Biology subjects

Ashfield, T.

Publications and source records attributed to Ashfield, T..

3 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

A multiscale approach to investigate fluorescence and NDVI imaging as proxy of photosynthetic traits in wheat

With the development of the digital phenotyping, repeated measurements of agronomic traits over time are easily accessible, notably for morphological and phenological traits. However high throughput methods for estimating physiological traits such as photosynthesis are lacking. This study demonstrates the links of fluorescence and reflectance imaging with photosynthetic traits. Two wheat cultivars were grown in pots in a controlled environment. Photosynthesis was characterised by gas-exchange and biochemical analysis at five time points, from booting to 21 days post anthesis. On the same days imaging was performed on the same pots, at leaf and plant scale, using indoor and outdoor phenotyping platforms, respectively. Five image variables (Fv/Fm and NDVI at the whole plant level and Fv/Fm, {Phi}(II)532 and {Phi}(NPQ)1077 at the leaf scale) were compared to variables from A-Ci and A-Par curves, biochemical analysis, and fluorescence instruments. The results suggested that the image variables are robust estimators of photosynthetic traits, as long as senescence is driving the variability. Despite contrasting cultivar behaviour, linear regression models which account for the cultivar and the interaction effects, further improved the modelling of photosynthesis indicators. Finally, the results highlight the challenge of discriminating functional to cosmetic stay green genotypes using digital imaging. HighlightA temporal and multi-scale study of fluorescence and NDVI imaging used as a proxy for photosynthetic parameters

plant biology↗

bioRxiv2020

The vesicular trafficking system component MIN7 is required for minimizing Fusarium graminearum infection

Plants have developed intricate defense mechanisms, referred to as innate immunity, to defend themselves against a wide range of pathogens. Plants often respond rapidly to pathogen attack by the synthesis and delivery of various antimicrobial compounds, proteins and small RNA in membrane vesicles to the primary infection sites. Much of the evidence regarding the importance of vesicular trafficking in plant-pathogen interactions comes from the studies involving model plants whereas this process is relatively understudied in crop plants. Here we assessed whether the vesicular trafficking system components previously implicated in immunity in Arabidopsis thaliana play a role in the interaction with Fusarium graminearum, a fungal pathogen notoriously famous for its ability to cause Fusarium head blight (FHB) disease in wheat. Among the analyzed vesicular trafficking mutants, two independent T-DNA insertion mutants in the AtMin7 gene displayed a markedly enhanced susceptibility to F. graminearum. Earlier studies identified this gene, encoding an ARF-GEF protein, as a target for the HopM1 effector of the bacterial pathogen Pseudomonas syringae pv. tomato, which destabilizes AtMIN7 leading to its degradation and weakening host defenses. To test whether this key vesicular trafficking component may also contribute to defense in crop plants, we identified the candidate TaMin7 genes in wheat and knocked-down their expression through Virus induced gene silencing. Wheat plants in which TaMIN7 were silenced displayed significantly more FHB disease. This suggests that disruption of MIN7 function in both model and crop plants compromises the trafficking of innate immunity signals or products resulting in hyper-susceptibility to various pathogens. One sentence summaryDisruption of an ARF-GEF protein encoding gene AtMin7 in Arabidopsis thaliana and silencing of the orthologous gene in wheat result in hyper susceptibility to the fungal pathogen Fusarium graminearum.

plant biology↗