Genome-Wide Identification of LACS Family Genes and Functional Characterization of CaLACS6/9 in Response to Cold Stress in Pepper (Capsicum annuum L.)

Long-chain acyl-CoA synthetase (LACS) is a crucial enzyme involved in cellular lipid metabolism, playing a significant role in plant development and adaptation to environmental stress. However, our understanding of the CaLACS gene family in pepper remains limited. In this study, we identified nine members of the CaLACS gene in the ‘UCD-10X-F1’ pepper genome and named them CaLACS1-CaLACS9 based on their chromosomal distribution. Phylogenetic analysis revealed that the subfamily I-A includes CaLACS1, CaLACS3, and CaLACS7; the subfamily I-C contains CaLACS2; the subfamily II comprises CaLACS4 and CaLACS8; and the subfamily III consists of the remaining members. Collinearity analysis showed that there were twelve collinear pairs between six CaLACS genes and five AtLACS genes, and two fragment replication gene pairs in the nine CaLACS genes of pepper. Furthermore, numerous cis-acting elements associated with stress response, hormonal regulation, development, and light response were identified in the promoter regions of the CaLACS genes. RNA-seq analysis indicated that CaLACS genes exhibit tissue specificity and are widely expressed in pepper leaves following treatment with exogenous plant hormones, and under conditions of cold, heat, drought, and salt stress. Additionally, virus-induced gene silencing (VIGS) technology was employed to further investigate the roles of CaLACS6 and CaLACS9. Silencing these target genes in pepper seedlings increased their sensitivity to cold stress, as evidenced by the accumulation of reactive oxygen species (ROS), reduced antioxidant defense capacity, and decreased expression levels of cold-responsive and ROS-related genes. The findings of this study provide valuable insights into the functional roles of the CaLACS gene family and highlight CaLACS6 and CaLACS9 as promising candidate genes for enhancing cold tolerance in pepper.