Abstract：Piriformospora indica is a root endophytic fungus, which can promote the growth of many plants, enhance crop yield, and also confer biotic and abiotic stress tolerance to its host plants. In this study, in order to confirm the influence of P. indica on drought resistance of Brassica napus, the differences of malondialdehyde (MDA) content, the relative conductance, proline(Pro) content, antioxidant enzymes(superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT)) activity and expression level of drought-related genes between B. napus colonized and un-colonized by P. indica were analysed after treating by 20% polyethylene glycol-6000(PEG) solution. The results showed that the concentration of MDA and the relative conductance in the leaves of B. napus colonized by P. indica was significantly lower than that in un-colonized ones. The Pro content in the leaves of B. napus colonized by P. indica were significantly higher than that in un-colonized ones, and it was 1.3 folds of that after PEG treatment for 72 h. The activity of SOD, POD and CAT in the leaves of B. napus colonized by P. indica were significantly higher than that in un-colonized plants, they were 1.17, 1.38 and 1.27 folds of the control ones after PEG treatment for 24 h, respectively. RT-PCR analysis showed that the expression of drought-related gene 575 which codes lipid-transfer protein was upregulated in leaves of B. napus colonized by P. indica, and the expression level was 3.2 folds of control plants after PEG treatment for 9 h. This study indicated that the drought resistance improvement of B. napus conferred by P. indica was related to MDA and Pro contents, plasmamembrane permeability, antioxidant enzymes activity and the expression level of drought-related genes. P. indica may enhance drought resistance of B. napus through improving total antioxidant ability, maintaining cell biomembrane integrity and cell osmotic pressure, and reducing the level of membrane lipid peroxidation of plants. This study preliminary confirms the role and partly mechanism of drought resistance of B. napus conferred by P. indica, and lays the foundation for further research on the role and related mechanisms of stresses resistance in B. napus conferred by P. indica.
