-ß-mannanase may be produced and sequestered in a mature-sized inactive form during early ripening. Most non-ripening mutants of tomato exhibit reduced softening and lower endo-ß-mannanase activity, but a cause-and-effect relationship between the enzyme and ripening is unlikely because some cultivars which ripen normally do not exhibit any endo-ß-mannanase activity in the fruit.
Structure activity studies with ABA analogs on germination and endo-B-mannanase activity in tomato and lettuce seeds
Toorop, P.E. ; Bewley, J.D. ; Abrams, S.R. ; Hilhorst, H.W.M. - \ 1999
Journal of Plant Physiology 154 (1999). - ISSN 0176-1617 - p. 679 - 685.
Galactomannan, soluble sugar and starch mobilization following germination of Trigonella foenum-graecum seeds
Dirk, L.M.A. ; Krol, A.R. van der; Vreugdenhil, D. ; Hilhorst, H.W.M. ; Bewley, J.D. - \ 1999
Plant Physiology and Biochemistry 37 (1999). - ISSN 0981-9428 - p. 41 - 50.
D. Endo-B-mannanase activity during dormancy alleviation and germination of white spruce (Picea glauca) seeds.
Downie, C. ; Hilhorst, H.W.M. ; Bewley, J.D. - \ 1997
Physiologia Plantarum 101 (1997). - ISSN 0031-9317 - p. 405 - 415.
Endo-B-mannanase isoforms are present in the endosperm and embryo of tomato seeds, but are not essentially linked to the completion of germination.
Toorop, P.E. ; Bewley, J.D. ; Hilhorst, H.W.M. - \ 1996
Planta 200 (1996). - ISSN 0032-0935 - p. 153 - 158.
A new assay for quantifying endo-beta-D-mannanase activity using Congo red dye.
Downie, B. ; Hilhorst, H.W.M. ; Bewley, J.D. - \ 1994
Phytochemistry 36 (1994). - ISSN 0031-9422 - p. 829 - 835.
Endo-beta-D-mannanase activity in mature, dry seeds of white spruce as detected by the Congo red assay.
Downie, B. ; Hilhorst, H.W.M. ; Bewley, J.D. - \ 1994
Acta botanica neerlandica 43 (1994). - ISSN 0044-5983 - p. 294 - 294.
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