Cloning and Expression of Pyrroline-5-carboxylate synthetase from Eucalyptus camaldulensis (Dehnh.) under Salt Stress

Abstract

Salt stress is one of the most signifi cant factors that negatively affect plant growth and development. Proline has been reported to be an osmoprotectant that confers tolerance to salinity in various plant species. A cDNA for Δ1-pyrroline-5-carboxylate synthetase (P5CS), a key enzyme involved in proline biosynthesis was isolated and characterized from E. camaldulensis (Dehnh.) (clone T5), now designated EuP5CS. The full-length EuP5CS gene has 2,944 bp containing an open reading frame of 2,142-bp that encodes for 713 amino acids. The deduced EuP5CS protein structure exhibited a high homology to the P5CS of other plant species, and was predicted to possess a glutamate 5-kinase domain at its N-terminal and a gamma-glutamyl phosphate reductase domain at its C-terminal. Semiquantitative reverse transcription polymerase chain reaction analysis revealed that the transcriptional expression level of the EuP5CS gene was considerably up-regulated by up to about 50% in response to NaCl treatments. This result indicated that EuP5CS is a salt-inducible gene and plays an important role in proline biosynthesis in E. camaldulensis clones subjected to salt stress.