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.

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    Organizer-Derived WOX5 Signal Maintains Root Columella Stem Cells through Chromatin-Mediated Repression of CDF4 Expression.
    Pi, L. ; Graaff, E. van der; Llavata Peris, C.I. ; Weijers, D. ; Henning, L. ; Groot, E. de; Laux, T. - \ 2015
    Developmental Cell 33 (2015)5. - ISSN 1534-5807 - p. 576 - 588.
    histone deacetylase - arabidopsis-thaliana - transcriptional repression - gene-expression - wuschel - meristem - shoot - topless - protein - fate
    Stem cells in plants and animals are maintained pluripotent by signals from adjacent niche cells. In plants, WUSCHEL HOMEOBOX (WOX) transcription factors are central regulators of stem cell maintenance in different meristem types, yet their molecular mode of action has remained elusive. Here we show that in the Arabidopsis root meristem, the WOX5 protein moves from the root niche organizer, the quiescent center, into the columella stem cells, where it directly represses the transcription factor gene CDF4. This creates a gradient of CDF4 transcription, which promotes differentiation opposite to the WOX5 gradient, allowing stem cell daughter cells to exit the stem cell state. We further show that WOX5 represses CDF4 transcription by recruiting TPL/TPR co-repressors and the histone deacetylase HDA19, which consequently induces histone deacetylation at the CDF4 regulatory region. Our results show that chromatin-mediated repression of differentiation programs is a common strategy in plant and animal stem cell niches.
    Rooting plant development
    Scheres, B. - \ 2013
    Development 140 (2013)5. - ISSN 0950-1991 - p. 939 - 941.
    arabidopsis root - cell fate - meristem - differentiation - mechanism - shoot - framework - epidermis - division - pattern
    In 1993, we published a paper in Development detailing the anatomical structure of the Arabidopsis root. The paper described how root growth was maintained by the precisely tuned activity of a small set of 'initials', which acted as the source of dividing and differentiating cells, and how these stem cell-like cells surrounded a few infrequently dividing cells. This work underpinned subsequent research on root developmental biology and sparked a detailed molecular analysis of how stem cell groups are positioned and maintained in plants.
    An efficient flat-surface collar-free grafting method for Arabidopsis thaliana seedlings
    Marsch-Martinez, N. ; Franken, J. ; Gonzalez-Aguilera, K.L. ; Folter, S. de; Angenent, G.C. ; Alvarez-Buylla, E.R. - \ 2013
    Plant Methods 9 (2013). - ISSN 1746-4811
    ft protein - shoot - transport - cotyledon - movement - plants - rnas - root
    Background: Grafting procedures are an excellent tool to study long range signalling processes within a plant. In the last decade, suitable flat-surface grafting procedures for young Arabidopsis seedlings using a collar to support the graft have been developed, allowing the study of long-range signals from a molecular perspective. Results: In the modification presented here, scion and stock are put together on the medium without supporting elements, while cotyledons are removed from the scion, resulting in increased grafting success that can reach up to 100%. At the same time, the protocol enables to process as many as 36 seedlings per hour, which combined with the high success percentage represents increased efficiency per time unit. Conclusions: Growing cotyledons usually push the scion and the rootstock away in the absence of a supporting element. Removing them at the grafting step greatly improved success rate and reduced post-grafting manipulations.
