Infection with Edwardsiella ictaluri, a causative agent of enteric septicemia of catfish, threatens profitable catfish production through inventory losses. We previously demonstrated that trans-cinnamaldehyde (TC) enhances the survival of catfish following E. ictaluri infection. The present study was conducted to investigate catfish immune responses to TC feeding and E. ictaluri infection. The expression of 13 proinflammatory, innate, and adaptive immune-related genes was evaluated over time in two sets of experiments using real-time polymerase chain reaction (PCR). In the first experiment, catfish were fed a basal diet with or without TC supplementation, while in the second they were fed a TC-supplemented or normal diet followed by infection with E. ictaluri. The catfish group infected with E. ictaluri and fed a TC-diet showed significant changes in the expression of innate and adaptive immune-related genes compared to control group. At 21 and 28 days post-infection, recovered fish showed significant increases in the expression of IgM in the anterior kidney and spleen. These results suggest that the supplemental dietary intake of TC can improve the immune status of catfish via engaging innate and adaptive immune responses and the production of memory cells in immunocompetent tissues. Together, this study provides an important foundation for the potential application of TC as an antimicrobial alternative in aquaculture.

Forests of the Southern Appalachian Mountains were historically dominated by hardwood species within the family Fagaceae, e.g., American chestnut (Castanea dentata) and white oak (Quercus alba) among others. Due to numerous biotic and abiotic stressors, including pathogen pressure, populations of many Fagaceae have been greatly reduced, or functionally eliminated as is the case with American chestnut. This has led to reforestation efforts designed to increase American chestnut and white oak populations in this region, but success has been minimal. Since soil fungal communities are crucial to plant health, understanding how reforestation efforts alter soil fungal communities will inform reforestation efforts. Here, using nursery-reared bareroot seedlings of American chestnut, Chinese chestnut, 3rd generation backcross chestnut hybrids (BC3F3), and white oaks outplanted at a locally xeric site in the Southern Appalachian Mountains, we investigated if and how these species and backcross families within species differentially impact soil fungal communities. We demonstrate that after three years of growth, plant-associated soil fungal communities change similarly among different Fagaceae and are distinct from pre-planting soil communities. Interestingly, we observed differential shifts in fungal functional guilds among the Fagaceae species, although these were rather minimal. Taken together, the largely convergent shifts in soil communities across Fagaceae species suggest that these tree species may have similar impacts on soils and/or share similar communities that become enriched in closely related fungal species. The similarity in shared mutualist fungal communities suggests that companion planting or reforestation of genetically disease resistant American chestnut adjacent to establishing white oak trees might enhance survival and growth of both species at xeric sites.

Aflatoxin is a secondary metabolite produced by Aspergillus fungi and presents a major food safety concern globally. Among the available methods for prevention and control of aflatoxin, the application of antifungal bacteria has gained favor in recent years. An endophytic bacterium MS455, isolated from soybean, exhibited broad-spectrum antifungal activity against economically important pathogens, including Aspergillus flavus. MS455 was identified as a strain of Burkholderia based on genomic analysis. Random and site-specific mutations were used in discovery of the genes that share high homology to the ocf gene cluster of Burkholderia contaminans strain MS14, which is responsible for production of the antifungal compound occidiofungin. RNA sequencing analysis demonstrated that ORF1, a homolog to the ambR1 LuxR-type regulatory gene, regulates occidiofungin biosynthesis in MS455. Additionally, 284 differentially expressed genes, including 138 upregulated and 146 downregulated genes, suggesting that, in addition to its role in occidiofungin production, ORF1 is involved in expression of multiple genes, especially those involved in ornibactin biosynthesis. Plate bioassays showed the growth of A. flavus was significantly inhibited by the wild-type strain MS455 as compared with the ORF1 mutant. Similarly, corn kernel assays showed that growth of A. flavus and aflatoxin production were reduced significantly by MS455 as compared with buffer control and the ORF1 mutant. Collectively, the results demonstrated that production of occidiofungin is essential for antifungal activity of the endophytic bacterium MS455. This research has provided insights about antifungal mechanisms of MS455 and development of biological approaches to prevent aflatoxin contamination in plant production.

