Isolation, characterization, and expression analysis of the MaMDH gene in banana.

摘要

A full-length cDNA isolated from banana fruit, named MaMDH, contains an open reading frame encoding 332 amino acids that represents the gene for cytoplasmic malic dehydrogenase (MDH). Sequence analysis showed that MaMDH shares high similarity with MDH from castor bean (XP_002533463), tobacco (CAC12826), peach (AAL11502) and chickpeas (CAC10208). Real-time quantitative PCR analysis of MaMDH spatial expression showed that it was expressed in all organs examined: roots, rhizomes, leaves, flowers and fruits. Expression was highest in flowers, followed by fruits and roots, whereas rhizomes and leaves displayed the lowest expression levels. Real-time quantitative PCR revealed that MaMDH exhibited differential expression patterns in postharvest banana fruits correlating with ethylene biosynthesis. In naturally ripened banana fruits, MaMDH expression was in accordance with ethylene biosynthesis. In accordance, for banana fruits treated with the ethylene analog 1-methylclopropene (1-MCP), MaMDH expression levels were inhibited and remained constant. After treatment with ethylene, MaMDH expression in banana fruits significantly increased with ethylene biosynthesis and peaked 3 days after harvest, which was 11 days earlier than that in naturally ripened banana fruits. Results suggested that MaMDH expression is induced by ethylene to regulate postharvest banana fruit ripening.