Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Plant J. 2010 Mar;61(5):767-81. doi: 10.1111/j.1365-313X.2009.04101.x. Epub 2009 Dec 9.
Mutant analyses in different eudicotyledonous flowering plants demonstrated that SEPALLATA-like MADS-box genes are required for the specification of sepals, petals, stamens and carpels, and for floral determinacy, thus defining class E floral organ identity genes. SEP-like genes encode MADS-domain transcription factors and constitute an angiosperm-specific gene clade whose members show remarkably different degrees of redundancy and sub-functionalization within eudicots. To better understand the evolutionary dynamics of SEP-like genes throughout the angiosperms we have knocked down SEP-like genes of rice (Oryza sativa), a distant relative of eudicots within the flowering plants. Plants affected in both OsMADS7 and OsMADS8 show severe phenotypes including late flowering, homeotic changes of lodicules, stamens and carpels into palea/lemma-like organs, and a loss of floral determinacy. Simultaneous knockdown of the four rice SEP-like genes OsMADS1, OsMADS5, OsMADS7 and OsMADS8, leads to homeotic transformation of all floral organs except the lemma into leaf-like organs. This mimics the phenotype observed with the sep1 sep2 sep3 sep4 quadruple mutant of Arabidopsis. Detailed analyses of the spatial and temporal mRNA expression and protein interaction patterns corresponding to the different rice SEP-like genes show strong similarities, but also gene-specific differences. These findings reveal conservation of SEP-like genes in specifying floral determinacy and organ identities since the separation of eudicots and monocots about 150 million years ago. However, they indicate also monocot-specific neo- and sub-functionalization events and hence underscore the evolutionary dynamics of SEP-like genes. Moreover, our findings corroborate the view that the lodicules of grasses are homologous to eudicot petals.
在不同的真双子叶植物开花植物中的突变体分析表明，SEPALLATA 样 MADS 框基因对于萼片、花瓣、雄蕊和心皮的特化以及花的定型是必需的，因此定义了 E 类花器官身份基因。SEP 样基因编码 MADS 结构域转录因子，构成一个被子植物特有的基因分支，其成员在真双子叶植物中表现出显著不同程度的冗余和亚功能化。为了更好地理解 SEP 样基因在整个被子植物中的进化动态，我们敲低了真双子叶植物远亲水稻（Oryza sativa）中的 SEP 样基因。在 OsMADS7 和 OsMADS8 中受到影响的植物表现出严重的表型，包括开花晚、浆片、雄蕊和心皮变成颖片/外稃样器官的同型异位转变，以及花定型的丧失。同时敲低四个水稻 SEP 样基因 OsMADS1、OsMADS5、OsMADS7 和 OsMADS8，导致除了外稃之外的所有花器官都变成叶状器官的同型异位转变。这模拟了拟南芥 sep1 sep2 sep3 sep4 四重突变体观察到的表型。对不同水稻 SEP 样基因对应的时空 mRNA 表达和蛋白相互作用模式的详细分析表明，存在强烈的相似性，但也存在基因特异性差异。这些发现揭示了 SEP 样基因在特化花定型和器官身份方面的保守性，因为真双子叶植物和单子叶植物大约在 1.5 亿年前就已经分离。然而，它们也表明了单子叶植物特有的新功能和亚功能化事件，因此强调了 SEP 样基因的进化动态。此外，我们的发现证实了观点，即禾本科植物的浆片与真双子叶植物的花瓣同源。