    Influence of transplant size on the above- and below-ground performance of four contrasting field-grown lettuce cultivars
    Kerbiriou, P.J. ; Stomph, T.J. ; Lammerts Van Bueren, E. ; Struik, P.C. - \ 2013
    Frontiers in Plant Science 4 (2013). - ISSN 1664-462X - 16 p.
    n-no3 solution concentration - root-growth - dynamics - plants - light - shoot - water - crop
    Background and aims: Modern lettuce cultivars underperform under conditions of variable temporal and spatial resource availability, common in organic or low-input production systems. Information is scarce on the impact of below-ground traits on such resource acquisition and performance of field-grow nlettuce; exploring genetic variation in such traits might contribute to strategies to select for robust cultivars, i.e., cultivars that perform well in the field, even under stress. Methods: To investigate the impact of below-ground (root development and resource capture) on above-ground (shoot weight, leaf area) traits, different combinations of shoot and root growth were created using transplants of different sizes in three field experiments.Genetic variation in morphological and physiological below- and above-ground responses to different types of transplant shocks was assessed using four cultivars. Results: Transplanting over-developed seedlings did not affect final yield of any of the four cultivars.Small transplant size persistently impacted growth and delayed maturity.The cultivars with overall larger root weights and rooting depth, “Matilda” and “Pronto,”displayed a slightly higher growth rate in the linear phase leading to better yields than “Mariska” which had a smaller root system and a slower linear growth despite a higher maximal exponential growth rate. “Nadine,” which had the highest physiological nitrogen-use efficiency (g dry matter produced per g N accumulated in the head) among the four cultivars used in these trials, gave most stable yields over seasons and trial locations. Conclusions: Robustness was conferred by a large root system exploring deep soil layers. Additional root proliferation generally correlates with improved nitrate capture in a soil layer and cultivars with a larger root system may therefore perform better in harsh environmental conditions; increased nitrogen use efficiency can also confer robustness at low cost for the plant, and secure stable yields under a wide range of growing conditions.
    East African highland bananas (Musa spp. AAA-EA) 'worry' more about potassium deficiency than drought stress
    Taulya, G. - \ 2013
    Field Crops Research 151 (2013). - ISSN 0378-4290 - p. 45 - 55.
    foliar nutrient status - biomass allocation - osmotic adjustment - plant-growth - root ratio - soil-water - nitrogen - shoot - fertilizer - weevil
    Drought stress, potassium (K) and nitrogen (N) deficiencies are major constraints to rain-fed East African highland banana (EAHB) production in Uganda. It was hypothesised that the reduction in fresh bunch mass and increase in dry matter (DM) allocation to corms with drought stress, K and N deficiency is additive. Individual plant measurements at harvest from two field trials in central and south western Uganda were analyzed to evaluate effects of cumulative rainfall (CRF) received 365 days from sucker emergence, mineral K and N inputs on EAHB bunch yields. Dry matter content in aerial shoot (leaves and pseudostems) relative to that in the subterranean corm was also analyzed to evaluate DM allocation plasticity due to drought stress, K and N deficiency. This was verified with allometric analysis using pre-harvest stage plants from farms of known K and N nutritional status and plants from a screen house drought stress pot trial in Uganda. Dry matter production and yields were mainly driven by K interacting with CRF. Within 12 months, K input (250-600 kg K ha(-1) yr(-1)) increased bunch yield from 8 to 15 Mg ha(-1) yr(-1) irrespective of whether dry (CRF <1100 mm) or wet (CRF >= 1100 mm) conditions prevailed, possibly due to K-mediated osmotic adjustment under dry conditions. Without K input, wet conditions increased bunch yield from 6 to 8 Mg ha(-1) yr(-1) while dry conditions decreased it from 6 to 4 Mg ha(-1) yr(-1) within 12 months. Total DM and its distribution between the biomass structures followed similar trends. Nitrogen input (150-400 kg N ha(-1) yr(-1)) neither affected bunch yield nor DM allocation at harvest stage. At pre-harvest stage, reduction in DM allocation to the corm per unit increase in total DM was 14-22% significantly lower with N and/or K deficiency compared with that under sufficient K and N. Drought stress per se had no effect on DM allocation but enhanced DM allocation shifts due to K deficiency. Drought-stressed EAHB thus increase DM allocation to subterranean structures only if K-deficient, unlike responses reported for other plant species. Potassium nutrition is perhaps a more viable entry point for mitigation of drought stress in EAHB cropping systems than irrigation but this requires further agronomic and economic evaluation. It may be important to account for carbon allocated to osmotic adjustment for realistic simulation of water- and K-limited growth in EAHB. (c) 2013 Elsevier B.V. All rights reserved.
