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An integrative model of the control of ovule primordia formation
Galbiati, F. ; Sihna Roy, D. ; Simonini, S. ; Cucinotta, M. ; Ceccato, L. ; Cuesta, C. ; Simaskova, M. ; Benkova, E. ; Kamiuchi, Y. ; Aida, M. ; Weijers, D. ; Simon, R. ; Masiero, S. ; Colombo, L. - \ 2013
The Plant Journal 76 (2013)3. - ISSN 0960-7412 - p. 446 - 455.
dependent auxin gradients - arabidopsis-thaliana - transcription factor - pattern-formation - early sporogenesis - direct target - gene - cytokinin - gynoecium - aintegumenta
Upon hormonal signaling, ovules develop as lateral organs from the placenta. Ovule numbers ultimately determine the number of seeds that develop, and thereby contribute to the final seed yield in crop plants. We demonstrate here that CUP-SHAPED COTYLEDON 1 (CUC1), CUC2 and AINTEGUMENTA (ANT) have additive effects on ovule primordia formation. We show that expression of the CUC1 and CUC2 genes is required to redundantly regulate expression of PINFORMED1 (PIN1), which in turn is required for ovule primordia formation. Furthermore, our results suggest that the auxin response factor MONOPTEROS (MP/ARF5) may directly bind ANT, CUC1 and CUC2 and promote their transcription. Based on our findings, we propose an integrative model to describe the molecular mechanisms of the early stages of ovule development.
A PHABULOSA/Cytokinin feedback loop controls root growth in Arabidopsis
Dello loio, R. ; Galinha, C. ; Fletcher, A.G. ; Grigg, S.P. ; Molnar, A. ; Willemsen, V. ; Scheres, B. - \ 2012
Current Biology 22 (2012)18. - ISSN 0960-9822 - p. 1699 - 1704.
stem-cell niche - gene family - cytokinin - meristem - auxin - differentiation - expression - polarity - biosynthesis - nitrate
The hormone cytokinin (CK) controls root length in Arabidopsis thaliana by defining where dividing cells, derived from stem cells of the root meristem, start to differentiate. However, the regulatory inputs directing CK to promote differentiation remain poorly understood. Here, we show that the HD-ZIPIII transcription factor PHABULOSA (PHB) directly activates the CK biosynthesis gene ISOPENTENYL TRANSFERASE 7 (IPT7), thus promoting cell differentiation and regulating root length. We further demonstrate that CK feeds back to repress both PHB and microRNA165, a negative regulator of PHB. These interactions comprise an incoherent regulatory loop in which CK represses both its activator and a repressor of its activator. We propose that this regulatory circuit determines the balance of cell division and differentiation during root development and may provide robustness against CK fluctuations.
One-Step Agrobacterium Mediated Transformation of Eight Genes Essential for Rhizobium Symbiotic Signaling Using the Novel Binary Vector System pHUGE
Untergasser, A. ; Bijl, G.J.M. ; Liu, W. ; Bisseling, T. ; Schaart, J.G. ; Geurts, R. - \ 2012
PLoS ONE 7 (2012)10. - ISSN 1932-6203
site-specific recombination - root-nodule organogenesis - selectable marker gene - genomic dna fragments - medicago-truncatula - plant transformation - nodulation factors - lotus-japonicus - host-range - cytokinin
Advancement in plant research is becoming impaired by the fact that the transfer of multiple genes is difficult to achieve. Here we present a new binary vector for Agrobacterium tumefaciens mediated transformation, pHUGE-Red, in concert with a cloning strategy suited for the transfer of up to nine genes at once. This vector enables modular cloning of large DNA fragments by employing Gateway technology and contains DsRED1 as visual selection marker. Furthermore, an R/Rs inducible recombination system was included allowing subsequent removal of the selection markers in the newly generated transgenic plants. We show the successful use of pHUGE-Red by transferring eight genes essential for Medicago truncatula to establish a symbiosis with rhizobia bacteria as one 74 kb T-DNA into four non-leguminous species; strawberry, poplar, tomato and tobacco. We provide evidence that all transgenes are expressed in the root tissue of the non-legumes. Visual control during the transformation process and subsequent marker gene removal makes the pHUGE-Red vector an excellent tool for the efficient transfer of multiple genes.
