Biology subjects

Wood, T.

Publications and source records attributed to Wood, T..

8 recordsLinked to original sources

bioRxiv2018

High-throughput characterisation of bull semen motility using differential dynamic microscopy

We report a high-throughput technique for characterising the motility of spermatozoa using differential dynamic microscopy. A large field of view movie (~ 10mm2) records thousands of cells (e.g. {approx} 5000 cells even at a low cell density of 20 x 106 cells/ml) at once and yields averaged measurements of the mean ({upsilon}) and standard deviation ({sigma}) of the swimming speed, a head oscillation amplitude (A0) and frequency (f0), and the fraction of motile spermatozoa (). Interestingly, the measurement of relies on the swimming spermatozoa enhancing the motion of the non-swimming population. We demonstrate the ease and rapidity of our method by performing on-farm characterisation of bull spermatozoa motility, and validate the technique by comparing laboratory measurements with tracking. Our results confirm the long-standing theoretical prediction that [Formula] for swimming spermatozoa.

biophysics↗

bioRxiv2018

Corticospinal neuroplasticity and sensorimotor recovery in rats treated by infusion of neurotrophin-3 into disabled forelimb muscles started 24 h after stroke

Stroke often leads to arm disability and reduced responsiveness to stimuli on the other side of the body. Neurotrophin-3 (NT3) is made by skeletal muscle during infancy but levels drop postnatally and into adulthood. It is essential for the survival and wiring-up of sensory afferents from muscle. We have previously shown that gene therapy delivery of human NT3 into the affected triceps brachii forelimb muscle improves sensorimotor recovery after ischemic stroke in adult and elderly rats. Here, to move this therapy one step nearer to the clinic, we set out to test the hypothesis that intramuscular infusion of NT3 protein could improve sensorimotor recovery after ischemic cortical stroke in adult rats. To simulate a clinically-feasible time-to-treat, twenty-four hours later rats were randomized to receive NT3 or vehicle by infusion into triceps brachii for four weeks using implanted minipumps. NT3 increased the accuracy of forelimb placement during walking on a horizontal ladder and increased use of the affected arm for lateral support during rearing. NT3 also reversed sensory deficits on the affected forearm. There was no evidence of forepaw sensitivity to cold stimuli after stroke or NT3 treatment. MRI confirmed that treatment did not induce neuroprotection. Functional MRI during low threshold electrical stimulation of the affected forearm showed an increase in peri-infarct BOLD signal with time in both stroke groups and indicated that neurotrophin-3 did not further increase peri-infarct BOLD signal. Rather, NT3 induced spinal neuroplasticity including sprouting of the spared corticospinal and serotonergic pathways. Neurophysiology showed that NT3 treatment increased functional connectivity between the corticospinal tracts and spinal circuits controlling muscles on the treated side. After intravenous injection, radiolabelled NT3 crossed from bloodstream into the brain and spinal cord in adult mice with or without strokes. Our results show that delayed, peripheral infusion of neurotrophin-3 can improve sensorimotor function after ischemic stroke. Phase I and II clinical trials of NT3 (for constipation and neuropathy) have shown that peripheral, high doses are safe and well tolerated, which paves the way for NT3 as a therapy for stroke.

neuroscience↗

bioRxiv2018

Homogenization of sub-genome secretome gene expression patterns in the allodiploid fungus Verticillium longisporum

