Expression profiles of genes involved in sugar metabolism during fruit development and ripening of paprika ( Capsicum annuum L.)

Paprika ( Capsicum annuum L.) is a mild pepper with larger fruit and thicker fruit skin than common chilli and bell peppers. The process of fruit development in paprika is relatively more complex, including expansion, sweetening, and pigmentation. However, the lack of genetic information in this species impedes our understanding of the molecular mechanisms involved in the development and ripening of paprika fruit. We preformed high-throughput transcriptome sequencing analysis to characterize gene expression profiles of paprika fruit during development and ripening. Differential gene expression analysis revealed that 725, 684, and 652 genes were detected in transcriptome comparison of early fruits with mature green fruits, mature green fruits with breaker fruits, and breaker fruits with mature red fruits, respectively. Kyoto encyclopedia of genes and genomes pathway enrichment analysis indicated that sugar metabolism-related pathways were highly enriched during fruit development and ripening, and starch and sucrose metabolic pathways were most highly enriched. Based on the pathway regulation analysis, sugar metabolism–related genes function to regulate sucrose hydrolysis and starch, cellulose, and trehalose biosynthesis; and these genes were specifically expressed at different stages of development in paprika fruit. The expression profiles investigated in our study lay the foundation for further research into genes correlated with sugar metabolism in the developmental stages of paprika fruit.