Location: Toxicology & Mycotoxin Research
2016 Annual Report
Accomplishments
1. Fungi are also capable of denitrification, and not just under low oxygen conditions. Bacteria have long been noted as the primary microbes responsible for denitrification, which is nitrate respiration under low oxygen resulting in release of atmospheric nitrogen (N2). In the past few years studies have shown that fungi may actually be the primary denitrifying microbes, and instead of releasing N2, fungi release the greenhouse gas N2O. Such emissions by fungi may explain agriculture’s significant contribution to global N2O levels. We have found that Fusarium (F.) species such as F. verticillioides are among a limited number of fungi having the full set of genes conferring denitrification and that these genes are highly expressed when the fungus is exposed to nitric oxide (NO). Further, NO induces these genes even when oxygen is available, indicating the pathway is not strictly a low oxygen respiration pathway but instead also functions to detoxify NO. We are fully characterizing these genes and will be seeking inhibitors of the encoded enzymatic functions as a strategy to reduce N2O emissions and also reduce the fitness of F. verticillioides. Such inhibition and reduced fitness should result in reduced production of fumonisin mycotoxins, thus resulting in corn that is safer for human and animal consumption.
2. Horizontal transfer of a gene cluster among three fungal pathogens of corn. ARS researchers in Athens, Georgia, and Peoria, Illinois, have discovered the presence and structural conservation of a gene cluster in Acremonium (A.) zeae, Colletotrichum (C.) graminicola, and Fusarium (F.) verticillioides that supports the hypothesis that corn, as the common host of these three fungi, is a driving force impacting the evolution of their genomes. Specifically they have shown the horizontal gene transfer of the FDB1 cluster between these distantly related fungi. Acquisition of the cluster presumably enhances their fitness by conferring the ability to degrade antifungal phytochemicals produced by corn. This discovery provides greater understanding of how these important plant pathogens have evolved and how corn-breeding efforts for increased production of these phytochemicals may have selected for these fungi and facilitated their frequency of plant infection.
3. Research under the advisement of ARS scientists in Athens, Georgia, has been recognized for its potential impact on soil-borne plant diseases and their control. A PhD student from the Department of Plant Pathology at the University of Georgia is conducting ARS-funded research related to Sub-objective 1.1 of our project plan, and this student has received a prestigious, highly competitive award from the Storkan-Hanes-McCaslin Research Foundation.
