Physiological response of Trichoderma asperellum to Na+ stress

Abstract:

[Background] Trichoderma asperellum agent has been widely used in biological control and secondary bioremediation of soil secondary salinization, while less is known about the salt-tolerant mechanism and salt accumulation potential of this strain under stress of salinization. [Objective] This research aimed to reveal the physiological response of Trichoderma asperellum CTCCSJ-W-SBW10264 (T264) to Na+-induced oxidative stress and the Na+ adsorption and accumulation characteristics of this strain. [Methods] Gradient concentrations of Na+ in broth were designed as stress factor in fermentation experiment of strain T264, then mycelia samples at different culture stages were collected for the measurement of cell oxidative damage indices including H2O2 content and malondialdehyde (MDA) level together with the activity of cellular antioxidant related enzymes. [Results] Result of Na+ stress cultivation experiment indicated that T264 could survive with Na+ concentration of 1.22 mol/L, and the growth of T264 was not significantly inhibited with Na+ concentration lower than 0.25 mol/L. The results of study on oxidative damage and oxidative damage responses revealed that the higher Na+ concentration lead to the higher cellular oxidation level (MDA content). Moreover, with the accumulation of MDA and H2O2 in hyphae of T264, the activity of antioxidative damage enzymes in cells was also increased significantly. After Na+ treatment for 24 h, the activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) were respectively highest under the Na+ stress of 0.5, 1.0 and 1.22 mol/L, respectively, which were 36.66, 3.34 and 233.3 U/mg. The experimental results of Na+ adsorption and accumulation characteristics showed that hyphae of T264 had a strong adsorption capacity for Na+. After being cultured in the 0.05 mol/L Na+ environment for 72 h, the surface Na+ adsorption capacity of mycelia was 1 347.6 mg/g, and the internal Na+ accumulation capacity of mycelia was 218.6 mg/g. The remove rate of Na+ in the culture medium reached 32% through surface adsorption and internal accumulation of T264 mycelia. [Conclusion] This experiment showed that the antioxidant damage-related enzymes of T264 play an important role in its resistance to Na+ stress, and the strain T264 has a strong adaptability to high concentration of Na+ and an efficient adsorption and accumulation effect of Na+ in the environment.