BLOTING TRANSITION SPECIFIC GENETIC & BIOCHEMICAL EVENTS IN ARABIDOPSIS THALIANA

这项建议的目的是扩展我们目前的研究表明，随着拟南芥植物经历从营养状态到生殖状态的根本发育转变，叶片组织中的ROS代谢发生了显着的变化。这一转变在本提案中被称为抽苔转变，包括将主茎顶端分生组织从一个产生叶子的分生组织转变为形成一个花分生组织的分生组织，该分生组织产生一个具有顶生花的长抽穗。我们已经证明抽苔转变与叶片组织中测得的抗坏血酸过氧化物酶(APX)活性的下降和伴随的脂质过氧化的增加有关。APX的下降和随后的过氧化被认为是为了提供细胞内信号，启动导致衰老的有序基因表达级联。在这项建议中，描述了一些实验，这些实验将测试抽苔转换特有的叶APX和脂氧合酶活性变化的特定机制。此外，还建议利用拟南芥系统的分子遗传优势，通过分离抽苔过渡诱导基因和筛选晚衰突变表型来研究从抽苔到衰老的遗传级联反应。提出了以下具体目标：1)在转录和转录后水平上分析叶片抗坏血酸过氧化物酶的特异下调；2)确定APX下降后脂氧合酶活性的诱导方法；3)分离、测序和鉴定差异显示法分离的在抽蕾过渡后叶片组织中表达水平立即变化的cDNA克隆或基因；以及4)筛选乙烯不敏感拟南芥突变体etr1-1的突变群体，寻找对黑暗诱导的衰老反应延迟的突变体。我们的长期目标是确定早在花过渡时期就诱导衰老的基因表达程序的总体方案。我们的观察到，花的启动改变了叶片组织中的ROS代谢，这为研究植物两个不同器官之间的通讯提供了机会。我们期望，对这些早期事件的研究将有助于阐明初始信号和信号信号，以及被称为衰老的生命结束基因表达程序的信号机制反应。

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.