DNA methylation mediated by RdDM pathway and demethylation affects furanone accumulation through regulation of QUINONE OXIDOREDUCTASE in strawberry

Recently, increasing evidence suggests that DNA methylation plays a crucial role in fruit ripening. However, the role of DNA methylation in regulating specific traits, such as flavor, remains unclear. Here, we report a role of DNA methylation in affecting furanone biosynthesis in strawberry. Strawberry quinone oxidoreductase (FaQR) is a key enzyme in furanone biosynthesis. There are four FaQR homologs in strawberry cultivar 'Yuexin', and one of them, FaQR3, contributes similar to 50% of FaQR transcripts, indicating a major role of FaQR3 in furanone biosynthesis. Through characterization of levels of DNA methylation and FaQR3 transcript and furanone contents during fruit ripening and after the application of DNA methylation inhibitor, we found that the DNA methylation level of the FaQR3 promoter was negatively correlated with FaQR3 expression and furanone accumulation, suggesting that DNA methylation may be involved in furanone biosynthesis through adjusting FaQR3 expression, and responded to different temperatures consistently. In addition, transient expression of a gene in the RNA-directed DNA methylation (RdDM) pathway, FaAG04, and enrichment analysis of the 24-nucleotide siRNAs suggested that DNA methylation in the FaQR3 promoter is mediated by the RdDM pathway. Transient RNA interference (RNAi) of FaDML indicated that the demethylation pathway may be involved in regulating furanone accumulation. These findings provide new insights into the role of DNA methylation and demethylation in affecting flavor quality in strawberry during fruit ripening.

Automated summary

Recent studies suggest that DNA methylation plays a significant role in fruit ripening, but its specific impact on flavor regulation remains unclear. In this study, researchers found that DNA methylation affects furanone biosynthesis in strawberries by adjusting the expression of the key enzyme FaQR3. The level of DNA methylation in the promoter region of FaQR3 has a negative correlation with its expression and furanone accumulation. Additionally, the study suggests that DNA methylation in the FaQR3 promoter is mediated by the RNA-directed DNA methylation (RdDM) pathway. The involvement of demethylation pathways in regulating furanone accumulation was also observed in the study.