DIFFERENTIAL EXPRESSION OF WATER-STRESS ASSOCIATED GENES IN TISSUES OF RICE PLANTS

We have isolated five genes preferentially expressed in polyethylene glycol (PEG)-adapted rice cells. The expression of each of these genes has been investigated in different tissues of rice plants grown under different conditions. We found that these genes are preferentially expressed in leaf sheath as compared with leaf blade and root and that their expression is enhanced by water stress, i.e. drying, exposure to salts, or polyethylene glycol. Therefore, the expression of these genes is associated with water-stress both in cultured cells and in differentiated rice tissues. This observation suggests that physiological analysis of cultured cells can serve as a simplified model system for studies on water-stress adaptation of rice plants. Moreover, we found that the expression of four of the five genes is stimulated by heat shock, suggesting that the response to heat and water stresses may share some common mechanisms. Abscisic acid (ABA) has no effect on two genes, suppresses the expression of two genes and stimulates the expression of two genes and stimulates the expression of one gene. The stimulative effect of ABA was found only at a relatively high ABA concentration (5 mg/L).