Physiological and molecular mechanisms underlying senescence and programmed cell death

本研究的长期目标是进一步了解植物衰老和程序性细胞死亡的分子机制，以及控制从生长发育阶段向衰老过渡的因素。我们已经证明，由脂肪酸去酯化引起的膜脂相分离发生在衰老级联的早期，导致膜渗漏和离子和代谢物梯度的丧失，这对正常细胞功能至关重要。我们将分离和表征介导这些膜分子组织变化的衰老诱导基因，并确定它们的表达是如何被调节的。我们还发现了独特的细胞质脂质蛋白颗粒，这些颗粒随着衰老的进展而从膜表面消失。我们将确定这些颗粒是如何形成的，以及它们的形成是否为以下方面的基础：1)衰老过程中膜的受控拆除，以及2)膜碳和氮的捕获，以便从衰老组织转运到发育中的种子。我们还确定了真核翻译起始因子5A （eIF5A）的不同亚型调节程序性细胞死亡和植物生长。我们将阐明这种调控的分子机制，并确定eIF5A亚型表达的调节是否能提高农业重要性状，包括易腐农产品的保质期、对病原体和环境胁迫的耐受性以及种子产量。这些研究结果将提高我们对植物衰老和生长的认识，并可能导致重要农艺学技术的发展。

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.