Transcriptome and carotenoids profiling of flowers in different Osmanthus fragrans cultivars provide insight into transcriptional control network of carotenoid-related genes expression

• The difference in the content and composition of carotenoids in four Osmanthus fragrans cultivars was investigated. • The critical genes contributing to carotenoids accumulation were identified. • Potential TF candidates participating in expression regulation of critical genes were predicated. • Nine TFs were identified having a similar expression pattern with OfCCD4 in two cultivars. • Established a possible regulatory network between transcription factors and critical genes. Carotenoids are important natural pigments and essential for the coloration formation in plant petals. The difference in the accumulation of carotenoids always leads to the difference in flower coloration in O. fragrans . In this study, flower petals from different O. fragrans groups with different coloration were used. The critical genes and corresponding transcription factor (TF) candidates playing important role in carotenoid accumulation in petals were investigated through the integrated carotenoid profiles and transcriptomic analysis. We found the difference in the contents and compositions of carotenoids endow flower petal with diversified coloration, and expression levels of OfNCED3, OfDXS2, OfCCD1, OfGGPPS2, OfDXR3, OfBCH2 , and OfCCD4 were critical factors modulating carotenoid accumulation. Further analysis showed that 61, 19, 21, 47, 16, 21, and 29 potential TF candidates with high Pearson correlation coefficients (|r|> 0.80) were but also for the first time speculated to interact with the promoter of OfNCED3, OfDXS2, OfCCD1, OfGGPPS2, OfDXR3, OfBCH2 , and OfCCD4 , respectively. In which, 17 TF candidates might bind to multiple gene promoters (>2) for affecting the carotenoid accumulation in O. fragrans petals. Furthermore, nine and one of OfCCD4 potential TFs presented similar and opposite expression pattern with OfCCD4 , respectively, further indicating they might potentially participate in OfCCD4 expression regulation. Collectively, our data established the possible regulatory network between the critical genes and potential TF candidates and provided useful information for studying the underlying transcriptional mechanism of carotenoid accumulation in O. fragrans .