Regulatory Mechanisms in the HPL Stress Signaling Network

植物已经进化出复杂的信号通路来协调对发育和环境信息的反应。氧脂素通路是一个关键的基于脂质的信号网络，它决定了植物适应各种刺激的能力。迄今为止，许多关于氧化脂素的研究都集中在涉及茉莉酸盐的分支途径上。平行的，应力诱导的氢过氧化物裂解酶（HPL）分支途径仍然缺乏表征。HPL酶催化脂肪酸氢过氧化物裂解成醛和氧酸。这些挥发性代谢物被认为在植物内部和植物之间以及植物/昆虫相互作用中发挥关键的信号作用。该项目将研究：(a) HPL基因在胁迫诱导下转录调控的信号转导机制，以及(b)衍生的HPL途径代谢物在介导植物内和植物间胁迫反应中的信号作用。初步实验证实，在野生型拟南芥中，HPL及其同源途径代谢产物的表达是受胁迫诱导的。为了开始识别这个信号网络中的调控成分，产生了一个HPL:：荧光素酶（LUC）转基因系。通过在基于成像的遗传筛选中使用这些植物，发现了组成性表达LUC的突变体，表明HPL启动子的组成性激活或抑制。为了表征醛在胁迫反应中的信号作用，鉴定了hpl敲除突变体，并在WT拟南芥中产生了过表达水稻hpl的转基因系，以及在突变背景下不能产生茉莉酸盐的转基因系。这些细胞系产生一系列的醛水平，从而提供了一个实验系统来确定内源醛水平和靶基因表达之间的联系。本提案的具体目标是确定负责应激诱导的HPL转录调控的分子成分，介导醛诱导的基因表达程序的转录调控网络，以及HPL途径代谢物在介导植物间应激反应中的作用。该项目将提供重要的见解，以控制一个复杂的和关键的信号网络的调控机制，这是植物对逆境反应的基础。该项目的更广泛影响包括培养本科生和研究生从事最先进的跨学科研究；发现调节具有重要商业意义的醛类生产的新成分，并为具有重要农艺学意义的作物开发生物技术应用工具；招收代表性不足的少数民族研究生；私营部门与学术界的合作；广泛传播我们的研究成果，包括论文、研讨会、会议报告和有关压力诱导信号通路的短期课程。

Plants have evolved complex signaling pathways to coordinate responses to developmental and environmental information. The oxylipin pathway is one pivotal lipid-based signaling network that determines the plant's ability to adapt to various stimuli. Much of the research on oxylipins to date has focused on the branch pathway involving jasmonates. The parallel, stress-inducible HYDROPEROXIDE LYASE (HPL) branch pathway remains poorly characterized. The HPL enzyme catalyzes the cleavage of fatty acid hydroperoxides into aldehydes and oxoacids. These volatile metabolites are postulated to play key signaling roles both within and between plants, as well as in plant/insect interactions. This project will investigate: (a) the signal transduction machinery responsible for stress-inducible transcriptional regulation of the HPL gene, and (b) the signaling role of the derived HPL-pathway metabolites in mediating intra- and inter-plant stress responses. Preliminary experiments have confirmed that, in wild type (WT) Arabidopsis, the expression of HPL and its cognate pathway metabolites are stress-induced. To begin to identify regulatory components in this signaling network, an HPL::luciferase(LUC)-transgenic line was generated. By using these plants in an imaging based genetic screen mutants were identified that express LUC constitutively, suggesting constitutive activation or derepression of the HPL promoter. To characterize the signaling role of the aldehydes in stress responses, hpl knockout mutants were identified, and transgenic lines that overexpress rice HPL in WT Arabidopsis were generated, as well as in a mutant background incapable of producing jasmonates. These lines produce a range of aldehyde levels, thus providing an experimental system to define the link between endogenous aldehyde levels and target-gene expression. The specific objectives of this proposal are to define the molecular components responsible for stress-inducible transcriptional regulation of HPL, the transcriptional regulatory networks that mediate the aldehyde-induced gene expression program and the role of HPL-pathway metabolites in mediating inter-plant stress-responses. This project should provide important insights into the regulatory mechanisms controlling a complex and crucial signaling network that underlies plant responses to stress. Broader impacts of the project include the training of undergraduate and graduate students in state-of-the-art interdisciplinary research; discovery of novel components regulating production of commercially important aldehydes, and generation of tools for biotechnological applications in agronomically important crops; recruitment of underrepresented minority graduate students; collaboration between the private and academic sectors; broad dissemination of our research results in papers, seminars, conference presentations, and short courses on stress-induced signaling pathways.