Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
Plant Cell. 2013 May;25(5):1709-25. doi: 10.1105/tpc.113.112052. Epub 2013 May 28.
Plasticity of root growth in response to environmental cues and stresses is a fundamental characteristic of land plants. However, the molecular basis underlying the regulation of root growth under stressful conditions is poorly understood. Here, we report that a rice nuclear factor, RICE SALT SENSITIVE3 (RSS3), regulates root cell elongation during adaptation to salinity. Loss of function of RSS3 only moderately inhibits cell elongation under normal conditions, but it provokes spontaneous root cell swelling, accompanied by severe root growth inhibition, under saline conditions. RSS3 is preferentially expressed in the root tip and forms a ternary complex with class-C basic helix-loop-helix (bHLH) transcription factors and JASMONATE ZIM-DOMAIN proteins, the latter of which are the key regulators of jasmonate (JA) signaling. The mutated protein arising from the rss3 allele fails to interact with bHLH factors, and the expression of a significant portion of JA-responsive genes is upregulated in rss3. These results, together with the known roles of JAs in root growth regulation, suggest that RSS3 modulates the expression of JA-responsive genes and plays a crucial role in a mechanism that sustains root cell elongation at appropriate rates under stressful conditions.
根系生长对环境信号和胁迫的可塑性是陆地植物的一个基本特性。然而，在胁迫条件下调节根系生长的分子基础还知之甚少。在这里，我们报告称，一个水稻核因子，RICE SALT SENSITIVE3（RSS3），在适应盐度时调节根细胞伸长。RSS3 功能丧失仅在正常条件下适度抑制细胞伸长，但在盐胁迫下会引发自发的根细胞肿胀，伴随严重的根生长抑制。RSS3 在根尖中优先表达，并与 class-C 碱性螺旋-环-螺旋（bHLH）转录因子和茉莉酸 ZIM 结构域蛋白形成三元复合物，后者是茉莉酸（JA）信号的关键调节剂。rss3 等位基因产生的突变蛋白不能与 bHLH 因子相互作用，并且 JA 响应基因的很大一部分表达在 rss3 中上调。这些结果，加上 JAs 在根生长调节中的已知作用，表明 RSS3 调节 JA 响应基因的表达，并在维持胁迫条件下根细胞以适当速率伸长的机制中发挥关键作用。
