Recovery from low-temperature photoinhibition is related to dephosphorylation of phosphorylated CP29 rather than zeaxanthin epoxidation in rice leaves

Abstract

During recovery from chilling-induced photoinhibition in rice leaves, we compared the reactivation kinetics of PSII photochemical efficiency (Fv/Fm) with that of zeaxanthin (Z) epoxidation and the dephosphorylation of CP34 (i.e., the phosphorylated form of CP29). The latter two processes were kinetically similar to the slow increase in Fv/Fm measured in our control leaves. However, the rate of Z epoxidation was significantly retarded by an epoxidase inhibitor, 5 mM salicylaldoxime (SA), without any significant changes in the processes of PSII reactivation and CP34 dephosphorylation. When chilled leaves were incubated at 10°C in the dark, both reactivation and dephosphorylation were significantly blocked, but Z epoxidation was not. Finally, we observed that the kinetics of CP34 dephosphorylation matched very well with those of PSII recovery in two rice cultivars with different chilling sensitivities. These results suggest that PSII reactivation from low-temperature photoinhibition is more closely related to CP34 dephosphorylation than to Z epoxidation.