    Multiple loci and genetic interactions involving flowering time genes regulate stem branching among natural variants of Arabidopsis
    Huang, X. ; Ding, J. ; Effgen, S. ; Turck, F. ; Koornneef, M. - \ 2013
    New Phytologist 199 (2013)3. - ISSN 0028-646X - p. 843 - 857.
    quantitative trait loci - axillary meristem formation - inbred line populations - allelic variation - inflorescence development - thaliana - shoot - associations - architecture - adaptation
    Shoot branching is a major determinant of plant architecture. Genetic variants for reduced stem branching in the axils of cauline leaves of Arabidopsis were found in some natural accessions and also at low frequency in the progeny of multiparent crosses. Detailed genetic analysis using segregating populations derived from backcrosses with the parental lines and bulked segregant analysis was used to identify the allelic variation controlling reduced stem branching. Eight quantitative trait loci (QTLs) contributing to natural variation for reduced stem branching were identified (REDUCED STEM BRANCHING 1-8 (RSB1-8)). Genetic analysis showed that RSB6 and RSB7, corresponding to flowering time genes FLOWERING LOCUS C (FLC) and FRIGIDA (FRI), epistatically regulate stem branching. Furthermore, FLOWERING LOCUS T (FT), which corresponds to RSB8 as demonstrated by fine-mapping, transgenic complementation and expression analysis, caused pleiotropic effects not only on flowering time, but, in the specific background of active FRI and FLC alleles, also on the RSB trait. The consequence of allelic variation only expressed in late-flowering genotypes revealed novel and thus far unsuspected roles of several genes well characterized for their roles in flowering time control
    Response of Cell Division and Cell Expansion to Local Fruit Heating in Tomato Fruit
    Fanwoua, J. ; Visser, P.H.B. de; Heuvelink, E. ; Angenent, G.C. ; Yin, X. ; Marcelis, L.F.M. ; Struik, P.C. - \ 2012
    Journal of the American Society for Horticultural Science 137 (2012)5. - ISSN 0003-1062 - p. 294 - 301.
    controlled environments - temperature - growth - load - endoreduplication - shoot - size - set
    To improve our understanding of fruit growth responses to temperature, it is important to analyze temperature effects on underlying fruit cellular processes. This study aimed at analyzing the response of tomato (Solanum lycopersicum) fruit size to heating as affected by changes in cell number and cell expansion in different directions. Individual trusses were enclosed into cuvettes and heating was applied either only during the first 7 days after anthesis (DAA), from 7 DAA until fruit maturity (breaker stage), or both. Fruit size and histological characteristics in the pericarp were measured. Heating fruit shortened fruit growth period and reduced final fruit size. Reduction in final fruit size of early-heated fruit was mainly associated with reduction in final pericarp cell volume. Early heating increased the number of cell layers in the pericarp but did not affect the total number of pericarp cells. These results indicate that in the tomato pericarp, periclinal cell divisions respond differently to temperature than anticlinal or randomly oriented cell divisions. Late heating only decreased pericarp thickness significantly. Continuously heating fruit reduced anticlinal cell expansion (direction perpendicular to fruit skin) more than periclinal cell expansion (direction parallel to fruit skin). This study emphasizes the need to measure cell expansion in more than one dimension in histological studies of fruit
    Towards a functional–structural plant model of cut-rose: simulation of light environment, light absorption, photosynthesis and interference with the plant structure
    Buck-Sorlin, G.H. ; Visser, P.H.B. de; Henke, M. ; Sarlikioti, V. ; Heijden, G.W.A.M. van der; Marcelis, L.F.M. ; Vos, J. - \ 2011
    Annals of Botany 108 (2011)6. - ISSN 0305-7364 - p. 1121 - 1134.
    axillary buds - growth - interception - elongation - canopies - leaves - wheat - shoot - l.
