Secondary cell wall not only provides rigidity and mechanical resistance to plants, but also has a large impact on plant growth and adaptation to environments. Biosynthesis of secondary cell wall is regulated by a complicated signaling transduction network; however, it is still unclear how the transcriptional regulation of secondary cell wall biosynthesis works at the molecular level. Here, we report in rice that OVATE family proteins 6 (OsOFP6) is a positive regulator in modulating expression of the genes related to biosynthesis of the secondary cell wall. Transgenic plants with knock-down of OsOFP6 by RNA interference showed increased leaf angle, which resulted from the thinner secondary cell wall with reduced amounts of cellulose and lignin, whilst overexpression of OsOFP6 in rice led to the thinker secondary cell wall with increased lignin content. Protein-protein interaction analysis revealed that OsOFP6 interacts with Oryza sativa homeobox 15 (OSH15), a class I KNOX protein. The interaction of OsOFP6 and OSH15 enhanced the transcriptional activity of OSH15 which binds to the promoter of OsIRX9 (Oryza sativa IRREGULAR XYLEM 9). Taken together, our study provides insights into the function of OsOFP6 in regulating leaf angle and the control of biosynthesis of secondary cell wall.

二次细胞壁不仅为植物提供了刚性和机械抗性，而且对植物的生长和对环境的适应性也有很大的影响。次级细胞壁的生物合成受复杂的信号转导网络调控。然而，尚不清楚次级细胞壁生物合成的转录调控在分子水平上如何起作用。在这里，我们在水稻中报告说，OVATE家族蛋白6（OsOFP6）在调节与次级细胞壁生物合成有关的基因的表达中是一个正调节剂。通过RNA干扰敲除OsOFP6的转基因植物显示出增加的叶角，这是由于次级细胞壁变薄，纤维素和木质素的量减少，而OsOFP6的过表达稻米中的木质素导致木质素含量增加的思想者次级细胞壁。蛋白质-蛋白质相互作用分析表明，OsOFP6与I类KNOX蛋白质Oryza sativa homeobox 15（OSH15）相互作用。OsOFP6和OSH15的相互作用增强了OSH15的转录活性，该活性与OsIRX9  （Oryza sativa IRREGULAR XYLEM 9）的启动子结合。综上所述，我们的研究提供了对OsOFP6在调节叶角和控制次生细胞壁生物合成中的功能的见解。