Transcriptome profiling reveals the regulatory mechanisms of ascorbic acid and flavonoid synthesis and metabolic processes in fruit development of Ribes nigrum

Abstract

Abstract Background The blackcurrant (Ribes nigrum L.) is rich in nutritional value. It is rich in ascorbic acid and flavonoids with excellent antioxidant properties. Fruit quality is an important factor affecting subsequent processing and production, yet the molecular mechanisms underlying the transcriptional regulation of blackcurrant fruit quality are largely unknown. Results In the current study, comparative transcriptome analysis investigated the similarities and differences between two blackcurrant varieties: 'Adelinia' and 'Heifeng' at four fruit developmental stages (young, expansion, veraison, and ripe fruit). Additionally, we observed variations in a number of physiological indicators during the growth of blackcurrant fruits. The results indicate that, during the development of blackcurrant fruits, ascorbic acid content continued to decrease, whereas flavonoid content was lowest in the veraison period. The fruit size of 'Adelinia' variety was larger than that of 'Heifeng' variety throughout the developmental. Based on the results of the transcriptome sequencing data, a total of 4295 up-regulated genes and 3529 down-regulated genes were obtained between 'Adelinia' and 'Heifeng' varieties; A total of 6,349 up-regulated and 5,770 down-regulated genes were identified between the four developmental periods, respectively. The expression of 4 genes, PMM, APX, GME, and PGI has a strong correlation with AsA content. while two APX, two AO, and one MDHAR genes showed a strong negative correlation with AsA content. A total of 19 genes related to flavonoid biosynthesis were screened. The KEGG pathway enrichment analysis showed that many DEGs were enriched in the plant hormone signal transduction (ko04075) pathway and the photosynthesis-antenna proteins (ko00196) pathway. Conclusions We predicted that the PMM, APX, GME, and PGI genes, which are positively correlated with ascorbic acid, may play an important role in the biosynthesis of AsA; while the negatively correlated APX, AO, and MDHAR genes may be critical for AsA in the recycling pathway. DFR, ANR, CHI, CHS, 4CL, and LAR genes are important regulators of flavonoid synthesis. Also predicted the regulatory influences of various plant hormones on the fruit size of blackcurrants. We provide genetic resources for improving fruit quality and size as well as for rationalizing the use of plant growth regulators to improve fruit quality.