Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: April 8, 2010
Publication Date: N/A
Interpretive Summary: In the process of photosynthesis, plants convert light into chemical energy. The energy produced by photosynthesis is then used to synthesize sugars and other foodstuffs. Heat stress inhibits photosynthesis, reducing the overall yield of the plant. Previous research from this research group identified an enzyme called Rubisco activase as the component of photosynthesis that is most sensitive to inhibition by heat. Rubisco activase is a regulatory enzyme that controls the activity of the major carbon dioxide-fixing enzyme in plants. In this manuscript, I review the literature and present potential strategies for improving the tolerance of photosynthesis to heat stress based on enhancing the stability of Rubisco activase. This information provides a future direction for research aimed at improving the efficiency of photosynthesis under heat stress.
Technical Abstract: This report discusses the possibility of increasing plant performance under moderate heat stress by improving the thermal stability of Rubisco activase. • The research is driven by the observation that photosynthesis is acutely sensitive to inhibition by moderate heat stress and that this inhibition can cause a significant reduction in grain yield. Data from several studies show that recent increases in global surface temperatures have already had a negative impact on crop yield and more severe reductions are predicted under even the most conservative warming scenario. • Inhibition of net photosynthesis by moderate heat stress correlates with a decrease in the activation state of Rubisco. At elevated temperatures, processes that inactivate Rubisco (i.e., catalytic misfire and decarbamylation) accelerate while the rate of reactivation of Rubisco by the chaperone, Rubisco activase, decreases. • Inhibition of Rubisco activase activity occurs at elevated temperatures and is a consequence of 1) the inherent thermal instability of the activase protein, 2) heat-induced changes in the chloroplast environment that negatively impact the activity and/or thermal stability Rubisco activase, or 3) a combination of the two. • Natural and engineered variations in Rubisco activase thermotolerance provide evidence that improvements in the thermal stability of Rubisco activase can lead to better photosynthetic performance under moderate heat stress. • Gaps still exist in our understanding of the role of Rubisco activase in the inhibition of photosynthesis by moderate heat stress, including questions about the mechanism for deactivation of Rubisco (catalytic misfire or decarbamylation) and the mechanistic basis for thermal inactivation of Rubisco activase. • Strategies for improving photosynthetic performance under moderate heat stress in crop plants include 1) increasing the thermotolerance of activase, 2) modifying Rubisco to reduce catalytic misfire, and 3) stabilizing activase during episodes of heat stress.