Submitted to: Eukaryotic Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2005
Publication Date: 11/1/2005
Citation: Gaffoor, I., Brown, D.W., Plattner, R.D., Proctor, R., Qi, W., Trail, F. 2005. Functional analysis of the polyketide synthase genes in the filamentous fungus Gibberella zeae (anamorph Fusarium graminearum). Eukaryotic Cell. 4(11):1926-1933. Interpretive Summary: Fusarium graminearum (Gibberella zeae) is the major cause of the wheat and barley disease Fusarium head blight, or scab. The fungus produces several toxic, polyketide chemicals, including the zearalenone, fusarins and aurofusarin, that are associated with a variety of animal diseases. Polyketides are often multi-carbon chemicals that are produced from simple, 2-carbon building blocks by an enzyme called a polyketide synthase (PKS). Each year Fusarium damage and toxin accumulation cause millions of dollars in losses to farmers. In this study, analysis of the entire genome sequence of F. graminearum revealed the presence of 15 genes that code for PKSs. All 15 genes were inactivated by gene disruption to determine their function. With this approach, the PKS genes responsible for the synthesis of all three toxins were identified as well as the gene responsible for synthesis of the black pigment present in the walls of F. graminearum sexual fruiting bodies. We examined the transcription profile of all PKSs under 18 different conditions and detected expression of all but one PKS. This is the first study to genetically characterize a complete set of PKS genes from a single organism.
Technical Abstract: Polyketides are a class of secondary metabolites that exhibit a vast diversity of form and function. In fungi, these compounds are produced by large, multi-domain enzymes classified as Type I polyketide synthases (PKS). In this study we identified and functionally disrupted 15 PKS genes from the genome of the filamentous fungus Gibberella zeae. We found that five of them are responsible for producing the mycotoxins zearalenone, aurofusarin, fusarin C and the black perithecial pigment. A comprehensive expression analysis of these genes revealed diverse expression patterns during grain colonization, plant colonization, sexual development, and mycelial growth. We were unable to detect expression of one of the PKS genes under any of 18 conditions tested. This is the first study to genetically characterize a complete set of PKS genes from a single organism.