Endophytic infection modulates ROS-scavenging systems and modifies cadmium distribution in rice seedlings exposed to cadmium stress

The relationship between endophytic infection and components of the Cd stress response was examined in the present study. Oryza sativa L. plants were grown in Hoagland's nutrient solution with and without infection with the endophytic fungus JP4 under different cadmium (Cd) stress conditions (0, 50, 100, and 150 mu M) for 2 weeks. Endophytic infection in the roots promoted rice seedling growth and decreased shoot Cd contents in comparison to non-infected treatments. Furthermore, the adsorbed Cd remained in the roots, and far less Cd was transported from the roots to the shoots. Compared to the non-infected rice seedlings, endophytic infection remarkably increased the pigment content, net photosynthetic rate (P-n), and chlorophyll fluorescence in all treatments, except for F-v/F-0 values and chlorophyll b content in the 100 mu M Cd treatment. Superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR) activity, as well as ascorbic acid (AsA) and glutathione (GSH) content, increased in EI seedlings relative to EF seedlings under Cd stress, while malondialdehyde (MDA) and H2O2 content decreased significantly. Inoculation of endophytic fungus JP4 in roots promoted rice seedling growth and ameliorated the negative effects of Cd stress on the growth of rice seedlings by triggering antioxidant systems and non-enzymatic systems, regulating photosynthetic activities and modifying the Cd distribution.