Characterization of a Novel Fungal-Specific Gene, FUG1, in Fusarium verticillioides

Filamentous fungi are responsible for numerous plant and animal diseases. The filamentous ascomycete Fusarium verticillioides is a globally important pathogen of maize, capable of causing severe yield reductions and economic losses. Also of substantial concern is the contamination of infected kernels with fumonisins, toxic secondary metabolites linked to toxicoses in humans and livestock. The number of sequenced fungal genomes is rapidly increasing. However, functional characterization of fungal genes has not progressed at a comparable rate. In pathogenic fungi, uncharacterized genes represent a source for novel virulence factors or anti-fungal targets. Therefore, to fully understand the genetic mechanisms underlying fungal pathogenesis, characterizing genes with no known function is important. In this work, a novel gene provisionally named FUG1 (Fungal Unknown Gene 1) was characterized in F. verticillioides via molecular genetics. Despite broad conservation among phylogenetically diverse groups of fungi, putative FUG1 orthologs have not been studied and have no known or predicted biological function. Targeted deletion of FUG1 in F. verticillioides resulted in a pleiotropic phenotype, including reduced radial growth and suppression of asexual reproduction. Importantly, deletion of FUG1 impaired colonization of maize kernels and reduced fumonisin accumulation in the kernel environment. The deletion strain was more sensitive to hydrogen peroxide and the antimicrobial compound, 2-benzoxazolinone (BOA), which provided evidence that FUG1 may have an important role in responding to mechanisms of host defense. Transcriptional profiling revealed that numerous categories of genes are differentially expressed in the kernel environment following deletion of FUG1, including genes involved in carbohydrate metabolism and oxidation-reduction processes. Moreover, deletion of FUG1 in the related pathogen Fusarium graminearum resulted in reduced colonization of maize silks and wheat heads, suggesting that FUG1 may have a conserved role in fungal pathogenesis. Taken together, these results implicate FUG1 in growth, development, and pathogenesis in two Fusarium spp. Additionally, this work illustrates the importance of characterizing unknown genes in filamentous fungi and supports the idea that uncharacterized genes represent a source for potential anti-fungal targets. Acknowledgements I would like to thank my advisor, Dr. Burt Bluhm, for making this project possible through his time, patience, and mentorship. I would also like to thank my committee, Drs. Ines Pinto, Ken Korth, and Jim Correll for direction and helpful discussion. Additionally, I would like to thank Jonathon Smith, Dr. Peter Horevaj, and Allen Cohn for providing technical assistance. This work was funded by the Arkansas Biosciences Institute and the Plant Powered Production (P3) Center, which is funded wholly or in part by the National Science Foundation EPSCoR Program and the Arkansas Science & Technology Authority. Additional support was provided by a National Science Foundation Graduate Research Fellowship. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Table of