Biology subjects

Weir, R.

Publications and source records attributed to Weir, R..

4 recordsLinked to original sources

bioRxiv2026

Adeno-associated virus serotype tropism and transduction in murine dorsal root ganglia following direct injection.

The peripheral nervous system (PNS) is highly heterogeneous, comprised of diverse subclasses of motor and sensory neurons. Optogenetics offers a high-resolution approach for interrogating neural circuits; however, optogenetic proteins must be selectively delivered to defined neuronal circuits in order to elucidate circuit-specific functional mechanisms. Adeno-associated viral vectors (AAVs) are widely used to deliver transgenes to the nervous system due to their relative safety and strong transgene expression. Multiple AAV serotypes are in common use, each capable of preferentially transducing distinct tissues and neuronal populations. However, characterization of the transduction behavior of these serotypes in the PNS, particularly in the dorsal root ganglia (DRG) and sensory nervous system (SNS), remain limited. This study evaluated the transduction efficiency of AAV8, AAV9, AAV2re, and PHP.S following direct intraganglionic injection into the DRG. AAV8, AAV9, and PHP.S exhibited comparable transduction efficiencies, whereas AAV2re transduced more than twofold fewer neurons. Despite similar overall efficiencies between AAV8, AAV9, and PHP.S, the neuronal volume distributions of transduced neurons were serotype-dependent. These results demonstrate that AAV serotype selection influences both the extent and size of transduced DRG neurons, indicating that serotype selection should be considered carefully when designing experiments that target peripheral sensory circuits.

neuroscience↗

bioRxiv2021

Knockdown of PHYTOENE DESATURASE in the field dodder, Cuscuta campestris, by Virus-Induced Gene Silencing

Cuscuta campestris is a globally distributed obligate holoparasitic plant, and economically important crop pest. There is an urgent need for safe and effective new herbicides to control Cuscuta spp. PHYTOENE DESATURASE (PDS) is a biosynthetic enzyme within the carotenoid synthesis pathway, which is a target for several commercially available herbicides. The low transpiration rate of C. campestris results in sub-optimal translocation of PDS-targeting herbicides throughout the parasite, and resistance to these herbicides, and others, should be anticipated. Here we demonstrate that RNA interference (RNAi) can effectively reduce the expression of PDS in C. campestris. Virus Induced Gene Silencing (VIGS) is capable of inducing PDS knockdown in C. campestris, when Tobacco Rattle Virus (TRV) is used to deliver a PDS-specific sequence through the host plant Arabidopsis thaliana. This leads to a reduction in the accumulation of beta carotene, which is synthesised from phytoene, and significantly reduced growth of C. campestris. We hypothesise that secondary amplification and spread of PDS double-stranded RNA within C. campestris may circumvent the translocation limitations of other xylem and phloem-spread PDS-specific herbicides. These data demonstrate for the first time that VIGS can be used for reverse genetics interrogation of the C. campestris genome.

plant biology↗

bioRxiv2020

Emergence of optrA-mediated linezolid resistance in multiple lineages and plasmids of Enterococcus faecalis revealed by long read sequencing

ObjectivesTo characterise the genetic environment of optrA in linezolid-resistant Enterococcus faecalis isolates from Scotland. MethodsLinezolid-resistant E. faecalis were identified in three Scottish Health Boards and confirmed to carry the optrA gene at the national reference laboratory. WGS was performed with short read (Illumina MiSeq) and long read (Oxford Nanopore MinION) technologies to generate complete genome assemblies. Illumina reads for 94 E. faecalis bloodstream isolates were used to place the optrA-positive isolates in a larger UK phylogeny. ResultsSix optrA-positive linezolid-resistant E. faecalis were isolated from urogenital samples in three Scottish Health Boards (2014-2017). No epidemiological links were identified between the patients, four were community-based, and only one had recent linezolid exposure. Reference-based mapping confirmed the isolates were genetically distinct (>13,900 core SNPs). optrA was located on a plasmid in each isolate and these plasmids showed limited nucleotide similarity. There was variable presence of transposable elements surrounding optrA, (including IS1216, IS3, and Tn3) and not always as a recognisable gene cassette. OptrA amino acid sequences were also divergent, resulting in four protein variants differing in 1-20 residues. One isolate belonged to ST16 and clustered with three other isolates in the UK collection (76-182 SNPs), otherwise the optrA-positive isolates were genetically distinct from the bloodstream isolates (>6,000 SNPs). ConclusionsWe report multiple variants of the linezolid resistance gene optrA in diverse E. faecalis strain and plasmid backgrounds, suggesting multiple introductions of the gene into the E. faecalis population and selection driving recent emergence.

microbiology↗

bioRxiv2019

ABC transporters alter plant-microbe-parasite interactions in the rhizosphere

Plants are master regulators of rhizosphere ecology, secreting a complex mixture of compounds into the soil, collectively termed plant root exudate. Root exudate composition is highly dynamic and functional, mediating interactions between plants and a wide range of beneficial / harmful soil organisms. Exudate composition is under selective pressure to diversify in response to pathogen perception, whilst maintaining interactions with beneficial organisms. However, crop domestication has exerted significant and unintended changes to crop root exudate composition, and we know very little about genotype - phenotype linkages that pertain to root exudates and rhizosphere interactions. Better understanding could enable the modulation of root exudate composition for crop improvement by promoting positive, and impeding negative, interactions. Root expressed transporters modulate exudate composition and could be manipulated towards the rational design of beneficial root exudate profiles. Using Virus Induced Gene silencing (VIGS), we demonstrate that knockdown of two root-expressed ABC transporter genes in tomato cv. Moneymaker, ABC-G33 and ABC-C6, alters the composition of semi-volatile compounds in collected root exudates. Root exudate chemotaxis assays demonstrate that knockdown of each transporter gene triggers the repulsion of economically relevant Meloidogyne and Globodera spp. plant parasitic nematodes, which are attracted to control treatment root exudates. Knockdown of ABC-C6 inhibits egg hatching of Meloidogyne and Globodera spp., relative to controls. Knockdown of ABC-G33 has no impact on egg hatching of Meloidogyne spp. but has a substantial inhibitory impact on egg hatching of G. pallida. ABC-C6 knockdown has no impact on the attraction of the plant pathogen Agrobacterium tumefaciens, or the plant growth promoting Bacillus subtilis, relative to controls. Silencing ABC-G33 induces a statistically significant reduction in attraction of B. subtilis, with no impact on attraction of A. tumefaciens. ABC-C6 represents a promising target for breeding or biotechnology intervention strategies as gene knockdown (-64.9%) leads to the repulsion of economically important plant parasites and retains attraction of the beneficial rhizobacterium B. subtilis. This study exposes the link between ABC transporters, root exudate composition, and ex planta interactions with agriculturally and economically relevant rhizosphere organisms, paving the way for an entirely new approach to rhizosphere engineering and crop protection.

plant biology↗