RESUMO
In flowering plants, seed development is initiated by the fusion of the maternal egg and central cells with two paternal sperm cells, leading to the formation of embryo and endosperm, respectively. The fertilization products are surrounded by the maternally derived seed coat, whose development prior to fertilization is blocked by epigenetic regulators belonging to the Polycomb Group (PcG) protein family. Here we show that fertilization of the central cell results in the production of auxin and most likely its export to the maternal tissues, which drives seed coat development by removing PcG function. We furthermore show that mutants for the MADS-box transcription factor AGL62 have an impaired transport of auxin from the endosperm to the integuments, which results in seed abortion. We propose that AGL62 regulates auxin transport from the endosperm to the integuments, leading to the removal of the PcG block on seed coat development.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/metabolismo , Endosperma/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Proteínas de Domínio MADS/genética , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/metabolismo , Transporte Biológico , Endosperma/genética , Endosperma/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Padrões de Herança , Proteínas de Domínio MADS/metabolismo , Mutação , Desenvolvimento Vegetal/genética , Polinização/genética , Proteínas do Grupo Polycomb/genética , Proteínas do Grupo Polycomb/metabolismoRESUMO
In flowering plants, seed development is preceded by a double fertilization event, whereby two male sperm cells fuse with two female gametes: the egg and central cells. The fertilized egg cell will form the embryo, and the fertilized central cell will give rise to the triploid endosperm, whose function is to nourish and support the embryo. Even though the endosperm has an unparalleled role for human nutrition, the molecular bases for its development are yet to be understood. Our results reveal that increasing auxin levels after fertilization drive the replication of the central cell in Arabidopsis thaliana. Auxin is sufficient to trigger central cell division and is necessary for correct endosperm development, a process dependent on the MADS-box transcription factor AGL62 (AGAMOUS-LIKE 62). We propose that the epigenetic regulators of the Polycomb group (PcG) family block central cell division before fertilization by repressing the expression of auxin biosynthesis genes in the female gametophyte.