United Graduate School of Agricultural Sciences, Iwate University, Morioka, 020-8550, Japan.
Department of Plant Bio Sciences, Faculty of Agriculture, Iwate University, Morioka, 020-8550, Japan.
Plant J. 2019 Feb;97(3):500-516. doi: 10.1111/tpj.14137. Epub 2018 Dec 17.
Endosomal trafficking plays an important role in regulating plant growth and development both at optimal and stressed conditions. Cold stress response in Arabidopsis root is directly linked to inhibition of the endosomal trafficking of auxin efflux carriers. However, the cellular components that link cold stress and the endosomal trafficking remain elusive. By screening available endosomal trafficking mutants against root growth recovery response under cold stress, we identified GNOM, a SEC7 containing ARF-GEF, as a major modulator of cold response. Contrasting response of partial loss of function mutant gnom and the engineered Brefeldin A (BFA)-resistant GNOM line, both of which contain mutations within SEC7 domain, to cold stress at the whole-plant level highlights the importance of this domain in modulating the cold response pathway of plants. Cold stress selectively and transiently inhibits GNOM expression. The engineered point mutation at 696 amino acid position (Methionine to Leucine) that makes GNOM resistant to BFA in fact results in overexpression of GNOM both at transcriptional and translational levels, and also alters its subcellular localization. Overexpression and altered cellular localization of GNOM were found to be directly linked to conferring striking cold-resistant phenotype in Arabidopsis. Collectively, these results provide a mechanistic link between GNOM, BFA-sensitive GNOM-regulated trafficking and cold stress.
内体运输在植物的生长和发育过程中起着重要作用，无论是在最佳条件下还是在胁迫条件下。拟南芥根系对冷胁迫的反应直接与生长素外排载体的内体运输抑制有关。然而，将冷胁迫与内体运输联系起来的细胞成分仍不清楚。通过筛选现有的内体运输突变体，我们发现含有 SEC7 的 ARF-GEF 的 GNOM 是冷响应的主要调节剂。部分功能丧失突变体 gnom 和工程化的 Brefeldin A（BFA）抗性 GNOM 系对植物冷响应途径具有重要的调节作用，这与整株植物水平上的冷胁迫反应相反，这两种突变体都在 SEC7 结构域内发生突变。冷胁迫选择性和瞬时抑制 GNOM 的表达。在 696 位氨基酸位置（蛋氨酸到亮氨酸）的工程点突变使 GNOM 对 BFA 具有抗性，实际上导致 GNOM 在转录和翻译水平上的过表达，并且还改变了其亚细胞定位。发现 GNOM 的过表达和细胞定位的改变与赋予拟南芥显著的抗冷表型直接相关。总之，这些结果为 GNOM、BFA 敏感的 GNOM 调节的运输和冷胁迫之间提供了一个机制联系。
