Investigations on the Mechanism of Development of a Novel Form of Photosynthesis

智力优势：光合作用，收集太阳能和吸收大气中的二氧化碳（CO2），代表着生命的“引擎”。在环境胁迫（干旱、高温、盐碱地）下，大多数陆地植物对二氧化碳的获取受到限制，光合作用和植物生长都会受到限制。一些植物进化出了一种代谢泵（称为C4），它能主动积累二氧化碳，这赋予了植物优势，尤其是在极端环境下。在2001年发现在单个光合细胞中执行C4的物种之前，C4植物的模式是两种细胞类型合作功能的要求。相比之下，单细胞C4物种具有独特的碳获取形式，其光合细胞中有两种不同类型的叶绿体，一种支持捕获大气中的二氧化碳，另一种用于将其同化为有机物。本项目需要研究的问题是单细胞C4光合作用发育和功能所需的基因和蛋白质的鉴定和表征。这包括鉴定两种类型叶绿体蛋白质组成的差异，负责它们合成的核编码光合作用基因，以及叶绿体分化的遗传控制。该方法将包括使用分子和显微技术来分析和鉴定导致这种形式C4发展的基因表达产物。该项目有望深入了解光合作用的特殊机制，以及细胞生物学中生化分化的调节。该研究项目还将涉及与德国汉诺威大学的S. Offermann博士的国际合作，该合作由国际科学与工程办公室赞助。这项合作将为研究生提供国际学习经验，并将扩展美国实验室的专业知识。更广泛的影响：该研究有望为教育、光合作用和植物适应机制的未来研究提供新的见解。在解决日益增长的全球生物资源限制方面有潜在的应用。单细胞机制是一种很有吸引力的模式，可用于开发具有更高生产力的作物，例如水稻，特别是在环境胁迫下。

Intellectual Merit: Photosynthesis, which harvests solar energy and assimilates atmospheric carbon dioxide (CO2), represents the "engine" of life. Constraints on photosynthesis and plant growth can occur in most land plants where access to CO2 becomes limiting under environmental stress (drought, high temperature, saline soils). Some plants evolved a metabolic pump (called C4) which actively accumulates CO2, conferring an advantage, especially under extreme environments. Prior to the 2001 discovery of species which perform C4 in individual photosynthetic cells, the paradigm for C4 plants was a requirement for cooperative function of two cell types. In contrast, the single-cell C4 species, which have a unique form of carbon acquisition, contain photosynthetic cells with two types of chloroplasts in separate compartments, one supporting the capture of atmospheric CO2, the other functioning in its assimilation into organic matter. Problems to be investigated in this project are identification and characterization of genes and proteins required for the development and function of single-cell C4 photosynthesis. This involves identification of differences in protein composition of the two types of chloroplasts, the nuclear-encoded photosynthetic genes responsible for their synthesis, and the genetic control of chloroplast differentiation. The approach will include use of molecular and microscopic techniques to analyze and identify the products of gene expression leading to development of this form of C4. This project is expected to gain insights into an exceptional mechanism of photosynthesis, and into regulation of biochemical differentiation in cell biology. The research project will also involve an international collaboration with Dr. S. Offermann of Hannover University in Germany, which is sponsored by the International Office of Science and Engineering. This collaboration will provide an international learning experience for the graduate students and will extend the expertise of the US lab. Broader Impacts: The research is expected to contribute new insights that will impact education, future research on photosynthesis, and mechanisms of adaptations in plants. There are potential applications for solving growing global limitations on bio-resources. The single-cell mechanism is an attractive model for developing crops, e.g. rice, with improved productivity, especially under environmental stress.