Genome-Wide Thioredoxin System in Cardamine hupingshanensis: Role in Se Stress and Metabolism

The thioredoxin system is crucial for maintaining redox balance and stress responses in plants, but its role in selenium hyperaccumulators remains poorly understood. To our knowledge, this study is the first to perform a genome-wide identification of the thioredoxin system in Se hyperaccumulator <i>Cardamine hupingshanensis</i>. <i>We</i> identified 74 <i>ChTRX</i> genes and 12 <i>ChTR</i> genes, among which <i>ChTRX</i> genes accounted for approximately 86.05% of the total identified thioredoxin system genes. Phylogenetic and structural analyses classified the ChTRXs into two types, typical (with the WCGPC active site) and atypical (with the XCXXC active site), with typical ChTRXs comprising about 48.65% and atypical ChTRXs about 51.35% of the total ChTRXs. Subcellular localization analysis revealed a diverse distribution, such as chloroplast, mitochondrion and cytoplasm. The chloroplast-localized ChTRXs are the most abundant, accounting for approximately 60% of all ChTRXs. Under Se stress, the expression of <i>ChTRX</i> genes exhibited significant tissue-specific differences: approximately 52.5% of <i>ChTRX</i> genes showed responsive expression in the roots, while only 31.25% responded in the leaves, suggesting that root-specific genes may play an important role in mitigating Se-induced oxidative damage. Through expression data and molecular docking analysis, we discovered that ChACHT4-1 can interact with the disulfide bonds of key Se metabolism related enzymes ChAPK and ChAPR, suggesting its potential reductive activity. Furthermore, we predicted stress-responsive ChTRXs regulated by multiple ChNTRs in TRX-TR regulatory pathway. Overall, our research indicates that the thioredoxin system influences Se metabolism in <i>C. hupingshanensis</i> through redox regulation, providing insights into the Se tolerance mechanisms of hyperaccumulating plants and offering perspectives for optimizing Se biofortification strategies in crops.