Primary cell wall cellulose is synthesized by the cellulose synthase complex (CSC) containing CELLULOSE SYNTHASE1 (CESA1), CESA3 and one of four CESA6‐like proteins in Arabidopsis. It has been proposed that the CESA6‐like proteins occupy the same position in the CSC, but their underlying selection mechanism remains unclear. We produced a chimeric CESA5 by replacing its N‐terminal zinc finger with its CESA6 counterpart to investigate the consequences for its homodimerization, a crucial step in forming higher‐order structures during assembly of the CSC. We found that the mutant phenotypes of prc1‐1, a cesa6 null mutant, were rescued by the chimeric CESA5, and became comparable to the wild type (WT) and prc1‐1 complemented by WT CESA6 in regard to plant growth, cellulose content, cellulose microfibril organization, CSC dynamics and subcellular localization. Bimolecular fluorescence complementation assays were employed to evaluate pairwise interactions between the N‐terminal regions of CESA1, CESA3, CESA5, CESA6 and the chimeric CESA5. We verified that the chimeric CESA5 explicitly interacted with all the other CESA partners, comparable to CESA6, whereas interaction between CESA5 with itself was significantly weaker than that of all other CESA pairs. Our findings suggest that the homodimerization of CESA6 through its N‐terminal zinc finger is critical in defining its functional properties, and possibly determines its intrinsic roles in facilitating higher‐order structures in CSCs.

中文翻译：

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CELLULOSE SYNTHASE6 的 N 末端锌指通过确定拟南芥中的同源二聚化水平来定义其功能特性至关重要。

原代细胞壁纤维素是由纤维素合酶复合物 (CSC) 合成的，该复合酶复合物含有纤维素合成酶 1 (CESA1)、CESA3 和拟南芥中的四种 CESA6 样蛋白之一。有人提出，CESA6 样蛋白在 CSC 中占据相同的位置，但其潜在的选择机制仍不清楚。我们通过用 CESA6 对应物替换其 N 端锌指来生产嵌合 CESA5，以研究其同源二聚化的后果，这是 CSC 组装过程中形成高阶结构的关键步骤。我们发现 prc1-1 的突变表型，一个cesa6无效突变体，被嵌合的 CESA5 拯救，并变得与野生型 (WT) 和prc1-1 相当在植物生长、纤维素含量、纤维素微纤维组织、CSC 动力学和亚细胞定位方面由 WT CESA6 补充。双分子荧光互补分析用于评估 CESA1、CESA3、CESA5、CESA6 和嵌合 CESA5 的 N 端区域之间的成对相互作用。我们验证了嵌合 CESA5 与所有其他 CESA 合作伙伴显式相互作用，与 CESA6 相当，而 CESA5 与自身之间的相互作用明显弱于所有其他 CESA 对。我们的研究结果表明，CESA6 通过其 N 端锌指的同二聚化对于定义其功能特性至关重要，并可能决定其在促进 CSC 中高阶结构中的内在作用。