Hybridization is an important evolutionary mechanism that can enable organisms to adapt to environmental challenges. It has previously been shown that the fungal allodiploid species Verticillium longisporum, causal agent of Verticillium stem striping in rape seed, has originated from at least three independent hybridization events between two haploid Verticillium species. To reveal the impact of genome duplication as a consequence of the hybridization, we studied the genome and transcriptome dynamics upon two independent V. longisporum hybridization events, represented by the hybrid lineages "A1/D1" and "A1/D3". We show that the V. longisporum genomes are characterized by extensive chromosomal rearrangements, including between parental chromosomal sets. V. longisporum hybrids display signs of evolutionary dynamics that are typically associated with the aftermath of allodiploidization, such as haploidization and a more relaxed gene evolution. Expression patterns of the two sub-genomes within the two hybrid lineages are more similar than those of the shared A1 parent between the two lineages, showing that expression patterns of the parental genomes homogenized within a lineage. However, as genes that display differential parental expression in planta do not typically display the same pattern in vitro, we conclude that sub-genome-specific responses occur in both lineages. Overall, our study uncovers the genomic and transcriptomic plasticity during evolution of the filamentous fungal hybrid V. longisporum and illustrate its adaptive potential. ImportanceVerticillium is a genus of plant-associated fungi that include a handful of plant pathogens that collectively affect a wide range of hosts. On several occasions, haploid Verticillium species hybridized into the stable allodiploid species Verticillium longisporum, which is, in contrast to haploid Verticillium species, a Brassicaceae specialist. Here, we studied the evolutionary genome and transcriptome dynamics of V. longisporum and the impact of the hybridization. V. longisporum genomes display a mosaic structure due do genomic rearrangements between the parental chromosome sets. Similar to other allopolyploid hybrids, V. longisporum displays an ongoing loss of heterozygosity and a more relaxed gene evolution. Also, differential parental gene expression is observed, with an enrichment for genes that encode secreted proteins. Intriguingly, the majority of these genes displays sub-genome-specific responses under differential growth conditions. In conclusion, hybridization has incited the genomic and transcriptomic plasticity that enables adaptation to environmental changes in a parental allele-specific fashion.

microbiology↗

bioRxiv2018

Dynamic virulence-related regions of the fungal plant pathogen Verticillium dahliae display remarkably enhanced sequence conservation

Selection pressure impacts genomes unevenly, as different genes adapt with differential speed to establish an organisms optimal fitness. Plant pathogens co-evolve with their hosts, which implies continuously adaption to evade host immunity. Effectors are secreted proteins that mediate immunity evasion, but may also typically become recognized by host immune receptors. To facilitate effector repertoire alterations, in many pathogens, effector genes reside in dynamic genomic regions that are thought to display accelerated evolution, a phenomenon that is captured by the two-speed genome hypothesis. The genome of the vascular wilt pathogen Verticillium dahliae has been proposed to obey to a similar two-speed regime with dynamic, lineage-specific regions that are characterized by genomic rearrangements, increased transposable element activity and enrichment in in planta-induced effector genes. However, little is known of the origin of, and sequence diversification within, these lineage-specific regions. Based on comparative genomics among Verticillium spp. we now show differential sequence divergence between core and lineage-specific genomic regions of V. dahliae. Surprisingly, we observed that lineage-specific regions display markedly increased sequence conservation. Since single nucleotide diversity is reduced in these regions, host adaptation seems to be merely achieved through presence/absence polymorphisms. Increased sequence conservation of genomic regions important for pathogenicity is an unprecedented finding for filamentous plant pathogens and signifies the diversity of genomic dynamics in host-pathogen co-evolution.

microbiology↗

bioRxiv2018

Nuclear and mitochondrial genomes of the hybrid fungal plant pathogen Verticillium longisporum display a mosaic structure

Allopolyploidization, genome duplication through interspecific hybridization, is an important evolutionary mechanism that can enable organisms to adapt to environmental changes or stresses. This increased adaptive potential of allopolyploids can be particularly relevant for plant pathogens in their quest for host immune response evasion. Allodiploidization likely caused the shift in host range of the fungal pathogen plant Verticillium longisporum, as V. longisporum mainly infects Brassicaceae plants in contrast to haploid Verticillium spp. In this study, we investigated the allodiploid genome structure of V. longisporum and its evolution in the hybridization aftermath. The nuclear genome of V. longisporum displays a mosaic structure, as numerous contigs consists of sections of both parental origins. V. longisporum encountered extensive genome rearrangements, whereas the contribution of gene conversion is negligible. Thus, the mosaic genome structure mainly resulted from genomic rearrangements between parental chromosome sets. Furthermore, a mosaic structure was also found in the mitochondrial genome, demonstrating its bi-parental inheritance. In conclusion, the nuclear and mitochondrial genomes of V. longisporum parents interacted dynamically in the hybridization aftermath. Conceivably, novel combinations of DNA sequence of different parental origin facilitated genome stability after hybridization and consecutive niche adaptation of V. longisporum.

