Abstract Detail

Host/Plant Pathogen Interactions and Plant Health Management

Montenegro Alonso, Ana Priscilla [1], Ali, Shawkat [2], Linning, Rob [3], Grewal, Tajinder [4], Bakkeren, Guus [3].

Functional characterization of barley smut fungus, Ustilago hordei, avirulence effector UhAvr1.

Effectors are small protein molecules secreted by pathogens that target host cells to overcome a host plant´s defenses and to create a favorable environment for its own propagation, including the diversion of nutrients. Studies on effectors in Basidiomycete fungi have lagged behind (in comparison with bacteria, ascomycetes and oomycetes) including studies on the two economically important related pathogens of cereals in Canada and world-wide, the wheat leaf rust fungus Puccinia triticina and the covered smut fungus Ustilago hordei. Here we will focus on the U. hordei-barley pathosystem as a model system and transfer gained knowledge about effectors and underlying molecular mechanisms to the ‘difficult to study’ leaf rust fungus. Immunity in the U. hordei-barley pathosystem is genetically dictated by a ‘gene-for-gene’ interaction and we recently isolated one of the fungal avirulence genes, UhAvr1, coding for a small effector protein of 171 amino acids including a 19 amino acid N-terminal signal peptide. Fungal isolates expressing this effector trigger an immune response in the resistant barley cultivar ‘Hannchen’ which carries the recognizing and genetically mapped resistance gene Ruh1. UhAvr1 is expressed only when U. hordei infects barley coleoptile cells and its interaction with Ruh1 leads to local cell death. In order to understand how this effector protein functions inside the host, we are identifying the cellular compartment that is being targeted by UhAvr1p and thus where possible recognition by Ruh1 occurs to trigger immunity. Preliminary experiments indicate that this effector may be directed to the apoplast as was shown for the Pep1 effector of the closely related corn smut fungus Ustilago maydis. To validate this, U. hordei strains expressing UhAvr1:GFP and infecting coleoptiles of susceptible barley cultivar ‘Odessa’ are tracked by confocal microscopy. Plasmolysis is induced to confirm the localization of the UhAvr1:GFP chimer. In a second approach, immunolocalization of wild-type UhAvr1p will be achieved using antibodies through electron microscopy or through confocal microscopy using fluorescently-labeled antibodies. These results will be presented as a first step to functionally characterize this effector and shed light on its virulence function and interacting host factors. The long term aim is to generate insight that can be used to develop control alternatives to the destructive rust fungi of cereals.

1 - University of British Columbia, Botany, Vancouver, BC, V6T 1Z4, Canada
2 - King Abdullah University of Science and Technology, Center for Desert Agriculture, Division of Biological and Environmental Sciences and Engineering, Thuwal, Kingdom of Saudi Arabia
3 - Agriculture & Agri-Food Canada, Pacific Agri-food Research Center, Summerland, BC, Canada
4 - University of Saskatchewan, Department of Plant Sciences, Saskatoon, SK, Canada

Keywords:
Ustilago hordei
covered smut fungus
barley
effector
UhAvr1.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PPA019
Abstract ID:757
Candidate for Awards:None