Root-Associated Fungi Shared Between Arbuscular Mycorrhizal and Ectomycorrhizal Conifers in a Temperate Forest.

Hirokazu Toju,Hirotoshi Sato

doi:10.3389/fmicb.2018.00433

Abstract

Arbuscular mycorrhizal and ectomycorrhizal symbioses are among the most important drivers of terrestrial ecosystem dynamics. Historically, the two types of symbioses have been investigated separately because arbuscular mycorrhizal and ectomycorrhizal plant species are considered to host discrete sets of fungal symbionts (i.e., arbuscular mycorrhizal and ectomycorrhizal fungi, respectively). Nonetheless, recent studies based on high-throughput DNA sequencing technologies have suggested that diverse non-mycorrhizal fungi (e.g., endophytic fungi) with broad host ranges play roles in relationships between arbuscular mycorrhizal and ectomycorrhizal plant species in forest ecosystems. By analyzing an Illumina sequencing dataset of root-associated fungi in a temperate forest in Japan, we statistically examined whether co-occurring arbuscular mycorrhizal (Chamaecyparis obtusa) and ectomycorrhizal (Pinus densiflora) plant species could share non-mycorrhizal fungal communities. Among the 919 fungal operational taxonomic units (OTUs) detected, OTUs in various taxonomic lineages were statistically designated as “generalists,” which associated commonly with both coniferous species. The list of the generalists included fungi in the genera Meliniomyces, Oidiodendron, Cladophialophora, Rhizodermea, Penicillium, and Mortierella. Meanwhile, our statistical analysis also detected fungi preferentially associated with Chamaecyparis (e.g., Pezicula) or Pinus (e.g., Neolecta). Overall, this study provides a basis for future studies on how arbuscular mycorrhizal and ectomycorrhizal plant species interactively drive community- or ecosystem-scale processes. The physiological functions of the fungi highlighted in our host-preference analysis deserve intensive investigations for understanding their roles in plant endosphere and rhizosphere.

Highlights

In terrestrial ecosystems, most plant species form intimate interactions with mycorrhizal fungi, which play essential roles in the growth and survival of their hosts (van der Heijden et al, 2008; Bever et al, 2010; Peay et al, 2016)
Arbuscular mycorrhizal fungi occurred almost exclusively on Chamaecyparis, while ectomycorrhizal and saprotrophic/endophytic fungi occurred on both plant species (Figure 2A)
We discuss fungi potentially mediating arbuscular mycorrhizal and ectomycorrhizal symbioses as well as those that preferentially interact with either mycorrhizal type of plant hosts

Summary

Introduction

Most plant species form intimate interactions with mycorrhizal fungi, which play essential roles in the growth and survival of their hosts (van der Heijden et al, 2008; Bever et al, 2010; Peay et al, 2016) Those fungi, for example, supply soil nitrogen and phosphorous to associated plants, thereby enhancing hosts’ physiological states (Smith and Read, 2008). Arbuscular mycorrhizal fungi (the phylum Glomeromycota) first appeared early in the history of land plants (Remy et al, 1994) and they associate with plant species in diverse plant taxa (Schüβler et al, 2001) They are obligate mutualistic symbionts and rely entirely on carbon supply from host plants (Smith and Read, 2008). Arbuscular mycorrhizal and ectomycorrhizal symbioses have been investigated separately in most mycological studies

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