Abstract
Terpene synthases (TPSs) are essential for forming terpenes, which play numerous functional roles in attracting pollinators, defending plants, and moderating the interaction between plants. TPSs have been reported in some orchids, but genome-wide identification of terpenes in Cymbidium faberi is still lacking. In this study, 32 putative TPS genes were classified in C. faberi and divided into three subfamilies (TPS-a, TPS-b, and TPS-e/f). Motif and gene structure analysis revealed that most CfTPS genes had the conserved aspartate-rich DDxxD motif. TPS genes in the TPS-a and TPS-b subfamilies had variations in the RRX8W motif. Most cis-elements of CfTPS genes were found in the phytohormone responsiveness category, and MYC contained most of the numbers associated with MeJA responsiveness. The Ka/Ks ratios of 12/13 CfTPS gene pairs were less than one, indicated that most CfTPS genes have undergone negative selection. The tissue-specific expression patterns showed that 28 genes were expressed in at least one tissue in C. faberi, and TPS genes were most highly expressed in flowers, followed by leaves and pseudobulbs. In addition, four CfTPS genes were selected for the real-time reverse transcription quantitative PCR (RT-qPCR) experiment. The results revealed that CfTPS12, CfTPS18, CfTPS23, and CfTPS28 were mainly expressed in the full flowering stage. CfTPS18 could convert GPP to β-myrcene, geraniol, and α-pinene in vitro. These findings of CfTPS genes of C. faberi may provide valuable information for further studies on TPSs in orchids.
Highlights
Terpenes, which contain isoprene (C5), monoterpenes (C10), sesquiterpenes (C15), and diterpenes (C20), constitute the most prominent family of volatile components in plants (Nagegowda, 2010; Tholl, 2015)
The theoretical isoelectric point values were in the range of 4.86 for CfTPS1 and CfTPS2 to 9.28 for CfTPS26, and the deduced grand average of hydrophilic (GRAVY) values were in the range of −0.358 for CfTPS26 to 0.073 for CfTPS6, suggesting that most CfTPS proteins were hydrophilic except for CfTPS1, CfTPS2, and CfTPS6
The aliphatic index (AI) of CfTPS-deduced proteins was in the range of 87.09 for CfTPS21 to 107.22 for CfTPS6, and the instability index (II) was in the range of 28.62 for CfTPS1 and CfTPS2 to 52.36 for CfTPS5
Summary
Terpenes, which contain isoprene (C5), monoterpenes (C10), sesquiterpenes (C15), and diterpenes (C20), constitute the most prominent family of volatile components in plants (Nagegowda, 2010; Tholl, 2015). They play significant roles in attracting pollinators, defending plants against herbivores and pathogens, and moderating the interaction between plants (Wagner and Elmadfa, 2003; Dudareva et al, 2006). Sesquiterpenes are the major floral scent compounds in Cymbidium goeringii (Ramya et al, 2019). The floral scent in orchids is closely related to flower development stages and is vital for pollination ecology (Ramya et al, 2018)
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