IMPROVING GRAPE ROOTSTOCK AND SCION PEST AND DISEASE RESISTANCE
Location: Grape Genetics Research
Title: Differential gene expression during conidiation in the grape powdery mildew fungus, Erysiphe necator
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 2, 2011
Publication Date: July 6, 2011
Citation: Wakefield, L., Gadoury, D.M., Seem, R.C., Milgroom, M.G., Sun, Q., Cadle Davidson, L.E. 2011. Differential gene expression during conidiation in the grape powdery mildew fungus, Erysiphe necator. Phytopathology. 101:839-846.
Interpretive Summary: The grape powdery mildew fungus spreads quickly through the vineyard by asexual reproduction and then uses sexual reproduction to form overwintering structures. We studied the genes that control asexual and sexual reproduction in this fungus and compared them to genes controlling reproduction in other fungi. We focused on 620 genes that we identified with differential expression in at least one developmental stage. One-fourth of the differentially-expressed sequences matched fungal genes of unknown function. The remaining genes had known function in metabolism, signaling, RNA transcription, transport, or protein fate. As expected, a portion of genes known to control development in other fungi functioned similarly in grape powdery mildew. Particularly noteworthy were several genes associated with the light-dependent control of sporulation, protein signaling, and transport into the cell’s nucleus. However, we found new genes that may be uniquely involved in development of powdery mildews due to their required interaction with plants. Knowledge of these genes and their function may provide targets for disease management.
Asexual sporulation (conidiation) is coordinately regulated in the grape powdery mildew fungus Erysiphe necator, but nothing is known about its genetic regulation. We hypothesized that genes required for conidiation in other fungi would be up-regulated at conidiophore initiation and/or full conidiation (relative to pre-conidiation vegetative growth and development of mature ascocarps), and that the obligate biotrophic lifestyle of E. necator would necessitate some novel gene regulation. cDNA-AFLP analysis with 45 selective primer combinations produced approximately 1,600 transcript-derived fragments (TDFs) of which 620 (39%) showed differential expression. TDF sequences were annotated using BLAST analysis of Genbank and of a reference transcriptome for E. necator developed by 454-FLX pyrosequencing of a normalized cDNA library. One-fourth of the differentially-expressed, annotated sequences had homology to fungal genes of unknown function. The remaining genes had annotated function in metabolism, signaling, transcription, transport, and protein fate. As expected, a portion of orthologs known in other fungi to be involved in developmental regulation were upregulated immediately prior to or during conidiation – particularly noteworthy were several genes associated with the light-dependent VeA regulatory system, G-protein signaling (Pth11 and a kelch repeat) and nuclear transport (importin-ß and Ran). Our results indicate that while control of conidiation in E. necator may share some basic elements with established systems, there are significant points of divergence as well, perhaps due in part to the obligate biotrophic lifestyle of E. necator.