Abstract: 【Objective】The objective of this experiment is to study the expression of CaM gene in temperature stress and fruit ripening of banana. Which is helpful to understand the effect of CaM gene in enhance the adaptation to temperature stress and reveal the mechanism of peel degreening during the ripening process of banana fruit.【Method】Degenerated primers were designed by comparative analysis of some species’ CaM amino acid sequence in NCBI database. The total RNA was extracted from banana peel by using hot borate method. In banana fruit, the rapid amplification of cDNA ends (RACE)-PCR techniques were used for 3’-UTR and fragment sequences cloning of the cDNA. The amino acid sequence of CaM was analyzed by using DNAMAN software and the NCBI website. Probe with DIG markers was made by using PCR DIG Probe Synthesis Kit. Northern blotting was performed to compare the expression of MaCaM gene in banana fruit under different temperature stresses and during ripening process. EGTA and calcium signal recovery treatment by using banana peels in vitro culture. The banana peel were treated by vacuum infiltration. The h values were measured by the color difference meter.【Result】A novel CaM gene, 648 bp, encoding 138 amino acids, named MaCaM (HM061077), was cloned from banana in this study. Sequence analysis showed that MaCaM gene contains 4 EF-Hand calcium binding regions. MaCaM gene has a high sequence similarity with MaCaM, OsCaM, ZmCaM, AtCaM3 and TaCaM1-2. Northern blotting results showed that the MaCaM gene expression was up-regulated rapidly at 0.5-24 h after heat shock (52℃ 3min). Banana fruits were stored at 7℃ (chilling injury temperature) for 10 days, the MaCaM gene expression increased gradually in the 7-10 d. When the banana fruits were stored at 7℃ after heat shock, MaCaM expression was higher in the 4 d and 7 d than those of at 7℃ alone. Ethylene was also observed to arouse the expression of MaCaM gradually. Furthermore, 30 mmol·L^-1 calcium ion chelator EGTA treatment inhibited fruit ripening and the expression of MaCaM to the same extent, while the EGTA combined with 30 mmol·L^-1 CaCl₂ treatment restored the normal ripening of banana and the expression of MaCaM gene to some degree.【Conclusion】These results showed that MaCaM gene takes an important role in enhancing the adaptation to temperature stress and MaCaM gene as a regulator is involved in the peel degreening during the ripening process of banana fruit.

Key words: banana fruit;ripening; CaM, gene expression, temperature stress