Effect of cold temperature on regulation of state transitions in Arabidopsis thaliana

Low temperature is one of the most important abiotic factors limiting growth, development and distribution of plants. The effect of cold temperature on phosphorylation and migration of LHCII has been studied by 77K fluorescence emission spectroscopy and immuno-blotting in Arabidopsis thaliana. It has been reported that the mechanism of state transitions has been well operated at optimum growth temperatures. In this study, exposure of leaves to cold conditions (10 °C for 180 min) along with low light treatment (for 3h) did not show any increase in F726 which corresponds to fluorescence from PSI supercomplex, whereas low light at optimal temperature (26±2 °C) could enhanced F726. Therefore these results conclude that low light at cold condition did not enhance PSI absorption cross-section. We have also observed low levels of LHCII phosphorylation in cold exposed leaves in dark or low light. Though LHCII phosphorylation was detectable, the lateral movement of phosphorylated LHCII is reduced due to high granal stacking in cold treated leaves either in light or dark. Apart from these results, it is suggested that increased OJ phase and decreased JI and IP phases of Chl a fluorescence transients were due to reduced electron transport processes in cold treated samples.