Comprehensive analysis of Vicia faba light-harvesting chlorophyll a/b binding protein (Lhc) revealed the roles of VfLhcb1.5, VfLhcb3.3, VfLhcb4, and VfLhca4 in photosynthesis and stress tolerance

• The faba bean genome contains 23 VfLhc genes. • VfLhcs show light-dependent, tissue-specific expression and stress responses. • Overexpression of VfLhcb1.5, VfLhcb3.3, and VfLhcb4 increases photosynthetic efficiency through elevated chlorophyll content. • VfLhcb1.5, VfLhcb4, and VfLhca4 were susceptibility genes, and their overexpression facilitated Phytophthora infestans infection. • VfLhcb1.5, VfLhcb4 and VfLhca4 modulate ROS homeostasis under stress conditions. In addition to its indispensable role in photosynthesis, L ight- h arvesting c hlorophyll a/b binding protein (Lhc) is also involved in plant growth, development, and stress responses. However, the specific roles of Vicia faba VfLhcs in photosynthesis and stress tolerance remain unclear. Here, in silico analysis and in vivo assays were conducted to investigate the characteristics and functions of VfLhcs. Phylogenetic analysis grouped 23 VfLhcs into three subfamilies. Their promoter regions were enriched with cis-elements responsive to light, plant hormones, abiotic stress, and plant growth and development. RT-qPCR analysis revealed that VfLhcs were highly expressed in chlorophyll-containing tissues and exhibited stress-specific regulation. Drought stress (20% PEG-6000, 72 h) induced a 4.9- to 50.1-fold upregulation in roots, whereas salt stress (200 mM NaCl, 72 h) and darkness (0 h light/24 h dark, 72 h) reduced expression by 93.0-99.3% and 78.2-100.0%, respectively. Confocal microscopy confirmed that VfLhcs were localized in chloroplasts. Overexpression of VfLhcb1.5, VfLhcb3.3 , and VfLhcb4 increased chlorophyll content by 20.0 -35.7%, which in turn enhanced the net photosynthetic rate by 13.5-23.1%. Under various stress conditions, VfLhcb1.5, VfLhcb4 , and VfLhca4 promoted significant over-accumulation of reactive oxygen species (ROS), disrupting ROS homeostasis. While this enhanced response improved tolerance to abiotic stresses, it paradoxically facilitated infection by the pathogen Phytophthora infestans , suggesting that these genes may act as susceptibility factors under biotic stress. In conclusion, this comprehensive analysis of VfLhcs highlights their roles in photosynthesis and responses to both abiotic and biotic stresses, providing a foundation for further exploration of their functional mechanisms.