PfERF106, a novel key transcription factor regulating the biosynthesis of floral terpenoids in Primula forbesii Franch

Flowers can be a source of essential oils used in the manufacture of substances with high economic value. The ethylene response factor (ERF) gene family plays a key role in regulating secondary metabolite biosynthesis in plants. However, until now, little has been known about the involvement of ERF transcription factors (TFs) in floral terpenoid biosynthesis. In this study, an aromatic plant, Primula forbesii Franch., was used as research material to explore the key regulatory effects of PfERF106 on the biosynthesis of terpenoids. PfERF106, which encodes an IXb group ERF transcription factor, exhibited a consistent expression trend in the flowers of P. forbesii and was transcriptionally induced by exogenous ethylene. Transient silencing of PfERF106 in P. forbesii significantly decreased the relative contents of key floral terpenes, including (z)-β-ocimene, sabinene, β-pinene, γ-terpinene, linalool, eremophilene, α-ionone, and α-terpineol. In contrast, constitutive overexpression of PfERF106 in transgenic tobacco significantly increased the relative contents of key floral terpenes, including cis-3-hexen-1-ol, linalool, caryophyllene, cembrene, and sclareol. RNA sequencing of petals of PfERF106-silenced plants and empty-vector control plants revealed 52,711 expressed unigenes and 9,060 differentially expressed genes (DEGs). KEGG annotation analysis revealed that the DEGs were enriched for involvement in secondary metabolic biosynthetic pathways, including monoterpene and diterpene synthesis. Notably, 10 downregulated DEGs were determined to be the downstream target genes of PfERF106 affecting the biosynthesis of terpenoids in P. forbesii. This study characterized the key positive regulatory effects of PfERF106 on the biosynthesis of terpenoids, indicating high-quality genetic resources for aroma improvement in P. forbesii. Thus, this study advances the artificial and precise directional regulation of metabolic engineering of aromatic substances.