Stress-responsive and developmental regulation of Delta(1)-pyrroline-5-carboxylate synthetase 1 (P5CS1) gene expression in Arabidopsis thaliana.

Delta(1)-Pyrroline-5-carboxylate synthetase 1 (P5CS1) is the rate-limiting enzyme in the biosynthesis of proline by Arabidopsis thaliana. Results of Northern analysis using aba1, abi1, and abi3 mutants of A. thaliana suggest that the expression of the P5CS1 gene under water stress is induced via abscisic acid (ABA)-biosynthesis-dependent and -independent pathways. Expression via ABA biosynthesis does not require protein synthesis. Analysis using transgenic A. thaliana containing a P5CS1 promoter/GUS fused gene indicated that the P5CS1 gene of A. thaliana is expressed in the whole plant under dehydration and in reproductive organs and tissues (flower buds and surrounding parts, pollen and pistils, and young siliques in the early stage of seed formation) under unstressed conditions. Cis-acting elements involved in dehydration-responsive gene expression are shown to be located in a 117-bp region between positions -621 and -504 upstream from the transcriptional initiation site.