Search for: All records

Due to climate change, drought frequencies and severities are predicted to increase across the United States. Plant responses and adaptation to stresses depend on plant genetic and environmental factors. Understanding the effect of those factors on plant performance is required to predict species’ responses to environmental change. We used reciprocal gardens planted with distinct regional ecotypes of the perennial grassAndropogon gerardiiadapted to dry, mesic, and wet environments to characterize their rhizosphere communities using 16S rRNA metabarcode sequencing. Even though the local microbial pool was the main driver of these rhizosphere communities, the significant plant ecotypic effect highlighted active microbial recruitment in the rhizosphere, driven by ecotype or plant genetic background. Our data also suggest that ecotypes planted at their homesites were more successful in recruiting rhizosphere community members that were unique to the location. The link between the plants’ homesite and the specific local microbes supported the “home field advantage” hypothesis. The unique homesite microbes may represent microbial specialists that are linked to plant stress responses. Furthermore, our data support ecotypic variation in the recruitment of congeneric but distinct bacterial variants, highlighting the nuanced plant ecotype effects on rhizosphere microbiome recruitment. These results improve our understanding of the complex plant host–soil microbe interactions and should facilitate further studies focused on exploring the functional potential of recruited microbes. Our study has the potential to aid in predicting grassland ecosystem responses to climate change and impact restoration management practices to promote grassland sustainability.

In this study, we used reciprocal gardens located across a steep precipitation gradient to characterize rhizosphere communities of distinct dry, mesic, and wet regional ecotypes of the perennial grassAndropogon gerardii. We used 16S rRNA amplicon sequencing and focused oligotyping analysis and showed that even though location was the main driver of the microbial communities, ecotypes could potentially recruit distinct bacterial populations. We showed that differentA. gerardiiecotypes were more successful in overall community recruitment and recruitment of microbes unique to the “home” environment, when growing at their “home site.” We found evidence for “home-field advantage” interactions between the host and host–root-associated bacterial communities, and the capability of ecotypes to recruit specialized microbes that were potentially linked to plant stress responses. Our study aids in a better understanding of the factors that affect plant adaptation, improve management strategies, and predict grassland function under the changing climate.

 

Climate change will result in more frequent droughts that can impact soil-inhabiting microbiomes (rhizobiomes) in the agriculturally vital North American perennial grasslands. Rhizobiomes have contributed to enhancing drought resilience and stress resistance properties in plant hosts. In the predicted events of more future droughts, how the changing rhizobiome under environmental stress can impact the plant host resilience needs to be deciphered. There is also an urgent need to identify and recover candidate microorganisms along with their functions, involved in enhancing plant resilience, enabling the successful development of synthetic communities.

In this study, we used the combination of cultivation and high-resolution genomic sequencing of bacterial communities recovered from the rhizosphere of a tallgrass prairie foundation grass,Andropogon gerardii. We cultivated the plant host-associated microbes under artificial drought-induced conditions and identified the microbe(s) that might play a significant role in the rhizobiome ofAndropogon gerardiiunder drought conditions. Phylogenetic analysis of the non-redundant metagenome-assembled genomes (MAGs) identified a bacterial genome of interest – MAG-Pseudomonas. Further metabolic pathway and pangenome analyses recovered genes and pathways related to stress responses including ACC deaminase; nitrogen transformation including assimilatory nitrate reductase in MAG-Pseudomonas,which might be associated with enhanced drought tolerance and growth forAndropogon gerardii.

Our data indicated that the metagenome-assembled MAG-Pseudomonashas the functional potential to contribute to the plant host’s growth during stressful conditions. Our study also suggested the nitrogen transformation potential ofMAG-Pseudomonasthat could impactAndropogon gerardiigrowth in a positive way. The cultivation of MAG-Pseudomonassets the foundation to construct a successful synthetic community forAndropogon gerardii. To conclude, stress resilience mediated through genes ACC deaminase, nitrogen transformation potential through assimilatory nitrate reductase in MAG-Pseudomonascould place this microorganism as an important candidate of the rhizobiome aiding the plant host resilience under environmental stress. This study, therefore, provided insights into the MAG-Pseudomonasand its potential to optimize plant productivity under ever-changing climatic patterns, especially in frequent drought conditions.

 

Plant communities and fungi inhabiting their phyllospheres change along precipitation gradients and often respond to changes in land use. Many studies have focused on the changes in foliar fungal communities on specific plant species, however, few have addressed the association between whole plant communities and their phyllosphere fungi. We sampled plant communities and associated phyllosphere fungal communities in native prairie remnants and post-agricultural sites across the steep precipitation gradient in the central plains in Kansas, USA. Plant community cover data and MiSeq ITS2 metabarcode data of the phyllosphere fungal communities indicated that both plant and fungal community composition respond strongly to mean annual precipitation (MAP), but less so to land use (native prairie remnants vs. post-agricultural sites). However, plant and fungal diversity were greater in the native remnant prairies than in post-agricultural sites. Overall, both plant and fungal diversity increased with MAP and the communities in the arid and mesic parts of the gradient were distinct. Analyses of the linkages between plant and fungal communities (Mantel and Procrustes tests) identified strong correlations between the composition of the two. However, despite the strong correlations, regression models with plant richness, diversity, or composition (ordination axis scores) and land use as explanatory variables for fungal diversity and evenness did not improve the models compared to those with precipitation and land use (ΔAIC < 2), even though the explanatory power of some plant variables was greater than that of MAP as measured by R². Indicator taxon analyses suggest that grass species are the primary taxa that differ in the plant communities. Similar analyses of the phyllosphere fungi indicated that many plant pathogens are disproportionately abundant either in the arid or mesic environments. Although decoupling the drivers of fungal communities and their composition – whether abiotic or host-dependent – remains a challenge, our study highlights the distinct community responses to precipitation and the tight tracking of the plant communities by their associated fungal symbionts.

