De novo transcriptome sequencing of blue honeysuckle fruit (Lonicera caerulea L.) and analysis of major genes involved in anthocyanin biosynthesis

Blue honeysuckle (Lonicera caerulea L.) is an economically important berry because its flavonoid and anthocyanin contents are generally higher than those of other fruits. However, research on anthocyanin accumulation in blue honeysuckle is limited by insufficient genome information. In this paper, Illumina HiSeq™ 2000 platform was used for the transcriptome sequencing of blue honeysuckle fruit in two periods (green-ripe and veraison periods). This platform was also used to obtain more than 116 million sequencing reads. Those reads were de novo assembled and produced 66,610 All-unigenes. After a comparison between currently available public databases (NR, Swiss-prot, KEGG, COG, and GO) and obtained annotated unigenes, 43,202 unigenes (64.86 %) showed similarity to known protein sequences (E value ≤0.00001). The KEGG pathway indicated that some genes related to anthocyanin biosynthesis existed mainly in the secondary metabolic pathway of the samples. A series of enzymes related to anthocyanin biosynthesis was identified in NR annotation; some candidate genes and their metabolic pathways were also found. We conducted a preliminary analysis on the expression of some important enzymes (PAL, CHS, F3H, ANS, and DFR) and transcription factors (MYB, bHLH, and WD40) related to anthocyanin biosynthesis through quantitative real-time PCR to explore the biosynthesis process of anthocyanin and the accuracy of sequencing results. Information on blue honeysuckle transcriptome can serve as an important reference for breeding and production.