Biochemical and Genetic Dissection of SUB1A/SAB18-mediated Tolerance to Submergence and Drought

为了生存，植物和动物必须承受环境压力。两种常见的植物环境压力源是洪水和干旱。成功完成提出的目标将验证新基因和相关途径的功能，这些功能允许植物在长时间的洪水中生存，矛盾的是，也允许植物在干旱条件下生存。研究人员和他们的同事发现，虽然大多数类型的水稻在洪水期间完全淹没三天后死亡，但那些携带淹水耐受1 （SUB1）基因的水稻可以承受这种压力，并在严重的洪水事件中存活下来。该项目将探索SUB1基因及其相互作用的基因如何能够促进对洪水和干旱的耐受性。拟议中的实验也有望导致对植物生物学的重要新见解，并将其应用于世界上最重要的作物之一的农业生产力。首席研究员罗纳德是加州大学戴维斯分校世界粮食中心粮食和农业知识研究所的教务主任，她将在那里继续致力于让公众参与与植物遗传学和粮食生产科学技术有关的问题。从高中实习生到博士后研究员的学生将参与开展工作和外展活动。大多数水稻植株在完全淹水3天后死亡，而携带耐淹基因1 （SUB1）的水稻植株则具有耐淹性。Ronald实验室及其合作者证明，水稻SUB1基因座编码三种乙烯响应因子（ERF）转录调控因子SUB1A、SUB1B和SUB1C，并且SUB1A的过表达足以使不耐淹的水稻品种具有耐淹性。SUB1基因座也被证明能促进植物在干旱时期的存活。Ronald实验室进一步证明了GT因子OsGTgamma-2家族的一个未知成员，一种名为SAB18 （SUB1A结合蛋白18）的新型含SANT结构域蛋白，在酵母中与SUB1A结合。SAB18过表达增强了sub1a依赖性的耐淹性和显著的抗旱性。此外，SUB1/SAB18ox植株表现出叶片水分流失和脂质过氧化的减少，表明SAB18增强了氧化胁迫耐受性。Ronald实验室还分离出三种快中子（FN）辐照突变体，它们作为SUB1 （sst）介导的应激耐受性的抑制因子。研究人员假设，SAB18通过与SUB1A形成一种蛋白复合物，结合并激活SUB1A、SAB18和/或赋予胁迫耐受性的基因的启动子，从而积极调节SUB1A介导的胁迫耐受性。进一步假设sst位点编码的基因是这些活性所必需的。为了验证这些模型，研究人员提出：1)确定由SAB18调控的基因和途径。2)确定SAB18/ sub1a介导的胁迫耐受的作用机制。3)利用全基因组重测序方法鉴定3个sst突变体，并鉴定突变对应的基因。

To survive, plants and animals must tolerate environmental stress. Two common environmental stressors of plants are flooding and drought. Successful completion of the proposed objectives will validate the function of novel genes and associated pathways that that allow the plant to live through periods of prolonged flooding, and paradoxically, also allow plants to survive drought conditions. The researchers and their colleagues have discovered that, while most types of rice die after three days of complete submergence during flooding, those carrying the Submergence tolerance 1 (SUB1) gene can tolerate this stress, and live through severe flooding events. This project will explore how the SUB1 gene, and the genes that it interacts with, are able to promote tolerance to flooding and to drought. The proposed experiments are also expected to lead to important new insights into plant biology with applications to agricultural productivity in one of the world's most important crops. The lead researcher, Ronald, serves as the faculty director of the UC Davis World Food Center's Institute for Food and Agricultural Literacy, where she will continue her work to engage the public on issues related to plant genetics and the science and technology of food production. Students at levels from high school interns to postdoctoral fellows, will be involved in carrying out the work and in outreach activities.Whereas most rice plants die after three days of complete submergence, those carrying the Submergence tolerance 1 (SUB1) locus are tolerant. The Ronald laboratory and collaborators demonstrated that the rice SUB1 locus encodes three Ethylene Responsive Factor (ERF) transcriptional regulators, SUB1A, SUB1B, and SUB1C and that overexpression of the SUB1A is sufficient to confer submergence tolerance to intolerant rice varieties. The SUB1 locus has also been shown to promote plant survival during drought. The Ronald lab further demonstrated that an uncharacterized member of the OsGTgamma-2 family of GT factors, a novel SANT domain-containing protein called SAB18, (SUB1A BINDING PROTEIN 18), binds SUB1A in yeast. SAB18 overexpression confers SUB1A-dependent enhanced submergence tolerance and remarkably robust drought tolerance. Furthermore SUB1/SAB18ox plants display a reduction of leaf water loss and lipid peroxidation indicating that SAB18 enhances oxidative stress tolerance. The Ronald lab also isolated three fast neutron (FN)-irradiated mutants that serve as SUPPRESSORS OF STRESS TOLERANCE MEDIATED BY SUB1 (sst). The researchers hypothesize that SAB18 positively regulates SUB1A-mediated stress tolerance by forming a protein complex with SUB1A, which binds and activates the promoters of SUB1A, SAB18 and/or genes conferring stress tolerance. It is further hypothesized that the genes encoded by the sst locus are required for these activities. To test these models the researchers propose to: 1) Identify genes and pathways regulated by SAB18. 2) Determine the mechanism of action of SAB18/SUB1A-mediated stress tolerance. 3) Characterize three sst mutants and identify the genes corresponding to the mutations using a whole genome resequencing approach.