Genome-wide identification of the Glutathione Peroxidase (GPX) gene family in Taxodium distichum and functional characterization of TdGPX9 in enhancing salt tolerance.
This study systematically identified 10 TdGPX genes in Taxodium distichum, demonstrating that the nucleocytoplasmic-localized TdGPX9 plays a pivotal role in salt stress response. Overexpression of TdGPX9 significantly enhances salt tolerance by strengthening the antioxidant defense system and improving root system plasticity under stress. Taxodium distichum is a premier coniferous species renowned for its exceptional waterlogging and salinity tolerance, serving as a vital forest resource for coastal afforestation and wetland ecological restoration. Within the physiological framework of plant stress resistance, the glutathione peroxidase (GPX) family represents a cornerstone of the antioxidant enzymatic system, playing a critical role in scavenging reactive oxygen species and maintaining cellular redox homeostasis. In this study, 10 TdGPX genes were identified via a comprehensive genome-wide analysis and mapped across eight chromosomes. These genes possess a highly conserved Thioredoxin_like domain, with structural and motif analyses revealing a well-maintained arrangement of conserved motifs within each subgroup. The promoter analysis identified a sophisticated regulatory network enriched with cis-acting elements responsive to light, phytohormones, and abiotic stresses, suggesting their integration into diverse signaling pathways. Expression profiling across various tissues and embryonic developmental stages further highlighted the versatile roles of TdGPX members in plant growth and organogenesis. Notably, qRT-PCR analysis identified the nucleocytoplasmic-localized TdGPX9 as a primary respondent to salinity. Functional validation demonstrated that TdGPX9 overexpression significantly enhances salt tolerance in transgenic Arabidopsis and T. distichum callus by strengthening the antioxidant defense system. Furthermore, TdGPX9 promoted root system plasticity under stress, as evidenced by increased lateral root density. These findings provide a systematic basis for understanding the redox-regulatory mechanisms in baldcypress and offer vital genetic resources for improving forest resilience in coastal wetland ecosystems.