Isolation, Characterization, and Expression Analysis of the MuBTB Gene in Banana

A full-length cDNA isolated from banana (Musa acuminata L. AAA group) fruit was named MuBTB, and it contains an open reading frame encoding 354 amino acids. Sequence analysis showed that MuBTB shares high similarity with broad complex, tramtrack, and bric-a-bracs from other plant species. Reverse transcriptase PCR analysis of MuBTB spatial expression showed that MuBTB was expressed in all organs examined: root, rhizome, leaf, flower, and fruit. Real-time quantitative PCR of postharvest banana revealed that MuBTB exhibited differential expression patterns that are associated with ethylene biosynthesis. In naturally ripened bananas, expression of MuBTB was in accordance with ethylene biosynthesis. In contrast, for 1-methylcyclopropene-treated bananas, MuBTB expression levels were inhibited and remained constant. Following treatment with ethylene, MuBTB expression in banana fruit significantly increased with ethylene biosynthesis and peaked 3 days after harvest, which was 11 days earlier than that for naturally ripened banana fruits. These results suggest that MuBTB expression is induced by ethylene for regulation of postharvest banana ripening. Finally, subcellular localization assays showed that the MuBTB protein localizes to the nucleus.