MicroRNA Identification and Integrated Network Analyses for Age-Dependent Flavonoid Biosynthesis in Ginkgo biloba

Ginkgo biloba leaves contain abundant flavonoids, and flavonoid accumulation is affected by age. MicroRNAs (miRNAs) play an important role in the plant aging pathway. However, the miRNAs involved in flavonoid biosynthesis related to age in G. biloba have rarely been studied. In this study, we compared 1-, 4-, and 7-year-old ginkgo seedings and found a significant decrease in the content of quercetin, kaempferol, and total flavonol aglycones with age. We then profiled miRNAs in G. biloba through high-throughput sequencing on leaf samples of 1-, 4-, and 7-year-old ginkgo. GO and KEGG analyses suggest that photosynthesis and hormones may influence the flavonoid content. In particular, we identified 29 miRNAs related to the aging pathway according to their miRNA expression patterns. Correlation analysis of age-related miRNAs and major flavonoid compounds screened 17 vital miRNAs, including miRN79, miR535a, miR166a, miR171a, and miR396. Interactive miRNA-transcription factor network analysis suggested that the pivotal miRN79-DELLA and miR535a-SPL modules may be involved in flavonoid biosynthesis and aging pathways through post-transcriptional regulation. Our findings provide insights into the age-dependent regulatory roles of miRNAs in flavonoid biosynthesis.