Specification of<i>Arabidopsis</i>floral meristem identity by repression of flowering time genes

Liu, Chang; Zhou, Jiawei; Bracha-Drori, Keren; Yalovsky, Shaul; Ito, Toshiro; Yu, Hao

doi:10.1242/dev.003103

Cited by 267 publications

(304 citation statements)

References 43 publications

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“…4 B and C). These results, together with the known function of SVP genes as suppressors of flowering and inflorescence development (30)(31)(32)(33), suggest that the three SVP genes work downstream of TAW1 to suppress SM identity. Using a two-component induction system, we confirmed that the induction of TAW1 transcription does indeed lead to the activation of the three SVP genes (Fig.…”

Section: Taw1 Is Expressed In the Meristem To Suppress The Transitionmentioning

confidence: 75%

TAWAWA1 , a regulator of rice inflorescence architecture, functions through the suppression of meristem phase transition

Yoshida

Sasao

Yasuno

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

202

210

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Inflorescence structures result from the activities of meristems, which coordinate both the renewal of stem cells in the center and organ formation at the periphery. The fate of a meristem is specified at its initiation and changes as the plant develops. During rice inflorescence development, newly formed meristems acquire a branch meristem (BM) identity, and can generate further meristems or terminate as spikelets. Thus, the form of rice inflorescence is determined by a reiterative pattern of decisions made at the meristems. In the dominant gain-of-function mutant tawawa1-D, the activity of the inflorescence meristem (IM) is extended and spikelet specification is delayed, resulting in prolonged branch formation and increased numbers of spikelets. In contrast, reductions in TAWAWA1 (TAW1) activity cause precocious IM abortion and spikelet formation, resulting in the generation of small inflorescences. TAW1 encodes a nuclear protein of unknown function and shows high levels of expression in the shoot apical meristem, the IM, and the BMs. TAW1 expression disappears from incipient spikelet meristems (SMs). We also demonstrate that members of the SHORT VEGETATIVE PHASE subfamily of MADS-box genes function downstream of TAW1. We thus propose that TAW1 is a unique regulator of meristem activity in rice and regulates inflorescence development through the promotion of IM activity and suppression of the phase change to SM identity.ALOG family | meristem identity | grain yield T he timing of each meristem phase change is crucial in the control of inflorescence architecture (1-3). In grass species, the basic architecture of inflorescence is defined by the spatial arrangement of spikelets, which are small branches containing a variable number of flowers. Among the meristems that are generated from the primary inflorescence meristem (IM) during inflorescence (panicle) development, early ones acquire an indeterminate branch meristem (BM) identity, whereas later ones are specified as determinate spikelet meristems (SMs) (Fig. 1A) (4, 5). The BMs themselves are eventually transformed into SMs after generating a certain number of branches and spikelets (Fig. 1B). Thus, the pattern of SM specification is a primary determinant of grass inflorescence form. Delays in SM specification lead to iterations of branching, resulting in larger panicles that could potentially produce more grain. Conversely, the acceleration of SM specification results in smaller panicles with fewer spikelets. Rice inflorescence development exhibits an additional unique feature in that the IM loses its activity after producing several BMs, leaving a vestige at the tip of the rachis, the inflorescence main stem (Fig. 1A). Therefore, the timing of IM abortion is also a critical factor determining the form of rice inflorescence.The competence of a meristem to become an SM gradually increases during inflorescence development; however, the molecular basis for the timing of SM specification is largely unknown.To date, several genes that control inflorescence form ...

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Section: Taw1 Is Expressed In the Meristem To Suppress The Transitionmentioning

confidence: 75%

TAWAWA1 , a regulator of rice inflorescence architecture, functions through the suppression of meristem phase transition

Yoshida

Sasao

Yasuno

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

202

210

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“…cytokinin pathway components) its target genes. We speculate that its interactions with partners in higher order complexes, and their interactions with chromatin modifiers, may determine its effect on gene expression, as is known for other transcription factor complexes (Sridhar et al, 2006;Liu et al, 2007;Smaczniak et al, 2012). The cumulative effects of these complexes on net target gene expression status culminates in a rice spikelet with a determinate floret with differentiated organs (Fig.…”

Section: Osmads1 Negatively Regulates Cytokinin Signaling In Florets mentioning

confidence: 90%

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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“…Total RNAs were isolated using the RNeasy RNA isolation kit (Qiagen) and reverse transcribed by the ThermoScript RT-PCR system (Invitrogen). Quantitative real-time PCR assays were performed in triplicate on a 7900HT Fast Real-Time PCR system (Applied Biosystems) using TUBULIN2 (TUB2) as an internal control as described previously (Liu et al, 2007). The efficiency of each pair of primers was determined based on its standard curve obtained from a series of 10-fold diluted template DNAs.…”

Section: Microarray Experiments and Data Analysismentioning

confidence: 99%

Global Identification of DELLA Target Genes during Arabidopsis Flower Development

Hou

Shen

et al. 2008

Plant Physiology

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Gibberellin (GA) plays important roles in regulating many aspects of plant development. GA derepresses its signaling pathway by promoting the degradation of DELLA proteins, a family of nuclear growth repressors. Although the floral organ identity is established in flowers of the GA-deficient mutant ga1-3, the growth of all floral organs is severely retarded. In particular, abortive anther development in ga1-3 results in male sterility. Genetic analysis has revealed that various combinations of null mutants of DELLA proteins could gradually rescue floral organ defects in ga1-3 and that RGA is the most important DELLA protein involved in floral organ development. To elucidate the early molecular events controlled by RGA during flower development, we performed whole-genome microarray analysis to identify genes in response to the steroid-inducible activation of RGA in ga1-3 rgl2 rga 35S:RGA-GR. Although DELLA proteins were suggested as transcriptional repressors, similar numbers of genes were down-regulated or up-regulated by RGA during floral organ development. More than one-third of RGA down-regulated genes were specifically or predominantly expressed in stamens. A significant number of RGA-regulated genes are involved in phytohormone signaling or stress response. Further expression analysis through activation of RGA by steroid induction combined with cycloheximide identified eight genes as immediate targets of RGA. In situ hybridization and transgenic studies further showed that the expression pattern and function of several selected genes were consistent with the predictions from microarray analysis. These results suggest that DELLA regulation of floral organ development is modulated by multiple phytohormones and stress signaling pathways.

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Specification ofArabidopsisfloral meristem identity by repression of flowering time genes

Cited by 267 publications

References 43 publications

TAWAWA1 , a regulator of rice inflorescence architecture, functions through the suppression of meristem phase transition

TAWAWA1 , a regulator of rice inflorescence architecture, functions through the suppression of meristem phase transition

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

Global Identification of DELLA Target Genes during Arabidopsis Flower Development

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