An understanding of flower and panicle development is crucial for improving yield and quality in majority of grass crops. In this study, we used mapping-based cloning to identify MULTI-FLORET SPIKELET2 (MFS2), which encodes a MYB transcription factor and regulates flower and spikelet development in rice (Oryza sativa). In the mfs2 mutant, specification of palea identity was severely disturbed and showed degradation or transformation into a lemma-like organ, and the number of all floral organs was increased to varying degrees. Due to the increase in the number of floral organs and development of extra transformed palea/marginal region of the palea-like organs, some mfs2 spikelets had a tendency to produce two florets. These defects implied that the mfs2 mutation caused abnormal specification of palea identity and partial loss of spikelet determination. We confirm that MFS2 is a transcriptional repressor that shows strong repression activity by means of two typical ethylene-responsive element binding factor-associated amphiphilic motifs, one of which locates at the C terminus and is capable of interaction with three rice TOPLESS and TOPLESS-related proteins. The results indicate that MFS2 acts as a repressor that regulates floral organ identities and spikelet meristem determinacy in rice by forming a repression complex with rice TOPLESS and TOPLESS-related proteins.

了解花和穗的发育对于提高大多数禾本科作物的产量和质量至关重要。在这项研究中，我们使用基于图谱的克隆来鉴定多花小穗2（MFS2），它编码MYB转录因子并调节水稻（Oryza sativa）花和小穗的发育。在mfs2突变体中，内稃的特性受到严重干扰，并表现出退化或转化为外稃样器官，并且所有花器官的数量都有不同程度的增加。由于花器官数量的增加和额外转化的内稃/类内稃器官的边缘区域的发育，一些mfs2小穗有产生两朵小花的倾向。这些缺陷表明mfs2突变导致内稃身份的异常规范和小穗测定的部分丧失。我们确认MFS2是一种转录抑制因子，通过两个典型的乙烯响应元件结合因子相关的两亲基序显示出强抑制活性，其中一个位于C末端，能够与三种水稻TOPLESS和TOPLESS相关的相互作用蛋白质。结果表明，MFS2作为阻遏蛋白，通过与水稻 TOPLESS 和 TOPLESS 相关蛋白形成抑制复合物，调节水稻花器官特性和小穗分生组织决定性。