Membrane-associated NAC transcription factor MaNAC169 is a positive regulator during banana fruit ripening

Abstract

Fruit ripening is a complex process involving physiological and metabolic changes that influence fruit color, flavor, aroma, and texture, which is modulated by various hormones and key genes. NAC with transmembrane motif-like (NTL) transcription factors belong to the NAC gene family with transmembrane motifs at their C-terminus and play important roles in plant growth, development, and stress responses. However, the role of NTL during fruit ripening remains enigmatic. Here, we identified a NTL gene, MaNAC169, that was regulated by ethylene during banana fruit ripening. MaNAC169 contained a conserved TM in its far C-terminal region and localized in the nucleus and plasma membrane. Its active form, MaNAC169-ΔC4, acted as a transcriptional activator. Importantly, MaNAC169 directly bound to the promoters of MaACO1, MaEXP2, MaXET1, and MaGWD1 and positively regulated their gene expression. MaNAC169 also activated its own expression and could form a dimer with itself. Moreover, transient MaNAC169-ΔC4 overexpression in banana fruit promoted ripening by inducing target gene expression. Taken together, MaNAC169 positively modulated fruit ripening by activating the expression of ripening-associated genes. Our findings provide new insights into the transcriptional regulatory mechanisms involved in fruit ripening.