AMF-induced salinity tolerance in durum wheat is associated with transcriptomic modulation of the Cation/Calcium Exchanger 1 (CCX1).

Salinity is a major abiotic stress that severely constrains durum wheat (Triticum turgidum subsp. durum) productivity. Although the beneficial effects of arbuscular mycorrhizal fungi (AMF) on plant performance under salt stress are well established, the molecular mechanisms underlying this symbiosis remain insufficiently characterized. In this study, we applied an integrated transcriptomic and network-based approach to identify regulatory components associated with AMF-mediated salt stress responses in durum wheat. Comparative RNA-Seq analysis between salinity-stressed and AMF-treated plants revealed 572 differentially expressed genes (DEGs). Network topology analysis identified the Cation/Calcium Exchanger 1 (TdCCX1) as a candidate hub gene with high centrality, suggesting a potential integrative role in ion and stress signaling pathways. Promoter analysis of TdCCX1 revealed multiple stress- and symbiosis-related cis-elements, indicating dual regulatory control. Physiological and biochemical validation in a salinity-susceptible durum wheat genotype showed that AMF inoculation, particularly with Rhizophagus irregularis, significantly improved shoot and root biomass, enhanced K⁺/Na⁺ homeostasis, increased phosphorus accumulation, and reduced oxidative damage under salinity. Notably, TdCCX1 expression was strongly induced by salt stress but significantly attenuated in AMF-colonized plants. These findings suggest that AMF colonization modulates ion-exchange-related transcriptional networks, potentially reducing the plant's reliance on energy-intensive internal transport processes. This study provides transcriptome-guided insights into AMF-host interactions under salinity and highlights TdCCX1 as a promising candidate for future functional studies.