Abstract:

Full-length cDNAs of Δ1-pyrroline-5-carboxylate synthetase（PpP5CS）and ornithine
aminotransferase（PpOAT）were isolated from peach fruit using degenerate RT-PCR and RACE（rapid
amplification of cDNA ends）method. The sequences of these two genes were then deposited in GenBank
database with the accession number KP973954 and KP973956，respectively. PpP5CS was 2 511 bp in full
length and encoded a predicted protein of 717 amino acids（ORF length 2 151 bp），and flanked by 123
nucleotides at the 5′-UTR and 235 nucleotides at the 3′-UTR. The full length of PpOAT was 1 686 bp with
ORF 1 416 bp，5′-UTR 151 bp and 3′-UTR 119 bp，which encoded a deduced polypeptide of 472 amino
acids. Phylogenetic analysis indicated that PpOAT and PpP5CS shared high similarity with otherplants with 88% and 91% homology with MhOAT and MhP5CS，respectively. Furthermore，the effect of
5 mmol · L-1 γ-aminobutyric acid treatment on chilling injury incidence and PpOAT and PpP5CS
expression，which were involved in proline biosynthesis，in postharvest peach fruit stored at 0 ℃ was
investigated. The results showed that 5 mmol · L-1 γ-aminobutyric acid treatment significantly inhibited the
decline of extractable juice，and alleviated chilling injury in peach fruit during cold storage. Meanwhile，
the expression of these two genes in peach fruit was induced by the treatment during cold storage. These
results suggested that γ-aminobutyric acid treatment could increase proline biosynthesis and accumulation
by up-regulating the expression levels of PpOAT and PpP5CS thereby promote chilling tolerance in
cold-stored peach fruit.

Key words: peach, fruit, PpP5CS, PpOAT, proline, chilling injury