Abstract：Peroxidase (POD) is one of the major oxidases involving in the oxidation of phenolsand and plays important roles in browning of fruits and vegetables. To investigate the function of POD in Luffa (Luffa cylindrical), the full- length cDNA of POD was cloned from luffa fruit by using rapid-amplification of cDNA ends (RACE) and reverse transcription-PCR (RT-PCR) techniques. This gene was named LcPOD, and the GenBank accession was KM506755. The full length cDNA of LcPOD was 1 117 bp, and this cDNA contained a 993 bp open reading frame (ORF) that encoded 331 amino acids，with a predicted molecular weight of 36.32 kD and a hypothetical isoelectric point of 5.545. LcPOD shared over 80% identity with the homologous proteins from melon (Cucumis melo, XP_008449774.1), zucchini (Cucurbita pepo, ABF68751.1) and cucumber (C. sativus, NP_001295810.1), proving that it was highly conservative. Motif Scan analysis showed that LcPOD protein had the characteristic amino acid sequences of peroxidase proximal heme-ligand in the position of 81~191 and heme active sites in the position of 55-66 sites,respectively, which suggested that LcPOD protein was a typical ClassⅢ POD. Wolf Psort protection indicated that LcPOD protein was located in the cytoderm. qRT-PCR analysis revealed that LcPOD can be expressed in various luffa tissues (i.e., roots, stems, leaves, flowers and fruits), and the expression level of LcPOD was the highest in root, followed by leaves and flowers, and the expression level was the lowest in stems.The expression levels of LcPOD were different among eight luffa varieties，and the expression in L. cylindrica was higher than that in L. acutangula. During post-harvest storage at 4 ℃, LcPOD expression level gradually increased and reached maximum at 2 d, then was down-regulated in 3 d and 4 d. During fresh-cut placement at 25 ℃, LcPOD expression level gradually increased and reached maximum at 2 h, then was down-regulated in the remaining time points (i.e., 4 h, 6 h and 8 h). The expression of LcPOD gene, POD activity and total phenolics were highly related to the browning of luffa during fresh-cut and post-harvest storage. LcPOD may play a regulation role in luffa browning process. These results provide a scientific basis for further revealing the mechanism of luffa browning and the genetic improvement on luffa.
