National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China.
University of Chinese Academy of Sciences, Beijing, People's Republic of China.
J Exp Bot. 2018 Jan 23;69(3):579-588. doi: 10.1093/jxb/erx419.
Proline plays a crucial role in the drought stress response in plants. However, there are still gaps in our knowledge about the molecular mechanisms that regulate proline metabolism under drought stress. Here, we report that the histone methylase encoded by CAU1, which is genetically upstream of P5CS1 (encoding the proline biosynthetic enzyme Δ1-pyrroline-5-carboxylate synthetase 1), plays a crucial role in proline-mediated drought tolerance. We determined that the transcript level of CAU1 decreased while that of ANAC055 (encoding a transcription factor) increased in wild-type Arabidopsis under drought stress. Further analyses showed that CAU1 bound to the promoter of ANAC055 and suppressed its expression via H4R3sme2-type histone methylation in the promoter region. Thus, under drought stress, a decreased level of CAU1 led to an increased transcript level of ANAC055, which induced the expression of P5CS1 and increased proline level independently of CAS. Drought tolerance and the level of proline were found to be decreased in the cau1 anac055 double-mutant, while proline supplementation restored drought sensitivity in the anac055 mutant. Our results reveal the details of a novel pathway leading to drought tolerance mediated by CAU1.
脯氨酸在植物的干旱胁迫响应中起着至关重要的作用。然而，我们对于调节脯氨酸代谢的分子机制的认识仍然存在空白。在这里，我们报告 CAU1 编码的组蛋白甲基转移酶，其在遗传上位于 P5CS1（编码脯氨酸生物合成酶 Δ1-吡咯啉-5-羧酸合成酶 1）的上游，在脯氨酸介导的耐旱性中起着关键作用。我们确定，在干旱胁迫下，野生型拟南芥中 CAU1 的转录水平下降，而 ANAC055（编码转录因子）的转录水平升高。进一步的分析表明，CAU1 结合到 ANAC055 的启动子上，并通过 H4R3sme2 型组蛋白甲基化在启动子区域抑制其表达。因此，在干旱胁迫下，CAU1 水平的降低导致 ANAC055 的转录水平升高，这独立于 CAS 诱导 P5CS1 的表达并增加脯氨酸水平。我们发现，cau1 anac055 双突变体的耐旱性和脯氨酸水平降低，而脯氨酸补充恢复了 anac055 突变体的干旱敏感性。我们的结果揭示了 CAU1 介导的耐旱性的新途径的详细信息。
