Gene Identification, Expression Analysis, and Molecular Docking of SAT/OASTL Reveal the Molecular Mechanisms of Selenocysteine Synthesis in Cardamine hupingshanensis

Abstract

Background A complex coupled with serine acetyltransferase (SAT) and O-acetyl serine (thiol) lyase (OASTL) is the key enzyme that catalyses selenocysteine synthesis in plants. The basic bioinformatics and functions of these two gene families have been reported for many plants in addition to Cardamine hupingshanensis, and the response of the ChSAT and ChOASTL family members under selenium stress has not been examined to date.Results In this study, genome-wide identification and comparative analysis of ChSAT and ChOASTL were performed. The eight genes from the ChSAT family were divided into three branches, and the thirteen genes from the ChOASTL family were divided into four branches by phylogenetic analysis and sequence alignment, indicating the evolutionary conservation of the gene structure and its association with other plant species. The expression of members in the ChSAT and ChOASTL families was studied under selenium stress, and ChSAT1;2 and ChOASTLA1;2 were upregulated by 9.4- and 7.4-fold, respectively, showing that these two proteins are involved in the synthesis of selenocysteine. Likewise, ChCS-like protein was upregulated by 8.8-fold, playing key roles in degradation. In addition, molecular docking simulations showed that ChOASTL binds to the test compound selenophosphate more strongly than selenide and sulfide, and the major motifs that bind the target compound are usually located at residues of amino acids Lys46, Gly181, Thr182, Gly183, Thr185 and Ser269.Conclusions This study revealed that selenophosphate was the optimal substrate of ChOASTL and participated in selenocysteine synthesis. The results of gene expression and molecular docking indicated that the ChSAT and ChOASTL genes were upregulated under selenium stress, and ChOASTL family genes could both synthesize and degrade cysteine/selenocysteine, which provided a theoretical basis for the regulation of selenocysteine synthesis.