Biology subjects

Champion, C.

Publications and source records attributed to Champion, C..

5 recordsLinked to original sources

bioRxiv2022

Reduced coenzyme Q synthesis confers non-target site resistance to the herbicide thaxtomin A

Herbicide resistance in weeds is a growing threat to global crop production. Non-target site resistance is problematic because a single resistance allele can confer tolerance to many herbicides (cross resistance), and it is often a polygenic trait so it can be difficult to identify the molecular mechanisms involved. Most characterized molecular mechanisms of non-target site resistance are caused by gain-of-function mutations in genes from a few key gene families - the mechanisms of resistance caused by loss-of-function mutations remain unclear. In this study, we first show that the mechanism of non-target site resistance to the herbicide thaxtomin A conferred by loss-of-function of the gene PAM16 is conserved in Marchantia polymorpha, validating its use as a model species with which to study non-target site resistance. To identify mechanisms of non-target site resistance caused by loss-of-function mutations, we generated 107 UV-B mutagenized M. polymorpha spores and screened for resistance to the herbicide thaxtomin A. We isolated 13 thaxtomin A-resistant mutants and found that 3 mutants carried candidate resistance-conferring SNPs in the MpRTN4IP1L gene. Mprtn4ip1l mutants are defective in coenzyme Q biosynthesis and accumulate higher levels of reactive oxygen species (ROS) than wild-type plants. Mutants are also defective in thaxtomin A metabolism, consistent with the hypothesis that loss of MpRTN4IP1L function confers non-target site resistance. We conclude that loss of MpRTN4IP1L function is a novel mechanism of non-target site herbicide resistance, and propose that other mutations which increase ROS levels or decrease thaxtomin A metabolism could confer thaxtomin A resistance in the field. AUTHOR SUMMARYModern agriculture relies on herbicides to control weed populations. However, herbicide resistance in weeds threatens the efficacy of herbicides and global crop production, similar to how antibiotic resistance poses a global health threat. Understanding the molecular mechanisms behind herbicide resistance helps to prevent resistance from evolving and to better manage herbicide resistant weeds in the field. Here, we use a forward genetic approach in the model species Marchantia polymorpha to discover novel mechanisms of herbicide resistance. We report the discovery of a novel mechanism of herbicide resistance caused by loss-of-function mutations in the MpRTN4IP1L gene. We find that Mprtn4ip1l mutants are resistant to the herbicides thaxtomin A and isoxaben, accumulate higher levels of reactive oxygen species than wild type plants, and are defective in thaxtomin A metabolism. We predict that loss-of-function mutations or treatments that increase reactive oxygen species production could contribute to thaxtomin A tolerance.

plant biology↗

bioRxiv2022

Transcriptome changes in chlorsulfuron-treated plants are caused by acetolactate synthase inhibition and not induction of a herbicide detoxification system in Marchantia polymorpha

A sensing mechanism in mammals perceives xenobiotics and induces the transcription of genes encoding proteins that detoxify these molecules. However, it is unclear if plants sense xenobiotics, and activate an analogous signalling system leading to their detoxification. Using the liverwort Marchantia polymorpha, we tested the hypothesis that there is a sensing system in plants that perceives herbicides resulting in the increased transcription of genes encoding proteins that detoxify these herbicides. Consistent with the hypothesis, we show that chlorsulfuron-treatment induces changes in the M. polymorpha transcriptome. However, these transcriptome changes do not occur in chlorsulfuron (CS)-treated target site resistant mutants, where the gene encoding the target carries a mutation that confers resistance to chlorsulfuron. Instead, we show that inactivation of the chlorsulfuron target, acetolactate synthase (ALS) (also known as acetohydroxyacid synthase (AHAS)), is required for the transcriptome response. These data are consistent with the changes in the transcriptome of chlorsulfuron-treated plants being caused by disrupted amino acid synthesis and metabolism resulting from acetolactate synthase inhibition. These conclusions suggest that chlorsulfuron is not sensed in M. polymorpha leading to induce a detoxification system. Author SummaryHerbicide use is increasing throughout the world, however we know little about how plants respond to herbicide treatment and regulate their metabolism. Some plants have evolved resistance to herbicides such as chlorsulfuron by increasing the detoxification of the herbicide compared to sensitive plants. It has been suggested that plants can directly sense the herbicide chemical which activates a detoxification response, in a similar way to the detoxification of foreign chemicals in mammalian cells. The liverwort Marchantia polymorpha is an excellent system to study plant herbicide responses due to its short generation time, ease of propagation and low genetic redundancy. We show that chlorsulfuron treatment alters the expression of many genes in M. polymorpha, however plants with a resistance-conferring mutation in the molecular target of chlorsulfuron do not show any changes in gene expression in response to chlorsulfuron treatment. This result indicates that transcriptome changes caused by chlorsulfuron depend on the inhibition of the target by chlorsulfuron. This suggests that plants do not sense chlorsulfuron and activate a detoxification system. This finding has implications for herbicide use and discovery.

