Abstract
As an important member of the MYB transcription factor (TF) family, the MYB-related TFs play multiple roles in regulating the synthesis of secondary metabolites and developmental processes, as well as in response to numerous biotic and abiotic stressors in plants. However, little is known regarding their roles in regulating the formation of floral volatile organic compounds (VOCs). In this study, we conducted a genome-wide analysis of MYB-related proteins in sweet osmanthus; 212 OfMYB-related TFs were divided into three distinct subgroups based on the phylogenetic analysis. Additionally, we found that the expansion of the OfMYB-related genes occurred primarily through segmental duplication events, and purifying selection occurred in all duplicated gene pairs. RNA-seq data revealed that the OfMYB-related genes were widely expressed in different organs of sweet osmanthus, and some showed flower organ/development stage-preferential expression patterns. Here, three OfMYB-related genes (OfMYB1R70/114/201), which were expressed nuclearly in floral organs, were found to be significantly involved in regulating the synthesis of floral VOCs. Only, OfMYB1R201 had transcriptional activity, thus implying that this gene participates in regulating the expression of VOC synthesis related genes. Remarkably, the transient expression results suggested that OfMYB1R70, OfMYB1R114, and OfMYB1R201 are involved in the regulation of VOC synthesis; OfMYB1R114 and OfMYB1R70 are involved in accelerating β-ionone formation. In contrast, OfMYB1R201 decreases the synthesis of β-ionone. Our results deepen our knowledge of the functions of MYB-related TFs and provide critical candidate genes for the floral aroma breeding of sweet osmanthus in the future.
Highlights
MYB-related transcription factors (TFs), named for their highly conserved 52 amino acid MYB domain, are predominant and critical members of the MYB TF family in plants (Riechmann and Ratcliffe, 2000; Dubos et al, 2010)
According to data on the sweet osmanthus genome, we found that the OfCCD4 promoter region contains numerous cis-acting regulatory elements, indicating that OfCCD4 might be regulated by other TFs (Yang et al, 2018)
To provide novel insight into the regulation of floral aroma by all MYB-related genes in sweet osmanthus, we comprehensively identified 212 putative MYB-related members by genome-wide analysis
Summary
MYB-related transcription factors (TFs), named for their highly conserved 52 amino acid MYB domain, are predominant and critical members of the MYB TF family in plants (Riechmann and Ratcliffe, 2000; Dubos et al, 2010). The MYB-related and R2R3MYB subfamily contain the highest quantity of genes within the MYB family (Liu et al, 2020). R2R3-MYB has been comprehensively characterized and reported to have diverse functions (Nesi et al, 2001; Koes et al, 2005; Ambawat et al, 2013), in enhancing volatile aroma production, promoting anthocyanin accumulation, and responding to abiotic stresses. Several MYB-related proteins control diverse physiological processes, the regulation of the anthocyanin biosynthesis pathway and the amelioration of multiple abiotic stresses. To date, the function of MYB-related genes in regulating the synthesis of floral aroma remains largely unknown
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