Arbuscular Mycorrhizal Fungi Increase Pb Uptake of Colonized and Non-Colonized Medicago truncatula Root and Deliver Extra Pb to Colonized Root Segment.

Yaru Zheng,Wei Ren,Manzhe Zhu,Yanpeng Li,Ming Tang,Haoqiang Zhang

doi:10.3390/microorganisms9061203

Abstract

Arbuscular mycorrhizal (AM) fungi establish symbiosis and improve the lead (Pb) tolerance of host plants. The AM plants accumulate more Pb in roots than their non-mycorrhizal counterparts. However, the direct and long-term impact of AM fungi on plant Pb uptake has been rarely reported. In this study, AM fungus (Rhizophagus irregularis) colonized and non-colonized roots of Medicago truncatula were separated by a split-root system, and their differences in responding to Pb application were compared. The shoot biomass accumulation and transpiration were increased after R. irregularis inoculation, whereas the biomass of both colonized and non-colonized roots was decreased. Lead application in the non-colonized root compartment increased the R. irregularis colonization rate and up-regulated the relative expressions of MtPT4 and MtBCP1 in the colonized root compartments. Rhizophagus irregularis inoculation increased Pb uptake in both colonized and non-colonized roots, and R. irregularis transferred Pb to the colonized root segment. The Pb transferred through the colonized root segment had low mobility and might be sequestrated and compartmented in the root by R. irregularis. The Pb uptake of roots might follow water flow, which is facilitated by MtPIP2. The quantification of Pb transfer via the mycorrhizal pathway and the involvement of MtPIP2 deserve further study.

Highlights

Heavy metal contamination in soil is a worldwide issue due to rapid urbanization, mining, sewage sludge, application of fertilizers, and other anthropogenic activities [1,2,3].Lead (Pb) is one of the most common heavy metal pollutants in China [4] and is a nonessential element that poses an immense risk especially for children [5,6]
The establishment of Arbuscular mycorrhizal (AM) symbiosis leads to the enhancement of host plant photosynthetic rates, transpiration flow, and water uptake [18,20,21,22,23]
The results described above indicated that inoculation of R. irregularis directly reduced average root diameter

Summary

Introduction

Heavy metal contamination in soil is a worldwide issue due to rapid urbanization, mining, sewage sludge, application of fertilizers, and other anthropogenic activities [1,2,3]. Lead (Pb) is one of the most common heavy metal pollutants in China [4] and is a nonessential element that poses an immense risk especially for children [5,6]. With AM fungal colonization, plants usually have higher biomass [17,18], increased antioxidant enzyme activities and photosynthetic rates, and improved Pb tolerance [18,19]. The establishment of AM symbiosis leads to the enhancement of host plant photosynthetic rates, transpiration flow, and water uptake [18,20,21,22,23]. The water transport from soil to leaves requires the participation of aquaporins (AQPs), which

Methods

Results

Conclusion