Pink-flowered strawberry is a new promising ornamental flower derived from intergeneric hybridization (Fragaria × Potentilla) with bright color, prolonged flowering period and edible fruits. However, the transcriptional events underlying anthocyanins biosynthesis pathway have not been fully characterized in its petal coloration. The pigment compounds accumulated in its fruits were the same as cultivated strawberry, but different from in its flowers. To gain insights into the regulatory networks related to anthocyanin biosynthesis and identify key genes, we performed an integrated analyses of the transcriptome and metabolomes involved in red petals at three development stages (Bud stage (L), Coloration beginning stage (Z) and Big bud stage (D)) of pink-flowered strawberry. Transcript and metabolite profiles were generated through high-throughput RNA-sequencing and high-performance liquid chromatography coupled with mass spectrometry, respectively. The results showed that the main pigments of red and dark pink petals were anthocyanins, among which cyanidins were the main compounds. There were no anthocyanins detected in white-flowered hybrids. A total of 50 285 non-redundant unigenes were obtained from the transcriptome databases, among which 59 differentially expressed genes could be identified as putative homologues of flower coloration related genes. Based on a comprehensive analysis relating pigmentation compounds to gene expression profiles, the mechanism of flower color formation was examined in pink-flowered strawberry. Furthermore, a new hypothesis explaining the lack of color phenotype of the white-flowered strawberry hybrids from the level of the transcriptome. The expression patterns of FpDFR gene and FpANS gene corresponded to the accumulation patterns of cyanidin contents in pink-flowered strawberry hybrids with different shades of pink; Whereas other anthocyanin biosynthesis genes were weakly related flower color deepened. Moreover, FpANS, FpBZ1 and FpUGT75C1 genes were the key factors that lead to the inability to accumulate anthocyanins in the white petals of PFS hybrids. Meanwhile, the competitive effect of FpFLS gene and FpDFR gene may further inhibit anthocyanin synthesis. The data presented herein are important for understanding of the molecular mechanisms underlying the petal pigmentation and will be powerful for integrating into novel genes that are potential targets for breeding new valuable pink-flowered strawberry cultivars.
Overall design: Three petal development stages [Bud stage (L,CK), Coloration beginning stage (Z) and Big bud stage (D)] of pink-flowered strawberry. were used to construct nine libraries with three biological replicates, which were named as PH_L1, PH_L2, PH_L3, PH_Z1, PH_Z2, PH_Z3, PH_D1, PH_D2 and PH_D3, respectively.
Less...