Tag Archives: podospora

Postdoc: Uppsala University on Meiotic Drive in Fungi

POST-DOCTORAL POSITION IN THE EVOLUTION OF MEIOTIC DRIVE

A two-year postdoctoral position is available in the research group of professor Hanna Johannesson, at the Evolutionary Biology Centre (EBC), Uppsala University.

Conflicts arising from selfish genetic elements are important drivers for evolutionary change and innovation, and thus of crucial importance for genetic form and function.  The main goal of this project is to study the evolutionary dynamics of meiotic drive in fungi.  The study system is the Spore killers of Podospora anserina, a filamentous ascomycete. The ultimate aim of our research group is to combine large-scale genomic analyses with theoretical and experimental investigations to study the evolutionary dynamics of this meiotic drive system, both on a short and a long evolutionary timescale. This postdoc project will be developed after the interest of the applicant, but should preferably encompass a combination of experimental and genomic aspects. It will be a part of a collaborative effort within our research group.

Applicants should have a PhD in biology/evolutionary biology. Documented skills in molecular phylogenetics and/or population genetics, experimental and genomic work, especially using fungal model systems, is highly valued.

Start date is flexible, ideally February 1, 2016. The position may be
extended for up to two more years.

Please send your application materials by November 25 to
Hanna.Johannesson@ebc.uu.se. The application shall include: 1) a cover letter stating research interests, 2) a CV, including publication
record, 3) a short (1-2 page) description of research accomplishments, and 4) name and contact information for three references.

Please feel free to contact me at the above listed e-mail with
questions.

Escaping the dung pile quickly: Speedy Pilobolus spores

ResearchBlogging.orgSporangiophore discharge in the fungus <em/>Pilobolus kleinii captured with high speed video. In a paper appearing today in PLoS One, “The Fastest Flights in Nature: High-Speed Spore Discharge Mechanisms among Fungi” Nicholas Money and colleagues including 6 undergraduates and 3 graduate students, have measured the speed of flight of spores discharging from several Ascomycete and Zygomycete dung fungi including Pilobolus kleinii, Basidiobolus ranarum, Podospora anserina, and Ascobolus immersus. The team used high speed cameras that recorded at 250,000 frames per second and were able to capture spores being launched at 25 meters per second at accelerations of 180,000 g. The publication also provides multimedia including a video of the spore discharge slowed down and set to music. Nik and Mark Fisher both presented portions of the work at the Mycological Society of America 2008 meeting this summer and showed clips of these dramatic videos, so it was great to see this in print shortly following the meeting.

By way of the press release the major findings from this work show that

… the discharge mechanisms in fungi are powered by the same levels of pressure that are characteristic of the cells that make up the feeding colonies of fungi. Therefore, the long flights enjoyed by spores result not from unusually high pressure, but from the way in which explosive pressure loss is linked to the propulsion of the spores. There appear to be some similarities between the escape of the spores and the expulsion of ink droplets through nozzles on inkjet printers.

As Dr Money has described in a humorous and humble manner before in his Mr Bloomfield’s Orchard, some of the coolest and fundamental observations about spore flight and discharge, from Buller to the present, have come from simple and careful observations of fungi. In this case they have used a new tools of ultra high speed photography to capture events. Some of the previous work from the Money lab on this front include a demonstration that conidia are actively launched and rather than being passively released by low velocity airflow in the toxic indoor mold Stachybotrys (Tucker et al FGB 2007; free at PMC)

Yafetto L, Carroll L, Cui Y, Davis DJ, Fischer MWF,Henterly AC,, Kessler JD, Kilroy HA, Shidler JB, Stolze-Rybczynski JL, Sugawara Z, Money NP (2008). The Fastest Flights in Nature: High-Speed Spore Discharge Mechanisms among Fungi PLoS One, 3 (9) DOI: 10.1371/journal.pone.0003237

Podospora genome published

P.anserinaThe genome of Podospora anserina S mat+ strain was sequenced by Genoscope and CNRS and published recently in Genome Biology. The genome sequence data has been available for several years, but it is great to see a publication describing the findings.  The 10X genome assembly with ~10,000 genes provides an important dataset for comparisons among filamentous Sordariomycete fungi. The authors primarily focused on comparative genomics of Podospora to Neurospora crassa, the next closest model filamentous species.  Within the Sordariomycetes there are now a very interesting collection of closely related species which can be useful for applying synteny and phylogenomics approaches.

The analyses in the manuscript focused on these differences between Neurospora and Podospora identifying some key differences in carbon utilization contrasting the coprophillic (Podospora) and plant saprophyte (Neurospora).  There are several observations of gene family expansions in the Podospora genome which could be interpreted as additional enzyme capacity to break down carbon sources that are present in dung.

The genome of Neurospora has be shaped by the action of the genome defense mechanisms like RIP that has been on interpretation of the reduced number of large gene families and paucity of transposons. The authors report a surprising finding that in their analysis that despite sharing orthologs of genes that are involved in several genome defense, they in fact find fewer repetitive sequences in Podospora while it still fails to have good evidence of RIP.

Overall, these data suggest that P. anserina has experienced a fairly complex history of transposition and duplications, although it has not accumulated as many repeats as N. crassaP. anserina possesses all the orthologues of N. crassa factors necessary for gene silencing, including RIP, meiotic MSUD and also vegetative quelling, a post transcriptional gene silencing mechanism akin to RNA interference

I think this data and observations interleaves nicely with the work our group is exploring on evolution of genome of several Neurospora species which have different mating systems. The fact that the gene components that play a role in MSUD and a RIP are found in Podpospora but yet the degree of RIP and the lack of any observed meiotic silencing suggests some interesting occurrences on the Neurospora branch to be explored.  The potentially different degrees of RIP efficiency and types of mating systems (heterothallic and pseudohomothallic) among the Neurospora spp may also provide a link to understanding how RIP evolved and its role on N. crassa evolution.

Senescence in Podospora

Another aspect of Podopsora biology that isn’t touched on, is the use of the fungus as a model for senescence.  The fungus exhibits maternal senescence which involves targeted changes in the mitochondria that leads to cell death.  The evolutionary and molecular basis for this process has been of interest to many research groups and the genome sequence can provide an additional toolkit for identifying the factors involved in the apoptosis process in this filamentous fungi. Whether it will help find a real link for aging research in other eukaryotes remains to be seen, but it is a good model system for some aspects of how aging and damage to mtDNA are linked.

Espagne, E., Lespinet, O., Malagnac, F., Da Silva, C., Jaillon, O., Porcel, B.M., Couloux, A., Aury, J., et al (2008). The genome sequence of the model ascomycete fungus Podospora anserina. Genome Biology, 9(5), R77. DOI: 10.1186/gb-2008-9-5-r77

More RIP without sex?

In followup to the Aspergillus RIP paper discussion, Jo Anne posted in the comments that her paper published in FGB about RIP in another asexual species of fungi also found that evidence for the meiosis-specific process of Repeat Induced Point-mutations (RIP).

Continue reading More RIP without sex?

Fungal Genetics 2007 details

I’m including a recapping as many of the talks as I remember. There were 6 concurrent sessions each afternoon so you have to miss a lot of talks. The conference was bursting at the seams as it was- at least 140 people had to be turned away beyond the 750 who attended.

If there was any theme in the conference it was “Hey we are all using these genome sequences we’ve been talking about getting”. I only found the overview talks that solely describe the genome solely a little dry as compared to those more focused on particular questions. I guess my genome palate is becoming refined.

Continue reading Fungal Genetics 2007 details