PARENT SESSION
Posters P3B Photosynthetic acclimation: Ecophysiology, diverse environments. Abstracts (479-522)

Compatible solutes curtail oxygenase activity of Rubisco as a strategy for stress adaptation. P. Pardha Saradhi^*,1, P. Sivakumar¹, P. Sharmila¹, ¹ Department of Environmental Biology, University of Delhi, North Campus, Delhi, Delhi, India

ABSTRACT- In nature, synthesis and accumulation of at least one type of compatible solute in plants under stress is ubiquitous (or universal phenomenon). Compatible solutes have been widely regarded to play an important role in protection of enzymes. Rubisco (EC.4.1.1.39) is one amongst the vital enzymes required for the existence of all autotrophic plants. Rubisco is a bifunctional enzyme with the capacity to competitively use CO₂ or O₂ and plants exposed to stress show enhanced oxygenation at the cost of carboxylation. Oxygenase activity of Rubisco has been reported to curtail overall crop productivity as it basically results in release of CO₂ instead of its fixation. Therefore, serious efforts are being made to look for a means to over come this problem. Although, various molecular approaches are being applied to tackle this problem so far no success has been achieved. In this report we are presenting the fascinating results obtained by us in significantly curtailing the oxygenase activity of Rubisco with compatible solutes. All the compatible solutes (viz. glycerol, glycinebetaine, inositol, mannitol, proline, sucrose and trehalose) have potential to significantly curtail the oxygenase activity of Rubisco even at concentrations as low as 50 mM. This unique and universal role of compatible solutes can be exploited for manipulation of Rubisco activity. Further, glycinebetaine brought about a significant enhancement in carboxylase activity while significantly curtailing oxygenase activity under salt stress. Therefore, here our unique observations illustrate that any efforts made in enhancing the production of glycinebetaine in chloroplasts can significantly enhance crop productivity by fine tuning Rubisco activity (i.e. by enhancing carboxylation and lowering oxygenation).

KEY WORDS: Oxygenase, Abiotic stress, Rubisco, Compatible solutes