Novel Structural and Functional Motifs in cellulose synthase (CesA) Genes of Bread Wheat (Triticum aestivum, L.)

Cellulose is the primary determinant of mechanical strength in plant tissues. Late-season lodging is inversely related to the amount of cellulose in a unit length of the stem. Wheat is the most widely grown of all the crops globally, yet information on its CesA gene family is limited. We have identified 22 CesA genes from bread wheat, which include homoeologs from each of the three genomes, and named them as TaCesAXA, TaCesAXB or TaCesAXD, where X denotes the gene number and the last suffix stands for the respective genome. Sequence analyses of the CESA proteins from wheat and their orthologs from barley, maize, rice, and several dicot species (Arabidopsis, beet, cotton, poplar, potato, rose gum and soybean) revealed motifs unique to monocots (Poales) or dicots. Novel structural motifs CQIC and SVICEXWFA were identified, which distinguished the CESAs involved in the formation of primary and secondary cell wall (PCW and SCW) in all the species. We also identified several new motifs specific to monocots or dicots. The conserved motifs identified in this study possibly play functional roles specific to PCW or SCW formation. The new insights from this study advance our knowledge about the structure, function and evolution of the CesA family in plants in general and wheat in particular. This information will be useful in improving culm strength to reduce lodging or alter wall composition to improve biofuel production.纤维素是决定植物组织机械强度的核心因素。作物生育后期倒伏与茎秆单位长度的纤维素含量呈负相关。小麦是全球种植范围最广的作物，但目前关于其CesA基因家族（CesA gene family）的研究信息仍较为有限。本研究从普通小麦中鉴定出22个CesA基因，涵盖来自三个基因组的全部部分同源基因，并将其命名为TaCesAXA、TaCesAXB或TaCesAXD，其中X代表基因编号，末尾后缀对应其所在基因组。对小麦CESA蛋白以及大麦、玉米、水稻及多种双子叶植物（拟南芥、甜菜、棉花、杨树、马铃薯、玫瑰桉和大豆）的直系同源蛋白进行序列分析后，发现了单子叶植物（禾本目，Poales）或双子叶植物特有的保守基序。本研究还鉴定出两个新型结构基序CQIC与SVICEXWFA，二者可区分所有物种中参与初生细胞壁（primary cell wall, PCW）与次生细胞壁（secondary cell wall, SCW）合成的CESA蛋白。此外，我们还识别出若干单子叶或双子叶植物特有的新基序。本研究鉴定得到的保守基序可能在初生或次生细胞壁的合成过程中发挥特异性功能。本研究获得的新见解加深了学界对植物（尤其是小麦）CesA基因家族的结构、功能与演化的认知。相关研究成果可为通过改良茎秆强度以降低倒伏风险，或通过调控细胞壁组分以提升生物燃料生产效率提供理论参考。