棉花纤维素合酶CesA的Cryo-EM结构和功能解析

我国常年种植棉花5000万亩，产值逾千亿，事关国计民生。我国棉花遗传资源狭窄，优质纤维缺乏造成高端棉织品竞争力不强是我国棉花生产的主要问题。棉纤维中纤维素含量约95%，纤维素是决定棉纤维品质的关键因素。纤维素合酶CesA及纤维素合酶复合体CSC的功能解析是棉花纤维品质改良的理论基础。本实验室鉴定了CesA家族基因序列，解析了次生壁合成相关的GhCesA7同源三聚Cryo-EM结构，构建了CesA家族的CRISPR/Cas9饱和棉花突变体库，发现GhCesA7的CRISPR/Cas9突变体纤维变长变细。将在已有的研究基础上，通过CesA单突双突等棉花突变体详细解析CesA家族成员的生物学功能，通过鉴定CesA启动子顺式作用元件和与之作用的转录因子阐明CesA表达调控机制，并结合结构生物学解析CSC的结构。为棉花纤维优质育种提供理论指导和优质资源，回答纤维素合成生化机制这个基本生物学问题。

There are more than 300 million hectares of cotton grown in China all the year round, with an output value of more than 100 billion, which is related to the national economy and people's livelihood. Cotton is an exotic species. The cotton genetic resources are narrow in China, and international competitiveness of high-end cotton fabrics is not strong due to lack of high-quality fibers, which is the main problem of our cotton production. Cellulose is the main component of cotton fiber and a key factor in determining the quality of cotton fiber. The functional analysis of cellulose synthase CesA and cellulose synthase complex CSC is the theoretical basis for cotton fiber quality improvement. We have identified CesA gene family members, elucidated the homotrimeric structure of GhCesA7 involved in secondary wall synthesis, developed a CRISPR/Cas9 saturated cotton mutant library of the CesA family, and found that the CRISPR/Cas9 mutants of GhCesA7 have longer finer fibers. Based on the research progress, this study will analyze the biological functions of CesA family members in detail through cotton CesA single/double mutants, clarify the mechanism of expression regulation of CesAs by identifying the cis-acting elements of the CesAs’ promoter and the transcription factors that interact with the elements, and analyze the Cryo-EM structure of CSC. We hope these results will provide a theoretical guidance and materials for cotton fiber quality breeding, and answer the basic biological question of the biochemical mechanism of cellulose synthesis.