Genome-wide investigation of WRKY transcription factors in sweet osmanthus and their potential regulation of aroma synthesis

Abstract

WRKY transcription factors, one of the largest transcription factor families, play important roles in regulating the synthesis of secondary metabolites. In sweet osmanthus (Osmanthus fragrans), the monoterpenes have been demonstrated as the most important volatile compounds, and the W-box, which is the cognate binding site of WRKY transcription factors, could be identified in most of the terpene-synthesis-related genes’ promoters. However, the role of the WRKY family in terpene synthesis in sweet osmanthus has rarely been examined. In this study, 154 WRKY genes with conserved WRKY domain were identified and classified into three groups. The group II was further divided into five subgroups, and almost all members of IId contained a plant zinc cluster domain. Eight OfWRKYs (OfWRKY7/19/36/38/42/84/95/139) were screened from 20 OfWRKYs for their flower-specific expression patterns in different tissues. Simultaneously, the expression patterns of OfWRKYs and emission patterns of volatile compounds during the flowering process were determined and gas chromatography-mass spectrometry results showed that monoterpenes, such as linalool and ocimene, accounted for the highest proportion, contributing to the floral scent of sweet osmanthus in two cultivars. In addition, correlation analysis revealed the expression patterns of OfWRKYs (OfWRKY7/19/36/139) were each correlated with distinct monoterpenes (linalool, linalool derivatives, ocimene and ocimene derivatives). Subcellular localization analysis showed that p35S::GFP–OfWRKY7/38/95/139 were localized in the nucleus and OfWRKY139 had very strong transactivation activity. Collectively, the results indicated potential roles of OfWRKY139 and OfWRKYs with plant zinc cluster domain in regulating synthesis of aromatic compounds in sweet osmanthus, laying the foundation for use of OfWRKYs to improve the aroma of ornamental plants.

Peer Review #3 of "Mining of candidate genes involved in the biosynthesis of dextrorotatory borneol in Cinnamomum burmannii by transcriptomic analysis on three chemotypes (v0.1)"

“…Transcription factor CitERF71 activates the terpene synthase encoding gene CitTPS16 involved in the biosynthesis of E-geraniol in Citrus sinensis Osbeck (Li et al 2017). Recently, a genome-wide investigation of WRKY transcription factors in Osmanthus Fragrans indicated potential roles for OfWRKY139 and OfWRKYs with plant zinc cluster domains in regulating biosynthesis of aromatic compounds in sweet osmanthus (Ding et al 2019); A study on monoterpene synthase promoter related transcription factors in Lavandula × Intermedia by yeast one-hybrid assay indicated that multiple transcription factors control monoterpene synthase expression in lavender, including MYB, bZIP, NAC, GeBP and SBPrelated proteins (Sarker et al 2019). In the present work, we identified one WRKY, two BHLH, one AP2/ERF and three MYB candidate genes, which exhibited the same expression pattern as CcTPS5 and CcTPS7.…”

Genome-Wide Identification and Comparative Analysis of WRKY Transcription Factors Related to Momilactone Biosynthesis in Calohypnum plumiforme

“…WRKY protein sequences in Arabidopsis thaliana were downloaded from UniProt protein database, 6 named as AtWRKY1-AtWRKY 70 (Ding et al, 2020). Subsequently, the Clustal W multiple sequences alignment of CpWRKY ( 19) and AtWRKY (70) proteins was performed using MEGA6 software.…”

An Update on the Function, Biosynthesis and Regulation of Floral Volatile Terpenoids

“…Gelsemiaceae (Z)-α-ocimene, α-farnesene [29] Gossypium hirsutum Malvaceae (3S)-linalool GhTPS12 [30,31] Jasminum spp. Oleaceae α-farnesene, linalool, β-ocimene, germacrene-D [32][33][34][35][36] Laurus nobilis Lauraceae sesquiterpenes, γ-cadinene, δ-cadinene [37] Lonicera japonica Caprifoliaceae linalool [38] Magnolia champaca Magnoliaceae (R)-linalool, linalool and its oxides [39] Malus domestica Rosaceae (E)-linalool oxide [40] Murraya paniculata Rutaceae E-β-ocimene, linalool, α-cubebene [41,42] Myrtus communis L. Myrtaceae α-pinene, linalool, 1,8-cineole [43] Osmanthus fragrans Oleaceae linalool and its derivatives, α-ionone, β-ionone OfTPS1, OfTPS2, OfTPS3 [44][45][46][47] Paeonia spp. Paeoniaceae β-caryophyllene, linalool [48,49] Psidium guajava Myrtaceae α-cadinol, β-caryophyllene, nerolidol [50] Rosa spp.…”

“…In O. fragrans flowers, WRKY transcription factors play important roles in regulating the biosynthesis of secondary metabolites. The expression of OfWRKY19/36/84/139 positively correlates with the biosynthesis of volatile monoterpenes; in contrast, the expression of OfWRKY7 negatively correlates with the biosynthesis of volatile monoterpenes [46]. In addition, the OfWRKYs regulate volatile monoterpene biosynthesis in O. fragrans by binding plant zinc cluster domains [45].…”