Mycorrhizopshere bacteria alleviated arsenic toxicity by regulating organic acids, glyoxalase defense system, and metal transporters in soybean plants

Abstract

Arsenic (As) contamination poses significant challenges to plant physiology and productivity. Rhizospheric microbes contribute to phytoremediation and can shield plants from As stress. However, there is still much to know about the tolerance mechanism of these microbes to As toxicity. Under As stress, soybean exhibited adverse physiological effects, including reduced shoot fresh weight (SFW) (-2%) and enhanced root fresh weight (RFW) (+24%), alongside compromised photosynthetic efficiency (-12%) and decreased crop yield (-35%). However, the co-applied synthetic community (SynCom) and arbuscular mycorrhizal fungi (AMF) resulted in significant improvements, with an increase in SFW (+71%) and RFW (+35%). Furthermore, colonization improved significantly, with an increase in root colonization rising and arbuscular abundance (+57%). This co-application not only increased nutrient intake but also built a strong root system, which improved stress tolerance. Furthermore, the negative impact of As on the antioxidative response was best counteracted with the co-application of AMF and SynCom which considerably increased the response of lipoxygenase (LOX) activity (+16.92%), malondialdehyde (MDA) levels (-23.37%), ascorbate peroxidase (APX) (+54.87%) and glutathione reductase (GR) (+23.97%). Metabolically, malate, succinate, and citrate levels were altered, showing the adaptive response of soybean to As stress, which was further increased by SynCom and AMF treatments. In addition, there were notable modifications in the relative expression of metal transporter genes in both shoot and root (HMA13, HMA18, and HMA19) via combined SynCom and AMF treatments to lessen the negative impact of As-induced stress. Overall, this study demonstrates the transformational potential of co-inoculation of SynCom and AMF in improving plant resistance to heavy metal stress particularly As-induced stress, providing useful insights into long-term remediation solutions for polluted areas.