The loss of Fagaceae species is an increasing concern globally, including in North American where American chestnut (Castanea dentata) has been virtually eliminated by non-native pathogens, and oaks (Quercus) are experiencing widespread regeneration failures and declines. Tree improvement and breeding programs are producing trees for disease resistance or improved performance traits but require field testing to refine efforts. We established a study in 2015 on a xeric pitch pine (Pinus rigida) site in the Blue Ridge Mountains of North Carolina to regenerate American chestnut and interspecies hybrids (BC3F3) and the co-occurring species of white oak (Q. alba) through planting bare-root, quality-graded seedlings. Chinese chestnut (C. mollissima) was also tested as a control species. We used pedigreed seed sources from open-pollinated genetic families that were nursery grown (1-0 bareroot seedlings for chestnut, 2-0 bareroot seedlings for white oak) to maximize overall size and competitive ability. Though there was variability within and among plant families in performance, American chestnut and BC3F3 hybrids generally outperformed Chinese chestnut (at least 13 % taller) and white oak (at least 29 % taller) for the first three years, but intraspecies differences among genetic families were significant for nearly all traits tested. Initial seedling root morphology poorly explained field performance (R2 < 0.17), but this relationship was significant for both white oak families and the only northern BC3F3 seed source. American chestnuts and BC3F3 hybrids had higher stem height to ground diameter ratios compared to white oak (at least 11 % greater), indicating that white oak likely concentrates more resources to root development while chestnut concentrates more resources to maintaining above-ground competitive advantages. Additionally, we investigated soil fungal communities, both pre-and post-tree establishment and tested if these fungal commu-nities can be used to predict plant performance or health. Soil fungi did a poor job predicting plant performance. Our results indicate that co-occurring Fagaceae species can be established in restoration plantings using well developed quality seedlings on relatively xeric sites. Managers should use diverse seed sources to avoid planting poor performing families and expect that chestnuts bred for blight resistance will outcompete planted white oak, at least in the short-term.

Burkholderia sp. strain MS389, an endophytic bacterium, was isolated from a healthy soybean plant growing adjacent to a patch of plants affected by charcoal rot disease, caused by the fungal pathogen Macrophomina phaseolina. Preliminary studies demonstrated that strain MS389 possesses antimicrobial activities against multiple plant pathogens. Burkholderia sp. strain MS389 was found to have three circular chromosomes of 3,563,380 bp, 3,002,449 bp, and 1,180,421 bp in size, respectively. The 7,746,250-bp genome, with 66.73% G+C content, harbors 6,756 protein coding genes in the predicted 6,985 genes. In total, 18 rRNAs, 68 tRNAs, and four ncRNAs were identified and 139 pseudogenes were annotated as well. The findings of this study will provide valuable data to explore the antimicrobial mechanisms of the endophytic bacterial strain.

Decades of fire suppression coupled with changing climatic conditions have increased the frequency and intensity of wildfires. The Southern Appalachia region of the United States is predicted to be particularly susceptible to climatic changes, with predicted increases in fire severity and occurrence. Following the record breaking fire season in 2016 in Southern Appalachia, we examined wildfire impacts on soil chemistry and below ground communities (fungi and bacteria - Illumina MiSeq) within two substrates (duff and soil) at two adjacent locations with similar plant communities (Great Smoky Mountains National Park - 'Chimney Top 2' Fire (GRSM) and Nantahala National Forest - 'Cliffside' Fire (NNF)) from replicate plots representing a range of fire severities (unburned, low severity, moderate severity, severe). Differing fire severities changed community composition, and fire severity played a stronger role in structuring bacterial communities than in structuring fungal communities. Further, fire impacts on soil communities and functional guilds responses were location- and substrate specific with NNF responding more strongly to fire than GRSM. Additionally, using a novel analysis tool (Axis Weighted Ordination Distance - AWOrD), domain and location specific responses to wildfire severity are demonstrated. Taken together, our results suggest context-dependency in microbial responses to fire that must be accounted for to generate ecosystem-wide recovery predictions.