Biology subjects

Fones, H. N.

Publications and source records attributed to Fones, H. N..

3 recordsLinked to original sources

bioRxiv2024

Long-term survival of asexual Zymoseptoria tritici spores in the environment

The fungal phytopathogen Zymoseptoria tritici, causal agent of the economically damaging Septoria tritici blotch of wheat, is different from most foliar fungal pathogens in that its germination occurs slowly and apparently randomly after arrival on the leaf surface and is followed by a potentially prolonged period of epiphytic growth and even reproduction, during which no feeding structures are formed by the fungus. Thus, understanding the cues for germination and the mechanisms that underpin survival in low-nutrient environments could provide key new avenues for disease control. In this work, we examine survival, culturability, and virulence of spores following transfer from a high nutrient environment to water. We find that a sub-population of Z. tritici spores can survive and remain virulent for at least 7 weeks in water alone, during which time multicellular structures split to single cells. The fungus relies heavily on stored lipids; however, if cell suspensions in water are dried, the cells survive without lipid utilisation. Changes in gene expression in the first hours after suspension in water reflect adaptation to stress, while longer term starvation (7 days) induces changes particularly in primary metabolism and cytochrome P450 (CYP) gene expression. Importantly, we also found that Z. tritici spores are equally or better able to survive in soil as in water, and that rain-splash occurring 49 days after soil inoculation can transfer cells to wheat seedlings growing in inoculated soil and cause Septoria leaf blotch disease.

microbiology↗

bioRxiv2023

Use of Chitin:DNA ratio to assess growth form in fungal cells

Dimorphism, the ability to switch between a yeast-like and a hyphal growth form, is an important feature of certain fungi, including important plant and human pathogens. The switch to hyphal growth is often associated with virulence, pathogenicity, biofilm formation and stress resistance. Thus, the ability to accurately and efficiently measure fungal growth form is key to research into these fungi, especially for discovery of potential drug targets. To date, fungal growth form has been assessed microscopically, a process that is both labour intensive and costly. Here, we unite quantification of the chitin in fungal cell walls and the DNA in nuclei to produce a methodology that allows fungal cell shape to be estimated by calculation of the ratio between cell wall quantity and number of nuclei present in a sample of fungus or infected host tissue. Using the wheat pathogen Zymoseptoria tritici as a test case, with confirmation in the distantly related Fusarium oxysporum, we demonstrate a close, linear relationship between the chitin:DNA ratio and the average polarity index (length/width) of fungal cells. We show the utility of the method for estimating growth form in infected wheat leaves, differentiating between the timing of germination in two different Z. tritici isolates using this ratio. We also show that the method is robust to the occurence of thick-walled chlamydospores, which show a chitin:DNA ratio that is distinct from either yeast-like blastospores or hyphae.

microbiology↗

bioRxiv2023

Biofilm formation in Zymoseptoria tritici

Zymoseptoria tritici is an economically damaging fungal pathogen of wheat which is able to survive for long periods on the leaf surface. In this environment, the fungus is exposed to many stresses, including fluctuations in temperature, UV radiation, drying, and foliar fungicide applications. We observed biofilm-like cell aggregations on the surface of wheat leaves infected with Z. tritici in both compatible and non-compatible interactions. A literature search revealed few examples of plant pathogenic fungi forming biofilms, but demonstrated that such biofilms have a number of key characteristics, which are shared with other biofilmforming microbes. These include adhesion of cells to the substrate, production of extracellular matrix, altered gene expression and increased tolerance to various stresses. We used a combination of microscopy, qRT-PCR and stress tolerance assays to determine whether putative Z. tritici biofilms possessed these diagnostic characteristics. We show that Z. tritici biofilms resemble in form and function those formed by other filamentous and dimorphic fungi, producing extra-cellular matrix in which cells become embedded, creating layers of hyphal bundles and blastospores. These biofilms show increased tolerance to drying and high temperature. There is also isolate-dependent resistance to reactive oxygen stress and the fungicide carboxin. Taken together, these findings demonstrate that Z. tritici is indeed able to produce genuine biofilms.

microbiology↗