Molecular mechanisms of stress resistance of photosynthetic apparatus

The mechanisms of action of environmental stress-inducing factors on plant photosynthetic apparatus (PA) are considered. The basic targets of stress produced by heat, cold, salt, osmotic imbalance, and light of high intensity are analyzed. It has been suggested that the stress factors have an influence first of all on the composition of thylakoid membranes and inhibit photosynthetic processes. However, recent studies demonstrated that strong light induces the photodamage to photosystem II (PSII) due to direct action of light on the oxygen-evolving complex, whereas accumulation of reactive oxygen species during the stress leads to inhibition of the recovery of the PSII by suppressing the synthesis of proteins in photosynthesis de novo. Such stressful environments as moderately high and low temperatures and salt suppress the repair of photodamaged PSII by inhibiting the synthesis of photosynthetic proteins de novo as well. On the other hand, the synthesis of protective lowmolecular compounds and stress proteins is stimulated. The main mechanisms of the PA acclimation and its protection from the damaging and inhibiting action of the environmental stress factors under light of different intensities are considered. Special attention is paid to investigations using cell cultures and mutants.