Comparative proteomic analysis reveals the positive effect of exogenous spermidine on photosynthesis and salinity tolerance in cucumber seedlings

Abstract

Our results based on proteomics data and physiological alterations proposed the putative mechanism of exogenous Spd enhanced salinity tolerance in cucumber seedlings. Current studies showed that exogenous spermidine (Spd) could alleviate harmful effects of salinity. It is important to increase our understanding of the beneficial physiological responses of exogenous Spd treatment, and to determine the molecular responses underlying these responses. Here, we combined a physiological analysis with iTRAQ-based comparative proteomics of cucumber (Cucumis sativus L.) leaves, treated with 0.1 mM exogenous Spd, 75 mM NaCl and/or exogenous Spd. A total of 221 differentially expressed proteins were found and involved in 30 metabolic pathways, such as photosynthesis, carbohydrate metabolism, amino acid metabolism, stress response, signal transduction and antioxidant. Based on functional classification of the differentially expressed proteins and the physiological responses, we found cucumber seedlings treated with Spd under salt stress had higher photosynthesis efficiency, upregulated tetrapyrrole synthesis, stronger ROS scavenging ability and more protein biosynthesis activity than NaCl treatment, suggesting that these pathways may promote salt tolerance under high salinity. This study provided insights into how exogenous Spd protects photosynthesis and enhances salt tolerance in cucumber seedlings.

Effects of Exogenous Spermidine on Root Metabolism of Cucumber Seedlings under Salt Stress by GC-MS

“…These results clearly suggested that the cucumber seedlings with Spd attributed to significant improvement in growth status under high salinity. The findings were consistent with existing research results [16,19,22].…”

“…For instance, PAs can protect negatively charged macromolecules, such as DNA, RNA, and certain proteins [14]. Moreover, recent studies have shown that PAs have diverse functions and roles in response to plant stress [15,16]. For instance, PAs can act as direct hydroxyl radical scavenging and influence antioxidant activity at molecular and gene expression level.…”

“…For instance, PAs can act as direct hydroxyl radical scavenging and influence antioxidant activity at molecular and gene expression level. In addition, PAs participate in signal transductions and form a complex network with nitric oxide, abscisic acid, ethylene, and Ca 2+ in response to stress conditions [14,16]. According to this complex network from the cell to the entire plant, changes in their metabolism may cause a shift in a series of cellular metabolism pathways, such as energy metabolism and plant hormone synthesis [15].…”

“…Furthermore, compared to other plant hormones, PAs are often present in high concentrations. Hence, high PAs concentrations have been linked to salt stress tolerance in many plant species [16]. As a result, exogenous application of PAs has been widely used as a strategy to enhance salinity tolerance.…”

“…Serious secondary salinization in greenhouse soils causes large-scale physiological diseases of cucumber, reduces the yield and quality of cucumber, and leads to huge losses of economic value [18]. Recent studies in cucumber have shown that exogenous application of Spd could enhance seedlings stress tolerance [16,19]. Despite many studies on the functions and the roles of exogenous Spd in salt stress resistance, it remains unclear how exogenous Spd regulates cucumber growth and molecular responses.…”