Biology subjects

James, G.

Publications and source records attributed to James, G..

4 recordsLinked to original sources

bioRxiv2025

Modes of action and in planta antifungal activity of Olea europaea defensin OefDef1.1-derived peptide variant

Peptide-based biopesticides represent a promising strategy for sustainable disease control in agriculture. Synthetic antifungal peptides incorporating the {gamma}-core motif of plant defensins offer multiple modes of action (MoA) and potential as biofungicides. We investigated a synthetic variant of the olive defensin OefDef1.1 for antifungal activity, structure-function relationships, and MoA against Botrytis cinerea, the necrotrophic pathogen causing gray mold. A disulfide-bridged peptide, GMAOe1C_V1*, derived from OefDef1.1 (G32-Y53) and modified with hydrophobic amino acid substitutions, inhibited B. cinerea growth in vitro and reduced lesion formation in detached leaves. Foliar application of GMAOe1C_V1* suppressed disease symptoms in pepper plants. Mechanistically, GMAOe1C_V1* rapidly permeabilized fungal plasma membranes and accumulated in vacuoles, triggering vacuolar expansion and cell death. It also inhibited protein synthesis in vitro and in vivo, suggesting a role as a translation inhibitor. Alanine scanning mutagenesis of the non-disulfide bridged variant identified the 7RHSKH11 motif as essential for antifungal activity. Circular dichroism revealed an unstructured conformation with minimal secondary structure. Transcriptomic analysis of GMAOe1C_V1* treated B. cinerea germlings showed downregulation of genes involved in mitochondrial function and amino acid biosynthesis. These findings demonstrate the potential of an olive defensin-derived peptide as a bio-inspired antifungal agent with multifaceted MoA, supporting its development for crop protection.

plant biology↗

bioRxiv2025

Miniature bioreactor arrays for modeling functional and structural dysbiosis in inflammatory bowel disease

Alterations in the gut microbiota, known as gut dysbiosis, are associated with inflammatory bowel disease (IBD). There is a need for model systems that can recapitulate the IBD gut microbiome to better understand the mechanistic impact of differences in microbiota composition and its functional consequences in a controlled laboratory setting. To this end, we introduced fecal samples from patients with Crohns disease (CD) and ulcerative colitis (UC), as well as from healthy control subjects, to miniature bioreactor arrays (MBRAs) and analyzed the microbial communities over time. We then performed two functional assessments. First, we evaluated the colitogenic potential of the CD microbiotas in genetically susceptible germ-free IL-10-deficient mice and found that colitogenic capacity was preserved in a bioreactor-cultivated CD microbiota. Second, we tested impaired colonization resistance against Clostridioides difficile in UC microbiotas using the MBRA system and found that UC microbiotas were innately susceptible to C. difficile colonization while healthy microbiotas were resistant, consistent with what is seen clinically. Overall, our results demonstrate that IBD microbiotas perform comparably to healthy donor microbiotas in the MBRA system, successfully recapitulating microbial structure while preserving IBD-specific functional characteristics. These findings establish a foundation for further mechanistic research into the IBD microbiota using MBRAs.

microbiology↗

bioRxiv2024

Perivascular adipose tissue remodeling impairs vasoreactivity in thermoneutral-housed rats

ObjectiveVascular pathology, characterized by impaired vasoreactivity and mitochondrial respiration, differs between the sexes. Housing rats under thermoneutral (TN) conditions causes vascular dysfunction and perturbed metabolism. We hypothesized that perivascular adipose tissue (PVAT), a vasoregulatory adipose depot with brown adipose tissue (BAT) phenotype, remodels to a white adipose (WAT) phenotype in rats housed at TN, driving diminished vasoreactivity in a sex-dependent manner. MethodsMale and female Wistar rats were housed at either room temperature (RT) or TN. Endpoints included changes in PVAT morphology, vasoreactivity in vessels with intact PVAT or transferred to PVAT of the oppositely-housed animal, vessel stiffness, vessel mitochondrial respiration and cellular signaling. ResultsRemodeling of PVAT was observed in rats housed at TN; animals in this environment showed PVAT whitening and displayed diminished aortae vasodilation (p<0.05), different between the sexes. Juxtaposing PVAT from RT rats onto aortae from TN rats in females corrected vasodilation (p<0.05); this did not occur in males. In aortae of all animals housed at TN, mitochondrial respiration was significantly diminished in lipid substrate experiments (p<0.05), and there was significantly less expression of peNOS (p<0.001). ConclusionsThese data are consistent with TN-induced remodeling of PVAT, notably associated with sex-specific blunting of vasoreactivity, diminished mitochondrial respiration, and altered cellular signaling.

physiology↗

bioRxiv2021

SARS-CoV-2 binding to ACE2 triggers pericyte-mediated angiotensin-evoked cerebral capillary constriction

The SARS-CoV-2 receptor, ACE2, is found on pericytes, contractile cells enwrapping capillaries that regulate brain, heart and kidney blood flow. ACE2 converts vasoconstricting angiotensin II into vasodilating angiotensin-(1-7). In brain slices from hamster, which has an ACE2 sequence similar to human ACE2, angiotensin II alone evoked only a small capillary constriction, but evoked a large pericyte-mediated capillary constriction generated by AT1 receptors in the presence of the SARS-CoV-2 receptor binding domain (RBD). The effect of the RBD was mimicked by blocking ACE2. A mutated non-binding RBD did not potentiate constriction. A similar RBD-potentiated capillary constriction occurred in human cortical slices. This constriction reflects an RBD-induced decrease in the conversion of angiotensin II to angiotensin-(1-7). The clinically-used drug losartan inhibited the RBD-potentiated constriction. Thus AT1 receptor blockers could be protective in SARS-CoV-2 infection by reducing pericyte-mediated blood flow reductions in the brain, and perhaps the heart and kidney.

neuroscience↗