Poster: Temperature responses

Abs # 146: Examining the role of Rubisco activase regulation in cotton plant photosynthesis in response to temperature stress

Presenter:	DeRidder, Ben P., bderidder@wcrl.ars.usda.gov
Authors	DeRidder, Ben P. (A)   Salvucci, Michael E. (A)   Crafts-Brandner, Steven J. (A)
Affiliations:	(A): United States Department of Agriculture, Agricultural Research Service, Western Cotton Research Laboratory

Various components of photosynthesis are affected by environmental fluctuations in temperature. Even moderate deviations from average growing temperatures may result in considerable reduction in net photosynthesis. Measured rates of photosynthesis in cotton (Gossypium hirsutum), a warm-climate species, is inhibited by both high (> 30^ο C) and low (< 20^ο C) temperatures. A decrease in the activation state of Rubisco appears to be a primary limitation to net photosynthesis at elevated temperature in cotton because of impairment of Rubisco activase, the enzyme responsible for reactivating Rubisco. Consequently, activase ultimately limits net photosynthesis at elevated temperatures in cotton. The current study attempts to further characterize the effect of heat-stress on the expression and activity of cotton activase, and seeks to define the potential role of activase in limiting photosynthesis at chilling temperatures. Presently, we are examining the impact of both heat- and chilling-stress on RNA and protein expression of cotton activases, including a newly identified member of the gene family, GhRCAα2. We are examining the impact of temperature fluctuation on the stability of activase protein in vivo, by expressing activase in transgenic Arabidopsis plants that lack this enzyme. Together, these studies will facilitate our understanding of the potential links between activase regulation at the transcriptional, translational and post-translational levels and better define the role of activase in limiting photosynthesis at temperature extremes.