Cold-resistant and cold-sensitive maize lines differ in the phosphorylation of the photosystem II subunit, CP29.

摘要

The effects of low temperature (3鳦) on the relative contributions of the reaction centre and the antenna activities to photosystem II (PSII) electron transport were estimated by chlorophyll fluorescence in cold-resistant and cold-sensitive maize lines 1873 and 1194, respectively. The inhibition of PSII photochemistry resulted from photodamage to the reaction centre and/or a reduced probability of excitation energy trapping by the reaction centre. Although cold treatment did not modify the proportion of the dimeric to monomeric PSII, it destabilized its main light-harvesting complex. Full protection of the reaction centre was achieved only in the presence of the phosphorylated PSII subunit, CP29. In a nonphosphorylating genotype the cold treatmentled to photoinhibitory damage. The phosphorylation of CP29 modified neither its binding to the PSII core nor its pigment content. Phosphorylated CP29 was isolated by flat-bed isoelectric focusing. Its spectral characteristics indicated a depletion of the chlorophyll spectral forms with the highest excitation transfer efficiency to the reaction centre. It is suggested that phosphorylated CP29 performs its regulatory function by an yet undescribed mechanism based on a shift of the equilibrium for the excitation energy toward the antenna.