Water-Deficit Response Is Not Affected by Glutathione Deficiency in <i>Arabidopsis thaliana pad</i>2-1 Plants

Abstract

Changes in glutathione and ascorbate content, hydrogen peroxide and abscisic acid were studied in developing leaves in wild-type (Col-0) and glutathione-deficient mutant pad 2-1 lines of Arabidopsis thaliana over a time period of 9 days of drought followed by re-watering. Glutathione deficient mutant ( pad 2-1) presents mechanisms of acclimation to water stress through the reduction of plant biomass and increase in endogenous concentrations of ascorbate and glutathione. These acclimation responses to stress appeared along with the first symptoms of stress and we suggest here that they are regulated by ABA and H 2 O 2 . Normally, wild type plants under conditions of stress require an initial response phase in which a decrease in antioxidants is observed before reaching acclimation through the increase in levels of antioxidants. pad 2-1 is more sensitive to stress and reacts to it ; however, it did not suffer more oxidative stress than Col-0 plants, even though pad 2-1 had higher levels of endogenous H 2 O 2 relative to wild-type. In both water stressed Col-0 and pad 2-1 plants increases in ABA were observed , however, more sharply in wild-type stressed plants. Low levels of glutathione together with high levels of H 2 O 2 may regulate endogenous ABA concentrations and could be related to the slow growth rates which were observed during the experiment. The results highlighted the double function of glutathione as an antioxidant and signal molecule and also, the different response patterns of wild-type and pad 2-1 when faced with drought stress. The results bring new insights to the responses of pad 2-1 under conditions of water stress.