Biology subjects

Gardner, D.

Publications and source records attributed to Gardner, D..

4 recordsLinked to original sources

bioRxiv2025

Molecular Insights into the Production of Extracellular Vesicles by Plants

Extracellular vesicles (EVs) produced by Arabidopsis are highly heterogeneous in protein content. Specific EV subpopulations have been proposed to participate in plant immunity, particularly during plant-fungal interaction. To understand the origins of plant EV heterogeneity, we used a proximity labeling approach to identify proteins and pathways involved in the secretion of distinct EV subpopulations. Proximity labeling, co-immunoprecipitation, and fluorescence microscopy in Nicotiana benthamiana all indicated a general role in EV secretion for EXO70 proteins (a subunit of the exocyst complex) and the immune-related protein RPM1-INTERACTING PROTEIN 4 (RIN4), while the ER-localized VAMP-ASSOCIATED PROTEIN 27(VAP27) was specifically associated with the EV marker protein TETRAPSANIN8 (TET8). Despite being secreted in separate EV populations, we found that TET8 and PENETRATION 1 (PEN1) co-localized in multivesicular body-like subcellular structures. Based on these results, we tested Arabidopsis mutants and identified several proteins involved in EV secretion, including members of the exo70 family, rin4, rabA2a, scd1 (a GTP-exchange factor for RabE GTPases), and vap27. We also uncovered a possible connection between trichomes and EVs, as the trichomeless mutant glabrous1 secreted approximately half the number of EVs as wild type. Furthermore, PEN1 MVB-like structures were prevalent in guard cells, suggesting that guard cells may contribute to secretion of PEN1+ EVs on the leaf surface. Lastly, we found that exo70 family mutants are more susceptible to infection with the fungal pathogen Colletotrichum higginsianum, underlining the importance of secretion for plant immunity. Together, our results unravel some of the complex mechanisms that give rise to EV subpopulations in plants.

plant biology↗

bioRxiv2025

Wnt signaling drives stromal inflammation in inflammatory arthritis

The concept that fibroblasts are critical mediators of inflammation is an emerging paradigm. In rheumatoid arthritis (RA), they are the main producers of IL-6 as well as a host of other cytokines and chemokines. Their pathologic activation also directly causes cartilage and bone degradation. Yet, therapeutic agents specifically targeting fibroblasts are not available. Here, we find that Wnt receptors and modulators are predominantly expressed in stromal populations in the synovium. Importantly, non-canonical Wnt activation induces robust inflammatory gene expression including an abundance of cytokines and chemokines in synovial fibroblasts in vitro. Strikingly, the addition of Wnt ligands or inhibition of Wnt secretion exacerbates or reduces arthritis severity, respectively, in vivo in a murine model of inflammatory arthritis. These observations are relevant in human disease, as Wnt activation signatures are enhanced in fibroblasts derived from inflamed RA synovial tissue as well as fibroblasts across other inflammatory diseases. Together, these findings implicate Wnt signaling as a major driver of fibroblast-mediated inflammation and joint pathology. They further suggest that targeting the Wnt pathway is a therapeutically relevant approach to rheumatoid arthritis, particularly in patients who do not respond to conventional treatments and who often express fibroblast-predominant synovial phenotypes.

immunology↗

bioRxiv2022

PAX4 loss of function alters human endocrine cell development and influences diabetes risk

Diabetes is a major chronic disease with an excessive healthcare burden on society1. A coding variant (p.Arg192His) in the transcription factor PAX4 is uniquely and reproducibly associated with an altered risk for type 2 diabetes (T2D) in East Asian populations2-7, whilst rare PAX4 alleles have been proposed to cause monogenic diabetes8. In mice, Pax4 is essential for beta cell formation but neither the role of diabetes-associated variants in PAX4 nor PAX4 itself on human beta cell development and/or function are known. Here, we demonstrate that non-diabetic carriers of either the PAX4 p.Arg192His or a newly identified p.Tyr186X allele exhibit decreased pancreatic beta cell function. In the human beta cell model, EndoC-{beta}H1, PAX4 knockdown led to impaired insulin secretion, reduced total insulin content, and altered hormone gene expression. Deletion of PAX4 in isogenic human induced pluripotent stem cell (hiPSC)-derived beta-like cells resulted in derepression of alpha cell gene expression whilst in vitro differentiation of hiPSCs from carriers of PAX4 p.His192 and p.X186 alleles exhibited increased polyhormonal endocrine cell formation and reduced insulin content. In silico and in vitro studies showed that these PAX4 alleles cause either reduced PAX4 expression or function. Correction of the diabetes-associated PAX4 alleles reversed these phenotypic changes. Together, we demonstrate the role of PAX4 in human endocrine cell development, beta cell function, and its contribution to T2D-risk.

developmental biology↗

bioRxiv2019

A suite of rare microbes interacts with a dominant, heritable, fungal endophyte to influence plant trait expression

Endophytes are microbes that live, for at least a portion of their life history, within plant tissues. Endophyte assemblages are often composed of a few abundant taxa and many infrequently-observed, rare taxa. The ways in which most endophytes affect host phenotype are unknown; however, certain dominant endophytes can influence plants in ecologically meaningful ways-including by affecting growth and contributing to immune responses. In contrast, the effects of rare endophytes have been unexplored, and how rare and common endophytes might interact is also unknown. Here, we manipulate both the suite of rare foliar endophytes (including both fungi and bacteria) and Alternaria fulva-a dominant, vertically- transmitted fungus-within the fabaceous forb Astragalus lentiginosus. We report that rare, low-biomass endophytes affected host size and foliar %N, but only when the dominant fungal endophyte (A. fulva) was not present. A. fulva also reduced plant size and %N, but these deleterious effects on the host could be offset by a striking antagonism we observed between this heritable fungus and a foliar pathogen. These results are unusual in that they are derived from experimental manipulation in a non-crop or non-grass system and demonstrate that interactions among taxa determine the net effect of endophytic assemblages on their hosts. We suggest that the myriad infrequently-observed endophytes within plant leaves may be more than a collection of uninfluential, commensal organisms, but instead have meaningful ecological roles.

ecology↗