The Superoxide dismutase (SOD) Gene Family in Litchi (Litchi chinensis Sonn.): Identification, Classification, and Expression Responses in Leaves Under Abiotic Stresses

Superoxide dismutase (SOD) serves as a critical enzyme that is involved in plant development and abiotic stresses by effectively detoxifying reactive oxygen species (ROS). Though the <i>SOD</i> gene family has been reported across various plant species, its specific members and functional roles in litchi (<i>Litchi chinensis</i> Sonn.) remain poorly understood. In this study, a total of seven <i>SOD</i> (christened <i>LcSOD</i>) genes were identified from the litchi genome and classified into three groups across six chromosomes. Notably, genes from the same evolutionary branch had more similar structures and motif distributions. The <i>LcSOD</i> genes were confirmed to have a stronger collinearity with dicotyledons than with monocotyledons. Cis-acting elements analysis indicated that the <i>LcSOD</i> gene family was deeply involved in orchestrating growth, development, and responses to multiple phytohormones and diverse stresses. Expression patterns of the <i>LcSOD</i> genes across different tissues revealed universal and specific expressions. In leaves, expression levels of the <i>LcSOD</i> genes were induced by cold, heat, drought, and salt stresses, and transcript levels correlated positively with concomitant changes in key physiological parameters under the same conditions. In addition, the <i>LcSOD</i> genes were characterized for their physicochemical properties, subcellular localizations, secondary and tertiary structures, gene ontology (GO) annotations, and protein-protein interactions. Our findings offer comprehensive insights into the <i>LcSOD</i> gene family, enriching genetic resources. They provide a framework for functional characterization and the development of stress-resistant cultivars, driving both basic research and applied breeding programs in litchi.