Arbuscular mycorrhizal fungi inoculation and exogenous indole-3-acetic acid application induce antioxidant defense response to alleviate cadmium toxicity in Broussonetia papyrifera

Abstract

Cadmium (Cd) contamination in soil poses a huge threat to plants even at low concentrations. Meanwhile, Broussonetia papyrifera has great potential in remediation of soil heavy metals contamination. To investigate the effect of arbuscular mycorrhizal fungi (AMF) and indole-3-acetic acid (IAA) on tolerance of B. papyrifera to Cd stress, two experiments were conducted. The first experiment was conducted to investigate the effect of AMF-Rhizophagus irregularis on tolerance of B. papyrifera to Cd stress. Then, the second experiment was conducted to investigate the combined effects of AMF inoculation and IAA application on tolerance of B. papyrifera to Cd stress, and parameters about endogenous hormone concentration, antioxidant response, malondialdehyde (MDA) content, gene expression related to antioxidant enzyme system and hormone were measured. Results indicated that AMF alleviated Cd toxicity of B. papyrifera by reducing MDA content, improving antioxidant enzyme acitivity and Cd absorption capacity. Furthermore, the combination of AMF inoculation and IAA application had a synergetic effect on tolerance of B. papyrifera to Cd stress through (1) upregulating BpAUX1 and BpAUX2 which might contribute to root growth and root xylem synthesis, (2) enhancing the antioxidant enzyme system by upregulating BpSOD2 and BpPOD34. This work provides new insight into the application of IAA in the remediation of soil Cd pollution by mycorrhizal plants.