Collaborative Research: Ecological Physiology of Plant Chloroplast Small Heat-Shock Proteins

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Heat-shock proteins (Hsps) are types of general stress proteins produced by virtually all organisms in response to most environmental and biological stresses, and are thought to protect cells from damage during stress or facilitate recovery. The importance of variation in the cellular quantity or biochemical efficiency of Hsps is unknown, particularly for plants and for the category of Hsps referred to as the low-molecular-weight or "small" Hsps. Progress in understanding Hsps has been hampered by the lack of appropriate biomolecular probes for specific Hsps and methods to experimentally manipulate and assess the effect of variation in Hsps. The PIs have developed molecular probes specific to the small Hsps in chloroplasts, the cell compartment where photosynthesis takes place in plants, as well as assays to assess Hsp effectiveness. Using these tools, they have shown that chloroplast small Hsps protect photosynthesis during heat and other environmental stresses, by protecting a key stress-sensitive step of photosynthesis (electron transport in Photosystem II). However, differences among plants in the ability of chloroplast small Hsp to protect photosynthesis during stress, such as predicted differences between heat-tolerant wild plants and heat-sensitive crops, have not been examined.In this series of studies, the PIs will examine chloroplast small Hsps in stress-sensitive vs. stress-tolerant wild plants to determine how they differ in the cellular quantity and biochemical efficiency of small Hsps and how this affects the protection of photosynthesis during heat stress. This would be the first such investigation for plant Hsps. They will explore molecular and biochemical variation in small Hsps across a range of species, they will examine correlations between small Hsp content and plant performance, and they will carry out experiments in vitro, using Hsps purified from a range of species, to determine how qualitative and quantitative variation in chloroplast small Hsps affects their protective function. These results will contribute both to understanding factors that affect stress-tolerance of plants in nature and to understanding factors that may be useful in agricultural research. Given the importance of chloroplast small Hsps in protecting photosynthesis during many stresses, the central role of photosynthesis in plants, and the high sensitivity of photosynthesis to environmental stress, the results should be especially useful for the bioengineering and breeding of more stress-tolerant crops.