Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/8/2015
Publication Date: 8/1/2015
Citation: Gao, S., Gold, S.E., Glenn, A.E. 2015. Horizontal gene transfer confers adaptive advantages to phytopathogenic fungi: a case study of catalase-peroxidase in Fusarium verticillioides . American Phytopathological Society Annual Meeting. August 1-5, 2015. Pasadena CA.
Interpretive Summary: Two genes hypothesized to play roles in combating plant oxidative stress defense response to attack, that show evidence of transfer by unrelated bacterial organisms to fungi including Fusarium verticillioides were identified. Deletion mutants for these two genes were generated and a double mutant was made by crossing. Deletion of each gene individually caused a noticeable increase in sensitivity to hydrogen peroxide an active oxygen species. The double mutant was dramatically more sensitive than either single mutant. Future experiments will analyze the roles of these genes in virulence to corn plants.
Technical Abstract: Horizontal gene transfer (HGT), the exchange and stable integration of genetic material between different evolutionary lineages, is widely observed in fungi. We hypothesize that successful stabilization of HGT elements provides adaptive advantages (e.g., virulence). Catalase/peroxidases (KatGs) are a superfamily of fungal reactive oxygen species (ROS)-degrading enzymes previously revealed via phylogenetic analysis to be horizontally acquired by ancient Ascomycota from bacteria. A subsequent gene duplication resulted in two KatGs paralogues: the widely distributed, intracellular group (KatG1), and the Sordariomycete-unique (mainly phytopathogens), extracellular group (KatG2). We functionally characterized FvCPO1 (KatG1) and FvCPO2 (KatG2) in the maize pathogen, Fusarium verticillioides. Single deletion mutants were generated by the OSCAR method, and double mutants were obtained from sexual crosses between two single mutants. Both 'FvCPO1 and 'FvCPO2 mutants, when compared to the wild type, showed moderate impaired tolerance to H2O2 in vitro, while the double mutant was dramatically sensitive to H2O2. The dual function encoded by these two genes appears to confer protection from exogenous oxidative stress, such as may occur during plant infection. Subsequent experiments will evaluate effects on virulence and endophytic infection of maize. Further genomic analyses are underway to identify additional HGTs in F. verticillioides given its plant-associated niches.