ABA Signaling Networks Controlling the Transition from Embryogenesis to Seedling Growth

健康的富含营养的种子的生产是由内部和环境信号的信息综合控制的，这些种子将发芽推迟到最适合生存的田间条件。种子成熟和萌发的主要内部调节因子之一是激素脱落酸（ABA）。遗传学研究已经确定了正常种子成熟和ABA敏感性萌发和幼苗生长所需的基因。这些基因中的许多编码转录因子，即与DNA结合并调节许多其他基因表达的蛋白质。其中两个因子，ABI4和ABI5，似乎各自调节不到10%的ABA调节基因，但当过量产生时，它们会对ABA和其他应激产生超敏反应，这表明它们调节的相对较小的一组基因是对这些信号反应的核心组成部分。比较缺乏或过量产生这些因子的品系中aba诱导的基因，发现了16个可能由ABI4或ABI5直接调控的潜在调控位点，此外还有许多被认为介导胁迫耐受的基因和大量功能未知的基因。本提案中概述的实验将使用遗传和分子研究来确定这些新发现的调节因子中哪些对种子成熟和特定胁迫反应重要。初步结果提出的一个有趣的可能性是，通过这些ABI位点的ABA信号可能通过增加适当受体的表达来增强对其他信号的反应。这些研究更广泛的影响包括培养博士后、研究生和本科生。最后，这些结果可能导致操纵种子营养、发芽或储存质量的策略，以防止数百万美元的作物损失。

Production of healthy nutrient-rich seeds that delay their germination until field conditions are optimal for survival is controlled by integration of information from internal and environmental signals. One of the major internal regulators of both seed maturation and germination is the hormone abscisic acid (ABA). Genetic studies have identified genes that are required for normal seed maturation and ABA sensitivity of germination and seedling growth. Many of these genes encode transcription factors, i.e. proteins that bind to DNA and regulate expression of many other genes. Two of these factors, ABI4 and ABI5, each appear to regulate less than 10% of all ABA-regulated genes but confer hypersensitivity to ABA and other stresses when overproduced, suggesting that the relatively small group of genes they regulate are a core component of response to these signals. Comparison of ABA-induced genes in lines that either lack or overproduce these factors identified 16 potential regulatory loci that appear to be directly regulated by ABI4 or ABI5, in addition to many genes thought to mediate stress tolerance and a large number of genes of unknown function. The experiments outlined in this proposal will use genetic and molecular studies to determine which of these newly identified regulators are important for seed maturation and specific stress responses. One intriguing possibility suggested by the preliminary results is that ABA signaling via these ABI loci may enhance responses to other signals by increasing expression of appropriate receptors. Broader impacts of these studies include training of postdocs, and graduate and undergraduate students. Finally, these results may lead to strategies for manipulation of seed nutritional, germination or storage qualities to prevent millions of dollars in crop losses.