Abstract: WRKY proteins are a class of plant-specific transcriptional factors (TFs), which play important roles in plant growth and development, leaf senescence and hormonal signaling. However, their relationship with banana fruit ripening and senescence remains unknown. In the present work, a WRKY TF, termed MaWRKY31, was obtained from banana fruit. Analysis of deduced amino acid sequence and phylogenetic tree revealed that MaWRKY31 contained a typical WRKY domain showing high homology with Arabidopsis thaliana WRKY31, and belonged to the Ⅱb sub-group. Realtime quantitative polymerase chain reaction displayed that MaWRKY31 was induced by ethylene, and up-regulated following banana fruit ripening and senescence. Sub-cellular localization and transcriptional activity analysis revealed that MaWRKY31 was a nuclear protein with transcriptional activation activity. In addition, dual-luciferase transient expression assay demonstrated that MaWRKY31 could activate the promoter activities of the ethylene biosynthetic genes MaACS1 and MaACO1 and the ripening-related gene MaSAG1. Taken together, these results suggest that MaWRKY31 may be involved in banana fruit ripening and senescence, possibly via the regulation of the expression of genes related to ethylene biosynthesis and ripening, which deepens the understanding of the transcriptional regulation mechanism of banana fruit ripening and senescence.

Key words: banana, fruit ripening and senescence, WRKY transcription factors, transcriptional regulation