The AcBBX4/6-AcHY5 Transcription Complex Mediates Flavonoid Biosynthesis during Pineapple Fruit Ripening

Area of Science:

• Plant Molecular Biology
• Biochemistry
• Fruit Ripening Physiology

Background:

• Flavonoid biosynthesis significantly impacts pineapple fruit pigmentation and quality.
• The precise transcriptional regulation of these pathways during ripening is not well understood.

Purpose of the Study:

• To identify key regulators of flavonoid biosynthesis in ripening pineapple.
• To elucidate the transcriptional mechanisms governing flavonoid accumulation.

Main Methods:

• Gene identification and characterization (AcBBX6, AcBBX4, AcHY5).
• Promoter analysis and gene expression assays.
• Protein-protein interaction studies (yeast two-hybrid, co-immunoprecipitation).
• Gene silencing and overexpression experiments in pineapple.

Main Results:

• AcBBX6 was identified as a positive regulator, activating flavonoid pathway genes by binding to G-box elements.
• AcBBX6 and AcHY5 synergistically enhance flavonoid biosynthesis; AcHY5 also interacts with AcBBX4.
• A ternary complex of AcBBX6-AcBBX4-AcHY5 showed enhanced activation.
• Silencing AcBBX6 or AcBBX4 reduced flavonoid accumulation, while overexpression increased it.
• Coordinated manipulation of AcBBX6, AcBBX4, and AcHY5 yielded the most significant phenotypic effects.

Conclusions:

• The AcBBXs-AcHY5 complex acts as a core transcriptional module regulating flavonoid biosynthesis in pineapple fruit.
• Understanding this regulatory network provides insights into controlling fruit quality and pigmentation.