Integrative metabolome and transcriptome analyses reveal the effects of plant growth regulator diethylaminoethyl hexanoate on flavonoid biosynthesis in hawthorn fruits

Abstract Because of its therapeutic and health-promoting properties, Crataegus has substantial commercial value. Flavonoids are the main functional ingredients of hawthorn fruits. The nutritional value and quality of hawthorn fruit are greatly enhanced by increasing its flavonoid content. The plant growth regulator diethylaminoethyl hexanoate (DA-6) has shown potential in this regard; however, little is known about its effects on hawthorn fruit quality, particularly flavonoid biosynthesis. This study investigated the transcriptome and metabolome of hawthorn fruit treated with DA-6. The results showed that by stimulating the activities of key synthases, treatment with 10 mg/L DA-6 increased flavonoid and anthocyanin contents. In total, 22 differentially accumulated flavonoid metabolites and 21 differentially expressed genes were identified. Key potential transcription factors associated with flavonoid biosynthesis, including MYB5, NAC82, bHLH62, ABI5, and WRKY44, were identified using the co-expression networks. Additionally, genetic and metabolic regulatory networks of flavonoid biosynthesis were proposed based on the differentially accumulated flavonoid metabolites and crucial genes. Overall, this study offers valuable insights for future research on the intricate molecular networks of flavonoid biosynthesis activated by the plant growth regulator DA-6.