Cloning, characterization and expression analysis of Δ1-pyrroline-5-carboxylate synthetase (P5CS) gene in harvested papaya (Carica papaya) fruit under temperature stress

Δ1-Pyrroline-5-carboxylate synthetase (P5CS) catalyzes the rate-limiting step in proline biosynthesis in plants. In the present study, a full-length cDNA, denominated as CpP5CS2 for Δ1-pyrroline-5-carboxylate synthetase (P5CS), was cloned from papaya using in silico cloning and 3′- or 5′-rapid amplification of cDNA ends (RACE). The full-length cDNA of CpP5CS2 was 2583 bp, with a 2151 bp open reading frame (ORF) encoding a 717 amino acid polypeptide. Sequence analysis showed that CpP5CS2 contained several substrate-binding and catalytic domains and had high homology to other plant P5CSs. The expression pattern of CpP5CS2 in papaya under low (7 °C) and high temperature (35 °C) stresses was examined using real-time quantitative PCR. The results showed that both stresses induced CpP5CS2 expression during the storage period, and the increased expression of CpP5CS2 preceded proline accumulation. In addition, the high temperature caused a more significant induction of CpP5CS2 expression and a higher level of accumulated proline than low temperature.

►A novel CpP5CS2 gene of papaya was isolated and characterized. ► Sequence analysis showed that CpP5CS2 showed high homology to other plant P5CSs. ► CpP5CS2 was induced both by high and low temperature stresses during storage. ► Our work provided a foundation for further study in improving papaya fruit quality.