    Background and Aims The production system of cut-rose (Rosa × hybrida) involves a complex combination of plant material, management practice and environment. Plant structure is determined by bud break and shoot development while having an effect on local light climate. The aim of the present study is to cover selected aspects of the cut-rose system using functional–structural plant modelling (FSPM), in order to better understand processes contributing to produce quality and quantity. Methods The model describes the production system in three dimensions, including a virtual greenhouse environment with the crop, light sources (diffuse and direct sun light and lamps) and photosynthetically active radiation (PAR) sensors. The crop model is designed as a multiscaled FSPM with plant organs (axillary buds, leaves, internodes, flowers) as basic units, and local light interception and photosynthesis within each leaf. A Monte-Carlo light model was used to compute the local light climate for leaf photosynthesis, the latter described using a biochemical rate model. Key Results The model was able to reproduce PAR measurements taken at different canopy positions, different times of the day and different light regimes. Simulated incident and absorbed PAR as well as net assimilation rate in upright and bent shoots showed characteristic spatial and diurnal dynamics for different common cultivation scenarios. Conclusions The model of cut-rose presented allowed the creation of a range of initial structures thanks to interactive rules for pruning, cutting and bending. These static structures can be regarded as departure points for the dynamic simulation of production of flower canes. Furthermore, the model was able to predict local (per leaf) light absorption and photosynthesis. It can be used to investigate the physiology of ornamental plants, and provide support for the decisions of growers and consultants.
    Efficient sweet pepper transformation mediated by the BABY BOOM transcription factor
    Heidmann, I. ; Lange, B. de; Lambalk, J. ; Angenent, G.C. ; Boutilier, K. - \ 2011
    Plant Cell Reports (2011). - ISSN 0721-7714 - 9 p.
    capsicum-annuum l. - direct somatic embryogenesis - in-vitro regeneration - plant-regeneration - agrobacterium-tumefaciens - genetic-transformation - chinense jacq. - arabidopsis - shoot - growth
    Pepper (Capsicum L.) is a nutritionally and economically important crop that is cultivated throughout the world as a vegetable, condiment, and food additive. Genetic transformation using Agrobacterium tumefaciens (agrobacterium) is a powerful biotechnology tool that could be used in pepper to develop community-based functional genomics resources and to introduce important agronomic traits. However, pepper is considered to be highly recalcitrant for agrobacterium-mediated transformation, and current transformation protocols are either inefficient, cumbersome or highly genotype dependent. The main bottleneck in pepper transformation is the inability to generate cells that are competent for both regeneration and transformation. Here, we report that ectopic expression of the Brassica napus BABY BOOM AP2/ERF transcription factor overcomes this bottleneck and can be used to efficiently regenerate transgenic plants from otherwise recalcitrant sweet pepper (C. annuum) varieties. Transient activation of BABY BOOM in the progeny plants induced prolific cell regeneration and was used to produce a large number of somatic embryos that could be converted readily to seedlings. The data highlight the utility of combining biotechnology and classical plant tissue culture approaches to develop an efficient transformation and regeneration system for a highly recalcitrant vegetable crop
    BABY BOOM target genes provide diverse entry points into cell proliferation and cell growth pathways
    Passarinho, P.A. ; Ketelaar, M.J. ; Xing, M. ; Arkel, J. van; Maliepaard, C.A. ; Weemen, W.M.J. ; Joosen, R.V.L. ; Lammers, M. ; Herdies, L. ; Boer, B. de; Geest, A.H.M. van der; Boutilier, K.A. - \ 2008
    Plant Molecular Biology 68 (2008)3. - ISSN 0167-4412 - p. 225 - 237.
