Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2006
Publication Date: 2/1/2007
Citation: Deridder, B.P., Salvucci, M.E. 2007. Recovery of rubisco activase gene expression during heat stress involves post-transcriptional control. Plant Science, 172: 246-254. Interpretive Summary: Photosynthesis is the process by which plants convert light energy from the sun into chemical energy in the form of sugars. These energy stores are essential for the proper growth and development of plants. Exposure to heat stress inhibits photosynthesis, resulting in loss of plant growth and crop yield. Previous research in our group revealed that an enzyme called Rubisco activase is unable to support the proper functioning of photosynthesis during periods of heat stress, due to its sensitivity to elevated temperature. Since gene expression is a prerequisite for enzyme synthesis, it is important to understand how heat stress affects the production and accumulation of the mRNA blueprints that precede activase protein synthesis. In this manuscript, we describe the impact of heat stress on the expression of activase genes in cotton. Using quantitative methods we discovered that activase gene expression is first reduced by, and then acclimates to, heat stress. Our results provide new insights into the mechanisms that support acclimation and suggest that the effects of elevated temperature on activase gene expression may play an important role in maintaining photosynthesis during periods of heat stress. In the future, this information may be used to enhance or maintain the expression of activase genes in order to reduce inhibition of photosynthesis by heat stress and increase crop yield
Technical Abstract: Inhibition of photosynthesis by heat stress involves deactivation of Rubisco and is exacerbated by the low thermal stability of Rubisco’s chaperone, activase. Activase structure, activity and protein expression have been the focus of previous work examining the effect of heat stress on this enzyme. Relatively little is known about the response of activase gene expression to moderate heat stress or the extent to which transcriptional mechanisms control acclimation of photosynthesis to heat stress. In the current study, the effect of moderate heat stress on the diurnal expression of three activase genes in cotton (Gossypium hirsutum L.), including a newly-identified member of the gene family, was examined. All three activase genes displayed a diurnal pattern of expression under optimal growth conditions, as determined by real-time RT-PCR. Although steady-state mRNA levels were reduced in the short-term by heat stress, transcript levels appeared to recover by the next diurnal cycle. Nuclear run-on assays suggested mRNA stability, not synthesis, was responsible for the observed acclimatization. Identification of activase transcripts with alternative 3’-untranslated regions suggests a possible means for increasing transcript stability and hastening recovery of steady-state mRNA levels during heat stress. Together the results indicate activase gene expression is influenced by post-transcriptional mechanisms that may contribute to acclimation of photosynthesis during extended periods of heat stress.