Transcriptome analysis of flower color variation in five Rhododendron species (Ericaceae)

Rhododendron genus is famous with important ecology impacts, ornamental values, and high medicine values. To obtain a comprehensive overview of anthocyanin regulatory networks, RNA-seq and de novo assembly of five Rhododendron species flower tissues were performed, generating 159,408 unigenes with an average length of 490 bp and an N50 of 552 bp. In particular, 106,766 unigenes could be annotated. Flavonoid biosynthesis was the most abundant KEGG pathway. Genes controlling flower color varied in different species: transcripts involving in carotenoid biosynthesis and isoflavonoid biosynthesis highly expressed in Rhododendron molle G. Don possessing yellow color flower; genes involved in flavone and flavonol biosynthesis showed higher abundance in Rhododendron fortune Lindl. with light pink flowers; transcripts of unigenes participated in flavonoid biosynthesis exhibited higher levels in Rhododendron mariesii Hemsl. with pink color; unigenes involved in anthocyanin biosynthesis showed higher mRNA levels in Rhododendron simsii Planch. with red color; genes involved in carotenoid biosynthesis and flavonoid biosynthesis showed higher expression levels in Rhododendron pulchrum Sweet with purplish red flowers. The five species were clustered into two main groups: group 1 (R. fortune and R. mariesii) and group 2 (R. simsii, R. molle and R. pulchrum) based on expression levels of differentially expressed genes (DEGs). In particular, R. molle showed a closer relationship with R. simsii. This study will provide rich genetic information for further mechanism analysis of flower color variation and genetic improvement of flower color in Rhododendron species.

Automated summary

The study conducted RNA-seq and de novo assembly of flower tissues from five Rhododendron species, revealing that different genes regulate flower color variation in different species. The species were clustered into two main groups based on the expression levels of differentially expressed genes (DEGs), with Rhododendron molle showing a closer relationship with R. simsii. This research provides valuable genetic information for further analysis of flower color variation and genetic improvement in Rhododendron species.