Stress-inducible synthesis of proline in transgenic rice confers faster growth under stress conditions than that with constitutive synthesis

Proline accumulation has been shown to correlate with tolerance to drought and salt stresses in plants. Our goal was to compare the growth rate of transgenic rice plants in which the expression of a mothbean Delta(1)-pyrroline-5-carboxylate synthetase (p5cs) cDNA was driven separately with a constitutive and a stress-inducible promoter. We found that both constitutive expression and stress-inducible expression of the p5cs cDNA in transgenic rice have led to the accumulation of p5cs mRNA and proline. Third-generation (R2) transgenic rice seedlings showed significantly higher tolerance to stress produced by high levels of NaCl or water deficiency as judged by faster growth of shoots and roots in comparison with non-transformed plants. However, stress-inducible expression of the P5CS transgene showed significant advantages over the constitutive expression in increasing the biomass production of transgenic rice grown in soil under stress conditions. (C) 2003 Elsevier Ireland Ltd. All rights reserved.