Genome-Wide Identification and Expression Analysis of the Pepper β-1,3-gucanase Gene Family in Response to <i>Phytophthora capsici</i> Stresses

Peppers are widely cultivated around the world, yet they suffer from infections caused by <i>Phytophthora capsici</i> fungi throughout the year, which severely impacts their yield. The β-1,3-glucanase gene has been shown in previous studies to significantly enhance plants’ ability to cope with both biotic and abiotic stresses, including fungal infections. However, its function in peppers has not been reported. In this study, 80 <i>CaBG</i> genes were initially identified, before being filtered down to 54 <i>CaBGs</i> in peppers, and analyses conducted on the physicochemical properties, chromosomal localization, phylogenetic tree relationships, synteny, promoters, and gene expression levels of the <i>BG</i> gene family. The results indicated that these 54 <i>CaBG</i> genes are located on 12 chromosomes. Phylogenetic tree analysis classified the <i>CaBG</i>s into three subfamilies, α, β, and γ, each with its own specific functions, with the γ subfamily being associated with disease resistance in peppers. Synteny analysis showed that CaBG genes are relatively conserved and have not undergone extensive whole-genome duplication events. Promoter analysis indicated that <i>CaBG</i>s are induced by plant hormones and various external stressors. Transcriptomic and RT-qPCR analyses revealed that the <i>CaBG7</i> and <i>CaBG12</i> genes were significantly activated following infection by <i>P. capsici</i>, with the expression levels of these two genes being markedly higher in resistant plants compared to susceptible ones. Based on the phylogenetic tree and gene expression analysis, we propose that <i>CaBG7</i> and <i>CaBG12</i> may be key genes for disease resistance in chili peppers. This study provides a theoretical basis for breeding <i>P. capsici</i>-resistant chili peppers by molecular breeding methods.