Vitamin C deficiency enhances the high light sensitivity of a xanthophyll cycle mutant of Arabidopsis thaliana

Abstract

The Arabidopsis thaliana npq1 mutant lacks violaxanthin de-epoxidase, an enzyme responsible for the conversion of violaxanthin to zeaxanthin in high light. Zeaxanthin is one of the requirements for nonphotochemical quenching, mechanisms that dissipate excess light energy harmlessly as heat. The npq1 mutant is more sensitive to photoinhibition and lipid peroxidation than the wild type when transferred from low light (LL) to high light (HL), but it is able to survive in HL. To investigate the role of antioxidant metabolism in acclimation of npq1 to HL, a vitamin C-deficient mutant, vtc2, was crossed to the npq1 mutant to produce the vtc2npq1 double mutant. Upon transfer from LL to HL, the vtc2npq1 double mutant showed obvious bleaching after only one day in HL. Bleaching occurred more slowly in the vtc2 mutant, and the npq1 mutant and wild type did not exhibit any obvious bleaching during the entire experiment (five days). The bleaching in vtc2npq1 and vtc2 was paralleled by an increase in lipid peroxidation and a drastic decrease in Fv/Fm, a fluorescence parameter used to estimate photoinhibition. All genotypes showed a progressive increase in alpha-tocopherol levels and xanthophyll cycle pool size. These results indicate that vitamin C is important for acclimation of wild-type and especially npq1 mutant plants to HL.