Recent Advances in the Research on the Regulatory Mechanisms of Anthocyanin Synthesis in Apple Fruits

Anthocyanin accumulation determines peel pigmentation, commodity value and nutritional quality of apple fruit, and its biosynthesis is controlled by an intricate multi-layer regulatory network integrating external environmental cues, transcriptional cascades, epigenetic modification, post-transcriptional modulation and metabolic pathway crosstalk. Unfavorable coloring widely restricts the economic benefits of apple cultivation worldwide, and clarifying the regulatory rules of anthocyanin metabolism is essential for targeted quality improvement. This review systematically sorts out the latest research progress on apple anthocyanin biosynthesis pathways, and elaborates core regulatory mechanisms from four dimensions: structural gene transcriptional regulation centered on the MBW complex, environmental induction (light, temperature, water and nutrients), phytohormone synergistic/antagonistic regulation, and epigenetic modification including DNA methylation, histone modification and non-coding RNA regulation. On this basis, this paper summarizes existing bottlenecks in current research and proposes future research directions relying on multi-omics and gene-editing technology. The conclusion provides theoretical support for regulated coloring cultivation, molecular marker-assisted breeding and precision gene editing breeding of high-color-quality apple varieties.