BLOTING TRANSITION SPECIFIC GENETIC & BIOCHEMICAL EVENTS IN ARABIDOPSIS THALIANA

这个建议的目标是扩大我们目前的研究表明，在活性氧（ROS）代谢的显着变化发生在叶组织拟南芥植物经历了从营养状态到生殖状态的根本发展转变。这种转变，在本提案中称为抽薹转变，涉及主茎顶端分生组织从产生叶子的分生组织转变为形成花分生组织的分生组织，该分生组织产生具有顶生花的长抽薹。我们已经证明，抽薹过渡与测得的抗坏血酸过氧化物酶（APX）活性的下降，并伴随着在叶组织中的脂质过氧化作用的增加。假设APX下降和随后的过氧化作用提供了细胞内信号，启动了导致衰老的基因表达的有序级联反应。 在这个建议中，实验描述，将测试特定的机制，抽薹过渡叶APX和脂氧合酶活性的具体变化。此外，实验拟利用拟南芥系统的分子遗传学优势，通过分离抽薹过渡诱导基因和筛选延迟衰老突变体表型来研究从抽薹到衰老的遗传级联。提出了以下具体目标：1）在转录和转录后水平分析叶片抗坏血酸过氧化物酶的抽薹转换特异性下调; 2）确定APX下降后诱导脂氧合酶活性的方式; 3）分离、测序和表征通过差异显示分离的cDNA克隆或基因，其表达水平在抽薹转换后立即在叶组织中发生变化;和4）筛选乙烯不敏感的拟南芥突变体etr 1 -1的诱变群体，以获得表现出对黑暗诱导的衰老的延迟跟随的突变体。我们的长期目标是确定衰老诱导的基因表达程序早在花转变的整体方案。我们的观察，花的启动改变ROS代谢在叶组织中提供了一个机会，调查在植物中的两个不同的器官之间的通信。我们期望对这些早期事件的研究将能够阐明生命终结基因表达程序（称为衰老）的初始信号、信号传导信号和信号传导机制。

The goal of this proposal is to expand on our current studies showing that significant changes in reactive oxygen species (ROS) metabolism occur in leaf tissue as Arabidopsis plants undergo the fundamental developmental transition from a vegetative state to a reproductive state. This transition, referred to in this proposal as the bolting transition, involves a conversion of the principal shoot apical meristem from one giving rise to leave to one forming a floral meristem which produces a long bolt with terminal flowers. We have demonstrated that the bolting transition is associated with a decline in measured ascorbate peroxidase (APX) activity and with a concomitant increase in lipid peroxidation in leaf tissue. The APX decline and subsequent peroxidation are hypothesized to provide intracellular signals initiating the ordered cascade of gene expressing leading to senescence. In this proposal, experiments are described that will test particular mechanisms of the bolting transition-specific alterations in leaf APX and lipoxygenase activities. In addition, experiments are proposed to exploit the molecular genetic advantages of the Arabidopsis system to investigate the genetic cascades from bolting to senescence by isolating bolting transition-induced genes and screening for late senescing mutant phenotypes. The following specific aims are proposed: 1) Analyze the bolting transition specific down-regulation of leaf ascorbate peroxidase at the transcriptional and post-transcriptional levels; 2) Determine the means of induction of lipoxygenase activity following APX decline; 3) Isolate, sequence, and characterize cDNA clones or genes isolated by differential display whose level of expression changes in leaf tissue immediately following the bolting transition; and 4) Screen mutagenized populations of the ethylene-insensitive Arabidopsis mutant etr1-1 for mutants exhibiting delayed following in response to darkness-induced senescence. Our long term objective is to determine the overall scheme of senescence induction in gene expression program induced as early as the floral transition. Our observation that floral initiation alters ROS metabolism in leaf tissue provides an opportunity to investigate communication between two distinct organs in the plant. We expect that the investigation of these early events will allow the elucidating of the initial signals and the signaling signals and the signaling mechanism response for the life-ending gene expression program known as senescence.