    actin-depolymerizing factor - arabidopsis tissue-culture - leafy cotyledon genes - somatic embryogenesis - embryo development - constitutive expression - transcription factor - wuschel gene - shoot - plant
    Ectopic expression of the Brassica napus BABY BOOM (BBM) AP2/ERF transcription factor is sufficient to induce spontaneous cell proliferation leading primarily to somatic embryogenesis, but also to organogenesis and callus formation. We used DNA microarray analysis in combination with a post-translationally regulated BBM:GR protein and cycloheximide to identify target genes that are directly activated by BBM expression in Arabidopsis seedlings. We show that BBM activated the expression of a largely uncharacterized set of genes encoding proteins with potential roles in transcription, cellular signaling, cell wall biosynthesis and targeted protein turnover. A number of the target genes have been shown to be expressed in meristems or to be involved in cell wall modifications associated with dividing/growing cells. One of the BBM target genes encodes an ADF/cofilin protein, ACTIN DEPOLYMERIZING FACTOR9 (ADF9). The consequences of BBM:GR activation on the actin cytoskeleton were followed using the GFP:FIMBRIN ACTIN BINDING DOMAIN2 (GFP:FABD) actin marker. Dexamethasone-mediated BBM:GR activation induced dramatic changes in actin organization resulting in the formation of dense actin networks with high turnover rates, a phenotype that is consistent with cells that are rapidly undergoing cytoplasmic reorganization. Together the data suggest that the BBM transcription factor activates a complex network of developmental pathways associated with cell proliferation and growth.
    Cytokinins act directly on lateral root founder cells to inhibit root initiation
    Laplaze, L. ; Benkova, E. ; Casimiro, I. ; Maes, L. ; Vanneste, S. ; Swarup, R. ; Weijers, D. ; Calvo, V. ; Parizot, B. ; Herrera-Rodriguez, M.B. ; Offringa, R. ; Graham, N. ; Doumas, P. ; Friml, J. ; Bogusz, D. ; Beeckman, T. ; Bennett, M. - \ 2007
    The Plant Cell 19 (2007)12. - ISSN 1040-4651 - p. 3889 - 3900.
    arabidopsis-thaliana - response regulators - tobacco plants - pea roots - auxin - shoot - gene - expression - pericycle - meristem
    In Arabidopsis thaliana, lateral roots are formed from root pericycle cells adjacent to the xylem poles. Lateral root development is regulated antagonistically by the plant hormones auxin and cytokinin. While a great deal is known about how auxin promotes lateral root development, the mechanism of cytokinin repression is still unclear. Elevating cytokinin levels was observed to disrupt lateral root initiation and the regular pattern of divisions that characterizes lateral root development in Arabidopsis. To identify the stage of lateral root development that is sensitive to cytokinins, we targeted the expression of the Agrobacterium tumefaciens cytokinin biosynthesis enzyme isopentenyltransferase to either xylem-pole pericycle cells or young lateral root primordia using GAL4-GFP enhancer trap lines. Transactivation experiments revealed that xylem-pole pericycle cells are sensitive to cytokinins, whereas young lateral root primordia are not. This effect is physiologically significant because transactivation of the Arabidopsis cytokinin degrading enzyme cytokinin oxidase 1 in lateral root founder cells results in increased lateral root formation. We observed that cytokinins perturb the expression of PIN genes in lateral root founder cells and prevent the formation of an auxin gradient that is required to pattern lateral root primordia.
