Role of Plasma Membrane NADPH Oxidase in Response to Salt Stress in Cucumber Seedlings

Abstract

Plasma membrane NADPH oxidases (RBOHs, EC 1.6.3.1) are known as the main ROS generators involved in plant adaptation to stress conditions. In the present work, regulation of NADPH oxidase was analyzed in cucumber (Cucumis sativus L. var. Krak) seedlings exposed to salinity. RBOH activity and gene expression, as well as H2O2 content, were determined in the roots of plants treated with 50 or 100 mM NaCl for 1 h, and 50 mM NaCl for 1 or 6 days. It was found that enzyme activity increased in parallel with an enhancement in the H2O2 level in roots exposed to 100 mM NaCl for 1 h, and to 50 mM NaCl for 1 day. The expression of some CsRboh genes was induced by salt. Moreover, an increase in the activity of G6PDH, providing the substrate for the NADPH oxidase, was observed. In seedlings subjected to salinity for a longer time, antioxidant enzymes—including superoxide dismutase, catalase, and ascorbate peroxidase—were activated, participating in maintaining a steady-state H2O2 content in the root cells. In conclusion, NADPH oxidase and endogenous H2O2 up-regulation seem to be early events in cucumber response to salinity.

Water and Nutrient Recovery for Cucumber Hydroponic Cultivation in Simultaneous Biological Treatment of Urine and Grey Water

“…In cucumber plants grown on NUGE, we observed increased H 2 O 2 levels, lipid peroxidation, APX activity, and proline content in the shoots ( Figure 5 ). The reaction of plants to salinity is often accompanied by increased production of H 2 O 2 [ 24 , 30 , 68 , 69 ]. NUGE-cultivated plants accumulated much more H 2 O 2 than the plants nourished with RCF ( Figure 5 A).…”

“…APX activity was slightly stimulated in cucumbers grown on NUGE ( Figure 5 D), whereas CAT activity did not change. Stimulation of both APX and CAT in response to NaCl has been reported in many plant species [ 30 , 76 ]. However, a greater increase in CAT activity was observed in salt-tolerant plants but not in salt-sensitive plants [ 77 ].…”

“…Cucumber has been successfully grown in hydroponic systems [ 13 ], so the conditions of its cultivation in hydroponics are well known and optimized. Finally, cucumber is a model plant used in our earlier studies concerning many aspects of the molecular mechanisms of cucumber adaptation to abiotic stress conditions, including salt stress, nutrient deficiency, extreme temperature, and heavy metals [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. It is worth emphasizing that our previous experiments on cucumber were conducted in hydroponic cultivations [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

“…Finally, cucumber is a model plant used in our earlier studies concerning many aspects of the molecular mechanisms of cucumber adaptation to abiotic stress conditions, including salt stress, nutrient deficiency, extreme temperature, and heavy metals [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. It is worth emphasizing that our previous experiments on cucumber were conducted in hydroponic cultivations [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. These detailed characteristics of the cucumber provide an excellent biological reference point for studying the possibility of its growth under specific new conditions.…”

Review of the Mechanisms by Which Transcription Factors and Exogenous Substances Regulate ROS Metabolism under Abiotic Stress

“…RBOH is a key producer of ROS in plants, and the specific regulation of RBOH expression plays an important role in plant resistance to stress [ 30 , 31 , 32 ]. Kabała et al reported that CsRBOHD and CsRBOHF1 expression are induced at the early stages of salt stress in cucumber seedlings, and H 2 O 2 is generated, which functions as a signaling molecule participating in the stress response [ 33 ]. This is consistent with the findings of Gémes et al in tobacco [ 34 ].…”