Yan Dawei, Zhang Xiaoming, Zhang Lin, Ye Shenghai, Zeng Longjun, Liu Jiyun, Li Qun, He Zuhua
National Key Laboratory of Plant Molecular Genetics, National Center for Plant Gene Research (Shanghai), Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Plant J. 2015 Apr;82(1):12-24. doi: 10.1111/tpj.12784. Epub 2015 Feb 21.
Floral organ specification is controlled by various MADS-box genes in both dicots and monocots, whose expression is often subjected to both genetic and epigenetic regulation in Arabidopsis thaliana. However, little information is known about the role of epigenetic modification of MADS-box genes during rice flower development. Here, we report the characterization of a rice gene, curved chimeric palea 1 (CCP1) that functions in palea development. Mutation in CCP1 resulted in abnormal palea with ectopic stigmatic tissues and other pleiotropic phenotypes. We found that OsMADS58, a C-class gene responsible for carpel morphogenesis, was ectopically expressed in the ccp1 palea, indicating that the ccp1 palea was misspecified and partially acquired carpel-like identity. Constitutive expression of OsMADS58 in the wild-type rice plants caused morphological abnormality of palea similar to that of ccp1, whereas OsMADS58 knockdown by RNAi in ccp1 could rescue the abnormal phenotype of mutant palea, suggesting that the repression of OsMADS58 expression by CCP1 is critical for palea development. Map-based cloning revealed that CCP1 encodes a putative plant-specific emBRYONIC flower1 (EMF1)-like protein. Chromatin immunoprecipitation assay showed that the level of the H3K27me3 at the OsMADS58 locus was greatly reduced in ccp1 compared with that in the wild-type. Taken together, our results show that CCP1 plays an important role in palea development through maintaining H3K27me3-mediated epigenetic silence of the carpel identity-specifying gene OsMADS58, shedding light on the epigenetic mechanism in floral organ development.
在双子叶植物和单子叶植物中，花器官的特化由多种MADS-box基因控制，在拟南芥中，这些基因的表达通常受到遗传和表观遗传的调控。然而，关于MADS-box基因的表观遗传修饰在水稻花发育过程中的作用，人们知之甚少。在此，我们报道了一个在稃片发育中起作用的水稻基因——弯曲嵌合内稃1（CCP1）的特征。CCP1突变导致内稃异常，带有异位柱头组织和其他多效性表型。我们发现，负责心皮形态发生的C类基因OsMADS58在ccp1内稃中异位表达，这表明ccp1内稃被错误指定，并部分获得了心皮样特征。在野生型水稻植株中组成型表达OsMADS58会导致内稃出现与ccp1类似的形态异常，而通过RNA干扰在ccp1中敲低OsMADS58可以挽救突变内稃的异常表型，这表明CCP1对OsMADS58表达的抑制对内稃发育至关重要。图位克隆显示，CCP1编码一种假定的植物特异性类胚胎花1（EMF1）蛋白。染色质免疫沉淀分析表明，与野生型相比，ccp1中OsMADS58基因座处的H3K27me3水平大大降低。综上所述，我们的结果表明，CCP1通过维持H3K27me3介导的指定心皮特征的基因OsMADS58的表观遗传沉默，在稃片发育中发挥重要作用，这为花器官发育的表观遗传机制提供了线索。