    Effect of methyl jasmonate on morphology and dormancy developmentin lily bulblets regenerated in vitro
    Jasik, J. ; Klerk, G.J.M. de - \ 2006
    Journal of Plant Growth Regulation 25 (2006)1. - ISSN 0721-7595 - p. 45 - 51.
    speciosum generated invitro - endogenous abscisic-acid - possible involvement - plants - shoot - arabidopsis - germination - induction - tuberisation - tuberization
    Scales of lily bulbs are swollen petioles. Lily scale fragments cultured in vitro regenerate bulblets consisting of scales that may or may not carry a leaf blade. The bulblets are dormant and require a cold treatment to sprout. We added the gaseous plant growth regulator methyl jasmonic acid (MeJA) in the headspace of the tissue-culture container and studied the effect on plantlet morphology (scale/leaf-blade formation) and dormancy development in three lilies, Lilium speciosum "Rubrum No. 10," L. longiflorum "Snow Queen," and the Asiatic hybrid "Connecticut King." Methyl jasmonic acid strongly reduced leaf-blade formation in Lilium longiflorum and Connecticut King. This was a specific effect as scale formation was affected much less. The specific inhibition of leaf-blade formation was not observed in Lilium speciosum. In this lily, high concentrations of methyl jasmonic acid (MeJA) inhibited leaf-blade and scale formation to similar extents. Methyl jasmonic acid reduced dormancy development in all three lilies, with the largest effect observed in Connecticut King. In this Asiatic hybrid, almost all bulblets that had regenerated at 300 or 1000 mu l l(-1) MeJA in the headspace, did not require a dormancy-breaking treatment to achieve sprouting after planting in soil. Previously, it has been found in lily that treatments that reduce leaf-blade formation promote dormancy development. The present findings with MeJA do not agree with this. In the three lilies, the various parameters that were studied-regeneration, scale weight, leaf-blade weight, and dormancy development-were very differently affected by MeJA.
    Genotype and planting density effects on rooting traits and yield in cotton (Gossypium hirsutum L.)
    Zhang, L.Z. ; Li, B.G. ; Yan, G.T. ; Werf, W. van der; Spiertz, J.H.J. ; Zhang, S.P. - \ 2006
    Journal of Integrative Plant Biology 48 (2006)11. - ISSN 1672-9072 - p. 1287 - 1293.
    water-uptake - length density - sample preparation - small-diameter - soil-water - growth - maize - systems - shoot - model
    Root density distribution of plants is a major indicator of competition between plants and determines resource capture from the soil. This experiment was conducted in 2005 at Anyang, located in the Yellow River region, Henan Province, China. Three cotton (Gossypium hirsutum L.) cultivars were chosen: hybrid Bt-cultivar CRI46, conventional Bt-cultivars CRI44 and CRI45. Six planting densities were designed, ranging from 1.5 to 12.0 plants/m2Root parameters such as surface area, diameter and length were analyzed by using the DT-SCAN image analysis method. The root length density (RLD), root average diameter and root area index (RAI), root surface area per unit land area, were studied. The results showed that RLD and RAI differed between genotypes; hybrid CRI46 had significantly higher (P <0.05) RLD and RAI values than conventional cultivars, especially under low planting densities, less than 3.0 plants/m2The root area index (RAI) of hybrid CRI46 was 61% higher than of CRI44 and CRI45 at the flowering stage. The RLD and RAI were also significantly different (P = 0.000) between planting densities. The depth distribution of RAI showed that at increasing planting densities RAI was increasingly distributed in the soil layers below 50 cm. The RAI of hybrid CRI46 was for all planting densities, obviously higher than other cultivars during the flowering and boll stages. It was concluded that the hybrid had a strong advantage in root maintenance preventing premature senescence of roots. The root diameter of hybrid CRI46 had a genetically higher root diameter at planting densities lower than 6.0 plants/m2Good associations were found between yield and RAI in different stages. The optimum planting density ranged from 4.50 plants/m2 to 6.75 plants/m2 for conventional cultivars and around 4.0¿5.0 plants/m2 for hybrids.
