Poster: Late and Moved Abstracts

Abs # 1390: Localization and abundance of chloroplast protein synthesis elongation factor (EF-Tu) and heat stability of chloroplast stromal proteins in maize

Presenter:	Momcilovic, Ivana , imomcilo@usd.edu
Authors	Momcilovic, Ivana  (A)   Ristic, Zoran  (A)
Affiliations:	(A): The University of South Dakota

Previous studies have shown that chloroplasts from a line of maize with higher levels of EF-Tu, ZPBL 1304, display greater heat stability than chloroplasts from a line with lower levels of EF-Tu, ZPL 389. We hypothesize that the greater heat stability of chloroplasts from ZPBL 1304 line may partly be attributed to EF-Tu; the EF-Tu may be protecting chloroplasts from heat injury. In this study, we investigated (1) the subcellular distribution of EF-Tu and (2) the heat stability of chloroplast stromal proteins in ZPBL 1304 and ZPL 389. Immunogold labeling and transmission electron microscopy revealed that the chloroplast EF-Tu is localized in the stroma and that agranal chloroplasts have higher relative level of this protein than granal chloroplasts. Light scattering experiments with chloroplast stromal extracts showed that stromal proteins from maize with higher levels of EF-Tu, ZPBL 1304, display greater heat stability than chloroplast stromal proteins from maize with lower levels of EF-Tu, ZPL 389. The results strongly support the hypothesis that maize EF-Tu plays a role in the development of heat tolerance possibly by acting as a molecular chaperone and protecting chloroplast stromal proteins from thermal aggregation.