RESUMO
Proper floral patterning, including the number and position of floral organs in most plant species, is tightly controlled by the precise regulation of the persistence and size of floral meristems (FMs). In Arabidopsis, two known feedback pathways, one composed of WUSCHEL (WUS) and CLAVATA3 (CLV3) and the other composed of AGAMOUS (AG) and WUS, spatially and temporally control floral stem cells, respectively. However, mounting evidence suggests that other factors, including phytohormones, are also involved in floral meristem regulation. Here, we show that the boundary gene SUPERMAN (SUP) bridges floral organogenesis and floral meristem determinacy in another pathway that involves auxin signaling. SUP interacts with components of polycomb repressive complex 2 (PRC2) and fine-tunes local auxin signaling by negatively regulating the expression of the auxin biosynthesis genes YUCCA1/4 (YUC1/4). In sup mutants, derepressed local YUC1/4 activity elevates auxin levels at the boundary between whorls 3 and 4, which leads to an increase in the number and the prolonged maintenance of floral stem cells, and consequently an increase in the number of reproductive organs. Our work presents a new floral meristem regulatory mechanism, in which SUP, a boundary gene, coordinates floral organogenesis and floral meristem size through fine-tuning auxin biosynthesis.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Ácidos Indolacéticos/metabolismo , Organogênese Vegetal/genética , Fatores de Transcrição/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Flores/genética , Flores/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Meristema/genética , Oxigenases de Função Mista/genética , Mutação , Fenótipo , Complexo Repressor Polycomb 2/genética , Células-Tronco/metabolismoRESUMO
As originally proposed by Goethe in 1790, floral organs are derived from leaf-like structures. The conversion of leaves into different types of floral organ is mediated by floral homeotic proteins, which, as described by the ABCE model of flower development, act in a combinatorial manner. However, how these transcription factors bring about this transformation process is not well understood. We have previously shown that floral homeotic proteins are involved in suppressing the formation of branched trichomes, a hallmark of leaf development, on reproductive floral organs of Arabidopsis Here, we present evidence that the activities of the C function gene AGAMOUS (AG) and the related SHATTERPROOF1/2 genes are superimposed onto the regulatory network that controls the distribution of trichome formation in an age-dependent manner. We show that AG regulates cytokinin responses and genetically interacts with the organ polarity gene KANADI1 to suppress trichome initiation on gynoecia. Thus, our results show that parts of the genetic program for leaf development remain active during flower formation but have been partially rewired through the activities of the floral homeotic proteins.
Assuntos
Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteína AGAMOUS de Arabidopsis/genética , Proteína AGAMOUS de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Citocininas/genética , Citocininas/metabolismo , Flores/genética , Flores/crescimento & desenvolvimento , Flores/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Domínio MADS/genética , Proteínas de Domínio MADS/metabolismo , Modelos Biológicos , Mutação , Reguladores de Crescimento de Plantas/genética , Reguladores de Crescimento de Plantas/metabolismo , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Plantas Geneticamente Modificadas , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Tricomas/crescimento & desenvolvimento , Tricomas/metabolismoRESUMO
The genetic and molecular mechanisms that underlie the formation of angiosperm flowers have been studied extensively for nearly three decades. This work has led to detailed insights into the gene regulatory networks that control this vital developmental process in plants. Here, we review some of the key findings in the field of flower development and discuss open questions that must be addressed in order to obtain a more comprehensive understanding of flower formation. In particular, we focus on the specification of the different types of floral organs and on how the morphogenesis of these organs is controlled to give rise to mature flowers. Central to this process are the floral organ identity genes, which encode members of the family of MADS-domain transcription factors. We summarize what is currently known about the functions of these master regulators and discuss a working model for the molecular mechanism that may underlie their activities.