    Arabidopsis thaliana Somatic Embryogenesis Receptor Kinase I protein is present in sporophytic and gametophytic cells and undergoes endocytosis
    Kwaaitaal, M.A.C.J. ; Vries, S.C. de; Russinova, E.T. - \ 2005
    Protoplasma 226 (2005)1-2. - ISSN 0033-183X - p. 55 - 65.
    leucine-rich repeat - signal-transduction - gene family - phosphatase - meristem - embryos - interacts - pathway - shoot - bak1
    Arabidopsis thaliana plants expressing AtSERK1 fused to yellow-fluorescent protein were generated. Fluorescence was detected predominantly at the cell periphery, most likely the plasma membrane, of cells in ovules, embryo sacs, anthers, and embryos and in seedlings. The AtSERK1 protein was detected in diverse cell types including the epidermis and the vascular bundles. In some cells, fluorescent receptors were seen in small vesicle-like compartments. After application of the fungal toxin Brefeldin A, the fluorescent receptors were rapidly internalized in the root meristem and root vascular tissue. We conclude that the AtSERK1 receptor functions in a common signalling pathway employed in both sporophytic and gametophytic cells.
    Are cuttings suitable for assessing maturity type in potato (Solanum tuberosum)?
    Struik, P.C. ; Visker, M.H.P.W. ; Pauwels, J.P. ; Colon, L.T. - \ 2005
    Annals of Applied Biology 147 (2005)1. - ISSN 0003-4746 - p. 27 - 34.
    photoperiod - growth - shoot - l.
    Two experiments were carried out to evaluate the potential of single-node cuttings of potato (Solanum tuberosum) as a tool to assess genotypic differences in maturity type. Plants were exposed to different photoperiodic treatments (different photoperiods, different numbers of photoperiodic cycles), and cuttings were taken at different plant ages. Cuttings from early (and to a lesser extent also late) maturing varieties exposed to short photoperiods showed strong induction to tuberise, irrespective of plant age; the induction increased with an increase in the number of short photoperiodic cycles. The response of cuttings taken from early-maturing varieties exposed to long photoperiods depended on plant age: cuttings showed stronger induction when mother plants were older; cuttings from late-maturing varieties hardly tuberised after exposure to long photoperiods. The tuberisation of the cuttings did not depend on the length of the long photoperiod (18 or 24 h) or on the number of cycles of a photoperiod of 18 h. Tuberisation on cuttings did not properly reflect the tuber formation on the mother plants, although within varieties, significant correlations between tuberisation on cuttings and tuber yield per plant 9 weeks after planting were found with different numbers of photoperiodic cycles of 12 h. Our experiments show that the cutting technique cannot be used on older plants to assess the maturity type of potato varieties, as there are interactions between photoperiod, genotype, plant age and number of photoperiodic cycles, in the reflection of the degree of induction to tuberise on single-node cuttings.
    The 14-Amino acid CLV3, CLE19 and CLE40 peptides trigger consumption of the root meristem in Arabidopsis through a CLAVATA2-dependent pathway
    Fiers, M.A. ; Golemiec, E. ; Xu, J. ; Geest, L. van der; Heidstra, R. ; Stiekema, W. ; Liu, C.M. - \ 2005
    The Plant Cell 17 (2005). - ISSN 1040-4651 - p. 2542 - 2553.
    asymmetric cell-division - receptor-like kinase - gene encodes - protein - plants - shoot - phytosulfokine - polypeptide - expression - clavata3
    CLAVATA3 (CLV3), CLV3/ESR19 (CLE19), and CLE40 belong to a family of 26 genes in Arabidopsis thaliana that encode putative peptide ligands with unknown identity. It has been shown previously that ectopic expression of any of these three genes leads to a consumption of the root meristem. Here, we show that in vitro application of synthetic 14–amino acid peptides, CLV3p, CLE19p, and CLE40p, corresponding to the conserved CLE motif, mimics the overexpression phenotype. The same result was observed when CLE19 protein was applied externally. Interestingly, clv2 failed to respond to the peptide treatment, suggesting that CLV2 is involved in the CLE peptide signaling. Crossing of the CLE19 overexpression line with clv mutants confirms the involvement of CLV2. Analyses using tissue-specific marker lines revealed that the peptide treatments led to a premature differentiation of the ground tissue daughter cells and misspecification of cell identity in the pericycle and endodermis layers. We propose that these 14–amino acid peptides represent the major active domain of the corresponding CLE proteins, which interact with or saturate an unknown cell identity-maintaining CLV2 receptor complex in roots, leading to consumption of the root meristem.