 

ABSTRACT Mosquito larvae encounter diverse assemblages of bacteria (i.e., “microbiota”) and fungi in the aquatic environments that they develop in. However, while a number of studies have addressed the diversity and function of microbiota in mosquito life history, relatively little is known about mosquito-fungus interactions outside several key fungal entomopathogens. In this study, we used high-throughput sequencing of internal transcribed spacer 2 (ITS2) metabarcode markers to provide the first simultaneous characterization of the fungal communities in field-collected Aedes albopictus larvae and their associated aquatic environments. Our results reveal unprecedented variation in fungal communities among adjacent but discrete larval breeding habitats. Our results also reveal a distinct fungal community assembly in the mosquito gut versus other tissues, with gut-associated fungal communities being most similar to those present in the environment where larvae feed. Altogether, our results identify the environment as the dominant factor shaping the fungal community associated with mosquito larvae, with no evidence of environmental filtering by the gut. These results also identify mosquito feeding behavior and fungal mode of nutrition as potential drivers of tissue-specific fungal community assembly after environmental acquisition. IMPORTANCE The Asian tiger mosquito, Aedes albopictus , is the dominant mosquito species in the United States and an important vector of arboviruses of major public health concern. One aspect of mosquito control to curb mosquito-borne diseases has been the use of biological control agents such as fungal entomopathogens. Recent studies also demonstrate the impact of mosquito-associated microbial communities on various mosquito traits, including vector competence. However, while much research attention has been dedicated to understanding the diversity and function of mosquito-associated bacterial communities, relatively little is known about mosquito-associated fungal communities. A better understanding of the factors that drive fungal community diversity and assembly in mosquitoes will be essential for future efforts to target mosquito-associated bacteria and fungi for mosquito and mosquito-borne disease control. 

Fire can impact terrestrial ecosystems by changing abiotic and biotic conditions. Short fire intervals maintain grasslands and communities adapted to frequent, low-severity fires. Shrub encroachment that follows longer fire intervals accumulates fuel and can increase fire severity. This patchily distributed biomass creates mosaics of burn severities in the landscape—pyrodiversity. Afforded by a scheduled burn of a watershed protected from fires for 27 years, we investigated effects of woody encroachment and burn severity on soil chemistry and soil-inhabiting bacteria and fungi. We compared soils before and after fire within the fire-protected, shrub-encroached watershed and soils in an adjacent, annually burned and non-encroached watershed. Organic matter and nutrients accumulated in the fire-protected watershed but responded less to woody encroachment within the encroached watershed. Bioavailable nitrogen and phosphorus and fungal and bacterial communities responded to high-severity burn regardless of encroachment. Low-severity fire effects on soil nutrients differed, increased bacterial but decreased fungal diversity and effects of woody encroachment within the encroached watershed were minimal. High-severity burns in the fire-protected watershed led to a novel soil system state distinct from non-encroached and encroached soil systems. We conclude that severe fires may open grassland restoration opportunities to manipulate soil chemistry and microbial communities in shrub-encroached habitats.

 

Aim: Roots and rhizospheres host diverse microbial communities that can influence the fitness, phenotypes, and environmental tolerances of host plants. Documenting the biogeography of microbiomes can detect the potential for a changing environment to disrupt host-microbe interactions, particularly in cases where microbes, such as root-associated Ascomycota, buffer hosts against abiotic stressors. We evaluated whether root-associated fungi had poleward declines in diversity as occur for many animals and plants, tested whether microbial communities shifted near host plant range edges, and determined the relative importance of latitude, climate, edaphic factors, and host plant traits as predictors of fungal community structure. Location: North American plains grasslands Taxon: Foundation North American grass species ⎯ Andropogon gerardii, Bouteloua eriopoda, B. gracilis, B. dactyloides, and Schizachyrium scoparium and their root-associated fungi Methods: At each of 24 sites representing three replicate latitudinal gradients spanning 17° latitude, we collected roots from 12 individual plants per species along five transects spaced 10 m apart (40 m × 40 m grid). We used next-generation sequencing of the fungal ITS2 region, direct fungal culturing from roots, and microscopy to survey fungi associated with grass roots. Results: Root-associated fungi did not follow the poleward declines in diversity documented for many animals and plants. Instead, host plant identity had the largest influence on fungal community structure. Edaphic factors outranked climate or host plant traits as correlates of fungal community structure; however, the relative importance of these environmental predictors differed among plant species. As sampling approached host species range edges, fungal composition converged among individual plants of each grass species. Main conclusions: Environmental predictors of root-associated fungi depended strongly on host plant species identity. Biogeographic patterns in fungal composition suggested a homogenizing influence of stressors at host plant range limits. Results predict that communities of non-mycorrhizal, root-associated fungi in the North American plains will be more sensitive to future changes in host plant ranges and edaphic factors than to the direct effects of climate.