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

为了生存，植物和动物必须忍受环境压力。植物的两个常见环境应激源是洪水和干旱。拟议目标的成功完成将验证新基因和相关途径的功能，这些新基因和相关途径使植物能够度过长期的洪涝灾害，而且矛盾的是，它还允许植物在干旱条件下生存。研究人员和他们的同事发现，尽管大多数类型的水稻在洪水期间被完全淹没三天后死亡，但那些携带耐淹基因1(SUB1)的水稻可以忍受这种压力，并能挺过严重的洪水事件。这个项目将探索SUB1基因及其相互作用的基因如何能够提高对洪水和干旱的耐受性。拟议中的实验还有望带来对植物生物学的重要新见解，将其应用于世界上最重要的作物之一的农业生产力。首席研究员罗纳德担任加州大学戴维斯分校世界粮食中心食品和农业扫盲研究所的教研室主任，在那里她将继续致力于让公众参与与植物遗传学和食品生产科学技术相关的问题。从高中实习生到博士后研究员的学生将参与到这项工作和外展活动中。大多数水稻植株在完全淹没三天后死亡，但那些携带耐淹1号(SUB1)基因的水稻植株是耐受的。Ronald实验室及其合作者证明，水稻SUB1基因座编码三种乙烯反应因子(ERF)转录调控因子，即SUB1A、SUB1B和SUB1C，并且SUB1A的过度表达足以赋予水稻品种耐淹性。SUB1基因座也被证明可以促进植物在干旱期间的存活。Ronald实验室进一步证明，GT因子OsGTGamma-2家族中的一个未知成员，一种新的包含SANT结构域的蛋白SAB18(SUB1A结合蛋白18)，与酵母中的SUB1A结合。SAB18的过表达增强了对SUB1A的依赖，增强了对淹水的耐受性，并显著增强了抗旱性。此外，SUB1/SAB18ox植株表现出叶片失水和脂质过氧化的减少，表明SAB18提高了氧化胁迫的耐受性。罗纳德实验室还分离出了三个快中子(FN)照射的突变体，它们作为SUB1(Sst)介导的应激耐受的抑制因子。研究人员假设，SAB18通过与SUB1A形成蛋白质复合体，结合并激活SUB1A、SAB18和/或与逆境耐受相关的基因的启动子，从而积极地调节SUB1A介导的应激耐受性。进一步假设，由sst基因座编码的基因是这些活动所必需的。为了测试这些模型，研究人员建议：1)确定受SAB18调控的基因和途径。2)确定SAB18/SuB1A介导的抗逆性的作用机制。3)利用全基因组重测序方法鉴定三个sst突变体，并确定与这些突变体相对应的基因。

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.