    Regulation of K uptake, water uptake, and growth of tomato during K starvation and recovery
    Amor, F.M. del; Marcelis, L.F.M. - \ 2004
    Scientia Horticulturae 100 (2004)1-4. - ISSN 0304-4238 - p. 83 - 101.
    nutrient interruption technique - ricinus-communis l - potassium recirculation - barley roots - plants - shoot - transport - arabidopsis - nutrition
    In order to analyze the dynamics of growth, water and K uptake, the effects of 1, 3 and 7 days of potassium starvation and the recovery capability during 7 days afterwards were investigated in vegetative tomato plants. After 7 days of K starvation, plant dry matter was reduced by 36% compared to control plants. After 3 days of starvation plants showed a 15% reduction in dry matter and a 25% reduction in growth rate (not statistically significant). K starvation reduced leaf area and specific leaf area (SLA) and it increased leaf dry matter percentage. K starvation enhanced dry matter partitioning into the roots at the expense of the stem. Plant K concentration was reduced by K starvation with the strongest effect in the leaves and roots. When a 3-day K starvation period was followed by 7 days of recovery with full strength nutrient solution, growth and plant K concentration completely recovered, but not after 7 days of K starvation. Xylem sap flow was reduced by K starvation and after 7 days of starvation the K concentration in the sap was reduced by 60%. During the starvation period, the reduction in relative growth rate was linearly related to the plant K concentration. The critical potassium concentration in the plant (the K concentration at which relative growth rate was reduced by 10%) was determined according to the nutrient interruption technique. The critical concentration was 4.3% K which was reached after 2.5 days of K starvation while the potassium concentration of control plants was 6.3%. During recovery the dry matter growth rate seemed to be the most important factor determining K uptake.
    Root-specific CLE19 overexpression and the sol1/2: Suppressors implicate a CLV-like pathway in the control of Arabidopsis root meristern maintenance
    Casamitjana-Martinez, E. ; Hofhuis, H.F. ; Xu, J. ; Liu, C.M. ; Heidstra, R. ; Scheres, B.J.G. - \ 2003
    Current Biology 13 (2003)16. - ISSN 0960-9822 - p. 1435 - 1441.
    stem-cell fate - radial organization - clavata1 - genes - shoot - carboxypeptidase - scarecrow - regulator - thaliana - wuschel
    In the Arabidopsis shoot apical meristem, an organizing center signals in a non-cell-autonomous manner to specify the overlying stem cells [1 and 2]. Stem cells express the small, secreted protein CLAVATA3 (CLV3; [3]) that activates the CLV1-CLV2 receptor complex, which negatively controls the size of the organizing center [4, 5 and 6]. Consistently, CLV3 overexpression restricts shoot meristem size [6]. The root meristem also contains a stem cell organizer, and here we show that localized overexpression in roots of CLE19, encoding a CLV3 homolog, restricts the size of the root meristem. This suggests that CLE19 acts by overactivating an endogenous CLV-like pathway involved in root meristem maintenance. Surprisingly, CLE19 restricts meristem size without directly interfering with organizer and stem cell specification. We isolated mutations in two loci, SOL1 and SOL2, which suppress the CLE19 overexpression phenotype. sol2 plants display floral phenotypes reminiscent of clv weak alleles; these phenotypes suggest that components of a CLV pathway are shared in roots and shoots. SOL1 encodes a putative Zn2+-carboxypeptidase, which may be involved in ligand processing.
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