Comparative transcriptome analysis reveals genes and pathways associated with anthocyanins in strawberry

BACKGROUND: Anthocyanins are not only one of the most important antioxidants in plants but also responsible for the coloration in strawberry (Fragaria x ananassa), it is suggested to be associated with ascorbic acid (AsA), sugars and plant hormones metabolism. OBJECTIVE: To elucidate the molecular differences of genes and pathways in the presence and absence of anthocyanins. METHODS: RNA sequencing (RNAseq) of red-fleshed strawberry 'Benihoppe' and its white-fleshed mutant 'Xiaobai' was performed. RESULTS: A total of 1,156 and 1,378 transcripts were differentially expressed (DE) in two cultivars at white stage and red stage respectively. Among them, 28, 49 and 72 DE transcripts were involved in AsA, sugars metabolism and plant hormones signaling respectively. Fruits of 'Benihoppe' with higher anthocyanins content contained higher AsA, the expression of D-galacturonate reductase (GalUR) in white-fleshed strawberry was down-regulated. Particularly, the expression of transcripts involved in sugars, jasmonic acid (JA) and abscisic acid (ABA) signaling was decreased, by contrast, the expression of transcripts involved in auxin and gibberellins (GAs) signaling was significantly increased. CONCLUSIONS: The lower AsA level in white-fleshed strawberry is possibly because of the lower flux of D-galacturonate biosynthesis pathway. Anthocyanins was associated with gene expression involved in AsA, sugars, and hormones signaling metabolisms.