A G protein-coupled receptor-like module regulates cellulose synthase secretion from the endomembrane system in Arabidopsis

背景回顾：Cellulose is produced at the plasma membrane of plant cells by cellulose synthase (CESA) complexes (CSCs). CSCs are assembled in the endomembrane system and then trafficked to the plasma membrane. Because CESAs are only active in the plasma membrane, control of CSC secretion regulates cellulose synthesis. 

主要发现：We identified members of a family of seven transmembrane domain-containing proteins (7TMs) that are important for cellulose production during cell wall integrity stress. 

结果1：7TMs are often associated with guanine nucleotide-binding (G) protein signaling and we found that mutants affecting the Gβγ dimer phenocopied the 7tm mutants. 

结果2：Unexpectedly, the 7TMs localized to the Golgi/trans-Golgi network where they interacted with G protein components. Here, the 7TMs and Gβγ regulated CESA trafficking but did not affect general protein secretion. 

结论：Our results outline how a G protein-coupled module regulates CESA trafficking and reveal that defects in this process lead to exacerbated responses to cell wall integrity stress.

 摘 要 

纤维素是由位于植物细胞质膜上的纤维素合酶CESA复合体CSCs所产生的。而CSCs在内膜系统中合成，后转运到质膜上。因为CESAs仅在质膜上的时候才具有活性，因此对于CSC分泌的控制能够调控个纤维素的合成。本文中，作者鉴定了含有7个跨膜结构域的蛋白7TMs，这些蛋白对于细胞壁完整性胁迫下纤维素的合成是非常重要的。7TMs通常与鸟嘌呤核苷酸结合（G）蛋白信号转导相关联，并且作者发现影响Gβγ二聚化的突变体的表型与7tm突变体的表型类似。出乎意料的是，7TMs定位于高尔基/反面高尔基网络，在这里7TMs会与G蛋白组分发生互作。在这里，7TMs和Gβγ调控CESA得到运输，但并不影响整体的蛋白分泌。本文的结果揭示了一个G蛋白偶联的模块调控CESA的运输，并且发现该过程的缺陷会导致细胞完整性胁迫下的响应更加剧烈。

 通讯作者 

** Staffan Persson **