Transcription factor AcAGL9 and AcBEH1 synergistically regulate carotenoid biosynthesis during pineapple fruit ripening

Abstract

Pineapple fruit ripening is closely associated with carotenoid biosynthesis, which is crucial for color development and contributes to the fruit's overall quality. However, the transcriptional mechanisms driving carotenoid biosynthesis in pineapple remain largely unexplored. In this study, we identify a MADS-box transcription factor, AcAGL9, as a positive regulator of carotenoid biosynthesis in pineapple. Biochemical analyses demonstrate that AcAGL9 activates the expression of carotenogenic genes (AcPSY, AcPDS, AcCRTISO, and AcLCYB) by directly binding to CArG-elements in their promoters. Additionally, AcAGL9 physically interacts with the positive regulator AcBEH1, synergistically enhancing the expression of these carotenogenic genes. Silencing AcAGL9 or AcBEH1 in pineapple fruit reduces the expression of carotenoid biosynthesis genes and inhibits carotenoid accumulation, while overexpression has the opposite effect. Co-silencing or co-overexpression of both AcAGL9 and AcBEH1 produces an even more pronounced impact. Collectively, our study highlights the critical role of the AcAGL9-AcBEH1 module in regulating carotenoid accumulation in pineapple fruit.