柳枝稷细胞壁富含纤维素和半纤维素，是重要的能饲兼用作物。然而由于细胞壁中木质素的存在，限制了上述多糖的有效利用，因此需要对柳枝稷木质素合成途径进行遗传改良。木质素单体的甲基化供体来自一碳代谢途径产生的S-腺苷甲硫氨酸（SAM）。我们研究发现，柳枝稷SAM合成酶PvSAMS和氧甲基转移酶PvCOMT的表达模式高度相关，而且抑制上述基因的表达均能够显著降低甲基化木质素单体的合成。但二者如何被精准调控影响木质素单体甲基化程度的机制尚不清楚。因此本项目拟利用酵母单杂交技术在柳枝稷中筛选共同调控PvCOMT和PvSAMS的转录因子，并进一步通过体外和体内分子实验解析候选转录因子（主要为PvDOF3）对PvCOMT和PvSAMS的协同调控机制。同时，通过系统分析转基因柳枝稷植株，解析PvDOF3对木质素合成、维管束形成及细胞壁降解效率的影响，从而为柳枝稷及其他经济作物的木质素改良提供更多新靶标。

Switchgrass is a multifunctional crop for feed and bioenergy production, and its cell wall is rich in fiber and hemicellulose. The degree of lignin methylation plays a key role in the cell wall saccharification efficiency. Therefore, improving the quality of the lignin is an important goal in switchgrass molecular breeding. S-adenosine methionine (SAM), the key molecule of one-carbon metabolism pathway, is the primary methyl donor molecular utilized in lignin biosynthesis. We find that the expression patterns of the SAM synthase gene SAMS and the O-methyltransferase gene COMT in lignin synthesis are highly consistent. Meanwhile, SAMS and COMT are functionally correlated. It is not clear how SAMS and COMT coordinately regulate the lignin biosynthesis in switchgrass. The main purpose of the project is to find the genes regulating synergistic expression of SAMS and COMT and analyze the molecular mechanism on how it affects lignin biosynthesis in switchgrass. The yeast one-hybrid assay shows that several transcription factors can coordinate with the promoters of SAMS and COMT, especially for PvDOF3. Moreover, we will elucidate a novel cooperative regulation mechanism of PvDOF3 regulating one carbon metabolism and lignin biosynthesis through a battery of in vitro (such as EMSA and dual-luciferase reporter assay) and in vivo (such as gene transformation and ChIP methods) experiments. This project will provide new target genes for lignin improvement in gramineae crops like switchgrass.