Dissecting the tolerance of Suillus to radiocesium:stable cesium and γ - radiation

Suilloid fungi and radioactivity. Dissecting the tolerance of Suillus to radiocesium: stable cesium and γ-radiations.
Samuele Guadagnino 1, Robin Nauts 2, Kenji Nanba3, Vasyl Yoschenko3, Nele Horemans 2, Joske Ruytinx1
1. Department of Bio-engineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel,
Belgium.
2. Belgian Nuclear Research Centre, Boeretang 200, B-2400, Mol, Belgium
3. Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan

Since the accident in Chernobyl 1986 and later with the one in Fukushima 2011, research have been focus on the impact of radionuclides on the environment. The forests around both power plants are mainly composed of coniferous tree and especially plants of the family Pinaceae which are known to have a symbiotic relationship with fungi of the genus Suillus. The suilloid fungi are key species for the wellbeing of coniferous forests and supposedly are involved in plant adaptations to potentially toxic elements, included radionuclides. The aim of this work is to evaluate the tolerance of strains of two different suilloid fungi to stable cesium and γ-radiation. The fungi have been isolated in areas contaminated or not by radiocesium in the Fukushima Province. This study is part of a pivotal work on morphological, physiological and genetic responses of mycorrhized Pines exposed to stable cesium and γ-radiations.
Six strains of Suillus luteus and two strains of Suillus granulatus have been exposed:
- for two weeks to a gradient of CsCl (0 to 2,4 mM Cs)
- one week to a gradient of γ-radiations (0 to 2140 mGy/h) after one week of preculturing.
At the end of the exposure period, morphometrical parameters have been measured to build dose-response curves. For the control and one chosen concentration/dose, the colonies have been extracted for their RNA in order to perform qRT-PCR to evaluate the expression of genes involved in ROS-scavenging molecular machinery.
Every strain has shown to be able to tolerate high concentration of cesium and high dose of γ-radiations without a significant difference between the ones deriving from contaminated site and not contaminated one suggesting the absence of adaptation. The genetic expression of γ-radiation exposed strains is still ongoing and the results of it will further shed light on the relationship between ectomycorrhizal fungi, their host plants and radioactive pollution and the role of mycorrhization in the adaptation of coniferous forests to abiotic stress.