Cloning the PvP5CS gene from common bean (Phaseolus vulgaris) and its expression patterns under abiotic stresses

A full-length cDNA denominated PvP5CS for Δ1-pyrroline-5-carboxylate synthetase (P5CS), an enzyme involved in the biosynthesis of proline, was cloned from common bean using a candidate gene approach. PvP5CS contains an open reading frame encoding a 716 amino acid polypeptide. Sequence analysis showed that PvP5CS shares 95.1% homology in nucleotide sequence and 93.2% identity in amino acid sequence with the mothbean (Vigna aconitifolia) P5CS. The expression patterns of PvP5CS in common bean treated with drought, cold (4 °C), and salt (200 mM NaCl) stresses were examined using real-time quantitative PCR. These abiotic stresses caused significant up-regulation of the expression of PvP5CS in leaves. The PvP5CS mRNA transcript increased to 2.5 times the control level after 4 d drought stress. A rapid up-regulation of PvP5CS, to about 16.3 times the control at 2 h post-treatment was observed under salt stress. A significant increase in PvP5CS expression (11.7-fold) was detected after 2 h of cold stress. The peaks of proline accumulation appeared at 8 d for drought, 24 h for cold and 9 h for salt stress, somewhat later than the peaks of PvP5CS expression. These results suggest that PvP5CS was a stress-inducible gene regulating the accumulation of proline in plants subjected to stress. Finally, subcellular localization assays showed that the PvP5CS protein was present in the nucleus and at the plasmalemma.