Date of Graduation

12-2015

Document Type

Thesis

Degree Name

Master of Science in Plant Pathology (MS)

Degree Level

Graduate

Department

Plant Pathology

Advisor

Burton Bluhm

Committee Member

John Rupe

Second Committee Member

Ainong Shi

Keywords

Biological sciences; Cercospora; Cersospora zeae-maydis; Fungal pathogen; G-protein signaling; Gray leaf spot; Pathogenesis

Abstract

Gray leaf spot, caused by Cercospora zeae-maydis, is one of the most destructive foliar diseases of maize worldwide. C. zeae-maydis orients hyphal growth towards stomata (stomatal tropism) and forms infectious structures (appressoria) that are necessary for successful infection. Although some genes involved in pathogenesis in C. zeae-maydis have been identified, the molecular mechanisms are not well understood. In fungi, heterotrimeric G-proteins consist of three subunits (α, β, and γ) and mediate responses to environmental stimuli. They regulate diverse functions, including nutrient detection, virulence, fungal development, conidiation, secondary metabolism, and pathogenesis in many plant pathogenic fungi. This research explored the role of each G-protein α (Gpα) subunit of C. zeae-maydis in pathogenesis. To this end, the three Gpα subunits identified in C. zeae-maydis were functionally characterized. All three Gpα genes were required for appressorium formation and pathogenesis. Additionally, all three Gpα genes regulated cercosporin biosynthesis and sporulation. Together, these data demonstrated that the Gpα subunits in Cercospora zeae-maydis regulate pathogenesis and suggest that environmental sensing has been impaired. This study links G-protein signaling to infectious development in C. zeae-maydis and sets up a study for transcriptomic analysis of genes regulated by the Gpα genes.

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