[Effects of exogenous Ca2+ on D1 protein phosphorylation and PS II performances of wheat leaf chloroplasts under high temperature and illumination stress].

ABSTRACT

Aimed to understand the effects of exogenous Ca2+ on the D1 protein phosphorylation and PS II performances of wheat leaf chloroplasts under high temperature and illumination stress, wheat leaves at grain-filling stage were sprayed with 10 mmol x L(-1) of CaCl2 or water (as control), and then subjected to high temperature and illumination stress (35 degrees C and 1600 micromol x m(-2) x S(-1)) for various hours, with the changes in photosynthetic electron transport rate (ETR), net photosynthetic rate, chlorophyll fluorescence parameters, and relative amount of phosphorylated and nonphosphorylated D1 protein in thylakoid membranes determined. After spraying with Ca2+, the PS II reaction center under the stress was reversibly inactivated, the net degradation of D1 protein was effectively restrained, the D1 protein phosphorylation was maintained at a higher level, and the ETR of whole chain and PS II, the maximal photochemical efficiency of PS II (F(v)/F(m)), the actual photochemical efficiency of PS II (phi(PS II), the photochemical quenching coefficient (qp), and net photosynthetic rate (P(n)) were all higher, suggesting that exogenous Ca2+ could improve the PS II performances and mitigate its damage under high temperature and illumination stress via regulating the turnover of D1 protein in wheat leaf chloroplasts.