Fungal model systems and the elucidation of pathogenicity determinants

This is the final version of the article. Available from Elsevier via the DOI in this record.Fungi have the capacity to cause devastating diseases of both plants and animals, causing significant harvest losses that threaten food security and human mycoses with high mortality rates. As a consequence, there is a critical need to promote development of new antifungal drugs, which requires a comprehensive molecular knowledge of fungal pathogenesis. In this review, we critically evaluate current knowledge of seven fungal organisms used as major research models for fungal pathogenesis. These include pathogens of both animals and plants; Ashbya gossypii, Aspergillus fumigatus, Candida albicans, Fusarium oxysporum, Magnaporthe oryzae, Ustilago maydis and Zymoseptoria tritici. We present key insights into the virulence mechanisms deployed by each species and a comparative overview of key insights obtained from genomic analysis. We then consider current trends and future challenges associated with the study of fungal pathogenicity.This review was carried out by members of the EU-Initial Training Network Ariadne (PITN-GA-2009-237936), which provided financial support for C.B., S.D., M.E.G., E.G., E.M., P.V.M., M.M., V.N., M.F.A.N., T.O., M.O.R., K.S. and L.W

Strongly Coupled Magnetic and Electronic Transitions in Multivalent Strontium Cobaltites

The topotactic phase transition in SrCoOx (x = 2.5-3.0) makes it possible to reversibly transit between the two distinct phases, i.e. the brownmillerite SrCoO2.5 that is a room-temperature antiferromagnetic insulator (AFM-I) and the perovskite SrCoO3 that is a ferromagnetic metal (FM-M), owing to their multiple valence states. For the intermediate x values, the two distinct phases are expected to strongly compete with each other. With oxidation of SrCoO2.5, however, it has been conjectured that the magnetic transition is decoupled to the electronic phase transition, i.e., the AFM-to-FM transition occurs before the insulator-to-metal transition (IMT), which is still controversial. Here, we bridge the gap between the two-phase transitions by density-functional theory calculations combined with optical spectroscopy. We confirm that the IMT actually occurs concomitantly with the FM transition near the oxygen content x = 2.75. Strong charge-spin coupling drives the concurrent IMT and AFM-to-FM transition, which fosters the near room-T magnetic transition characteristic. Ultimately, our study demonstrates that SrCoOx is an intriguingly rare candidate for inducing coupled magnetic and electronic transition via fast and reversible redox reactions

Glycoprotein gene truncation in avian metapneumovirus subtype C isolates from the United States

The length of the published glycoprotein (G) gene sequences of avian metapneumovirus subtype-C (aMPV-C) isolated from domestic turkeys and wild birds in the United States (1996–2003) remains controversial. To explore the G gene size variation in aMPV-C by the year of isolation and cell culture passage levels, we examined 21 turkey isolates of aMPV-C at different cell culture passages. The early domestic turkey isolates of aMPV-C (aMPV/CO/1996, aMPV/MN/1a-b, and 2a-b/97) had a G gene of 1,798 nucleotides (nt) that coded for a predicted protein of 585 amino acids (aa) and showed >97% nt similarity with that of aMPV-C isolated from Canada geese. This large G gene got truncated upon serial passages in Vero cell cultures by deletion of 1,015 nt near the end of the open reading frame. The recent domestic turkey isolates of aMPV-C lacked the large G gene but instead had a small G gene of 783 nt, irrespective of cell culture passage levels. In some cultures, both large and small genes were detected, indicating the existence of a mixed population of the virus. Apparently, serial passage of aMPV-C in cell cultures and natural passage in turkeys in the field led to truncation of the G gene, which may be a mechanism of virus evolution for survival in a new host or environment

Exploring SDHI resistance in Botrytis cinerea : from mutagenesis to enzymatic assays.

Botrytis cinerea is a phytopathogenic ascomycete responsible for grey mould on many crops. Respiration inhibitors play an increasing role in the control of this disease. Succinate dehydrogenase inhibitors (SDHIs, including carboxamides) inhibit the fungal respiration by blocking the ubiquinonebinding site of the mitochondrial complex II. Old SDHIs (i.e. carboxin), essentially active against Basidiomycetes were replaced in the 2000s by a new generation of SDHIs with a broader spectrum including Ascomycetes. Boscalid is the only representative of this new generation in France up to now. A few years after its market introduction, field mutants of B. cinerea, resistant to boscalid were isolated in France and Germany. At least six different phenotypes, named CarR1 to CarR6, have been pinpointed by characterizing their resistance pattern towards 20 SDHIs. CarR1 to R4 phenotypes exhibit low to medium level of resistance, whereas CarR5 and R6 show high level of resistance to different SDHIs, including boscalid. CarR1 and CarR2 strains are currently the most frequent strains detected in German and French vineyards. The resistance mechanism was investigated for the different phenotypes by searching for putative alterations in the SDH proteins, which could be responsible for the observed resistance. Our findings show point mutations in the sdhB gene lead to a specific amino acid change in SdhB for each phenotype. Isogenic mutants have been generated through a gene replacement strategy to confirm the role of these mutations in the various SDHI resistance phenotypes. We have shown that each mutation of the sdhB gene confers resistance to at least one SDHI. Isogenic mutants show similar resistance factors compared to field mutants carrying the same mutation. SDH enzyme activity and inhibition by different SDHIs were measured in these mutants. Our results provide evidence for differential SDH inhibition profiles according to the tested mutations, correlating with the mutants’ resistance pattern. SDH enzyme affinity to different SDHIs will be measured in these mutants