Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720;
Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2021 Jul 27;118(30). doi: 10.1073/pnas.2021790118.
Cellulose is synthesized at the plasma membrane by cellulose synthase (CESA) complexes (CSCs), which are assembled in the Golgi and secreted to the plasma membrane through the -Golgi network (TGN) compartment. However, the molecular mechanisms that guide CSCs through the secretory system and deliver them to the plasma membrane are poorly understood. Here, we identified an uncharacterized gene, (), that is transcriptionally coregulated with the genes required for primary cell wall synthesis. The mutant exhibits enhanced sensitivity to cellulose synthesis inhibitors; reduced cellulose content; and defective dynamics, density, and secretion of CSCs to the plasma membrane as compared to wild type. TVA is a plant-specific protein of unknown function that is detected in at least two different intracellular compartments: organelles labeled by markers for the TGN and smaller compartments that deliver CSCs to the plasma membrane. Together, our data suggest that TVA promotes trafficking of CSCs to the plasma membrane by facilitating exit from the TGN and/or interaction of CSC secretory vesicles with the plasma membrane.
纤维素是由纤维素合酶（CESA）复合物（CSCs）在质膜上合成的，CSCs 在高尔基体中组装，并通过 -高尔基体网络（TGN）隔室分泌到质膜。然而，引导 CSCs 通过分泌系统并将其递送至质膜的分子机制还知之甚少。在这里，我们鉴定了一个未被描述的基因， （），其转录与合成初生细胞壁所需的 基因密切相关。与野生型相比， 突变体对纤维素合成抑制剂表现出更高的敏感性；纤维素含量降低；CSC 的动力学、密度和分泌到质膜的缺陷。Tva 是一种植物特异性的未知功能蛋白，至少在两个不同的细胞内隔室中被检测到：用 TGN 标记物标记的细胞器和将 CSCs 递送至质膜的较小隔室。总之，我们的数据表明，Tva 通过促进从 TGN 中输出和/或 CSC 分泌小泡与质膜的相互作用，促进 CSCs 向质膜的运输。
