Stress-induced degradation of D1 protein and its photoprotection by DCPIP in isolated thylakoid membranes of barley leaf

Effects of various stress treatments such as NaCl, hydrogen peroxide, hydroxyl free radical, and high irradiance (HI, 1 000 μmol m⁻² s⁻¹) on the photosystem (PS) 2 mediated electron transport rate and the degradation of D1 protein in the thylakoid membranes of barley were studied. The applied stresses caused significant reduction in the PS 2-mediated electron transport and a degradation of D1 protein that was highest during the HI-treatment. Presence of 2,6-dichlorophenol indophenol (DCPIP), which is an artificial electron acceptor from water, significantly minimizes the HI-induced deleterious effect on the PS 2-mediated electron transport rate, disarrangement of PS machinery, and degradation of the D1 protein. HI in the absence of an acceptor resulted in production of reactive oxygen species due to electron transfer to oxygen.