Elucidating the mechanism of MaGWD1-mediated starch degradation cooperatively regulated by MaMADS36 and MaMADS55 in banana

Abstract

Banana (Musa acuminata) is a common starch-conversion fruit. Starch is rapidly degraded and converted to soluble sugars during postharvest banana fruit ripening. The conversion efficiency directly influences fruit firmness, sweetness, and shelf life. Glucan, water dikinase (GWD) is the first rate-limiting enzyme of starch metabolism. Musa acuminata glucan water dikinase 1 (MaGWD1) plays an important role in banana starch metabolism and its expression is regulated by transcription factors (TFs). However, the regulation of MaGWD1 by MADS-box TFs remains unclear. In this study, the molecular mechanism underlying the cooperative regulation of MaGWD1-mediated starch degradation by MaMADS36 and MaMADS55 was investigated. The results indicated that MaMADS36 interacts with MaMADS55. Both MaMADS36 and MaMADS55 could directly bind to the same position on the CA/T(r)G box within the MaGWD1 promoter. MaMADS36 and MaMADS55 cooperatively regulate banana fruit starch degradation via transcriptional control of MaGWD1.These findings improve our understanding of how TFs regulate starch degradation; this information may be used for banana fruit quality improvement and to support the development of the banana industry.