plant biology↗

bioRxiv2020

Human liver microbiota modeling strategy at the early onset of fibrosis

To understand the pathophysiological impact of liver microbiota on the early stages of fibrosis we identified the corresponding microbiota sequences and overcome the impact of different group size and patient origins with adapted statistical approaches. Liver samples with low liver fibrosis scores (F0, F1, F2) were collected from Romania(n=36), Austria(n=10), Italy(n=19), and Spain(n=17). The 16SrDNA gene was sequenced. We considered the frequency, sparsity, unbalanced sample size between cohorts to identify taxonomic profiles and statistical differences. Multivariate analyses, including adapted spectral clustering with L1-penalty fair-discriminant strategies, and predicted metagenomics were used to identify that 50 % of liver taxa were Enterobacteriaceae and Pseudomonadaceae. The Caulobacteraceae, Flavobacteriaceae and Propionibacteriaceae discriminated between F0 and F1. The preQ0 biosynthesis and pathways involving glucoryranose and glycogen degradation were negatively associated with liver fibrosis F1-F2 vs F0. Altogether, our results suggest a role of bacterial translocation to the liver in the progression of fibrosis. This statistical approach can identify microbial signatures and overcome issues regarding sample size differences, the impact of environment, and sets of analyses.

pathology↗

bioRxiv2020

Skill acquisition and gaze behavior during laparoscopic surgical simulation

BackgroundExperts consistently exhibit more efficient gaze behaviors than non-experts during motor tasks. In surgery, experts have been shown to gaze more at surgical targets than surgical tools during simple simulations and when watching surgical recordings, suggesting a proactive control strategy with greater use of feedforward visual sampling. To investigate such expert gaze behaviors in a more dynamic and complex laparoscopic surgery simulation, the current study measured and compared gaze patterns between surgeons and novices who practiced extensively with laparoscopic simulation. MethodsThree surgeons were assessed in a testing visit and five novices were trained and assessed (at pre-, mid-, and post-training points) in a 5-visit protocol on the Fundamentals of Laparoscopic Surgery peg transfer task. The task was adjusted to have a fixed action sequence to allow recordings of dwell durations based on pre-defined areas of interest (AOIs). Novices individualized learning curves were analyzed using an inverse function model, and group-level differences were tested using analysis of variance on both behavioral performance and dwell duration measures. ResultsTrained novices were shown to reach more than 98% (M = 98.62%, SD = 1.06%) of their behavioral learning plateaus, leading to equivalent behavioral performance to that of surgeons. Despite this equivalence in behavioral performance, surgeons continued to show significantly shorter dwell durations at visual targets of current actions and longer dwell durations at future steps in the action sequence than trained novices (ps [≤] .03, Cohens ds > 2). ConclusionThis study demonstrates that, whereas novices can train to match surgeons on behavioral performance, their gaze pattern is still less efficient than that of surgeons, suggesting that eye-tracking metrics might be more sensitive than behavioral performance in detecting surgical expertise. Such insight can be applied to develop training protocols so non-experts can internalize experts "gaze templates" to accelerate learning. Article SummaryGaze pattern differences persist between laparoscopic surgery experts and novices who have been trained to reach over 98% of individualized behavioral learning plateaus in the Fundamentals of Laparoscopic Surgery (FLS) peg transfer task. The importance of this finding lies in motivating the decision and method of including gaze behaviors via eyetracking technology in the present surgical training programs.

neuroscience↗

bioRxiv2019

Neofunctionalisation of basic helix loop helix proteins occurred when plants colonised the land

ROOT HAIR DEFECTIVE SIX-LIKE (RSL) genes control the development of structures - rhizoids, root hairs, gemmae, mucilage papillae - that develop from single cells at the surface of diverse groups of land plants. RSL proteins constitute a subclass (VIIIc) of the basic helix loop helix (bHLH) class VIII transcription factor family. We set out to determine if the function of RSL genes in the control of cell differentiation in land plants was inherited from streptophyte algal ancestor. The Charophyceae are a monophyletic class of streptophyte algae with tissue-like structures and rhizoids. We identified the single class VIII bHLH gene from the charophyceaen alga Chara braunii (CbbHLHVIII). Phylogenetic analysis suggests that this protein is sister to the RSL (bHLH subclass VIIIc) proteins and together they constitute a monophyletic group. Expression of CbbHLHVIII does not compensate for loss of the RSL function in either Marchantia polymorpha or Arabidopsis thaliana. Furthermore, CbbHLHVIII is expressed at sites of morphogenesis in C. braunii - the apices, nodes and gametangia - but not in rhizoids. This indicates that C. braunii class VIII protein is functionally different from land plant RSL proteins; they control rhizoid development in land plants but not in the charophycean algae. These data are consistent with the hypothesis that RSL proteins and their function in the differentiation of cells at the plant surface evolved in the lineage leading to land plants after the divergence of the land plants and C. braunii from their last common ancestor. This may have occurred by neofunctionalisation at or before the colonisation of the land by streptophytes.

evolutionary biology↗