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Scott A Finlayson – 1st expert on this subject based on the ideXlab platform
vegetative Axillary Bud dormancy induced by shade and defoliation signals in the grassesPlant Signaling & Behavior, 2010Co-Authors: Tesfamichael H Kebrom, Thomas P Brutnell, Dirk B Hays, Scott A FinlaysonAbstract:
Vegetative Axillary Bud dormancy and outgrowth is regulated by several hormonal and environmental signals. In perennials, the dormancy induced by hormonal and environmental signals has been categorized as eco-, endo- or para-dormancy. Over the past several decades para-dormancy has primarily been investigated in eudicot annuals. Recently, we initiated a study using the monoculm phyB mutant (phyB-1) and the freely branching near isogenic wild type (WT) sorghum (Sorghum bicolor) to identify molecular mechanisms and signaling pathways regulating dormancy and outgrowth of Axillary Buds in the grasses. In a paper published in the January 2010 issue of Plant Cell and Environment, we reported the role of branching genes in the inhibition of Bud outgrowth by phyB, shade and defoliation signals. Here we present a model that depicts the molecular mechanisms and pathways regulating Axillary Bud dormancy induced by shade and defoliation signals in the grasses.
suppression of sorghum Axillary Bud outgrowth by shade phyb and defoliation signalling pathwaysPlant Cell and Environment, 2009Co-Authors: Tesfamichael H Kebrom, Thomas P Brutnell, Scott A FinlaysonAbstract:
: In recent years, several genetic components of vegetative Axillary Bud development have been defined in both monocots and eudicots, but our understanding of environmental inputs on branching remains limited. Recent work in sorghum (Sorghum bicolor) has revealed a role for phytochrome B (phyB) in the control of Axillary Bud outgrowth through the regulation of Teosinte Branched1 (TB1) gene. In maize (Zea mays), TB1 is a dosage-dependent inhibitor of Axillary meristem progression, and the expression level of TB1 is a sensitive measure of Axillary branch development. To further explore the mechanistic basis of branching, the expression of branching and cell cycle-related genes were examined in phyB-1 and wild-type sorghum Axillary Buds following treatment with low-red : far-red light and defoliation. Although defoliation inhibited Bud outgrowth, it did not influence the expression of sorghum TB1 (SbTB1), whereas changes in SbMAX2 expression, a homolog of the Arabidopsis (Arabidopsis thaliana) branching inhibitor MAX2, were associated with the regulation of Bud outgrowth by both light and defoliation. The expression of several cell cycle-related genes was also decreased dramatically in Buds repressed by defoliation, but not by phyB deficiency. The data suggest that there are at least two distinct molecular pathways that respond to light and endogenous signals to regulate Axillary Bud outgrowth.
arabidopsis teosinte branched1 like 1 regulates Axillary Bud outgrowth and is homologous to monocot teosinte branched1Plant and Cell Physiology, 2007Co-Authors: Scott A FinlaysonAbstract:
Axillary Bud outgrowth is controlled by developmental and environmental signals through the integrated action of hormones and other factors that probably regulate the cell cycle in the Buds. While hormonal regulators have been studied extensively, less is known about downstream mechanisms regulating Bud outgrowth. The TCP domain protein TEOSINTE BRANCHED1 (TB1) is a putative transcriptional regulator that represses Bud outgrowth in grasses. Phylogenetic analyses have indicated that three hypothetical Arabidopsis (Arabidopsis thaliana) proteins, TCP1, TCP12 and TCP18 [TEOSINTE BRANCHED1-LIKE 1 (TBL1)], are closely related to monocot TB1 proteins. A reverse genetics approach was used to identify TBL1 and TCP12 mutants to assess the function of the hypothetical proteins. No obvious phenotype was observed in tcp12 mutants. tbl1 null mutants exhibited a non-pleiotropic hyperbranching phenotype that was due to enhanced outgrowth of primary and secondary Buds. The role of TBL1 as a repressor of Bud outgrowth was supported by TBL1 mRNA accumulation: abundance was high in unelongated Buds, and decreased to low levels in Buds that were elongating. Analyses of TBL1 expression in hormone signaling mutants with aberrant branching suggest that TBL1 acts downstream of auxin and the MAX-related hormone to coordinate Bud outgrowth. The data are consistent with Arabidopsis TBL1 providing functionality similar to monocot TB1, and highlight the conservation of mechanisms regulating branching across large evolutionary distances.
Richard G H Immink – 2nd expert on this subject based on the ideXlab platform
Role of Tulipa gesneriana TEOSINTE BRANCHED1 (TgTB1) in the control of Axillary Bud outgrowth in bulbsPlant Reproduction, 2017Co-Authors: Natalia M. Moreno-pachon, Marie-chantal Mutimawurugo, Eveline Heynen, Lidiya Sergeeva, Anne Benders, Ikram Blilou, Hendrikus Wilhelmus Maria Hilhorst, Richard G H ImminkAbstract:
Key messageTulip vegetative reproduction.AbstractTulips reproduce asexually by the outgrowth of their Axillary meristems located in the axil of each bulb scale. The number of Axillary meristems in one bulb is low, and not all of them grow out during the yearly growth cycle of the bulb. Since the degree of Axillary Bud outgrowth in tulip determines the success of their vegetative propagation, this study aimed at understanding the mechanism controlling the differential Axillary Bud activity. We used a combined physiological and “bottom-up” molecular approach to shed light on this process and found that first two inner located Buds do not seem to experience dormancy during the growth cycle, while mid-located Buds enter dormancy by the end of the growing season. Dormancy was assessed by weight increase and TgTB1 expression levels, a conserved TCP transcription factor and well-known master integrator of environmental and endogenous signals influencing Axillary meristem outgrowth in plants. We showed that TgTB1 expression in tulip bulbs can be modulated by sucrose, cytokinin and strigolactone, just as it has been reported for other species. However, the limited growth of mid-located Buds, even when their TgTB1 expression is downregulated, points at other factors, probably physical, inhibiting their growth. We conclude that the time of Axillary Bud initiation determines the degree of dormancy and the sink strength of the Bud. Thus, development, apical dominance, sink strength, hormonal cross-talk, expression of TgTB1 and other possibly physical but unidentified players, all converge to determine the growth capacity of tulip Axillary Buds.
Howard M Goodman – 3rd expert on this subject based on the ideXlab platform
max1 a regulator of the flavonoid pathway controls vegetative Axillary Bud outgrowth in arabidopsisProceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Gabor Lazar, Howard M GoodmanAbstract:
We show that MAX1, a specific repressor of vegetative Axillary Bud outgrowth in Arabidopsis, acts a positive regulator of the flavonoid pathway, including 11 structural genes and the transcription factor An2. Repression of Bud outgrowth requires MAX1-dependent flavonoid gene expression. As the flavonoidless state leads to lateral outgrowth in Arabidopsis, our data suggest that a flavonoid-based mechanism regulates Axillary Bud outgrowth and that this mechanism is under the control of MAX1. Flavonoid gene expression results in the diminished expression of auxin transporters in the Bud and stem, and this, in turn, decreases the rate of polar auxin transport. We speculate that MAX1 could repress Axillary Bud outgrowth via regulating flavonoid-dependent auxin retention in the Bud and underlying stem. Because MAX1 is implicated in synthesis of the carotenoid-derived branch regulator(s) from the root, it likely links long-distance signaling with local control of Bud outgrowth.