Abstract Detail

Host/Plant Pathogen Interactions and Plant Health Management

Goulet, Kristi [1], Saville, Barry [2].

Altered antisense RNA expression reduces Ustilago maydis pathogenesis through a xylitol dehydrogenase.

Biotrophic fungal plant pathogens cause billions of dollars in losses to North American crops annually. The model for functional investigation of these fungi is Ustilago maydis, the causal agent of common smut of corn. During genome annotation of this model organism, a number of long non-coding RNAs (lncRNAs) were discovered. A subset of these transcripts, antisense RNAs (asRNAs), is complementary to coding genes. Some of these asRNAs are present at high levels in the teliospore but detected at very low levels or not at all in haploid cells. Expression of three such asRNAs (as-um02150, embedded; ncRNA1, 3’ overlap; as-um02151, 3’ overlap) is controlled by a common genomic region. Deletion of this DNA control region increased transcript levels of all three asRNAs and attenuated pathogenesis. A second deletion that removed the majority of ncRNA1 increased expression of the other two asRNAs and similarly attenuated pathogenesis. These observations led to the hypothesis that reduced virulence in these control region deletions was the result of asRNAs altering the expression of their respective complementary genes. To test this hypothesis, um02151 and um02150 were independently deleted in a solopathogenic background strain of U. maydis (SG200) and the impact on pathogenesis was assessed. Pathogenesis by the SG200Δum02151 strain was not significantly different than the wild-type strain; however, SG200Δum02150 pathogenesis was reduced to a degree similar to the control region deletion mutants. This virulence phenotype indicates that as-um02150 expression could cause the observed decrease in pathogenesis by sufficiently suppressing expression of um02150. S1 nuclease experiments on RNA isolated from as-um02150-expressing haploid cells revealed that as-um02150 forms double-stranded regions with its complementary mRNA (um02150), confirming that the two transcripts interact. This suggests a mechanism whereby asRNA could inhibit mRNA expression by inhibiting its translation. um02150 codes a xylitol dehydrogenase, an enzyme responsible for catalyzing the oxidation of xylitol into D-xylulose. It is possible that deletion or translation suppression of a xylitol dehydrogenase could alter carbon metabolism by the fungus and reduce its pathogenic development. The impact of this deletion on carbon use in culture will be presented along with pathogenesis assay results and the results of antisense-sense interaction experiments. Future experiments will include assessing changes in protein levels using antibodies raised against Um02150 peptides.

Related Links:
Saville Laboratory Website

1 - Trent University, Environmental and Life Sciences, DNA Building, 2140 East Bank Drive, Peterborough, ON, K9J 7B8, Canada
2 - Trent University, Environmental and Life Sciences; Forensic Science, DNA Building, 2140 East Bank Drive, Peterborough, ON, K9J 7B8, Canada

Keywords:
Ustilago maydis
Antisense RNA
Non-Coding RNA
Xylitol Dehydrogenase
pathogenesis.

Presentation Type: Oral Paper:Papers for Topics
Session: 57
Location: Salon 9/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 8:30 AM
Number: 57003
Abstract ID:1166
Candidate for Awards:CPS Best Student Presentation Awards