Transcriptomic analysis revealed distinctive modulations of arbuscular mycorrhizal fungi inoculation in halophyte Suaeda salsa under moderate salt conditions

As the area of soil salinization increases, the ecological niche of halophytes is important given their high salt tolerance. The physiological response of mycorrhizal halophytes is not completely consistent with that of mycorrhizal glycophytes under salt conditions. However, less information is known about the regulation of genes included by arbuscular mycorrhizal (AM) fungi in halophytes. A greenhouse pot experiment with inoculation (Funneliformis mosseae) treatments was performed to research the physiological and transcriptomic responses in the halophyte Suaeda salsa under 100 mM NaCl. The results revealed that AM symbiosis significantly increased shoot biomass, shoot height and shoot Na+ accumulation. AM fungi decreased the Na+ concentration and soluble sugar concentration in the shoots of S. salsa. Transcriptomic analysis revealed 1316 and 424 differentially expressed genes (DEGs) in shoots and roots, respectively. DEGs in shoots were involved in carbohydrate and energy metabolism; photosynthesis; amino acid metabolism; cofactors and vitamins metabolism, such as glyoxylate and dicarboxylate metabolism; carbon fixation in photosynthetic organisms; and vitamin B6 metabolism. Interestingly, the expression of DEGs related to photosynthesis was downregulated by AM fungi in S. salsa under 100 mM NaCl. DEGs of roots were enriched in starch and sucrose metabolism; and auxin transmembrane transporters. These distinctive modulations of AM fungi in genes and physiological parameters are potentially associated with the growth of halophytes under moderate salt conditions. This study will improve our understanding of the effect of AM fungi in halophytes under moderate salt conditions and suggests that the phytoextractive strategy of halophytes combined with AM fungi hold significant ecological potential in salinized ecosystems.