Preliminary study on the coloring mechanism of red flowers in a hybrid between cymbidium goeringii and cymbidium hybridum

In order to explore the coloring mechanism of red flower in Cymbidium hybrids, the hybrid Huangjinmei with red flowers between C. georigingii with green flowers and C. hybridum with yellow flowers was selected as the experimental material. The key structural genes and the regulatory genes affecting the color were selected based on the transcription sequencing data of the petals at little flower bud and initial bloom stages. The differentially expressed unigenes (DEGs) was verified by qPCR, and the contents of the pigments (carotenoid, chlorophyll a, chlorophyll b, anthocyanin, total flavonoids) in the petals were detected by the spectrophotometer. The results showed that a total of 113780 Unigenes was obtained by transcriptome sequencing, the ratio of Unigenes with length of 200-300 bp was 42.68%, among which 44088 Unigenes were annotated. Compared to the little flower bud stage, there were 1855 DEGs were up-regulated and 2494 were down-regulated at initial bloom stage. DEGs were assigned into 47 gene ontology (GO) terms, and 1219 DEGs were assigned into 166 kyoto encyclopedia of genes and genomes (KEGG) pathways. According to the KEGG pathway and the gene annotations, 54 key structural genes and 21 transcriptional regulatory genes associated with the flower color were screened. The expression levels of DFR, ANS, 3, 5GT genes and Zm1, Hv1, MYB305 transcription factors of anthocyanin biosynthesis was up-regulated at initial bloom stage. Blasting to the homology genes in the NCBI, DFR, ANS, 3GT genes were found having the highest homology with the genes of Cymbidium hybrid cultivar, 5, 3GT, 3, 5GT, Zm1 genes having the highest homology with the genes of Phalaenopsis equestris and Dendrobium catenatum, and the transcription factors Hv1, MYB305 having the highest homology with the genes of C. ensifolium. The qPCR results showed that the expressions of genes were consistent with the resulting transcription sequencing. The contents of total flavonoids in the petals were higher than the contents of carotenoid and chlorophyll at different stages, and the contents of anthocyanin went up at initial bloom stage. The results of this study provide a reference for the study of the function analysis of flower color genes in Cymbidium hybrids. (authors)