Molecular Characterization of MaCCS, a Novel Copper Chaperone Gene Involved in Abiotic and Hormonal Stress Responses in Musa acuminata cv. Tianbaojiao.

Copper/zinc superoxide dismutases (Cu/ZnSODs) play important roles in improving banana resistance to adverse conditions, but their activities depend on the copper chaperone for superoxide dismutase (CCS) delivering copper to them. However, little is known about CCS in monocots and under stress conditions. Here, a novel CCS gene (MaCCS) was obtained from a banana using reverse transcription PCR and rapid-amplification of cDNA ends (RACE) PCR. Sequence analyses showed that MaCCS has typical CCS domains and a conserved gene structure like other plant CCSs. Alternative transcription start sites (ATSSs) and alternative polyadenylation contribute to the mRNA diversity of MaCCS. ATSSs in MaCCS resulted in one open reading frame containing two in-frame start codons to form two protein versions, which is supported by the MaCCS subcellular localization of in both cytosol and chloroplasts. Furthermore, MaCCS promoter was found to contain many cis-elements associated with abiotic and hormonal responses. Quantitative real-time PCR analysis showed that MaCCS was expressed in all tested tissues (leaves, pseudostems and roots). In addition, MaCCS expression was significantly induced by light, heat, drought, abscisic acid and indole-3-acetic acid, but inhibited by relatively high concentrations of CuSO₄ and under cold treatment, which suggests that MaCCS is involved in abiotic and hormonal responses.