Pairwise Transcriptomic Analysis of the Interactions Between the Ectomycorrhizal Fungus Laccaria bicolor S238N and Three Beneficial, Neutral and Antagonistic Soil Bacteria

Abstract

Ectomycorrhizal fungi are surrounded by bacterial communities with which they interact physically and metabolically during their life cycle. These bacteria can have positive or negative effects on the formation and the functioning of ectomycorrhizae. However, relatively little is known about the mechanisms by which ectomycorrhizal fungi and associated bacteria interact. To understand how ectomycorrhizal fungi perceive their biotic environment and the mechanisms supporting interactions between ectomycorrhizal fungi and soil bacteria, we analysed the pairwise transcriptomic responses of the ectomycorrhizal fungus Laccaria bicolor (Basidiomycota: Agaricales) when confronted with beneficial, neutral or detrimental soil bacteria. Comparative analyses of the three transcriptomes indicated that the fungus reacted differently to each bacterial strain. Similarly, each bacterial strain produced a specific and distinct response to the presence of the fungus. Despite these differences in responses observed at the gene level, we found common classes of genes linked to cell-cell interaction, stress response and metabolic processes to be involved in the interaction of the four microorganisms.

Transcriptional Responses of the Bacterium Burkholderia terrae BS001 to the Fungal Host Lyophyllum sp. Strain Karsten under Soil-Mimicking Conditions

“…So far, only few studies have unraveled the complex nature of bacterial-fungal interactions at the transcriptional level [8–10, 56, 57]. Recently, C. fungivorans strain 331 was shown to invest substantial cellular resources into the capacity to utilize compounds provided by its host fungus A. niger , as well as in the production of antifungal agents [9].…”

“…On another notice, Collimonas fungivorans Ter331, upon confrontation with Aspergillus niger N400, did not only utilize compounds provided by the fungus but also expressed genes responsible for the production of antifungal agents [9]. Finally, the ectomycorrhizal fungus Laccaria bicolor S238N was found to respond in different and quite complex ways to antagonistic, neutral and beneficial soil bacteria [10]. Notwithstanding this growing body of knowledge on bacterial-fungal interactions in soil settings, none of the aforementioned studies assessed the behavior of bacteria with well-characterized genomes that contain—next to a core genome—a very large accessory part (such as B. terrae BS001) [3].…”

Transcriptomic responses of a simplified soil microcosm to a plant pathogen and its biocontrol agent reveal a complex reaction to harsh habitat

“…In nature microbes have evolved mechanisms not only to fight, but also to adapt, and in some cases to support each other [5]. The microbial transcriptional response differs strongly during antagonistic, neutral and beneficial interactions [75] and defence-related processes are generally downregulated during mutualistic interactions [5]. Therefore, the simplified soil microcosm was probably able to recognise A. mellea as a non-competitive intruder and it did not stimulate early antagonistic reactions, but rather neutral adaptation processes to this exogenous fungus.…”

Entomotoxic and nematotoxic lectins and protease inhibitors from fungal fruiting bodies

“…AAL was expressed in vegetative mycelium and in fruiting bodies (Ogawa et al 1998). Expression of LbTec2 in vegetative mycelium has been shown to be upregulated in the presence of mycorrhizal helper bacteria (Deveau et al 2015).…”