中国科学家发现水稻耐冷信号新途径

植物承受低温胁迫的能力是决定植物生长季节和地理分布的先决条件。例如，东北温暖气候持续时间短，只能种一季水稻，而海南地处热带，可以种双季和三季稻。

如果想提高水稻品种耐冷能力，需要明确它们对冷信号途径的调节机制。

中国科学院植物研究所（Institute of Botany of the Chinese Academy of Sciences）的种康（CHONG Kang）院士研究团队最近在《Developmental Cell》发表文章，报道了一个通过OsMAPK3-OsbHLH002-OsTPP1介导的水稻耐冷新通路。

OsbHLH002是水稻bHLH转录因子家族成员之一，与拟南芥的ICE1蛋白同源性最高，ICE1蛋白是参与拟南芥冷信号途径的核心成员，因此OsbHLH002也被称为OsICE1。

2009年研究团队曾发现过表达野生水稻基因OrbHLH2可增强拟南芥对渗透性胁迫的耐受能力。

根据团队最新发表的这篇文章，冷激活蛋白激酶OsMAPK3能磷酸化转录因子OsbHLH002/OsICE1，直接增强其转录活性。

此外，OsMAPK3能减弱OsbHLH002和E3泛素连接酶OsHOS1之间的相互作用，导致OsbHLH002泛素化降解水平下降。

提高OsbHLH002转录和蛋白质表达水平，有效地激活了OsTPP1表达，后者编码海藻糖-6-磷酸酶（trehalose-6-phosphatase），从而促进了海藻糖-6-磷酸（trehalose-6-phosphate）水解以及海藻糖含量提高，水稻耐冷性上升。

综上，这项研究勾勒出一个全新的信号转导途径：OsMAPK3-OsbHLH002-OsTPP1，该途径能将冷信号转化为促进耐渗透保护剂生产信号，从而调节水稻耐冷性。（来源：生物通 伍松）

OsMAPK3 Phosphorylates OsbHLH002/OsICE1 and Inhibits Its Ubiquitination to Activate OsTPP1 and Enhances Rice Chilling Tolerance

Abstract Improvement of chilling tolerance is a major target in rice breeding. The signaling pathways regulating chilling consist of complex networks, including key transcription factors and their targets. However, it remains largely unknown how transcription factors are activated by chilling stress. Here, we report that the transcription factor OsbHLH002/OsICE1 is phosphorylated by OsMAPK3 under chilling stress. The osbhlh002-1 knockout mutant and antisense transgenic plants showed chilling hypersensitivity, whereas OsbHLH002-overexpressing plants exhibited enhanced chilling tolerance. OsbHLH002 can directly target OsTPP1, which encodes a key enzyme for trehalose biosynthesis. OsMAPK3 interacts with OsbHLH002 to prevent its ubiquitination by the E3 ligase OsHOS1. Under chilling stress, active OsMAPK3 phosphorylates OsbHLH002, leading to accumulation of phospho-OsbHLH002, which promotes OsTPP1expression and increases trehalose content and resistance to chilling damage. Taken together, these results indicate that OsbHLH002 is phosphorylated by OsMAPK3, which enhances OsbHLH002 activation to its target OsTPP1 during chilling stress.

原文链接：http://www.cell.com/developmental-cell/pdf/S1534-5807(17)30951-6.pdf

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