Cloning and characterization of an ascorbate peroxidase gene regulated by ethylene and abscisic acid during banana fruit ripening

Abstract

An ascorbate peroxidase (APX) cDNA, designated MaAPX1, was isolated from banana fruit by suppression  subtractive hybridization (SSH). MaAPX1 shares an extensive sequence identity (79 to 83%) with other plant APX homologues. Southern blot analysis revealed only two copies of the APX gene in the banana genome.  Reverse-transcriptase PCR analysis of MaAPX1 expression confirmed its expression in the root, leaf, flower  and fruit, with higher levels detected in the leaf compared to other organs. Real-time quantitative polymerase chain reaction was used to explore expression patterns of MaAPX1 in banana postharvest. In naturally ripened banana fruits, MaAPX1 expression gradually peaked at day 6 after harvest, and subsequently decreased. In  ethylene-treated fruits, MaAPX1 expression increased to a maximum at day 3 and then decreased. Meanwhile, in banana treated with abscisic acid, MaAPX1 levels were suppressed from day 0 to 8. These data suggest that MaAPX1 may play distinct roles in the multiple mechanisms that underlie banana fruit ripening.

Key words: Banana, postharvest ripening, ascorbate peroxidase, gene expression, ethylene, abscisic acid.