Identification of pepper genes involved in the response to CO 2 enrichment using RNA-Seq analysis

Pepper is widely cultivated, and the application of CO2 promotes photosynthesis and increases its yield. However, the molecular mechanisms underlying this are still unclear. In this study, the photosynthetic correlation indexes under elevated CO2 and control conditions were compared. The application of CO2 increased the photosynthetic capacity of pepper. Moreover, RNA-Seq analysis was used to identify genes that were differentially expressed between pepper leaves grown in CO2-enriched conditions and those grown in control conditions. The 149 differentially expressed genes (DEGs) were found to be involved in photosynthesis and other metabolic processes. According to GO significant enrichment analysis, the proteins encoded by the DEGs were mainly found to be located in the chloroplast, the chloroplast matrix, and the apoplast. According to KEGG significant enrichment analysis, the DEGs were found to be involved in glutathione metabolism; starch and sucrose metabolism; and stilbenoid, diarylheptanoid, gingerol, flavonoid, and phenylpropanoid biosynthesis. The DEGs were also involved in the pentose phosphate pathway, carbon metabolism, and porphyrin and chlorophyll metabolism. Based on the GO annotation and the KEGG database analysis, ten of the DEGs identified were suggested to be involved in photosynthesis and related processes; these genes were predicted to have roles in carbohydrate, soluble sugar, and glutathione metabolism, and in raffinose, cysteine, nucleotide, and ABA biosynthesis. These DEGs are involved in the pentose phosphate pathway and tricarboxylic acid cycle of carbon assimilation during photosynthesis. One of the DEGs was also found to be involved in chlorophyll biosynthesis. These results lay the foundation for further investigation of the molecular mechanisms and genes involved in the response to CO2 enrichment in peppers.