<i>barren inflorescence2</i>Encodes a Co-Ortholog of the<i>PINOID</i>Serine/Threonine Kinase and Is Required for Organogenesis during Inflorescence and Vegetative Development in Maize

McSteen, Paula; Malcomber, Simon T.; Skirpan, Andrea L.; Lunde, China; Wu, Xianting; Kellogg, Elizabeth A.; Hake, Sarah

doi:10.1104/pp.107.098558

Cited by 165 publications

(174 citation statements)

References 71 publications

(114 reference statements)

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“…Recently, one of the rice PIN1-like genes has been implicated in tiller bud outgrowth and adventitious root initiation (31), but its contributions to inflorescence structure are not known. Furthermore, the maize BIF2 (co-ortholog of PINOID-like serine/threonine kinase) regulates the initiation of axillary meristem and lateral primordia (32), underscoring the importance of auxin signaling for primordia emergence in grasses. Our data provide starting points for further investigations on RFL mechanism of action.…”

Section: Discussionmentioning

confidence: 99%

Distinct regulatory role for RFL , the rice LFY homolog, in determining flowering time and plant architecture

Rao

Prasad²,

Kumar³

et al. 2008

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

170

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Activity of axillary meristems dictates the architecture of both vegetative and reproductive parts of a plant. In Arabidopsis thaliana, a model eudicot species, the transcription factor LFY confers a floral fate to new meristems arising from the periphery of the reproductive shoot apex. Diverse orthologous LFY genes regulate vegetative-to-reproductive phase transition when expressed in Arabidopsis, a property not shared by RFL, the homolog in the agronomically important grass, rice. We have characterized RFL by knockdown of its expression and by its ectopic overexpression in transgenic rice. We find that reduction in RFL expression causes a dramatic delay in transition to flowering, with the extreme phenotype being no flowering. Conversely, RFL overexpression triggers precocious flowering. In these transgenics, the expression levels of known flowering time genes reveal RFL as a regulator of OsSOC1 (OsMADS50), an activator of flowering. Aside from facilitating a transition of the main growth axis to an inflorescence meristem, RFL expression status affects vegetative axillary meristems and therefore regulates tillering. The unique spatially and temporally regulated RFL expression during the development of vegetative axillary bud (tiller) primordia and inflorescence branch primordia is therefore required to produce tillers and panicle branches, respectively. Our data provide mechanistic insights into a unique role for RFL in determining the typical rice plant architecture by regulating distinct downstream pathways. These results offer a means to alter rice flowering time and plant architecture by manipulating RFL-mediated pathways.axillary meristem ͉ inflorescence branching ͉ flowering transition ͉ tillering A rabidopsis thaliana LFY and its homologs encode an evolutionarily conserved land plant-specific transcription factor. Early studies on the expression pattern and phenotypes of loss-of-function mutations in LFY and FLO, homologs in two dicots A. thaliana and Antirrhinum majus, showed them to confer a floral fate to new meristems arising on the flanks of the shoot apex (1, 2). LFY homologs from species as diverse as gymnosperms, primitive land plants, and from many angiosperms retain the ability to at least partially complement Arabidopsis lfy mutants (3). These data show activation of floral meristem fate to be a conserved LFY function. Protein domains recognizable in all LFY homologs are an N-terminal proline-rich domain and a C-terminal domain; substitutions in these largely conserved DNA-binding domains are suggested to contribute to its potentially divergent functions (3). In fact, mutations in some LFY homologs show additional developmental roles (e.g., compound leaf development in pea and cell division in moss) (4, 5).Unlike the simple inflorescence of Arabidopsis, grass inflorescences are striking in the multiple kinds of branch meristems made from the apical inflorescence meristem. In rice upon transition to reproductive phase, the vegetative apical meristem transforms to an inflorescence meristem. The...