Delayed senescence in cauliflower transformed with an autoregulated isopentenyl transferase gene
Nguyen, K.H. ; Jordi, W.J.R.M. ; Dun, K. ; Schepers, F. ; Davelaar, E. ; Stoopen, G.M. ; Dix, P.J. ; Kane, E.J. - \ 2008
International Journal of Plant Sciences 169 (2008)3. - ISSN 1058-5893 - p. 339 - 347.
leaf senescence - tobacco plants - cytokinin - agrobacterium - expression - cultures
Cauliflower (Brassica oleracea var. botrytis) was transformed, using Agrobacterium tumefaciens, with an autoregulated isopentenyl transferase (ipt) gene under the control of a senescence-associated gene promoter, pSAG12, isolated from Arabidopsis thaliana. The effect of introducing this chimeric construct on cytokinin (CK) content, chlorophyll retention, and plant morphology and development were investigated. A range of CK and chlorophyll contents was found among the individual primary transformants. Progeny were studied from one of the primary transformed lines that did not have elevated cytokinin content and was phenotypically similar to the parent line but displayed delayed leaf senescence. The pSAG12:ipt gene was inherited in a Mendelian manner, and the effect of this gene on senescence-related parameters was observed in a number of the progeny. While the pSAG12:ipt progeny did exhibit delayed leaf senescence, it was accompanied by undesirable agronomic traits, including less synchronous curd initiation, smaller curd size, and greater susceptibility to fungal infection.
Functional significance of shade-induced leaf senescence in dense canopies: an experimental test using transgenic tobacco
Boonman, A. ; Anten, N.P.R. ; Dueck, T.A. ; Jordi, W.J.R.M. ; Werf, A.K. van der; Voesenek, L.A.C.J. ; Pons, T.L. - \ 2006
American Naturalist 168 (2006)5. - ISSN 0003-0147 - p. 597 - 607.
nitrogen-use efficiency - multispecies canopy - carbon gain - photosynthesis - plants - leaves - light - area - cytokinin - respiration
Canopy photosynthesis models have predicted an optimal leaf area index (LAI; leaf area per unit surface area) and leaf nitrogen distribution at which whole-plant carbon gain per unit N is maximized. In this study we experimentally tested these models, using transgenic PSAG12-IPT tobacco (SAG; Nicotiana tabacum L.) plants with delayed leaf senescence and therefore a greater LAI and more uniform N distribution than the wild type (WT). In a competition experiment, the increased density of surrounding WT plants caused a greater reduction in dry mass of mature SAG target plants than in that of WT target plants, indicating negative effects of delayed leaf senescence on performance at high canopy density. Vegetative SAG plants achieved a lower calculated daily carbon gain than competing WT plants because the former retained leaves with a negative carbon gain in the shaded, lower part of the canopy. Sensitivity analyses showed that the carbon gain of SAG plants would increase if these lower leaves were shed and the N reallocated from these leaves were used to form additional leaf area at the canopy top. This strategy, which is adopted by the WT, is most advantageous because it results in the shading of competing neighbors. Keywords: carbon gain, senescence, transgenic plants, competition, canopy light gradient.
Anticytokinin effect on apical dominance release in in vitro cultured Rosa hybrida L.
Kapchina-Toteva, V.M. ; Somleva, M. ; Telgen, H.J. van - \ 2002
Biologia Plantarum 45 (2002)2. - ISSN 0006-3134 - p. 183 - 188.
cytokinin - induction - invitro - growth
Effects of two cytokinin antagonists - 2-chloro-4-cyclobutyl-amino-6-ethylamino-1,3,5-triazine and N-(4-pyridyl)-O-(4-chlorophenyl)carbamate - on bud break and outgrowth in single nodes from two Rosa hybrida cultivars differing in their apical dominance were studied. The compounds were applied at three different concentrations separately or in combination with benzyladenine. Cytokinin antagonists reduced the number of the sprouted buds in both cultivars at different extent. Their effect was strongly dependent on both concentration applied and culture period duration. The replacement of anticytokinins with benzyladenine in the medium resulted in overcoming of the bud break suppression. Both compounds significantly inhibited bud outgrowth as well