Tillering in rice is one of the most important agronomic traits. Rice tiller development can be divided into two main processes: the formation of the axillary bud and its subsequent outgrowth. Several genes critical for bud formation in rice have been identified by genetic studies; however, their molecular functions and relationships are still largely unknown. Here, we report that MONOCULM 1 (MOC1) and MONOCULM 3/TILLERS ABSENT 1/STERILE AND REDUCED TILLERING 1 (MOC3/TAB1/SRT1), two vital regulators for tiller formation in rice, physically interact to regulate tiller bud outgrowth through upregulating the expression of FLORAL ORGAN NUMBER1 (FON1), the homolog of CLAVATA1 in rice. We found that MOC3 is able to directly bind the promoter of FON1 and subsequently activate FON1 expression. MOC1 functions as a co-activator of MOC3, whereas it could not directly bind the FON1 promoter, and further activated FON1 expression in the presence of MOC3. Accordingly, FON1 is highly expressed at axillary meristems and shows remarkably decreased expression levels in moc1 and moc3 mutants. Loss-of-function mutants of FON1 exhibit normal bud formation but defective bud outgrowth and reduced tiller number. Collectively, these results shed light on a joint transcriptional regulatory mechanim by MOC1 and MOC3, and establish a new framework for the control of tiller bud formation and outgrowth.

水稻分iller是最重要的农艺性状之一。水稻分till发育可以分为两个主要过程：腋芽的形成和随后的生长。遗传研究已经鉴定出几个对水稻芽形成至关重要的基因。然而，它们的分子功能和关系仍然是未知的。在这里，我们报告MONOCULM 1（MOC1）和MONOCULM 3 /耕作者缺席/不育和减少分ILL1（MOC3 / TAB1 / SRT1），这两个水稻分till形成的重要调节剂，通过向上调节谷氨酸分physical的生长而物理相互作用来调节分er芽的生长。水稻中CLAVATA1的同源基因FLORAL ORGAN NUMBER1（FON1）的表达 我们发现MOC3能够直接结合FON1的启动子然后激活FON1表达。MOC1充当MOC3的共激活因子，而不能直接结合FON1启动子，并在MOC3存在的情况下进一步激活FON1表达。因此，FON1在腋生分生组织中高度表达，并且在moc1和moc3突变体中显示出明显降低的表达水平。功能丧失的FON1突变体表现出正常的芽形成，但芽生长不良，且分till数减少。这些结果共同揭示了MOC1和MOC3的联合转录调控机制，并为控制分er芽的形成和生长建立了新的框架。