NSF Postdoctoral Fellowship in Biology FY 2019: Improving C4 Crop Tolerance for Heat Stress by Engineering Thermostable Rubisco Activase

这一行动为NSF国家植物基因组计划2019财年生物学博士后研究奖学金提供了资金。该奖学金支持在东道主实验室为该研究员制定的研究和培训计划，该研究员还提出了扩大生物学参与度的计划。萨拉·斯坦布鲁克的这项研究和培训计划的标题是“通过工程耐热Rubisco激活酶提高C4作物对高温胁迫的耐受性”。该奖学金的主办机构是唐纳德·丹福斯植物科学中心(DDPSC)，赞助科学家是汝章博士。全球人口增长，加上向依赖生物燃料的过渡，到2050年，玉米和其他粮食作物的产量将翻一番。然而，预计2050年气温上升3.5摄氏度将使全球玉米产量减少23%。即使是现在，美国在1980年、1988年和2012年经历的热浪也可能摧毁农业生产力，估计损失分别为550亿美元、710亿美元和310亿美元。解决这一迫在眉睫的粮食安全危机的方法之一是通过关注与光合作用有关的最温度敏感的酶Rubisco激活酶(RCA)来提高作物抵御高温胁迫的耐热性。该项目将利用不同植物中RCA的自然变异来寻找或创造一种RCA酶变体，以提高玉米抵御高温的能力。更广泛的影响包括教授非专业的本科生物课以提高科学素养，以及通过DDPSC.C3、C4和CAM的突变谷子推广计划指导来自贫困或少数族裔背景的高中生。C3、C4和CAM是植物用来固定碳的三种不同的光合作用过程。在热应激过程中，限制碳固定的主要因素之一是碳固定酶Rubisco的激活状态。Rubisco必须被其催化伴侣Rubisco激活酶(RCA)激活。据估计，如果能够找到或创造出耐热的RCA，玉米的净光合作用速率在40摄氏度时可以翻一番。本研究将致力于从C4作物玉米和高粱以及与之密切相关的模式草狗尾草中分离和鉴定RCA变异酶。来自这些植物的RCA分离物将通过体外碳同化分析来表征，并与从完整植物中获得的叶绿素荧光和气体交换测量相关联。来自这些植物以及来自不同环境的C3、C4和CAM植物的热适应分离物将进行类似的检测，以确定RCA耐热性的自然变异范围。此外，蛋白质工程技术将用于提高RCA的热稳定性。将把具有改进性质的变异体引入S绿色植物中，以验证工程耐热酶提高了转基因植物的光合作用的耐热性。一旦得到验证，这种基因工程的耐热RCA将被引入玉米。该项目产生的所有表型和生化数据，包括来自不同气候的植物的数据，都将被添加到一个公众可访问的数据库中维护的现有遗传信息中，并通过同行评议的出版物和会议发言进一步传播。关键词：耐热性、固碳、玉米、C4光合作用、Rubisco活性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This action funds an NSF National Plant Genome Initiative Postdoctoral Research Fellowship in Biology for FY 2019. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Sarah Stainbrook is "Improving C4 Crop Tolerance for Heat Stress by Engineering Thermostable Rubisco Activase". The host institution for the fellowship is the Donald Danforth Plant Science Center (DDPSC) and the sponsoring scientist is Dr. Ru Zhang.Global population growth, coupled with a transition to dependence on biofuels, will require a doubling of production of maize and other grain crops by 2050. However, the projected 3.5 degrees Celsius temperature increase in 2050 will reduce global maize production by 23%. Even now, heat waves such as those experienced by the U.S. in 1980, 1988 and 2012 could devastate agricultural productivity, with losses estimated at 55, 71, and 31 billion dollars, respectively. One solution to this impending food security crisis is by improving the thermotolerance of crops to withstand heat stress by focusing on Rubisco activase (Rca), the most thermosensitive enzyme involved in photosynthesis. This project will leverage naturally occurring variation in Rca in different plants to find or create a Rca enzyme variant that can improve the ability of maize to withstand high temperatures. Broader impacts include teaching a non-majors undergraduate biology class to improve science literacy and mentoring high school students from underprivileged or minority backgrounds through the Mutant Millets outreach program at the DDPSC.C3, C4, and CAM are three different photosynthetic processes that plants use to fix carbon. One of the primary factors limiting carbon fixation during heat stress is the activation state of the carbon fixation enzyme Rubisco. Rubisco must be activated by its catalytic chaperone, Rubisco activase (Rca). It is estimated that the net photosynthesis rate of maize could be doubled at 40 degrees Celsius if a thermostable Rca could be found or created. This research will focus on identifying and isolating variant Rca enzymes from C4 crops maize and sorghum, as well as the closely related model grass, Setaria viridis. Rca isolates from these plants will be characterized by in vitro carbon assimilation assays and correlated to chlorophyll fluorescence and gas exchange measurements taken from intact plants. Heat-adapted isolates from these plants, as well as from C3, C4 and CAM plants from a variety of environments, will be similarly assayed to determine the range of naturally occurring variation in Rca thermotolerance. Additionally, protein engineering techniques will be used to improve Rca thermostability. Variants with improved properties will be introduced into S viridis to verify that the engineered thermostable enzyme improves thermotolerance of photosynthesis in the transgenic plant. Once verified, the engineered thermostable Rca will be introduced into maize. All phenotypic and biochemical data generated in this project, including from plants from diverse climates, will be added to existing genetic information maintained in a publicly accessible database and further disseminated through peer-reviewed publications and conference presentations. Keywords: thermotolerance, carbon fixation, maize, C4 photosynthesis, Rubisco activase.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.