Consequences of simultaneous interactions of fungal endophytes and arbuscular mycorrhizal fungi with a shared host grass

Yang

et al. 2013

J. Basic Microbiol.

Many studies have examined pair‐wise interactions between plants and endophytes, while overlooking the interplays among multiple endosymbionts and their combined impacts on hosts. In this study, Atractylodes lancea plantlets were inoculated with endophytic fungus Acremonium strictum AL16, or endophytic bacterium Acinetobacter sp., or both, to investigate the impacts of the three‐way symbiosis on the host. Our results showed that defense‐related responses of the co‐inoculated plantlets were delayed and weakened relative to plantlets with single inoculants, but no detrimental effects on phyto‐physiology (growth, photosynthesis) were observed after combined inoculations. Quantitative PCR analysis verified a decrease in AL16 colonization density within plants after co‐inoculation with the endobacteria. An in vitro assay was then performed to elucidate the suppressed plant defense responses and reduced fungal colonization by dual inoculation. The data showed that the presence of Acinetobacter sp. reduced AL16 colony diameter and spore germination rate without negatively affecting fungal morphology. Additionally, direct hyphal attachment of the bacterium to AL16 in vitro was visualized by scanning electronic microscopy. Therefore, we propose that a balanced and compatible symbiosis might require constraints conferred by the antagonistic endophyte Acinetobacter sp. on the fungus AL16 in the tripartite endophytic bacterium–fungus–plant system.

Section: Introductionmentioning

confidence: 99%

Consequences of antagonistic interactions between endophytic fungus and bacterium on plant growth and defense responses in Atractylodes lancea

Yang

et al. 2013

J. Basic Microbiol.

“…Endophytes can alter the functioning of different groups of soil microorganisms, including decomposers (Omacini et al , Jenkins et al ), and other microbial symbionts (Omacini et al , Larimer et al , ). For example, previous studies showed that aerial endophytes and arbuscular mycorrhizal fungi can interact additively (Larimer et al ), antagonistically (Liu et al ) or neutrally regarding host growth (Omacini et al , Mack and Rudgers ), depending on the environmental context and the symbiont and host genotype (Larimer et al , Liu et al ). Even though the coexistence of symbionts in neighbouring plants is highly probable (Stanton , Bonfante and Anca ), studies on their interactive effects are rare.…”

mentioning

confidence: 99%

Multi‐symbiotic systems: functional implications of the coexistence of grass–endophyte and legume–rhizobia symbioses

García-Parisi

Lattanzi

Grimoldi

et al. 2014

Oikos

The coexistence of symbionts with different functional roles in co‐occurring plants is highly probable in terrestrial ecosystems. Analyses of how plants and microbes interact above‐ and belowground in multi‐symbiotic systems are key to understand community structure and ecosystem functioning. We performed an outdoor experiment in mesocosms to investigate the consequences of the interaction of a provider belowground symbiont of legumes (nitrogen‐fixing bacteria) and a protector aerial fungal symbiont of grasses (Epichloё endophyte) on nitrogen dynamics and aboveground net primary productivity. Four plants of Trifolium repens (Trifolium, a perennial legume) either inoculated or not with Rhizobium leguminosarum, grew surrounded by 16 plants of Lolium multiflorum (Lolium, an annual grass), with either low or high levels of the endophyte Neotyphodium occultans. After five months, we quantified the number of nodules in Trifolium roots, shoot biomass of both plant species, and the contribution of atmospheric nitrogen fixation vs. soil nitrogen uptake to above ground nitrogen in each plant species. The endophyte increased grass biomass production (+ 16%), and nitrogen uptake from the soil – the main source for the grass. Further, it reduced the nodulation of neighbour Trifolium plants (−50%). Notably, due to a compensatory increase in nitrogen fixation per nodule, this reduced neither its atmospheric nitrogen fixation – the main source of nitrogen for the legume – nor its biomass production, both of which were doubled by rhizobial inoculation. In consequence, the total amount of nitrogen in aboveground biomass and aboveground productivity were greatest in mesocosms with both symbionts (i.e. high rhizobia + high endophyte). These results show that, in spite of the deleterious effect of the endophyte on the establishment of the rhizobia–legume symbiosis, the coexistence of these symbionts, leading to additive effects on nitrogen capture and aboveground productivity, can generate complementarity on the functioning of multi‐symbiotic systems.

“…Facultative positive interactions between host species and their associates often involve multiple species (Bronstein 1994, Stanton 2003), including those that differ in spatial and temporal colonization dynamics (Mack and Rudgers 2008, Larimer et al 2012). Variation in the ability of these multiple associate species to provide services to the host is common and can affect the benefits of the relationship (Bronstein 1994, Stachowicz and Whitlatch 2005).…”

mentioning

confidence: 99%

Independent and interactive effects of two facilitators on their habitat‐providing host plant, Spartina alterniflora

Hughes

Moore

Piehler

2013

Oikos

The role of habitat‐providing species in facilitating associated species abundance and diversity is recognized as a key structuring force in many ecosystems. Reciprocal facilitation by associates, often involving multiple species, can be important for the maintenance of the host species. As with other multi‐species interactions (e.g. multiple predator effects), non‐additive relationships may be common among these associates, yet relatively few studies have examined potential interactions among multiple facilitator species. We combined field surveys and a mesocosm experiment to examine the independent and interactive effects of two co‐occurring facilitator species, ribbed mussels Geukensia demissa and fiddler crabs Uca pugilator, on their host salt marsh plant species, cordgrass Spartina alterniflora. We also experimentally examined how these relationships varied across different host plant genotypes. Overall, facilitator effects increased with increasing facilitator density. There was a significant interaction between mussel and fiddler crab presence, indicating that the effects of each species on cordgrass were dependent on the presence of the other facilitator species. In addition, there were strong interactions among mussels, fiddler crabs, and plant genotype, with greater variation in the performance of individual genotypes when fiddler crabs were absent. Our work reinforces the importance of considering multiple responses when assessing the functional redundancy of co‐occurring facilitators, as species are seldom completely redundant across the range of services they provide. It also highlights that the strength and direction of species interactions can vary due to genetic variation within the interacting species.