Arbuscular mycorrhizal fungi and the associated bacterial community influence the uptake of cadmium in rice

Cadmium (Cd)-contaminated rice imposes severe health risks to human. The present study investigated the role of arbuscular mycorrhizal fungi (AMF) in sculpting the rhizospheric bacterial community, and the potential effects on the Cd uptake by rice. AMF Funneliformis mosseae (Fm) or Rhizophagus intraradices (Ri) were inoculated to rice grown in soils spiked with 0 or 10 mu M Cd. Initial Cd concentration in soil was 0.18 mg/kg. AMF colonization rate, plant biomass, Cd content in rice, soil properties, rice Cd transporters (Nramp5 and HMA3) and soil bacterial community were analysed. Both AMF decreased (P < 0.05) root and shoot Cd concentrations, especially for Ri treatment. The higher relative abundance of Actinobacteria (mostly from genus Arthrobacter) observed in Ri treatment probably absorbed Cd in soil, and hence decreased the Cd availability for rice. Expression of genes Nramp5 and HMA3 in root were lower in Ri treatment, but higher in Fm treatment. The gene expressions were in line with the results of lower root Cd content in Ri treatment, and higher in Fm treatment. The present study firstly revealed that AMF can reduce rice Cd uptake by changing the expression of Cd transporters and soil bacterial community in a pot experiment. Effects of plants-bacteria-fungi interaction on both plant productivity and toxicants uptake deserved further study.