Biology subjects

Deeks, M. J.

Publications and source records attributed to Deeks, M. J..

4 recordsLinked to original sources

bioRxiv2023

The trichothecene mycotoxin deoxynivalenol facilitates cell-to-cell invasion during wheat-tissue colonisation by Fusarium graminearum

Fusarium Head Blight (FHB) disease on small grain cereals is primarily caused by the ascomycete fungal pathogen Fusarium graminearum. Infection of floral spike tissues is characterised by the biosynthesis and secretion of potent trichothecene mycotoxins, of which deoxynivalenol (DON) is widely reported due to its negative impacts on grain quality and consumer safety. The TRI5 gene encodes an essential enzyme in the DON biosynthesis pathway and the single gene deletion mutant,{Delta} Tri5, is widely reported to restrict disease progression to the inoculated spikelet. In this study, we present novel bioimaging evidence revealing that DON facilitates the traversal of the cell wall through plasmodesmata, a process essential for successful colonisation of host tissue. Chemical complementation of{Delta} Tri5 did not restore macro- or microscopic phenotypes, indicating that DON secretion is tightly regulated both spatially and temporally. A comparative qualitative and quantitative morphological cellular analysis revealed infections had no impact on plant cell wall thickness. Immuno- labelling of callose at plasmodesmata during infection indicates that DON can increase deposits when applied exogenously, but is reduced when F. graminearum hyphae are present. This study highlights the complexity of the inter-connected roles of mycotoxin production, cell wall architecture and plasmodesmata in this highly specialised interaction.

plant biology↗

bioRxiv2023

AUTOMATIC EXTRACTION OF ACTIN NETWORKS IN PLANTS

AO_SCPLOWBSTRACTC_SCPLOWThe actin cytoskeleton is essential in eukaryotes, not least in the plant kingdom where it plays key roles in cell expansion, cell division, environmental responses and pathogen defence. Yet, the precise structure-function relationships of properties of the actin network in plants are still to be unravelled, including details of how the network configuration depends upon cell type, tissue type and developmental stage. Part of the problem lies in the difficulty of extracting high-quality, three-dimensional, quantitative measures of actin network features from microscopy data. To address this problem, we have developed DRAGoN, a novel image analysis algorithm that can automatically extract the actin network across a range of cell types, providing seventeen different quantitative measures that describe the network at a local level. Using this algorithm, we then studied a number of cases in Arabidopsis thaliana, including several different tissues, a variety of actin-affected mutants, and cells responding to powdery mildew. In many cases we found statistically-significant differences in actin network properties. In addition to these results, our algorithm is designed to be easily adaptable to other tissues, mutants and plants, and so will be a valuable asset for the study and future biological engineering of the actin cytoskeleton in globally-important crops.

plant biology↗

bioRxiv2022

Wheat cells show positional responses to invasive Zymoseptoria tritici

The stomatal complex of grasses consists of two guard cells and two adjacent subsidiary cells that cooperate during stomatal closure. Zymoseptoria tritici, the main causal agent of Septoria tritici blotch in wheat, enters the host via stomata. Here we test the hypothesis that the stomatal complex shows focused sub-cellular responses to invading Z. tritici hyphae. We have combined live-cell transmission light microscopy, immunofluorescence and CRS microscopy to identify cell wall modifications triggered by hyphal invasion. Furthermore, we have used confocal fluorescence microscopy and automated quantitative image analysis to assess whether host cells respond to hyphae through spatial redistribution of organelles. We find that subsidiary cells construct papillae that are accurately aligned with hyphal position even when hyphae are occluded by guard cells. These are distinct from those induced by powdery mildew, with callose restricted to a crust that surrounds content with a high-amplitude Raman signal in the CH-band. Peroxisome populations in subsidiary cells show distributions with modes weakly correlated with hyphal position but do not differ significantly between compatible and incompatible interactions. Our data suggest local changes to cell wall architecture and focal accumulation of organelles in subsidiary cells could play roles in crop defence during host leaf penetration by Z. tritici. Molecular strategies to amplify these responses may provide novel routes for crop protection.

plant biology↗

bioRxiv2021

Differences between apoplastic and cytosolic reactive oxygen species production in Arabidopsis during pattern-triggered immunity

Despite an ever-increasing interest in reactive oxygen species (ROS) signalling during plant-microbe interactions, very little information exists, mainly for technical reasons, on the molecular mechanisms regulating intracellular hydrogen peroxide (H2O2) signalling during PAMP-triggered immunity. Here, we used a sensitive fluorimetry method and the H2O2 sensor roGFP2-Orp1, which revealed unsuspected features on the regulation of cytoplasmic H2O2 and thiol redox dynamics upon pathogen-associated molecular patterns (PAMPs) perception by Arabidopsis thaliana. Extended PAMP-induced cytosolic roGFP2-Orp1 oxidation was distinct from the transient oxidative burst in the apoplast measured by luminol oxidation. Pharmacological and genetic analyses indicate that the prolonged PAMP-induced H2O2 increase in the cytoplasm was largely independent on NADPH oxidases and apoplastic peroxidases. By contrast, the NADPH oxidase mutant rbohF was hyper-sensitive to roGFP2-Orp1 oxidation by H2O2 and PAMP indicating a lower antioxidant capacity. Unlike previous reports, the rbohF mutant, but not rbohD, was impaired in PAMP-triggered stomatal closure and ROS production measured by a fluorescein-based probe in guard cells resulting in defects in stomatal defences against bacteria. However, stomatal closure was not correlated with an increase in roGFP2-Orp1 oxidation in guard cells. Interestingly, RBOHF also participated in PAMP-induced apoplastic alkalinisation. Altogether, our results provide novel insights on the interplay between apoplastic and cytosolic ROS dynamics and highlight the importance of RBOHF in plant immunity. Significance statementPlants mount defence responses to pathogens by detecting pathogen-associated molecular patterns (PAMPs). One response is a rapid and transient burst of reactive oxygen species (ROS, e.g. superoxide and hydrogen peroxide) in the cell wall (apoplast) produced by NADPH oxidases and cell wall peroxidases. Using a genetically-encoded hydrogen peroxide sensor roGFP2-Orp1, we found that, in contrast to the transient apoplastic ROS burst, there is also prolonged hydrogen peroxide production in the cytosol upon PAMP perception which is independent of NADPH oxidase and cell wall peroxidases. Our results suggest that apoplastic ROS rather than intracellular hydrogen peroxide is a signal triggering stomatal closure during PAMP-triggered immunity. Additionally, we re-address the relative contribution of the NADPH oxidases D and F in stomatal immunity.

plant biology↗