Aldose reductase in rice (Oryza sativa L.): stress response and developmental specificity

Aldose reductase (AR) protein and enzyme (alditol: NAD (P)(+) 1-oxidoreduct ase, EC 1.1.1.21) activity have been identified in mature seeds of indica r ice cultivars. The protein begins to accumulate 15 days after pollination, reaches a peak at seed maturity and disappears upon imbibition. Furthermore , AR is induced in vegetative tissues in response to exogenous ABA applicat ion and other stress conditions, such as PEG mediated water stress and sali nity. Increase in AR protein levels upon stress are in close agreement with a similar increase in enzyme activity. Varietal differences in AR levels h ave been demonstrated. Interestingly, all tested tolerant cultivars (as den oted by breeders) accumulate AR in vegetative tisssue in response to ABA ap plication, while the sensitive line, Hamsa, does not do this under similar stress conditions, suggesting that AR may be associated with stress toleran ce. Furthermore, AR protein has been identified in mature seeds of some sel ected cereals indicating the conserved nature of AR across grasses. (C) 200 0 Elsevier Science Ireland Ltd. All rights reserved.