Melanin produced by a dark septate endophyte, Exophiala pisciphila, was isolated and purified. The solubility properties, Ultraviolet-visible and Fourier transform infrared spectra of the purified E. pisciphila melanin were similar to those of typical melanin. Inhibition of melanin production was observed when colonies exposed to tricyclazole (1,8-dihydroxynaphthalene (DHN) melanin inhibitor), but not to kojic acid (3,4-dihydroxyphenylalanine melanin inhibitor). Thus the E. pisciphila melanin was a member of DHN melanin family. In addition, the antioxidant activities of E. pisciphila melanin were evaluated in vitro by 1,1-diphenyl-2-picryl-hydrazyl radical-scavenging assay. E. pisciphila melanin exhibited a strong antioxidant activity. Addition of 50-350 mg L -1 Cd(II) to the medium increased the melanin production in E. pisciphila.

Dark septate endophytes (DSE) are widely distributed in plant roots grown in stressful habitats, especially in heavy metal-polluted soils. But little is known about the physiological interactions between DSE and plants under heavy metal stress. In the present study, the growth, Cd content, and physiological response of Zea mays L. to a root-colonized DSE, Exophiala pisciphila, were analyzed under Cd stress (0, 5, 10, 20, and 40 mg/kg) in a sand culture experiment. Under high Cd (10, 20, and 40 mg/kg) stress, the DSE colonization in roots increased the maize growth, kept more Cd in roots, and decreased Cd content in shoots. The DSE colonization improved the photosynthesis and induced notable changes on phytohormones but had no significant effect on the antioxidant capability in the maize leaves. Moreover, there were significant positive correlations between the gibberellic acid (GA) content and transpiration rate, zeatin riboside (ZR) content, and photosynthetic rate in maize leaves. These results indicated that the DSE's ability to promote plant growth was related to a decrease on Cd content and the regulation on phytohormone balance and photosynthetic activities in maize leaves.

In this study, we investigated the effects of the arbuscular mycorrhizal fungi (AMF) Funneliformis mosseae and Diversispora spurcum on the growth, antioxidant physiology, and uptake of phosphorus (P), sulfur (S), lead (Pb), zinc (Zn), cadmium (Cd), and arsenic (As) by maize (Zea mays L.) grown in heavy metal-polluted soils though a potted plant experiment. F. mosseae significantly increased the plant chlorophyll a content, height, and biomass; decreased the HO and malondialdehyde (MDA) contents; and enhanced the superoxide dismutase (SOD) and catalase (CAT) activities and the total antioxidant capacity (T-AOC) in maize leaves; this effect was not observed with D. spurcum. Both F. mosseae and D. spurcum promoted the retention of heavy metals in roots and increased the uptake of Pb, Zn, Cd, and As, and both fungi restricted heavy metal transfer, resulting in decreased Pb, Zn, and Cd contents in shoots. Therefore, the fungi reduced the translocation factors for heavy metal content (TF) and uptake (TF') in maize. Additionally, F. mosseae promoted P and S uptake by shoots, and D. spurcum increased P and S uptake by roots. Moreover, highly significant negative correlations were found between antioxidant capacity and the HO, MDA, and heavy metal contents, and there was a positive correlation with the biomass of maize leaves. These results suggested that AMF alleviated plant toxicity and that this effect was closely related to antioxidant activation in the maize leaves and increased retention of heavy metals in the roots.

A high Cd-tolerant dark septate endophyte (DSE), Exophiala pisciphila, was inoculated into maize (Zea mays L.) roots under Cd stress. The Cd content, enzymes activity and thiol compound content relevant to glutathione (GSH) metabolism in maize leaves were analyzed. The Cd content in maize shoots increased with increasing Cd stress, but the DSE significantly reduced the Cd content at the 40 mg/ kg Cd treatment. Cd stress increased the enzyme activity of glutathione reductase (GR), glutathione S-transferase (GST) and glutathione peroxidase (GSH-Px) as well as the thiol compound contents of sulfur, thiols (-SH) and oxidized glutathione (GSSG). The content of reduced GSH and the GSH/GSSG ratio reached a peak at the 5 mg/kg Cd treatment but then decreased with increasing Cd stress. Furthermore, the DSE significantly enhanced the GR and GSH-Px activity and increased the contents of-SH and GSH under low Cd stress (5 and 10 mg/kg), but decreased the γglutamylcysteine synthetase and GST activity under high Cd stress (20 and 40 mg/kg). Highly positive correlations between the Cd content with enzymes activity and enzymes activity with thiol compound content were observed. Results indicated that DSE played a role in activating GSH metabolism in maize leaves under Cd stress.

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The traditional rice variety "Baijiaolaojing" was planted in Yuanyang terraces (1600 m altitude) under field conditions. The effects of enhanced UV-B radiation (0 kJ m, 2.5 kJ m, 5.0 kJ m and 7.5 kJ m) on the rice-Magnaporthe oryzae system were studied with respect to the Magnaporthe oryzae infection, the disease-resistance physiology of the rice and the rice blast disease condition. The results showed that under enhanced UV-B radiation, the infectivity of Magnaporthe oryzae was decreased, which could significantly inhibit its growth and sporulation. The activities of rice leaf disease-resistance-related enzymes (phenylalanine ammonia-lyase, lipoxygenase, chitinase and β-1,3-glucanase) were significantly increased under enhanced UV-B radiation. Following inoculation with Magnaporthe oryzae, levels of disease-resistance-related substances in the rice leaves were significantly increased. Among the results, it was found that leaves after UV-B radiation had a more significant resistance response. The level of UV-B irradiation showed a parabolic relationship with the rice blast index (r = 0.85, P < 0.01; in the control group, r = 0.88, P < 0.01). The disease index decreased with increase in irradiation. The DI was at a minimum with enhanced UV-B irradiance of 4 kJ m; thereafter, it increased with increasing irradiation. The enhanced UV-B radiation had a direct impact on the growth of rice and Magnaporthe oryzae, and it indirectly changed the rice-Magnaporthe oryzae system. UV-B radiation could reduce the harmful impact of rice blast.