Conservation and dynamics of class E floral homeotic gene function in flowering plants

【摘要】：正Mutant studies in different eudicotyledonous flowering plants have recently identified a novel type of organ identity genes, termed class E floral homeotic genes. These genes encode AGL2-like MADS-domain proteins, such as the SEPALLATA-proteins in Arabidopsis. AGL2-like genes constitute small gene subfamilies showing different degrees of functional redundancy and subfunctionalization in diverse eudicots. Here we demonstrate a knockout phenotype of two AGL2-like genes from a monocot, affecting OsMADS8 and OsMADS7, SEP3 orthologues of rice. Mutant plants show severe phenotypes including extremely early flowering, homeotic changes of lodicules and carpels into palea/lemma-like organs, and a loss of floral determinacy. These findings demonstrate a strong conservation of class E floral homeotic gene functions in specifying floral determinacy and organ identity since the separation of eudicots and monocots about 150 million years ago. However, they reveal also monoct-specific neo-and subfunctionalisation of SEP-like genes and hence underscore the evolutionary dynamics of the AGL2-like gene subfamily. Moreover, our findings corroborate the view that the lodicules of grasses are homologous to eudicot petals.