JsMYB170 modulates flavonols biosynthesis through facilitation of JsFLS1/5 expression in pellicle of Juglans...

J. sigillata produces abundant flavonols such as rutin and myricetin in pellicle, which provide various benefits to human health. However, the transcriptional regulation of flavonols biosynthesis in pellicle of J. sigillata remains unclear. Our study showed that the JsMYB170 is a transcriptional activator involved in the biosynthesis of flavonols in J. sigillata. In the pellicle of J. sigillata, the transient silencing of the JsMYB170 gene can significantly reduce its expression level, as well as the expression of JsFLS1/5 and the accumulation of flavonols such as rutin, myricetin, quercetin and kaempferol. In contrast, the transient over-expression of JsMYB170 can significantly increase the content of flavonols in the pellicle. Similarly, qRT-PCR detection in mature fruits of JsMYB170 over-expressing transgenic T₃ generation tomato showed that, the expression levels of JsMYB170 and SlFLS also significantly increased. At the same time, HPLC analysis showed that the content of flavonols also significantly increased. Through DAP-seq, 25 downstream target genes of JsMYB170 were screened out. The dual luciferase assay conducted on tobacco leaves and the subsequent yeast one-hybrid assay both indicated that JsMYB170 can positively regulate the transcriptional expression of JsFLS1/5 by binding to the AC element of the promoter. As a key enzyme gene for flavonol synthesis, the same transient expression of JsFLS1/5 also showed that JsFLS1/5 could positively regulate the accumulation of flavonols in pellicle of walnut. These research results provide new insights into the molecular regulatory pathways of functional substance flavonols accumulation on walnut pellicle.