Does lutein play a key role in the protection of photosynthetic apparatus in arabidopsis under severe oxidative stress?

Many environmental stresses result in increased generation of reactive oxygen species (ros),such as superoxide (·o2 -),hydrogen peroxide (h2o2),and hydroxyl radical (·oh),in plant cells. a mild or moderate stress induces a significant increase in the generation of ·o2 - and h2o2 and a severe stress induces a significant increase in the generation of ·oh. the three ros: ·o2 -,h2o2 and ·oh were used to treat leaf discs of the wild type (wt),the npq1 mutant lacking zeaxanthin and the lut2 mutant lacking lutein in arabidopsis by chlorophyll fluorescence imaging to test our previous hypothesis that lutein might play an important photoprotective role under severe stress. during the ·o2 - and h2o2-treatment under light,fv/fm,psii,etr,qp and npq exhibited the sequence of sensitivity to ros in the leaves of the three phenotypes: npq1 > lut2 > wt. however,during the ·oh-treatment under light,these chlorophyll parameters exhibited another different sequence: lut2 > npq1 > wt. thus,it can be concluded that xanthophyll cycle plays a key role under mild and moderate stress but lutein plays a key role under severe stress. these results provided more experimental evidence to support our previous hypothesis.