genomics↗

bioRxiv2017

Variable impact of Verticillium longisporum on oilseed rape yield in field trials in the United Kingdom

The Verticillium genus comprises economically important plant pathogens that collectively affect a broad range of annual and perennial crops. Verticillium longisporum mainly infects brassicaceous hosts, including oilseed rape. The most conspicuous symptom of V. longisporum infection on oilseed rape is black stem striping that appears towards the end of the cropping season. Thus far, the impact of V. longisporum infection on oilseed yield remains unclear. Verticillium stem striping recently emerged as a new disease in UK and currently displays a widespread occurrence in England. In this study, we assessed the impact of Verticillium stem striping on British oilseed rape production. To this end, four cultivars (Incentive, Vision, Harper and Quartz) were grown in field plots with different levels of V. longisporum disease pressure at different locations over two consecutive years. Whereas Incentive and Vision developed relatively few stem striping symptoms, Harper and especially Quartz showed severe symptoms during these field experiments. Furthermore, higher inoculum levels induced more severe symptoms in these cultivars. Intriguingly, significant yield reductions upon V. longisporum infection only occurred in a single field trial on all tested oilseed rape cultivars. Thus we conclude that Verticillium stem striping does not consistently impact oilseed rape yield, despite the occurrence of abundant disease symptoms.

plant biology↗

bioRxiv2017

The emerging British Verticillium longisporum population consists of aggressive Brassica pathogens

The impact of diseases depends on the dynamic interplay between host, pathogen and the environment. Newly emerging diseases may be the consequence of novel pathogen introductions that are typically associated with unpredictable outcomes, as their interaction with the host in a novel environment is unprecedented. Alternatively, new diseases may emerge from latent, previously established, pathogen populations that are triggered by changes in environmental factors like weather, agricultural practices and ecosystem management. Verticillium stem striping recently emerged in British oilseed rape (Brassica napus) production from a latent Verticillium longisporum population. V. longisporum is a hybrid fungal pathogen consisting of three lineages, each representing a separate hybridization event. Despite its prevalence, little is known of the pathogenicity of the British V. longisporum population. In this study, the pathogenicity of British isolates was tested on four different cultivars of three different Brassica crop species as well as on the model plant Arabidopsis thaliana and compared with previously characterized V. longisporum strains from other regions of the world, including representatives of all three hybrid lineages. Intriguingly, the British isolates appeared to be amongst the most pathogenic strains on Brassica crops. In conclusion, Verticillium stem striping poses a genuine threat to oilseed rape production as the British V. longisporum population consists of aggressive pathogens that have the potential to significantly impact Brassica crops.

plant biology↗

bioRxiv2017

A previously established divergent lineage of the hybrid fungal pathogen Verticillium longisporum emerges as stem striping pathogen in British oilseed rape

Population genetic structures illustrate evolutionary trajectories of organisms adapting to differential environmental conditions. Pathogen populations are typically shaped by co-evolution with their hosts through genetic co-structuring. Verticillium stem striping was mainly observed in continental Europe, but has recently emerged in other countries including the United Kingdom. The disease is caused by the hybrid fungal species Verticilliumlongisporum that originates from at least three separate hybridization events, yet strains from the hybridization event between Verticillium progenitor species A1 and D1 are mainly responsible for Verticillium stem striping. By using multi-locus genotype analysis, we reveal a hitherto un-described dichotomy within V. longisporum lineage A1/D1 that correlates with the geographic distribution of the isolates with an \"A1/D1 West\" and an \"A1/D1 East\" cluster according to their relative location in Europe. Genome comparison between representatives of the A1/D1 West and East clusters confirmed mutual common origin, excluding distinctiveness through separate hybridization events. The A1/D1 West population is responsible for the sudden emergence of Verticillium stem striping in the UK. Remarkably, this emergence is caused by a British V. longisporum population that is genetically more diverse than the entire A1/D1 East cluster. Conceivably, V. longisporum has previously established in the UK, but remained latent or undiagnosed as an oilseed rape pathogen until recently. This finding illustrates that a recent introduction is not a prerequisite for a pathogen to emerge, as environmental factors and cultural practices can also play a pivotal role in outbreaks of novel diseases.

microbiology↗