We hiked up Creux du Van near Neuchâtel. We were joined by the good people from the Plant Pathology at the ETH Zürich and it was a fun day out. Creux du Van is a pretty stunning rock formation left behind by a retreating glacier (long ago).
Post by Nikhil Kumar Singh who started his PhD in March 2017 in our lab.
From the beginning of my academic career, I was more inclined towards investigating the behaviour of microbes, their inter- and intraspecies interactions and their response towards a changing environment. My master thesis was based on understanding the spatial and temporal dynamics of the soil microbial population that were exposed to an exogenous bacterial species in different environmental conditions. We all have witnessed a global rise in all kinds of pollution. However, the microbial community in any specific habitat is usually not specialized to degrade a particular pollutant. A very popular biological approach to eliminate such pollutants is the use of microbial species that have evolved the ability to transform a specific pollutant into less toxic or non-toxic forms. The question here is how will the original endogenous microbial population behave if such specialised “pollutant degraders” species are introduced into their habitat. My Masters project aimed to use fluorescence and time-lapse microscopy, and systems biology tools to understand the community dynamics when exposed to toxic compounds in the presence of exogenous species.
After my masters, I got more interested in understanding the genetic basis microbial adaptations with respect to their immediate environment. The environment that a specific microbe inhabits can be very variable, for example, it could be a toxic soil environment or the body of a host in case of pathogens. My PhD project will focus on understanding the genetic basis of host-pathogen interactions between wheat and Zymoseptoria tritici which is a major pathogenic fungus of wheat. I will use genome wide association (GWA) mapping as a tool to identify the genetic basis of different phenotypes including the pathogenicity of Z. tritici under different environmental conditions.
Please see here (PDF) for the announcement details.
Post by Ursula Oggenfuss who started her PhD in our lab in January 2017.
Three months ago, I started my PhD project in the evolutionary genetics group at University Neuchâtel. After a month in the “old” plant pathology group at ETH Zurich, where I learned the most important lab methods and got in touch with a lot of researchers on Zymoseptoria tritici, I started in the lab in Neuchâtel.
Although my research and personal interests are very broad, I mostly worked with fungi during my studies. During my bachelor at ETH Zurich I was introduced to forest pathology, and I was working for my bachelor thesis with the fungal endophytes in Fraxinus excelsior leaves that are already infected with the new fungal disease Hymenoscyphus fraxineus. With this work, I got a first insight into laboratory work. After I wrote my term paper on Clavicipitaceae, fungal grass endophytes that can act antagonistically against herbivores, I went back to H. fraxineus for my master thesis. I had the opportunity to work on the population structure of a newly found Mitovirus (a virus inside of the mitochondria of a fungi) in H. fraxineus. For this thesis, I could expand my experiences into the wet laboratory work, and I learned how to work with level 2 organisms in the newly built plant protection lab at WSL Birmensdorf. Next to the laboratory work, I had an extended insight into bioinformatics and phylogenetics.
After my Master, I shortly worked in the plant pathology group at ETH, where I helped developing a qPCR protocol for two agricultural filamentous plant pathogens. After that I worked in the mycorrhiza group at WSL Birmensdorf, mostly with Cenococcum geophilum and different truffle species.
In my PhD project, I would like to concentrate on the diversity, population dynamics and influence on the infection potential of transposable elements in Z. tritici. I’m looking forward to work in this dynamic and well connected laboratory, as well as in the very diverse institute of biology.
By Fanny and Daniel
How a fungal pathogen evolved host specialization by chromosomal rearrangements
Our paper on host specialization by chromosomal rearrangements in a fungal pathogen of wheat just came out in The ISME Journal and is now available online:
Despite the use of fungicides and resistant crop varieties, fungi cause major economic losses in agriculture. One major concern is the ability of plant pathogens to circumvent crop resistance and adapt to exploit the host. In plant-pathogen interactions, the specific recognition of a pathogen effector by a host resistance protein can trigger plant defences and prevent invasion by the pathogen. Mutations or deletions in pathogen effector genes are thought to enable pathogens to escape host recognition. However, we know very little about the loci and the mechanisms enabling virulence evolution in pathogen populations. A better understanding of these mechanisms is essential for the control of fungal diseases.
