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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #171756
Title: IDENTIFICATION AND EXPRESSION ANALYSIS OF REGULATORY GENES ENRICHED DURING CONIDIATION IN EXSEROHILUM TURCICUM

Author
item Flaherty, Joseph
item Dunkle, Larry

Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2005
Publication Date: 4/5/2005
Citation: Flaherty, J.E., Dunkle, L.D. 2005. Identification and expression analysis of regulatory genes enriched during conidiation in exserohilum turcicum. Fungal Genetics and Biology. 42(5):471-481.

Interpretive Summary: Fungi must produce abundant quantities of spores (conidia) to be successful plant pathogens, but little is known about factors that regulate spore formation or the genes that are expressed during the process. In this research, we found that spore formation by Exserohilum turcicum, the fungus causing northern leaf blight of corn, is inhibited by light and induced by darkness, and we discovered and measured the expression a group of genes that convert the light/dark environmental cues into developmental processes. The results will be important to plant pathologists and geneticists attempting to develop innovative strategies for disease control. The genes discovered and characterized in this work represent potential targets for control and can serve as reporters to determine the ability of host (corn) metabolites to affect the expression or function of the genes.

Technical Abstract: Cultures of the filamentous ascomycete, Exserohilum turcicum, grown under continuous white light or blue light (~465-480 nm) were developmentally arrested after the formation of conidiophores, whereas cultures grown in continuous darkness or a light/dark cycle produced mature conidia. Transferring conidiophore-producing cultures to darkness for a minimum of 2-hr initiated synchronous conidiation. Vegetative growth of cultures was more extensive in light-dark cycles than in constant light or darkness, and those observations were supported by analyses of ergosterol content and quantitative real-time PCR. To identify genes involved in dark-induced conidiation, we constructed subtractive cDNA libraries from cultures grown under conidiation-permissive and repressive conditions. From 816 sequenced EST clones in the conidiation-permissive library and 310 in the repressive library, we analyzed the expression of 12 putative regulatory genes by quantitative real-time PCR. The expression of the majority of those genes reached a maximum by 2 hr after initiation of the dark period and then declined to initial levels by 4 - 24 hr. Expression of two genes, which remained elevated after 24 hr in the dark, was reset to initial levels when cultures were returned to light. This study revealed several genes that exhibit increased expression shortly after dark induction of conidiation, suggesting that they may encode regulators of asexual development in E. turcicum.