Banana fruit NAC transcription factor MaNAC1 is a direct target of MaICE1 and involved in cold stress through interacting with MaCBF1.

Our previous studies have indicated that the banana ripening-induced MaNAC1, a NAC (NAM, ATAF1/2 and CUC2) transcription factor (TF) gene, is regulated by ethylene during fruit ripening, and propylene, a functional ethylene analogue, induces cold tolerance of banana fruits. However, the involvement of MaNAC1 in propylene-induced cold tolerance of banana fruits is not understood. In the present work, the possible involvement of MaNAC1 in cold tolerance of banana fruits was investigated. MaNAC1 was noticeably induced by cold stress or following propylene treatment during cold storage. Transient protoplast assays showed that MaNAC1 promoter was activated by cold stress and ethylene treatment. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA) and transient expression assays demonstrated MaNAC1 as a novel direct target of MaICE1, and that the ability of MaICE1 binding to MaNAC1 promoter might be enhanced by MaICE1 phosphorylation and cold stress. Moreover, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses revealed physical interaction between MaNAC1 and MaCBF1, a downstream component of inducer of C-repeat binding factor (CBF) expression 1 (ICE1) in cold signalling. Taken together, these results suggest that the cold-responsive MaNAC1 may be involved in cold tolerance of banana fruits through its interaction with ICE1-CBF cold signalling pathway, providing new insights into the regulatory activity of NAC TF.