PARENT SESSION
Poster Session 1: Photosynthesis and Water Relations
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Variation in the production, function, and gene sequence of small heat-shock proteins and adaptation to habitat.
Joshi, Puneet*,1, Noor Qureshi, Samina2, Hamilton, E. William3, Luthe, Dawn2, Heckathorn, Scott1, 1 Dept. of Earth, Ecological, & Environmental Sciences, Toledo, OH, USA2 Dept. of Biochemistry & Molecular Biology, Mississippi State, MS, USA3 Dept. of Biology, Lexington, VA, USA
ABSTRACT- Heat-shock proteins (HSPs), which help protect and repair cells from stress-related damage, are general stress proteins produced by all organisms in response to most environmental stresses. Little is known regarding the ecological importance of HSPs in plants, or of the "small" (low-molecular-weight) HSPs in general. Chloroplast small HSPs (csHSPs) protect photosynthesis during stress, and natural variation in the quantity of csHSP produced during heat stress is positively correlated with in vivo photosynthetic thermotolerance. However, variation in the functional efficiency of csHSP, such as between heat-tolerant and -sensitive genotypes, has not been examined. We investigated variation in csHSP function among and within species, (1) by determining the extent to which sHSPs protect photosynthesis using in vitro assays wherein we experimentally disrupted sHSP function, and (2) by determining differences in photosynthetic stress tolerance associated with unique species-specific characteristics of chloroplast sHSPs by adding purified sHSPs from one species to another and monitoring in vitro protection. We then sequenced the chloroplast sHSP genes to determine how genetic variation in csHSP related to variation in sHSP function and photosynthetic thermotolerance. Our results indicate that (1) thermotolerant species derive proportionally greater protection of photosynthesis from csHSP than sensitive species; (2) this increased protection results from both increased production of csHSP, as well as increased functional efficiency of csHSP; and (3) increases in functional efficiency of csHSP and thermotolerance are correlated with genetic variation in csHSP. These results indicate that natural variation in both quantity and quality of csHSPs contributes to variation in photosynthetic thermotolerance, and thus, that evolutionary adaptation to habitat thermal characteristics involved selection on both HSP quantity and quality.
Key words: stress proteins, photosynthesis, evolution, heat stress