Foliar Endophytic Fungi Alter Plant Host Chemistry

Colonization by fungal endophytes have broad benefits for plants, including increased resistance against herbivores and pathogens. Endophytes in culture have been shown to produce secondary metabolites that can suppress herbivore and pathogen damage. It is unknown if these toxins are also synthesized during symbiosis within the host plant, or if endophytes stimulate plant chemical responses, thus affecting plant interactions with their enemies. We tested how endophyte colonization alters the production of defensive compounds in the toxic plant white snakeroot (Ageratina altissima), a native Kentucky wildflower. We inoculated endophyte-free seedlings with one of three treatments: 1) inoculation by a single, dominant endophyte (Colletotrichum sp.), 2) inoculation with rainwater captured underneath wild snakeroot plants as a natural fungal spore source, or 3) application of sterile water as a control. After endophyte communities established in seedlings, we quantified colonization success using a culture-based approach, coupled with Sanger sequencing. Plants inoculated with rainwater had the most diverse endophyte communities. To determine if endophyte community composition and diversity affected plant chemistry, we extracted phenolics from leaf tissue and performed liquid chromatography-mass spectrometry. Comparing the phenolic profiles across the three treatments revealed microbial colonizers alter the production of secondary metabolites in plants. Plants treated with Colletotrichum sp. and rainwater had a significantly larger breadth of chemical compounds in their tissues than uninoculated seedlings. Additionally, abundance of individual phenolic compounds varied between treatments. Future work will examine if these chemicals were produced by endophytes or were produced by plant pathways triggered by fungal colonization

NGF-TrkA signaling dictates neural ingrowth and aberrant osteochondral differentiation after soft tissue trauma

: Pain is a central feature of soft tissue trauma, which under certain contexts, results in aberrant osteochondral differentiation of tissue-specific stem cells. Here, the role of sensory nerve fibers in this abnormal cell fate decision is investigated using a severe extremity injury model in mice. Soft tissue trauma results in NGF (Nerve growth factor) expression, particularly within perivascular cell types. Consequently, NGF-responsive axonal invasion occurs which precedes osteocartilaginous differentiation. Surgical denervation impedes axonal ingrowth, with significant delays in cartilage and bone formation. Likewise, either deletion of Ngf or two complementary methods to inhibit its receptor TrkA (Tropomyosin receptor kinase A) lead to similar delays in axonal invasion and osteochondral differentiation. Mechanistically, single-cell sequencing suggests a shift from TGFβ to FGF signaling activation among pre-chondrogenic cells after denervation. Finally, analysis of human pathologic specimens and databases confirms the relevance of NGF-TrkA signaling in human disease. In sum, NGF-mediated TrkA-expressing axonal ingrowth drives abnormal osteochondral differentiation after soft tissue trauma. NGF-TrkA signaling inhibition may have dual therapeutic use in soft tissue trauma, both as an analgesic and negative regulator of aberrant stem cell differentiation

Candida albicans selection for human commensalism results in substantial within-host diversity without decreasing fitness for invasive disease.

Candida albicans is a frequent colonizer of human mucosal surfaces as well as an opportunistic pathogen. C. albicans is remarkably versatile in its ability to colonize diverse host sites with differences in oxygen and nutrient availability, pH, immune responses, and resident microbes, among other cues. It is unclear how the genetic background of a commensal colonizing population can influence the shift to pathogenicity. Therefore, we examined 910 commensal isolates from 35 healthy donors to identify host niche-specific adaptations. We demonstrate that healthy people are reservoirs for genotypically and phenotypically diverse C. albicans strains. Using limited diversity exploitation, we identified a single nucleotide change in the uncharacterized ZMS1 transcription factor that was sufficient to drive hyper invasion into agar. We found that SC5314 was significantly different from the majority of both commensal and bloodstream isolates in its ability to induce host cell death. However, our commensal strains retained the capacity to cause disease in the Galleria model of systemic infection, including outcompeting the SC5314 reference strain during systemic competition assays. This study provides a global view of commensal strain variation and within-host strain diversity of C. albicans and suggests that selection for commensalism in humans does not result in a fitness cost for invasive disease

The role of neutrophil extracellular traps and TLR signaling in skeletal muscle ischemia reperfusion injury

Ischemia reperfusion (IR) injury results in devastating skeletal muscle fibrosis. Here, we recapitulate this injury with a mouse model of hindlimb IR injury which leads to skeletal muscle fibrosis. Injury resulted in extensive immune infiltration with robust neutrophil extracellular trap (NET) formation in the skeletal muscle, however, direct targeting of NETs via the peptidylarginine deiminase 4 (PAD4) mechanism was insufficient to reduce muscle fibrosis. Circulating levels of IL‐10 and TNFα were significantly elevated post injury, indicating toll‐like receptor (TLR) signaling may be involved in muscle injury. Administration of hydroxychloroquine (HCQ), a small molecule inhibitor of TLR7/8/9, following injury reduced NET formation, IL‐10, and TNFα levels and ultimately mitigated muscle fibrosis and improved myofiber regeneration following IR injury. HCQ treatment decreased fibroadipogenic progenitor cell proliferation and partially inhibited ERK1/2 phosphorylation in the injured tissue, suggesting it may act through a combination of TLR7/8/9 and ERK signaling mechanisms. We demonstrate that treatment with FDA‐approved HCQ leads to decreased muscle fibrosis and increased myofiber regeneration following IR injury, suggesting short‐term HCQ treatment may be a viable treatment to prevent muscle fibrosis in ischemia reperfusion and traumatic extremity injury.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163638/2/fsb220999_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163638/1/fsb220999.pd