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

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.