Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Laboratory of Molecular and Cellular Biology of Totipotency, Graduate School of Biostudies, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan.
ACS Chem Biol. 2021 Aug 20;16(8):1566-1575. doi: 10.1021/acschembio.1c00451. Epub 2021 Aug 11.
The phytohormone abscisic acid (ABA) plays an important role in plant stress response, mainly against desiccation. Hence, ABA receptor agonists may function as agents to enhance drought tolerance in crops. ABA exhibits diverse functions that impact plant development and are regulated by various ABA receptor subfamilies. Indeed, we previously reported that 3'-alkyl ABAs exhibit diverse receptor specificities and that 3'-butyl ABA induced a drought stress response without eliciting growth inhibitory effects in seedlings. Thus, to further investigate plant responses induced by 3'-butyl ABA, as well as the receptors that control the opposing stress and growth responses, we designed new 3'-alkyl ABA derivatives. In addition to the 3'-alkyl chain, a cyclopropyl group was attached to position 3 of ABA to occupy the C6 cleft in the ABA-binding pocket of the receptors, which served to increase the binding affinity and specificity to a certain receptor set. Additionally, the inhibitory activity of pyrabactin resistance 1 (PYR1) and PYR1-like (PYL1) proteins against type 2C protein phosphatase increased following incorporation of the 3-cyclopropyl group in all tested 3'-alkyl ABAs. Interestingly, 3'-butyl ABA induced the highest tolerance against drought stress, compared with 3-cyclopropyl derivatives. To investigate the molecular mechanism underlying the effects elicited by different chemical treatments, those of ABA derivatives on stomatal closure, growth, and gene expression were studied. Evaluation of the receptors activated by ABA derivatives and the plant responses revealed the induction of , , , and , mediated stomatal closure, and regulated transcription, consequently leading to drought tolerance in plants.
植物激素脱落酸 (ABA) 在植物应激反应中起着重要作用，主要是对抗干旱。因此，ABA 受体激动剂可能作为增强作物耐旱性的试剂。ABA 表现出多种影响植物发育的功能，并受各种 ABA 受体亚家族的调节。事实上，我们之前曾报道过 3'-烷基 ABA 表现出不同的受体特异性，并且 3'-丁基 ABA 在没有引起幼苗生长抑制作用的情况下诱导了干旱应激反应。因此，为了进一步研究 3'-丁基 ABA 诱导的植物反应，以及控制相反应激和生长反应的受体，我们设计了新的 3'-烷基 ABA 衍生物。除了 3'-烷基链外，还在 ABA 的 3 位连接了一个环丙基，占据了受体中 ABA 结合口袋的 C6 裂缝，这有助于提高对特定受体组的结合亲和力和特异性。此外，在所有测试的 3'-烷基 ABA 中加入 3-环丙基后，吡喃并抗药性 1 (PYR1) 和 PYR1 样 (PYL1) 蛋白对 2C 型蛋白磷酸酶的抑制活性增加。有趣的是，与 3-环丙基衍生物相比，3'-丁基 ABA 诱导了最高的耐旱性。为了研究不同化学处理引起的效应的分子机制，研究了 ABA 衍生物对气孔关闭、生长和基因表达的影响。对 ABA 衍生物激活的受体和植物反应的评估揭示了诱导 、 、 、 和 介导气孔关闭，并调节转录，从而导致植物耐旱性。
