Table_1_Genetic control of the lateral petal shape and identity of asymmetric flowers in mungbean (Vigna radiata L.).xlsx

Broad diversity of flowers in Fabaceae provides a good system to investigate development and evolution of floral symmetry in higher plants. Many studies have demonstrated a conserved mechanism controlling development of zygomorphic flower during last decades. However, the molecular basis of how asymmetric flower established is largely unknown. In this study, we characterized mutants named keeled wings (kw) in mungbean (Vigna radiata L.), which is a legume species with asymmetric flowers. Compared to those in the wild type plants, the lateral petals were ventralized in the kw mutants. Map-based cloning showed that KW was VrCYC3 gene in mungbean, the ortholog of Lotus japonicus CYC3 (LjCYC3) and Pisum sativum CYC3 (PsCYC3). In addition, another two CYC-like genes named VrCYC1 and VrCYC2 were identified from mungbean genome. The three CYC-like genes displayed distinct expression patterns in dorsal, lateral and ventral petals. It was found that VrCYC3 was located in nucleus. Further analysis showed that VrCYC3 had transcription activity and could interact with VrCYC1 and VrCYC2 in yeast cell. Moreover, the deletion of two amino acid residues in the R domain of VrCYC3 protein could decrease its interaction with VrCYC1 and VrCYC2 proteins. Our results suggest that LjCYC3/VrCYC3 orthologs play conserved roles determining the lateral petal shape and identity of zygomorphic flower as well as asymmetric flower in Papilionoideae.

豆科（Fabaceae）植物拥有极为丰富的花部多样性，为研究高等植物的花对称性发育与演化提供了优良的研究系统。近数十年来，多项研究已阐明了控制两侧对称花（zygomorphic flower）发育的保守调控机制。然而，不对称花的建成分子基础仍在很大程度上未被明确。本研究以具有不对称花的豆科物种绿豆（Vigna radiata L.）为材料，鉴定得到了命名为龙骨翅（keeled wings，简称kw）的突变体。与野生型植株相比，kw突变体的侧瓣出现了腹化表型。图位克隆（map-based cloning）结果显示，KW基因为绿豆的VrCYC3基因，其为百脉根（Lotus japonicus）CYC3（LjCYC3）与豌豆（Pisum sativum）CYC3（PsCYC3）的同源基因（ortholog）。此外，研究人员从绿豆基因组中还鉴定到另外两个CYC类基因，分别命名为VrCYC1与VrCYC2。这三个CYC类基因在背瓣、侧瓣与腹瓣中的表达模式存在显著差异。亚细胞定位分析显示，VrCYC3定位于细胞核。进一步实验表明，VrCYC3具有转录活性（transcription activity），且可在酵母细胞中与VrCYC1、VrCYC2发生蛋白相互作用。此外，VrCYC3蛋白R结构域（R domain）中两个氨基酸残基的缺失，会减弱其与VrCYC1、VrCYC2蛋白的相互作用能力。本研究结果表明，在蝶形花亚科（Papilionoideae）植物中，LjCYC3/VrCYC3的同源基因发挥着保守功能，可决定两侧对称花与不对称花的侧瓣形态及属性。