The herbaceous landlord: integrating the effects of symbiont consortia within a single host

Abstract

Plants are typically infected by a consortium of internal fungal associates, including endophytes in their leaves, as well as arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in their roots. It is logical that these organisms will interact with each other and the abiotic environment in addition to their host, but there has been little work to date examining the interactions of multiple symbionts within single plant hosts, or how the relationships among symbionts and their host change across environmental conditions. We examined the grass Agrostis capillaris in the context of a climate manipulation experiment in prairies in the Pacific Northwest, USA. Each plant was tested for presence of foliar endophytes in the genus Epichloë, and we measured percent root length colonized (PRLC) by AMF and DSE. We hypothesized that the symbionts in our system would be in competition for host resources, that the outcome of that competition could be driven by the benefit to the host, and that the host plants would be able to allocate carbon to the symbionts in such a way as to maximize fitness benefit within a particular environmental context. We found a correlation between DSE and AMF PRLC across climatic conditions; we also found a fitness cost to increasing DSE colonization, which was negated by presence of Epichloë endophytes. These results suggest that selective pressure on the host is likely to favor host/symbiont relationships that structure the community of symbionts in the most beneficial way possible for the host, not necessarily favoring the individual symbiont that is most beneficial to the host in isolation. These results highlight the need for a more integrative, systems approach to the study of host/symbiont consortia.

Common mycelial networks impact competition in an invasive grass

“…The degree of mycorrhizal colonization was admittedly low in both species, although it is typical of grasses to have widely varying and often low colonization percentages (Busby et al, 2011; Jordan et al, 2011, 2012), especially in B. sylvaticum , which was found to have between 9 and 90% colonization (Lee, 2014; Vandegrift et al, 2015). In this experiment, we generally disregarded colonization percentage, as it appeared to not correlate directly with plant growth response.…”

Effects of Epichloë gansuensis Endophyte on the Root and Rhizosphere Soil Bacteria of Achnatherum inebrians Under Different Moisture Conditions

“…Our study similarly found that E. gansuensis enhanced the diversity and richness of rhizosphere soil bacteria community. Some previous studies had shown that the effects of Epichloë endophytes on belowground bacteria may be caused by secondary metabolites (Vandegrift et al, 2015;Rojas et al, 2016;Soto-Barajas et al, 2016), such as root exudates (Guo et al, 2015), alkaloids (Franzluebbers and Hill, 2005), and root volatile organic compounds (Rostás et al, 2015). A study had demonstrated that an Epichloë endophyte altered the composition of root exudates, such as the total phenolic content and TOC (Guo et al, 2015); in addition, studies also found that root exudates could construct the belowground bacterial community (Badri and Vivanco, 2009;Bakker et al, 2013).…”

“…These factors alter rhizosphere soil microbial communities by changing soil physical and chemical properties, nutrient cycling and phytohormones production (Zhang et al, 2014b;Francioli et al, 2017;Zhalnina et al, 2018). Previous research also indicated that plant genotype and vegetation growth stage transforms the plant bacterial diversity, and which can promote release of secondary metabolites from roots, influencing microbial diversity and community composition in rhizosphere soil (Guo et al, 2015;Vandegrift et al, 2015;Rojas et al, 2016;Soto-Barajas et al, 2016).…”

Peer Review #1 of "Knowing your neighbourhood—the effects of Epichloë endophytes on foliar fungal assemblages in perennial ryegrass in dependence of season and land-use intensity (v0.1)"

“…While infections with Epichloë endophytes has been shown to affect mycorrhizal colonization of grasses (Mack and Rudgers 2008;Omacini et al 2012;Vandegrift et al 2015), it had no significant PeerJ reviewing PDF | (2017:11:22068:2:0:NEW 6 Mar 2018)…”

“…Manuscript to be reviewed colonization of mycorrhizal fungi (Siegel and Latch 1991;Yue et al 2000;Clarke et al 2006;Mack and Rudgers 2008;Kumar and Kaushik 2012;Omacini et al 2012;Vandegrift et al 2015).…”