Functional Analysis of the High-Light-Inducible Proteins (HLIP) in Synechocystis PCC 6803

光合作用是地球上几乎所有生物食物中能量的最终来源。然而，当光合细胞吸收的光能超过光合能力时，细胞中产生活性氧，对蛋白质、脂质和光合色素造成氧化损伤。这些不利影响因其他环境压力（如低温、干旱）而扩大。在次优生长条件下，植物或藻类不能有效地利用光合作用产生的还原力。这降低了过度光吸收导致光损伤的光强度。因此，光合生物在所有其他胁迫条件下也必然面临光胁迫。 然而，尽管光胁迫对作物生产力的重要性，但植物或光合微生物对光胁迫反应的分子机制尚未阐明。该项目的目标是确定光合生物保护自己免受高强度光的分子机制。该研究的重点是分析模式生物集胞藻PCC 6803中一个由四种高光诱导蛋白（HLIP）组成的家族的功能。HLIPs在其一级序列中类似于高等植物的捕光叶绿素a/b结合蛋白。他们已被证明是必不可少的蓝藻生存暴露于强光。它也可能在高等植物中发挥关键作用。为了研究HLIPs和相关蛋白在强光下细胞存活中的功能，将进一步表征调节剂PfsR（光合作用，Fe稳态和应激反应调节剂），以了解其在保护免受高强度光的作用。将确定在强光下恢复四重hli缺失突变体的活力的五个抑制子中的至少一个中的第二位点突变。这些研究将揭示细胞存活的机制以及HLIP在强光下的功能。 此外，HLIP和光系统I三聚体相互作用的影响和色素结合基序在HLIP中的作用将通过定点诱变来确定。此外，一个新的高光诱导，类胡萝卜素结合蛋白复合物的类囊体膜的特点。总的来说，这项研究将提高对光合生物在强光条件下生存机制的理解，并最终提高为工程植物或藻类开发合理策略以获得更好的胁迫耐受性的能力。该研究允许学生和博士后研究员将遗传学，生物化学和生物物理学的方法整合到他们的教育和研究计划中，促进对农业和生物燃料生产非常重要的具有高度竞争力和新颖的研究计划。它将使受训者为独立的研究事业做好准备。此外，它还将提高阿肯色州的光合作用研究实力。该项目将使PI继续让代表性不足的少数民族学生参与研究，为他们在高等教育中的保留做出贡献。大约35%的UALR本科生（4000多名学生）来自代表性不足的群体，但由于实验室空间和活跃的教师研究计划短缺，很少有机会进行研究培训。此外，该项目还将通过国家或UALR赞助的涉及少数民族学生的方案，为本科生的培训提供更多资金。

Intellectual MeritLight is required for photosynthesis, which is the ultimate source of energy in food for almost all living things on earth. However, when the light energy absorbed by photosynthetic cells exceeds the photosynthetic capacities, reactive oxygen species are generated in the cells, causing oxidative damage to proteins, lipids, and photosynthetic pigments. These detrimental effects are amplified by other environmental stresses (e.g. low temperature, drought). Under suboptimal growth conditions plants or algae cannot efficiently use the reducing power generated by photosynthesis. This lowers the light intensity at which excess light absorption leads to photo-damage. Hence, photosynthetic organisms unavoidably face light stress as well during all other stress conditions. However, in spite of the importance of light stress in relation to crop productivity, the molecular mechanisms of light-stress responses have not yet been elucidated in plants or photosynthetic microbes. The goal of this project is to determine the molecular mechanisms by which photosynthetic organisms protect themselves from high intensity light. The research focuses on analysis of the functions of a family of four high light-inducible proteins (HLIP) in the model organism Synechocystis PCC 6803. HLIPs resemble the light-harvesting chlorophyll a/b-binding proteins of higher plants in their primary sequences. They have been proven to be essential for cyanobacteria to survive exposure to high light. It may also play a critical role in higher plants as well. To investigate the functions of HLIPs and associated-proteins in cell survival during exposure to high light, the regulator PfsR (photosynthesis, Fe homeostasis and stress-response regulator) will be further characterized in order to understand its roles in protection against high intensity light. The second-site mutation in at least one of the five suppressors that restore viability in high light to the quadruple hli deletion mutant will be pinpointed. These studies will reveal the mechanisms of cell survival and the functions of HLIPs in high light. In addition, the effects of HLIP and photosystem I trimer interaction and the role of the pigment-binding motifs in HLIPs will be defined by site-directed mutagenesis. Furthermore, a novel high light-inducible, carotenoid-binding protein complex in the thylakoid membrane will be characterized. Overall, the research will improve understanding of the mechanisms for survival of photosynthetic organisms under high light conditions and will eventually enhance the ability to develop rational strategies for engineering plants or algae for better stress tolerance.Broader ImpactThe research subject is of general interest to plant biologists. The research allows students and postdoctoral fellows to integrate approaches of genetics, biochemistry and biophysics in their educational and research programs, fostering highly competitive and novel research initiatives important to agriculture and biofuel production. It will prepare the trainees for independent research careers. In addition, it will improve the strength of photosynthesis research in Arkansas. The project will allow the PI to continue involving underrepresented minority students in research, contributing to their retention in higher education. About 35% UALR undergraduates (more than 4000 students) are from underrepresented groups, but few have opportunities for research training due to the shortage of laboratory space and active faculty research programs. Furthermore, this project will stimulate additional funding for the training of undergraduate students through State- or UALR-sponsored programs that involve minority students.