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Abstract Background 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. Results 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. Conclusion 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.

Abstract Alcea rosea L. is a traditional flower with a long cultivation history. It is extensively cultivated in China and is widely planted in green belt parks or used as cut flowers and potted ornamental because of its rich colors and flower shapes. Double-petal A. rosea flowers have a higher aesthetic value compared to single-petal flowers, a phenomenon determined by stamen petaloid. However, the underlying molecular mechanism of this phenomenon is still very unclear. In this study, an RNA-based comparative transcriptomic analysis was performed between the normal petal and stamen petaloid petal of A. rosea. A total of 3,212 differential expressed genes (DEGs), including 2,620 up-regulated DEGs and 592 down-regulated DEGs, were identified from 206,188 unigenes. Numerous DEGs associated with stamen petaloid were identified through GO and KEGG enrichment analysis. Notably, there were 63 DEGs involved in the plant hormone synthesis and signal transduction, including auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, jasmonic acid, and salicylic acid signaling pathway and 56 key transcription factors (TFs), such as MADS-box, bHLH, GRAS, and HSF. The identification of these DEGs provides an important clue for studying the regulation pathway and mechanism of stamen petaloid formation in A. rosea and provides valuable information for molecular plant breeding.