Proteomic Changes Of Salt Stress Response In Kandelia Candel Leaves And Analysis Of Differentially Expressed Proteins

Salinity in agricultural land is a major problem worldwide, placing a severeconstraint on crop growth and productivity in many regions, and increasedsalinization of arable land is expected to have devastating global effects.Kandeliacandel is a kind of typical mangrove and saline plant. Mangrove plants are diversecommunities in intertidal zones of tropical and subtropical coastal rivers, estuaries andbays. The characteristic of mangrove habitat is high salt. Kandelia candel is majormangrove species of the eastern group and is dominant along South China coast. Tostudy the mechanism of salt resistance is of important theoretical significance andbroad application prospects. It also plays an important role in guiding the naturalizedplant, genetic optimization and so on. To understand the molecular mechanisms of saltstress on Kandelia candel, a comparative proteomic approach was carried out toidentify the salt stress-responsive proteins. Four-leaves-old Kandelia candel seedlingswere expose to150(control group),300,450, or600mM NaCl. Proteins extractedfrom the leaves of Kandelia candel seedlings were separated. To complement theproteomic results, several enzymatic activity assays were also carried out, to gainfurther insight in the mechanism behind salt stress response.To obtain detailed information about the proteome changes, we scanned the gelsand analyzed them using Image-master software. The quantitative analysis revealedthat49protein spots were differentially expressed over2times. These49proteinswere analyzed by by matrix-assisted laser desorption ionization-time of flight-tandemmass spectrometry (MALDI-TOF-MS/MS).48proteins were identified successfully.Of these48proteins,36were up-regulated,7were down-regulated and5wereundulatory-regulated. Moreover, they have been subdivided in functional categories:photosynthesis-related proteins(16.7%), protein metabolism(8.3%), amino acidmetabolism related proteins(10.4%), energy and carbohydrate metabolism (31.3%),detoxifying and antioxidation (4.2%), Signal transduction (4.2%), chaperone (10.4%)and other proteins(14.6%). Proteins involved in energy and carbohydrate metabolism were up-regulated,suggesting that energy and carbohydrate metabolism of Kandelia candel seedlings isvery active in the process of salt stress, which can provide the necessary energy andmaterial for physiological activities. Vacuolar H~+_ATPase establishes and maintainsan electrochemical proton grandient across the tonoplast Na~+/H~+antiporter, providingthe driving force for active transport of metabolites and ions, The electrochemicalproton can compartmentalize Na~+into the vacuole. Vacuolar sequestration of Na~+is avital and effective strategy for osmotic adjustment that reduces the Na~+concentrationin the cytosol in plants. The increase of vacuolar H~+-ATPase may underlieion-selective absorption and homeostasis in leaves cells of Kandelia candel seedlingswhich have adapted to environmental stress.Salt stress induces an accumulation of active oxygen species (ROS) that damagethe balance of ROS metabolism system. In order to scavenge these ROS, some plantcan maintain and enhance the avtivity of ROS-scavenging enzymes. Finally,regulation of signaling networks, such as up-regulation of14-3-3protein, couldenhance the stress signal induction and a normal physiological state.The studis about the machanism of plant salt resistance mainly were focus onhalophytes and nonhalophytes. Mangrove have evolved a set of salt resistancemechanism, which is different from terrestrial plants or fresh water plant. Kandeliacandel is ideal materials for researching the mechanism of plant salt resistance. Todate, there is still a lack of researches as to how salt stress affects the expression ofproteins in Kandelia candel. In this study, proteome analysis was used to identify themechanisms responsible for the effects of salt stress on Kandelia candel. The resultscould provide peoteomic evidence for explaining mechanism of salt resistance, andlay the foundation for the further research of expanding salt-resistant gene resources,revealing molecular mechanisms of salt resistance and breeding salt-resistant plants.