Comparative Proteomic Analysis Reveals the Regulatory Effects of HS on Salt Tolerance of Mangrove Plant .

As a dominant mangrove species, is distributed in an intertidal marsh with an active HS release. Whether HS participates in the salt tolerance of mangrove plants is still ambiguous, although increasing evidence has demonstrated that HS functions in plant responses to multiple abiotic stresses. In this study, NaHS was used as an HS donor to investigate the regulatory mechanism of HS on the salt tolerance of seedlings by using a combined physiological and proteomic analysis. The results showed that the reduction in photosynthesis (Pn) caused by 400 mM of NaCl was recovered by the addition of NaHS (200 μM). Furthermore, the application of HS enhanced the quantum efficiency of photosystem II (PSII) and the membrane lipid stability, implying that HS is beneficial to the survival of seedlings under high salinity. We further identified 37 differentially expressed proteins by proteomic approaches under salinity and NaHS treatments. Among them, the proteins that are related to photosynthesis, primary metabolism, stress response and hormone biosynthesis were primarily enriched. The physiological and proteomic results highlighted that exogenous HS up-regulated photosynthesis and energy metabolism to help to cope with high salinity. Specifically, HS increased photosynthetic electron transfer, chlorophyll biosynthesis and carbon fixation in leaves under salt stress. Furthermore, the abundances of other proteins related to the metabolic pathway, such as antioxidation (ascorbic acid peroxidase (APX), copper/zinc superoxide dismutase (CSD2), and pancreatic and duodenal homeobox 1 (PDX1)), protein synthesis (heat-shock protein (HSP), chaperonin family protein (Cpn) 20), nitrogen metabolism (glutamine synthetase 1 and 2 (GS2), GS1:1), glycolysis (phosphoglycerate kinase (PGK) and triosephosphate isomerase (TPI)), and the ascorbate-glutathione (AsA-GSH) cycle were increased by HS under high salinity. These findings provide new insights into the roles of HS in the adaptations of the mangrove plant to high salinity environments.