RNA interference-mediated suppression of xanthine dehydrogenase reveals the role of purine metabolism in drought tolerance in Arabidopsis

We have previously demonstrated that RNA interference-mediated suppression of xanthine dehydrogenase (XDH), the rate-limiting enzyme in purine degradation, causes defects in the normal growth and development of Arabidopsis thaliana. Here, we investigated a possible role for XDH in drought tolerance, since this enzyme is also implicated in plant stress responses and acclimatization. When XDH-suppressed lines were subjected to drought stress, plant growth was markedly reduced in conjunction with significantly enhanced cell death and H₂O₂ accumulation. This drought-hypersensitive phenotype was reversed by pretreatment with exogenous uric acid, the catalytic product of XDH. These results suggest that fully functional purine metabolism plays a role in the Arabidopsis drought acclimatization.