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.
陸生植物根系生長的可塑性對于其應答外界環(huán)境信號和脅迫是一種基本的的特征。然而，我們對脅迫下根生長的調(diào)控的分子機制還不是很清楚。本文，我們報道了一個水稻細胞核因子RSS3，在適應鹽脅迫環(huán)境下，控制著水稻根細胞的伸長。RSS3功能喪失性突變在正常環(huán)境下僅能適度的抑制細胞的伸長。但在鹽脅迫下，它能促進根細胞的膨脹，并伴隨著嚴重的根生長抑制。RSS3主要在根尖部位表達，能通過與C類堿性bHLH類轉(zhuǎn)錄因子和JA信號轉(zhuǎn)導中的重要調(diào)控子JAZ蛋白形成三元復合物，rss3的等位形式的突變蛋白不能與bHLH因子互作，而在rss3突變背景下，JA應答基因出現(xiàn)顯著的上調(diào)。以上結(jié)果表明RSS3除在與熟知的JAs在共同調(diào)控根方面的作用之外，也能調(diào)控JA應答基因的表達，并在脅迫環(huán)境下維持根細胞以適宜速率伸長方面起到重要作用。