The role of hormones in shoot apical meristem function

Shani, Eilon; Yanai, Osnat; Ori, Naomi

doi:10.1016/j.pbi.2006.07.008

Cited by 230 publications

(167 citation statements)

References 51 publications

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“…However, GA4, a gene involved in the biosynthesis of gibberellins, has recently been identified among the targets of AG (Gomez-Mena et al, 2005). Gibberellins oppose meristem activity (for review, see Shani et al, 2006), raising the possibility that AG promotes FM termination by modifying phytohormone levels within the FM (discussed by Sablowski, 2007b). Clarifying the roles of SUP, CRC, and phytohormones appears as the next frontier in a better understanding of this developmental process.…”

Section: Resultsmentioning

confidence: 99%

Time to Stop: Flower Meristem Termination

Prunet¹,

Morel²,

Negrutiu³

et al. 2009

Plant Physiol.

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Section: Resultsmentioning

confidence: 99%

Time to Stop: Flower Meristem Termination

Prunet¹,

Morel²,

Negrutiu³

et al. 2009

Plant Physiol.

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“…In addition to the ABCDE class of organ fate regulators, a number of hormone signaling pathways influence floral transition, organ numbers, fertility, and floral meristem (FM) determinacy. Dynamic interactions are reported between transcription factors and specific hormone signaling factors during the establishment of Arabidopsis FMs (Sessions et al, 1997;Leibfried et al, 2005;Shani et al, 2006), but links between floral organ patterning and hormone signaling are not entirely clear.In the ancient LOFSEP clade, grass-specific genes constitute a subgroup diversified from other monocot and eudicot family members (Prasad et al, 2001;Malcomber and Kellogg, 2005). The rice (Oryza sativa) inflorescence (also called a panicle), a model for grass species, is branched and produces many kinds of lateral meristems.…”

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confidence: 99%

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confidence: 99%

RiceLHS1/OsMADS1Controls Floret Meristem Specification by Coordinated Regulation of Transcription Factors and Hormone Signaling Pathways

2013

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SEPALLATA (SEP) MADS box transcription factors mediate floral development in association with other regulators. Mutants in five rice (Oryza sativa) SEP genes suggest both redundant and unique functions in panicle branching and floret development. LEAFY HULL STERILE1/OsMADS1, from a grass-specific subgroup of LOFSEP genes, is required for specifying a single floret on the spikelet meristem and for floret organ development, but its downstream mechanisms are unknown. Here, key pathways and directly modulated targets of OsMADS1 were deduced from expression analysis after its knockdown and induction in developing florets and by studying its chromatin occupancy at downstream genes. The negative regulation of OsMADS34, another LOFSEP gene, and activation of OsMADS55, a SHORT VEGETATIVE PHASE-like floret meristem identity gene, show its role in facilitating the spikelet-to-floret meristem transition. Direct regulation of other transcription factor genes like OsHB4 (a class III homeodomain Leu zipper member), OsBLH1 (a BEL1-like homeodomain member), OsKANADI2, OsKANADI4, and OsETTIN2 show its role in meristem maintenance, determinacy, and lateral organ development. We found that the OsMADS1 targets OsETTIN1 and OsETTIN2 redundantly ensure carpel differentiation. The multiple effects of OsMADS1 in promoting auxin transport, signaling, and auxin-dependent expression and its direct repression of three cytokinin A-type response regulators show its role in balancing meristem growth, lateral organ differentiation, and determinacy. Overall, we show that OsMADS1 integrates transcriptional and signaling pathways to promote rice floret specification and development.Patterning an angiosperm flower requires the combined and individual functions of class A, B, C, D, and E MADS box transcription factors (Krizek and Fletcher, 2005;Thompson and Hake, 2009). In Arabidopsis (Arabidopsis thaliana), the class E activity is conferred by four redundant proteins, SEPALLATA1 (SEP1), SEP2, SEP3, and SEP4, that are cofactors in complexes with other MADS box factors that determine floral organ identities and meristem determinacy (Pelaz et al., 2000). Studies on loss-and gain-of-function mutants in SEP genes together with protein interaction analyses point to their pivotal role in mediating interactions among other floral organ-patterning genes (Honma and Goto, 2001;Ditta et al., 2004;Immink et al., 2009). The largely shared functions of Arabidopsis SEP genes differ from observations that homologs in other plants often have discrete roles in floral development (Malcomber and Kellogg, 2005), but the molecular mechanism underlying their species-specific roles is not well studied. In addition to the ABCDE class of organ fate regulators, a number of hormone signaling pathways influence floral transition, organ numbers, fertility, and floral meristem (FM) determinacy. Dynamic interactions are reported between transcription factors and specific hormone signaling factors during the establishment of Arabidopsis FMs (Sessions et al., 1997;Leibfried et al., ...

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“…In plants, TFs are often involved in the control of hormone pathways and several recent studies in Arabidopsis (Arabidopsis thaliana) provide new insight into how TFs and phytohormones interact to control plant development (Long and Benfey, 2006;Shani et al, 2006). However, only a small portion of plant TFs have been functionally characterized by mutation analysis (Riechmann et al, 2000).…”

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confidence: 99%

GeBP and GeBP-Like Proteins Are Noncanonical Leucine-Zipper Transcription Factors That Regulate Cytokinin Response in Arabidopsis

et al. 2007

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Understanding the role of transcription factors (TFs) is essential in reconstructing developmental regulatory networks. The plant-specific GeBP TF family of Arabidopsis thaliana (Arabidopsis) comprises 21 members, all of unknown function. A subset of four members, the founding member GeBP and GeBP-like proteins (GPL) 1, 2, and 3, shares a conserved C-terminal domain. Here we report that GeBP/GPL genes represent a newly defined class of leucine-zipper (Leu-zipper) TFs and that they play a redundant role in cytokinin hormone pathway regulation. Specifically, we demonstrate using yeast, in vitro, and split-yellow fluorescent protein in planta assays that GeBP/GPL proteins form homo-and heterodimers through a noncanonical Leu-zipper motif located in the C-terminal domain. A triple loss-of-function mutant of the three most closely related genes gebp gpl1 gpl2 shows a reduced sensitivity to exogenous cytokinins in a subset of cytokinin responses such as senescence and growth, whereas root inhibition is not affected. We find that transcript levels of type-A cytokinin response genes, which are involved in the negative feedback regulation of cytokinin signaling, are higher in the triple mutant. Using a GPL version that acts as a constitutive transcriptional activator, we show that the regulation of Arabidopsis response regulators (ARRs) is mediated by at least one additional, as yet unknown, repressor acting genetically downstream in the GeBP/GPL pathway. Our results indicate that GeBP/GPL genes encode a new class of unconventional Leu-zipper TF proteins and suggest that their role in the cytokinin pathway is to antagonize the negative feedback regulation on ARR genes to trigger the cytokinin response.

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The role of hormones in shoot apical meristem function

Cited by 230 publications

References 51 publications

Time to Stop: Flower Meristem Termination

Time to Stop: Flower Meristem Termination

RiceLHS1/OsMADS1Controls Floret Meristem Specification by Coordinated Regulation of Transcription Factors and Hormone Signaling Pathways

GeBP and GeBP-Like Proteins Are Noncanonical Leucine-Zipper Transcription Factors That Regulate Cytokinin Response in Arabidopsis

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