What can enzymes of C4 photosynthesis do for C3 plants under stress?

Phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), and pyruvate, phosphate dikinase (PPDK) participate in the process of concentrating CO2 in C4 photosynthesis. Non-photosynthetic counterparts of these enzymes, which are present in all plants, play important roles in the maintenance of pH and replenishment of Krebs cycle intermediates, thereby contributing to the biosynthesis of amino acids and other compounds and providing NADPH for biosynthesis and the antioxidant system. Enhanced activities of PEPC and/or NADP-ME and/or PPDK were found in plants under various types of abiotic stress, such as drought, high salt concentration, ozone, the absence of phosphate and iron or the presence of heavy metals in the soil. Moreover, the activities of all of these enzymes were enhanced in plants under biotic stress caused by viral infection. The functions of PEPC, NADP-ME and PPDK appear to be more important for plants under stress than under optimal growth conditions.

Research highlights▶ Enzymes of C4 photosynthesis have various functions in C3 plants. ▶ PEPC, NADP-ME and PPDK are also involved in plant defence responses. ▶ Replenishment of Krebs cycle intermediates and supply of NADPH are important. ▶ These enzymes participate in protection against oxidative stress damage.