26 research outputs found
Improved Vectors for Selecting Resistance to Hygromycin
Resistance to hygromycin B is an important dominant selectable marker in fungal transformation. Our goal was to improve vectors for hygromycin selection by making the gene more compact, by eliminating sites for commonly used restriction enzymes, and by subcloning the modified gene into convenient vectors. These improvements were made by modifying pCSN43 (Staben et al. 1989 Fungal Genetics Newsl. 36:79-81) through three rounds of megaprimer mutagenesis (Aiyar and Leis, 1993 Biotechniques 14:366-368 ), a technique based on polymerase chain reaction amplification. Plasmid pCSN43 has a 2.4 kb SalI fragment containing the bacterial hph gene (Gritz and Davies, 1983 Gene 25:179-188), encoding hygromycin B phosphotransferase, under control of the Aspergillus nidulans trpC promoter and terminator (Mullaney et al. 1985 MGG 199:37-45
HYR1-Mediated Detoxification of Reactive Oxygen Species Is Required for Full Virulence in the Rice Blast Fungus
During plant-pathogen interactions, the plant may mount several types of defense
responses to either block the pathogen completely or ameliorate the amount of
disease. Such responses include release of reactive oxygen species (ROS) to
attack the pathogen, as well as formation of cell wall appositions (CWAs) to
physically block pathogen penetration. A successful pathogen will likely have
its own ROS detoxification mechanisms to cope with this inhospitable
environment. Here, we report one such candidate mechanism in the rice blast
fungus, Magnaporthe oryzae, governed by a gene we refer to as
MoHYR1. This gene (MGG_07460) encodes a glutathione
peroxidase (GSHPx) domain, and its homologue in yeast was reported to
specifically detoxify phospholipid peroxides. To characterize this gene in
M. oryzae, we generated a deletion
mutantΞhyr1 which showed growth inhibition with
increased amounts of hydrogen peroxide (H2O2). Moreover,
we observed that the fungal mutants had a decreased ability to tolerate ROS
generated by a susceptible plant, including ROS found associated with CWAs.
Ultimately, this resulted in significantly smaller lesion sizes on both barley
and rice. In order to determine how this gene interacts with other (ROS)
scavenging-related genes in M. oryzae, we compared expression
levels of ten genes in mutant versus wild type with and without
H2O2. Our results indicated that the
HYR1 gene was important for allowing the fungus to tolerate
H2O2
in vitro and in planta and that this ability
was directly related to fungal virulence
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Comparative Genome Analysis of Filamentous Fungi Reveals Gene Family Expansions Associated with Fungal Pathogenesis
Fungi and oomycetes are the causal agents of many of the most serious diseases of plants. Here we report a detailed comparative analysis of the genome sequences of thirty-six species of fungi and oomycetes, including seven plant pathogenic species, that aims to explore the common genetic features associated with plant disease-causing species. The predicted translational products of each genome have been clustered into groups of potential orthologues using Markov Chain Clustering and the data integrated into the e-Fungi object-oriented data warehouse (http://www.e-fungi.org.uk/). Analysis of the species distribution of members of these clusters has identified proteins that are specific to filamentous fungal species and a group of proteins found only in plant pathogens. By comparing the gene inventories of filamentous, ascomycetous phytopathogenic and free-living species of fungi, we have identified a set of gene families that appear to have expanded during the evolution of phytopathogens and may therefore serve important roles in plant disease. We have also characterised the predicted set of secreted proteins encoded by each genome and identified a set of protein families which are significantly over-represented in the secretomes of plant pathogenic fungi, including putative effector proteins that might perturb host cell biology during plant infection. The results demonstrate the potential of comparative genome analysis for exploring the evolution of eukaryotic microbial pathogenesis