Abstract
Despite its indispensable function in the symbiotic association between legumes and rhizobia, for the vast majority of plants, the physiological role of purine metabolism remains elusive. We have previously demonstrated that RNA interference-mediated suppression of xanthine dehydrogenase (XDH), the rate-limiting enzyme in purine degradation, causes defects in normal growth and development of Arabidopsis thaliana. Here, we investigated a possible role of XDH in drought tolerance, because this enzyme is also implicated in stress responses and acclimatization of plants. Compared with wild-type seedlings, XDH-suppressed lines showed significantly reduced growth and chlorophyll content after drought shock, which accompanied increased cell death and higher H2O2 levels. Such drought-hypersensitive phenotype of XDH-suppressed lines, however, was restored by exogenous supplementation of urate, the metabolite of XDH catalysis. These results suggest the importance of XDH in the acclimatization to drought, possibly through production of purine metabolites, such as urate and ureides, with antioxidant capacity.
