Submitted to: Phytopathology Supplement; APSnet (Plant Pathology Online)
Publication Type: Abstract Only
Publication Acceptance Date: May 13, 2013
Publication Date: June 15, 2013
Citation: Baldwin, T.T., Glenn, A.E. 2013. Nitric oxide detoxification by Fusarium verticillioides involves flavohemoglobins and the denitrification pathway [abstract]. Phytopathology 103(Suppl. 2):S2.11. DOI: 10.1094/PHYTO-103-6-S2.11 Interpretive Summary: Abstract - no summary required.
Technical Abstract: Nitric oxide (NO) is a highly mobile and potent signaling molecule, yet as a free radical it can also cause nitrosative stress to cells. To alleviate negative effects from excessive accumulation of endogenous NO or from potential exogenous sources, flavohemoglobin proteins can convert NO into nontoxic nitrate ions. We have investigated the flavohemoglobins in Fusarium verticillioides, a mycotoxigenic pathogen of maize. Two genes encoding putative flavohemoglobin homologs, denoted FHB1 and FHB2, were identified. Microarray analysis revealed a significant induction of FHB2 (17-fold) when the fungus was exposed to exogenous NO (1.5 mM of NO-donor DETA NONOate). FHB1 had a 2-fold increase. Noteworthy was the 246-fold increase of the dissimilatory nitrite reductase (NIR1) and high induction of other genes from the denitrification pathway. Deletion mutants (fhb1, fhb2, and nir1) were challenged with 1.5 mM NO-donor, and fhb1 and fhb2 mutants had reduced growth compared to wild type, whereas the nir1 mutant exhibited no decrease in growth. Strains with fhb1/fhb2 double deletion were unable to grow when challenged with NO. All mutants were able to grow on nitrate medium, yet fhb2 and nir1 mutants were unable to grow on nitrite. Overall, the flavohemoglobins may have differential roles for converting endogenous NO (FHB1) versus exogenous NO (FHB2) to nitrate. Our results also demonstrate a significant role of the denitrification pathway in NO detoxification.