Abstract
Excess light exposure leads to inhibition of photosynthetic electron transport and photooxidative stress in plants. In this study we characterised photooxidative stress response of the knockout mutant of A. thaliana in signal recognition particle (cpSRP43) named chaos, which has permanently reduced photosystem II antenna. Chlorophyll fluorescence parameter and oxygen evolution data indicated that photosynthesis was more strongly inhibited by excess light (2,000 μmol/m2/s) illumination in chaos compared to WT. However, when returned to low light conditions chaos recovered faster from photoinhibition. ATP/ADP ratio was higher in chaos than in WT in low light-acclimated condition. When plants were subjected to photooxidative stress conditions (650 μmol/m2/s, 4 °C), chaos exhibited better photosynthetic performance and survival compared to that observed for WT. It is concluded that a lack of functional cpSRP43 protein leads to a higher energy conservation and to constitutive tolerance to photooxidative stresses.
