Effects of arbuscular mycorrhizal fungi on the physiology and saponin synthesis of Paris polyphylla var.yunnanensis at different nitrogen levels

It has been confirmed that inoculation with AMF(Arbuscular Mycorrhizal fungi) can improve the efficiency of N utilization by plants, but the effect of AMF inoculation on the relationship between plant secondary metabolite synthesis and N levels has not been reported. In this experiment, the physiological indexes and genes related to saponin synthesis were determined by applying different concentration gradients of nitrogen to the medicinal plant Paris . polyphylla var.yunnanensis(Ppy) infested by AMF as the test material. It was found that nitrogen addition increased the biomass, chlorophyll content, and nutrient content of above- and below-ground plant parts, and increased the content of saponin content of Ppy to some extent, but AMF inoculation increased the saponin content of Ppy more significantly. AMF inoculation also promoted the expression of genes related to the saponin synthesis pathway, including HMGS, SE1, and CAS, which is in according with the accumulation of saponin in plant. It also may increase the saponin content of AMF plants by altering the expression of P450s and UGTs related to saponin synthesis.