Physiological and molecular mechanisms underlying senescence and programmed cell death

这项研究的长期目标是加深对植物衰老和程序性细胞死亡的分子机制的理解，以及对从发育的生长阶段向衰老过渡的因素的理解。我们已经表明，由脂肪酸脱酯化引起的膜脂质相分离发生在衰老级联的早期，导致膜渗漏和正常细胞功能所必需的离子和代谢物梯度的损失。我们将分离和表征衰老诱导的基因，介导这些膜的分子组织的变化，并确定它们的表达是如何调节的。我们还确定了独特的胞质脂质蛋白颗粒，从膜表面的衰老过程中被清空。我们将确定这些颗粒是如何形成的，以及它们的形成是否是以下的基础：1）衰老期间膜的受控拆除，以及2）捕获膜碳和氮，以便从衰老组织转移到发育中的种子。我们还建立了真核生物翻译起始因子5A（eIF5A）的不同亚型调节程序性细胞死亡和植物生长。我们将阐明这种调节的分子机制，并确定是否调制eIF5A亚型的表达增强农业重要性的性状，包括易腐产品的保质期，对病原体和环境胁迫的耐受性，以及种子产量。这些研究的结果将增强我们对植物衰老和生长的理解，并可能导致农学上重要技术的发展。

The long-term objective of this research is to gain an increased understanding of the molecular mechanisms underlying senescence and programmed cell death in plants, and of the factors that govern transition from the growth phase of development to senescence. We have shown that membrane lipid phase separations induced by fatty acid de-esterification occur early in the senescence cascade, resulting in membrane leakiness and loss of ion and metabolite gradients essential for normal cell function. We will isolate and characterize senescence-induced genes that mediate these changes in the molecular organization of membranes, and determine how their expression is regulated. We have also identified unique cytosolic lipid-protein particles that are voided from membrane surfaces as senescence progresses. We will determine how these particles are formed, and whether their formation is the basis for: 1) controlled dismantling of membranes during senescence, and 2) the capture of membrane carbon and nitrogen for translocation out of senescing tissues to developing seeds. We have also established that distinct isoforms of eukaryotic translation initiation factor 5A (eIF5A) regulate programmed cell death and plant growth. We will elucidate the molecular mechanisms underlying this regulation, and determine whether modulation of the expression of eIF5A isoforms enhances traits of agricultural importance, including the shelf life of perishable produce, tolerance to pathogens and environmental stress, and seed yield. Results from these studies will enhance our understanding of plant senescence & growth, & may lead to the development of agronomically important technology.