Integrative analysis of transcriptome and metabolome reveal the differential tolerance mechanisms to low and high salinity in the roots of facultative halophyte Avicennia marina.

This article focuses on the differential tolerance mechanisms of the facultative halophyte mangrove Avicennia marina roots under low (250 mM NaCl) and high (500 mM NaCl) salinity, revealed through integrative transcriptomic and metabolomic analyses. Under low salinity, A. marina upregulates the potassium transporter HAK8 to enhance K⁺ uptake, activates abscisic acid (ABA) signaling, and accumulates mannitol, unsaturated fatty acids, amino acids, and L-ascorbic acid to maintain osmotic balance and antioxidant defense. In contrast, high salinity induces strong expression of AKT1 and NHX2 transporters for K⁺ transport and Na⁺ compartmentalization, downregulates cytokinin, jasmonic acid, and jasmonic acid-isoleucine signaling, promotes glycolysis and the TCA cycle to supply energy, and triggers fatty acid degradation and amino acid consumption for secondary metabolite synthesis. These findings indicate that A. marina’s salt tolerance involves complex regulatory networks with distinct physiological and metabolic adjustments depending on salinity level.