Our study system was the highly damaging fungal pathogen Zymoseptoria tritici. This pathogen is causing Septoria tritici blotch (STB) on wheat that leads to large economic losses worldwide. We obtained a collection of 106 Z. tritici isolates sampled in four locations across the geographical range of the pathogen. For all strains, we assessed virulence on two Swiss wheat cultivars that had different levels of resistance. We generated whole-genome sequences for each strain and performed genome-wide association studies (GWAS) to identify loci linked to virulence.
We identified multiple loci in the pathogen genome associated with virulence on each cultivar. However, the loci identified for the two different cultivars hardly overlapped showing that the pathogen evolved distinct loci to exploit genetically different wheat. The strongest association in the pathogen genome was linked to the deletion of a gene. This gene encoded a small secreted protein that was highly expressed during the appearance of the first disease symptoms. The deletion of the gene was associated to a gain in virulence on one cultivar only. This is likely due to the fact that this cultivar has the ability to detect this specific protein and activate defences. The pathogen gene seems to be very young, because we found no evidence in any of the most closely related species. We also found that the deletion of the gene happened thanks to the action of a large block of repetitive DNA containing selfish genomic elements (transposable elements). Hence, the pathogen likely benefited from the action of selfish elements to become more virulent on wheat. In summary, our study demonstrates that chromosomal rearrangements can play a major role in host specialization in fungal pathogens.
Fanny very convincingly passed her PhD defence at the ETH Zurich Friday 20 January! Warmest congratulations from the entire group. See below for the enthusiastic tweet by Fanny's external examiner Pascal Frey (@pascal_frey) from the INRA Nancy (France). Now, it's time to celebrate.
The pathogen genomics group has now officially become the Laboratory of Evolutionary Genetics at the University of Neuchâtel. Also, the lab was just joined by its first new member, Ursula Oggenfuss - welcome! But we still maintain a presence at the ETH Zürich with Norfarhan, Clémence, Fanny and Simone staying on for a while.
More updates of what's happening in Neuchâtel will be posted in the coming months.
View from the new offices in Neuchâtel. Definitely the place to be to watch pretty sunsets.
Daniel was invited to speak at Peter Solomon's (Australian National University) fantastic annual meeting on molecular plant pathology near Canberra. The meeting took place up at the Stromlo observatory overlooking the beautiful surroundings. For more information about the meeting, check this link here: http://www.wheatbiosecurity.com/stromlo
by Farhan and Daniel
The evolution of azole resistance in agricultural fields
Our paper on multilocus resistance evolution to azoles in a fungal plant pathogen is online now.
The evolution of fungicide resistance is truly worrisome for farmers and at the same time extremely fascinating as a case study of rapid adaptive evolution.
One of the most commonly used classes of fungicides are azoles. Resistance to azoles has been well established in human and animal pathogenic fungi, and includes a wide array of mechanisms to cope with stress induced by fungicides. The analysis of resistance in plants pathogens was largely focused on mutations in a specific gene called CYP51. This gene encodes the protein that is directly targeted by azoles. Additional mechanisms were rarely explored in field populations.
We studied an ubiquitous pathogen of barley called Rhynchosporium commune. We obtained a pathogen collection across the world comprising regions where fungicides were used frequently and others were the pathogen was unlikely to have been exposed yet. Then, we sequenced the entire genome of all strains and screened for loci associated with increased resistance to azoles. For this, we used genome-wide association mapping (or GWAS), which is a widely used tool in human and plant genetics.
Our study that just came out in Molecular Ecology showed that several previously unknown genes contributed to azole resistance. These genes encoded for proteins related to stress responses, regulation of transcription and other processes. Then, we analyzed whether some mutations that conferred higher resistance had an impact on the growth of the fungus. We found that some mutations had no detectable impact on growth and are likely to become fixed in resistant populations. But we also found resistance mutations that were associated with slower growth. Such trade-offs in the evolution of resistance (or "cost of resistance") are important, because we may be able to exploit such "weaknesses" of the pathogen to devise more sustainable control strategies.
Please find here the announcement for the PhD positions.
We were sad to say goodbye last week to Juliana Benevenuto from the University of São Paulo (USP/ESALQ) in Brazil. Juliana obtained a 6-month fellowship from the FAPESP (São Paulo Research Foundation) to join our lab. During her stay, Juliana made fantastic progress on her PhD project on the comparative genomics of smut fungi. All the best for completing your PhD, Juliana!
Juliana (5th hiker) on our trip up the Grosser Mythen in summer 2016
The University of Neuchâtel?