Comprehensive analysis of Capsicum annuum CaLhcs uncovered the roles of CaLhca5.1 and CaLhcb1.7 in photosynthesis and stress tolerance

The light-harvesting chlorophyll a/b-binding proteins (Lhcs) are integral to plants' capture and transfer of light energy during photosynthesis. However, the Lhc gene family remains unexplored in pepper. In this study, 37 CaLhcs (Capsicum annuum Lhc) were identified from the reference genome and classified into five subfamilies (Lhca, Lhcb, CP24, CP26, and CP29) based on phylogenetic relationships and conserved domains, with members of each subfamily displaying similar conserved motifs and gene structures. Cis-element analysis revealed an enrichment of light-responsive elements within CaLhcs (46.1%). Transcriptome analysis showed that most CaLhcs are specifically expressed in leaves, flowers, and pericarp and are responsive to stressors, including NaCl, cold, heat, H2O2, and d-mannitol. Post-transcriptional regulation analysis identified 11 miRNAs that target nine CaLhcs through cleavage. RT-qPCR analysis validated the involvement of CaLhcs in response to NaCl stress. Localization studies confirmed that CaLhca4.1, CaLhcb1.1, CaLhca1.7, CaLhcb1.11, and CaLhcb6.1 are chloroplast-localized, whereas CaLhca5.1 localizes in the nucleus. Overexpression of CaLhcb1.7 and CaLhca5.1 increased chlorophyll content and net photosynthetic rate, enhancing photosynthesis. Additionally, CaLhcb1.7 and CaLhca5.1 reduced ROS accumulation, bolstering the plant's resistance to pathogens and salt stress. These findings provide a foundation for further exploration of CaLhcs in photosynthesis and stress tolerance mechanisms.