MicroPIXE technique to understand the distribution of heavy metals in arbuscular mycorrhizal symbiosis

STATELLO, MARINA; COLOMBO, ROXANA P.; DE LA FOURNIERE, EMMANUEL; DEBRAY, MARIO; GODEAS, ALICIA M.; SILVANI, VANESA A.

REVISTA ARGENTINA DE MICROBIOLOGíA

ASOCIACION ARGENTINA MICROBIOLOGIA

Lugar: Buenos Aires; Año: 2024

0325-7541

Soil colloids tend to retain heavy metals (HMs) potentially reaching toxic concentrations. Phytoremediation, a decontamination technique, involves plants and their associated microorganisms to mitigate the toxicity of HMs in the environment. Most plant species employed in phytoremediation establish symbiotic associations with arbuscular mycorrhizal fungi (AMF). AMF can adsorb or uptake HMs through their hyphal network, subsequently translocating them towards the host plant. Particle-induced X-ray Emission with a micro-focused beam (microPIXE) enables the micrometric mapping of elements in a sample, helping to determine the concentration and distribution of HMs. In this work, we used microPIXE to analyze the distribution and accumulation of copper (Cu) in structures of the AMF Rhizophagus intraradices GC3 strain associated to Ri T-DNA carrot roots under in vitro condition. This would enable us to understand the role of AMF in HM-polluted soils. In vitro assay was performed using bi-compartmentalized Petri plates. The root compartment (RC) contained solid minimal medium (MM) with transformed carrot roots colonized by GC3. The hyphal compartment (HC), where only AMF developed, contained sterile soil artificially-contaminated with Cu (300 mg/kg). After three months, roots and intraradical vesicles from RC and extraradical mycelium from HC were sampled for microPIXE analysis. The map of Ca, a major element in biological systems, helped us to visualize the biological structures and locate other elements; P was selected as indicator of AMF structures. P, Cu and Mn, a MM compound, were mainly detected in vesicles, and to a lesser extent in colonized roots (considering the dimensions of structures), while P and Mn were mostly localized in extraradical mycelium. These results showed a significant Cu accumulation in intraradical fungal structures but not in root cells, set the foundation for future studies with Mn and indicating a possible mechanism of toxicity alleviation for host plant.