Zhang Shuang, Yang Yuanzhi, Chang Ruhui, Yao Shiqi, Xue Fengbo, Hou Zhaoyin, Liu Guanjun, Xu Zhiru
State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040, China; College of Life Science, Northeast Forestry University, Harbin 150040, China.
State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040, China; School of Forestry, Northeast Forestry University, Harbin 150040, China.
Int J Biol Macromol. 2025 Jun;311(Pt 2):143891. doi: 10.1016/j.ijbiomac.2025.143891. Epub 2025 May 5.
Cell wall invertase (CWINV) catalyzes the hydrolysis of sucrose into glucose and fructose in the apoplastic unloading pathway, with carbon sources provided for sink tissues. However, its role in wood formation remains undetermined. Therefore, transgenic lines overexpressing PtrCWINV3 or with knocked-out PtrCWINV3 expression were generated in Populus trichocarpa. Compared with wild type, the PtrCWINV3-knockout lines showed decreased CWINV activity (by 7.4 %-10.8 %), which resulted in a 1.5 %-1.8 % decrease in cellulose content, a 0.82 %-0.98 % decrease in hemicellulose content, and an increase in lignin content (by 2.9 %-4.7 %). These changes in structural carbohydrate contents were accompanied with anomalies in the late stages of secondary xylem development, characterized by reduced width of the secondary xylem, fewer cell layers in secondary xylem, and thinner fiber cell walls. The lines overexpressing PtrCWINV3 under the control of the DX15 promoter in the developing xylem showed the opposite phenotype. Transcriptome data from the developing xylem indicated that PtrCWINV3 regulated the expression of genes involved in the biosynthesis of cellulose (CesA, EG, and CB), hemicellulose/pectin (UGD, AXS, GATL, UAM, PAE, and GAUT), and starch (GBSS), which suggested its involvement in multiple polysaccharide metabolic pathways. Ultimately, this facilitated the synthesis of structural carbohydrate components such as cellulose and hemicellulose, which promoted the later stages of secondary xylem development. These findings not only demonstrate the significant role of CWINV activity in wood formation, but also highlight an excellent candidate gene for breeding new poplar varieties with high cellulose and low lignin contents.
细胞壁转化酶（CWINV）在质外体卸载途径中催化蔗糖水解为葡萄糖和果糖，为库组织提供碳源。然而，其在木材形成中的作用仍未确定。因此，在毛果杨中构建了过表达PtrCWINV3或敲除PtrCWINV3表达的转基因株系。与野生型相比，PtrCWINV3敲除株系的CWINV活性降低（降低了7.4%-10.8%），导致纤维素含量降低1.5%-1.8%，半纤维素含量降低0.82%-0.98%，木质素含量增加（增加了2.9%-4.7%）。结构碳水化合物含量的这些变化伴随着次生木质部发育后期的异常，其特征是次生木质部宽度减小、次生木质部细胞层数减少以及纤维细胞壁变薄。在发育中的木质部中，由DX15启动子控制过表达PtrCWINV3的株系表现出相反的表型。发育中的木质部的转录组数据表明，PtrCWINV3调节参与纤维素（CesA、EG和CB）、半纤维素/果胶（UGD、AXS、GATL、UAM、PAE和GAUT）和淀粉（GBSS）生物合成的基因的表达，这表明它参与了多个多糖代谢途径。最终，这促进了纤维素和半纤维素等结构碳水化合物成分的合成，从而促进了次生木质部发育的后期阶段。这些发现不仅证明了CWINV活性在木材形成中的重要作用，还突出了一个用于培育高纤维素、低木质素含量新杨树品种的优良候选基因。
