Genome-Wide Transcriptome Analysis Reveals GRF Transcription Factors Involved in Methyl Jasmonate-Induced Flavonoid Biosynthesis in

Flavonoids are key bioactive compounds in plants that play important defense roles against abiotic stress and are involved in plant growth and development. Methyl jasmonate (MeJA) is a significant growth regulator that promotes the accumulation of flavonoids in a variety of plants, but the effect of MeJA in Hedera helix remains poorly understood. In the present study, the flavonoid content was significantly increased after MeJA treatment and peaked at 6 h post-treatment. A total of 31,931 genes were identified using transcriptome, and 6484 DEGs were identified at 6 h post-treatment. Through GO and KEGG enrichment analysis, it was shown that DEGs were primarily enriched in phenylpropanoid biosynthesis pathways. Based on the putative transcription factors derived from DEGs, growth-regulating factor (GRF), a transcription factor potentially linking MeJA signaling to flavonoid accumulation and participating in plant growth and stress responses, was further identified. A total of 20 Hh-GRFd genes were identified on the whole genome level and clustered into five phylogenetic groups with conserved subfamily characteristics. Abundant MeJA-responsive cis-elements were presented in the promoter regions of HhGRF1-HhGRF20. They exhibited a tissue-specific expression variation, and HhGRF10 was dominantly expressed in leaves of H. helix. Notably, HhGRF10 exhibited MeJA-induced expression that correlated temporally with flavonoid accumulation, suggesting that HhGRF10 might play a potential role in promoting flavonoid biosynthesis, and overexpression and knockout assay substantiated this conclusion. The finding provides the first transcriptome-wide resource for flavonoid biosynthesis in H. helix and identifies the candidate GRF-mediated regulator for flavonoid accumulation.