Metagenomic analysis of the community structure and functional potential of Tamarix rhizosphere microbiomes along a soil salinity gradient

Together, these results support a salinity-driven transition in microbial functional strategy from "growth expansion" toward "homeostasis maintenance." Under high salinity, microbes appear to allocate more resources to maintaining cellular integrity and coping with stress, consistent with the observed enrichment of genetic information processing and repair-related functions. Mechanistically, the increased representation of Na⁺/H⁺ antiporter systems and V/A-type ATPases in the very high salinity group suggests that energy-dependent ion homeostasis is a prominent adaptation, helping regulate intracellular ion balance and mitigate salt toxicity. In contrast, pathways for compatible solute synthesis (e.g., betaine and ectoine biosynthesis) were relatively reduced, indicating that osmoprotection may rely less on de novo solute production and more on ion regulation and maintenance processes along this gradient. Overall, the metagenomic evidence clarifies how <i>Tamarix</i> rhizosphere microbiomes restructure taxonomically and functionally with increasing salinity and highlights key candidate mechanisms underpinning salt-stress adaptation. These insights provide a microbial basis for understanding plant-microbe interactions in desert saline-alkali soils and may inform ecological restoration and management in salinized regions.