Abstract
As a dominant mangrove species, Kandelia obovata is distributed in an intertidal marsh with an active H2S release. Whether H2S participates in the salt tolerance of mangrove plants is still ambiguous, although increasing evidence has demonstrated that H2S functions in plant responses to multiple abiotic stresses. In this study, NaHS was used as an H2S donor to investigate the regulatory mechanism of H2S on the salt tolerance of K. obovata 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 H2S enhanced the quantum efficiency of photosystem II (PSII) and the membrane lipid stability, implying that H2S is beneficial to the survival of K. obovata 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 H2S up-regulated photosynthesis and energy metabolism to help K. obovata to cope with high salinity. Specifically, H2S increased photosynthetic electron transfer, chlorophyll biosynthesis and carbon fixation in K. obovata 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 H2S under high salinity. These findings provide new insights into the roles of H2S in the adaptations of the K. obovata mangrove plant to high salinity environments.
Highlights
Mangroves comprise a complex and unique ecosystem that distributes along tropical and subtropical coastal tidal zone [1]
Jayatissa et al reported that there is an optimal growth for Sonneratia caseolaris with the lowest salt tolerance at 3–5 ppt salinity, and there is an optimal growth for Avicennia marina with the highest salt tolerance at 25–27 ppt salinity [2]
As a dominant species of mangrove plants, Kandelia obovata can distribute in areas with salinities up to 27.58 ppt seawater level [3]
Summary
Mangroves comprise a complex and unique ecosystem that distributes along tropical and subtropical coastal tidal zone [1]. Different mangrove species have different salinity preferences and achieve optimal growth at different salinity levels. Jayatissa et al reported that there is an optimal growth for Sonneratia caseolaris with the lowest salt tolerance at 3–5 ppt salinity, and there is an optimal growth for Avicennia marina with the highest salt tolerance at 25–27 ppt salinity [2]. As a dominant species of mangrove plants, Kandelia obovata can distribute in areas with salinities up to 27.58 ppt seawater level [3]. The salinity between 5 and 15 ppt is suitable for indoor-cultured K. obovata growth, while salinity up to 20 ppt inhibits the photosynthesis and growth of K. obovata [4]
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