Abstract
Lily is a popular flower around the world not only because of its elegant appearance, but also due to its appealing scent. Little is known about the regulation of the volatile compound biosynthesis in lily flower scent. Here, we conducted an approach combining two-dimensional analysis and weighted gene co-expression network analysis (WGCNA) to explore candidate genes regulating flower scent production. In the approach, changes of flower volatile emissions and corresponding gene expression profiles at four flower developmental stages and four circadian times were both captured by GC-MS and RNA-seq methods. By overlapping differentially-expressed genes (DEGs) that responded to flower scent changes in flower development and circadian rhythm, 3,426 DEGs were initially identified to be candidates for flower scent production, of which 1,270 were predicted as transcriptional factors (TFs). The DEGs were further correlated to individual flower volatiles by WGCNA. Finally, 37, 41 and 90 genes were identified as candidate TFs likely regulating terpenoids, phenylpropanoids and fatty acid derivatives productions, respectively. Moreover, by WGCNA several genes related to auxin, gibberellins and ABC transporter were revealed to be responsible for flower scent production. Thus, this strategy provides an important foundation for future studies on the molecular mechanisms involved in floral scent production.
Highlights
Flower scent attracts and guides pollinators to angiosperms to aid in fertilization[1]
Terpenoids are derived from dimethylallyl pyrophosphate (DMAPP) and isopentenyl pyrophosphate (IPP), which are condensed by prenyltransferases into geranyl pyrophosphate (GPP) and farnesyl pyrophosphate (FPP), two direct precursors of various terpenoid products[6]
Two divergent pathways are involved in biosynthesis of terpenoids: the methylerythritol phosphate (MEP) pathway operates in the plastids[7] and is responsible for mono- and diterpene production[8], whereas the mevalonic acid (MVA) pathway occurs in the cytosol, endoplasmic reticulum, and peroxisome[9,10] and gives rise to volatile sesquiterpenes
Summary
Flower scent attracts and guides pollinators to angiosperms to aid in fertilization[1]. Three classes of volatile compounds dominate flower scent: terpenoids, phenylpropanoids/benzenoids, and fatty-acid derivatives[4]. Phenylpropanoids/benzenoids represent the second largest class of flower scent compounds[12], and are exclusively derived from the aromatic amino acid L-phenylalanine (L-Phe). Fatty acid derivatives constitute the third class of flower volatile compounds, and are initiated by a stereo-specific oxygenation of octadecanoid precursors and subsequently produced by the lipoxygenase (LOX) pathway. Is the fourth most popular cut flower worldwide, prized for both its appearance and its fragrance Terpenoids and benzenoids, such as linalool, (E)-β-ocimene, myrcene, 1,8-cineole, isoeugenol, benzyl alcohol, ethyl benzoate, and methyl benzoate, are abundant in lily flower aromas[37,38,39]. Recent studies have shown that scent emissions of lily is in concert with floral development stages[41], and exhibited rhythmic patterns[37]
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