Regulation of jasmonate biosynthesis by posttranslational modification of oxophytodienoate reductase (OPR) 3

植物对食草昆虫的防御反应是由茉莉酸介导的，茉莉酸在昆虫攻击或伤害后几分钟内开始积累。这些植物激素的快速形成是如何启动的，仍然是防御信号领域一个重要的开放性问题。茉莉酸盐的快速积累不能用基因表达的变化来解释，而是需要翻译后的调节机制。根据我们的工作假设，翻译后调控在12-氧植物二烯酸还原酶（OPR3）水平上起作用，OPR3是茉莉酸生物合成的中心酶。我们认为OPR3的活性取决于它的寡聚状态，这是由可逆磷酸化控制的。本研究旨在通过分析植物中OPR3的低聚状态，包括其响应环境和发育线索的动态变化，来证实这一假设。将确定OPR3磷酸化位点，并量化伤口诱导的磷酸化变化。我们进一步的目标是鉴定和表征负责OPR3磷酸化的蛋白激酶，并确定它在防御信号传导中的作用。这项工作将大大有助于更好地理解茉莉酸生物合成、植物防御信号、OPR3中的结构活性关系，以及植物中可逆蛋白磷酸化的相关性，特别是在防御反应的调节方面。

The induction of plant defense responses against insect herbivores is mediated by jasmonates which start to accumulate within minutes after insect attack or wounding. How the rapid formation of these phytohormones is initiated, remains an important open question in the defense signaling field. Rapid accumulation of jasmonates cannot be explained by changes in gene expression, but calls for post-translational mechanisms of regulation. According to our working hypothesis, post-translational regulation operates at the level of 12-oxophytodienoate reductase (OPR3), a central enzyme of jasmonate biosynthesis. We suggest that OPR3 activity depends on its oligomeric state which is controlled by reversible phosphorylation. The proposed research aims to substantiate this hypothesis by analyzing the oligomeric state of OPR3 in planta including its dynamic changes in response to environmental and developmental cues. OPR3 phosphorylation site(s) will be identified and wound-induced changes in phosphorylation quantified. We further aim to identify and characterize the protein kinase(s) responsible for OPR3 phosphorylation and determine it’s(their) role in defense signaling. This work will contribute substantially to a better understanding of jasmonate biosynthesis, plant defense signaling, structure activity relationships in OPR3, and the relevance of reversible protein phosphorylation in plants, particularly with respect to the regulation of defense responses.