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Section: Discussionmentioning

confidence: 99%

Distinct regulatory role for RFL , the rice LFY homolog, in determining flowering time and plant architecture

Rao

Prasad²,

Kumar³

et al. 2008

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

170

165

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“…Mutants in rice and maize (Zea mays) coorthologs for Arabidopsis auxin biosynthesis factors, auxin transport, and signaling factors display defects in inflorescence axillary meristem development, spikelet and FM initiation, and organ numbers and organ development (McSteen et al, 2007;Morita and Kyozuka, 2007;McSteen, 2010;Phillips et al, 2011). Our microarray data showed that the second largest functional category of affected genes encodes signaling factors, and we note global effects on auxin metabolism and response (Supplemental Table S3; Supplemental Fig.…”

Section: Osmads1 Regulates Oskanadi2 and Oskanadi4 Expressionmentioning

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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“…Moreover, ZmPIN1a activity rescues Arabidopsis pin1-3, resulting in the re-establishment of auxin maxima and the re-formation of FMs, which indicates that the auxin transport mechanism during FM initiation might be conserved between Arabidopsis and grasses (Gallavotti et al, 2008b). Interestingly, the phosphorylation and localization of ZmPIN1a is also regulated by a homologue of PID, BARREN INFLORESCENCE2 (BIF2) (McSteen et al, 2007;Skirpan et al, 2009), which suggests similarities in the regulation of auxin transporter trafficking between maize and Arabidopsis. In rice (Oryza sativa), OsPID, another orthologue of PID, has been suggested to function in polar auxin transport (Morita and Kyozuka, 2007), but its role in FM initiation is so far unknown.…”

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confidence: 93%

Coming into bloom: the specification of floral meristems

2009

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In flowering plants, the founder cells from which reproductive organs form reside in structures called floral meristems. Recent molecular genetic studies have revealed that the specification of floral meristems is tightly controlled by regulatory networks that underpin several coordinated programmes, from the integration of flowering signals to floral organ formation. A notable feature of certain regulatory genes that have been newly implicated in the acquisition and maintenance of floral meristem identity is their conservation across diverse groups of flowering plants. This review provides an overview of the molecular mechanisms that underlie floral meristem specification in Arabidopsis thaliana and, where appropriate, discusses the conservation and divergence of these mechanisms across plant species. IntroductionFlowering plants, also known as angiosperms (see Glossary, Box 1), were the last of the seed-bearing plant groups to evolve. The most obvious features that distinguish angiosperms from other seedbearing plants are their reproductive organs, the flowers. In the course of flowering, plants undergo a transition from vegetative to reproductive growth (see Glossary, Box 1), known as the floral transition. Flowers contain reproductive structures, such as stamens and carpels (see Glossary, Box 1; see also Fig. 1), and upon fertilization a subset of carpels develops into fruits. These fruits contain seeds, from which new plants can grow, thus permitting the transfer of genetic information to the next generation.When plants initiate flowering, the vegetative shoot apical meristem (SAM; see Glossary, Box 1), which gives rise to all the parts of a plant that are above ground, is transformed into an inflorescence meristem (IM; see Glossary, Box 1). The IM, in turn, generates a collection of undifferentiated cells called floral meristems (FMs) that give rise to floral organs. As FMs arise in response to multiple flowering signals and eventually differentiate into various types of floral organ, the regulation of FM development is a crucial and dynamic switch that allows for the successful reproductive development of flowering plants in an unpredictable environment.Morphological changes of flower development have been monitored in detail in the model plant Arabidopsis thaliana (Smyth et al., 1990), in which flower development is divided into 12 stages according to a series of landmark events. Floral primordia that are present prior to visible floral organogenesis are generally considered to be FMs. Even though floral anlagen are morphologically invisible before stage 1, they have already become distinguishable from other cells in IMs, as is apparent from the expression of certain marker genes. One such marker gene is AINTEGUMENTA (ANT), which encodes a transcription factor of the plant-specific AP2/EREBP family ( Fig. 2A). Floral anlagen at this transitional phase are usually referred to as stage 0 FMs (Long and Barton, 2000). Stage 1 FMs emerge as outward bulges on the flank of the IM, with each new FM forming at an...

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barren inflorescence2Encodes a Co-Ortholog of thePINOIDSerine/Threonine Kinase and Is Required for Organogenesis during Inflorescence and Vegetative Development in Maize

Cited by 165 publications

References 71 publications

Distinct regulatory role for RFL , the rice LFY homolog, in determining flowering time and plant architecture

Distinct regulatory role for RFL , the rice LFY homolog, in determining flowering time and plant architecture

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

Coming into bloom: the specification of floral meristems

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