Canadian Forest Service Publications

Infection assays in Arabidopsis reveal candidate effectors from the poplar rust fungus that promote susceptibility to bacteria and oomycete pathogens. 2018. Germain, H.; Joly, D.L.; Mireault, C.; Plourde, M.B.; Letanneur, C.; Stewart, D.; Morency, M.-J.; Petre, B.; Duplessis, S.; Séguin, A. Mol. Plant Pathol. 19: 191-200.

Year: 2018

Issued by: Laurentian Forestry Centre

Catalog ID: 37889

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1111/mpp.12514

† This site may require a fee

Mark record


Fungi of the Pucciniales order cause rust diseases which, altogether, affect thousands of plant species worldwide and pose a major threat to several crops. How rust effectors—virulence proteins delivered into infected tissues to modulate host functions—contribute to pathogen virulence remains poorly understood. Melampsora larici-populina is a devastating and widespread rust pathogen of poplar, and its genome encodes 1184 identified small secreted proteins that could potentially act as effectors. Here, following specific criteria, we selected 16 candidate effector proteins and characterized their virulence activities and subcellular localizations in the leaf cells of Arabidopsis thaliana. Infection assays using bacterial (Pseudomonas syringae) and oomycete (Hyaloperonospora arabidopsidis) pathogens revealed subsets of candidate effectors that enhanced or decreased pathogen leaf colonization. Confocal imaging of green fluorescent protein-tagged candidate effectors constitutively expressed in stable transgenic plants revealed that some protein fusions specifically accumulate in nuclei, chloroplasts, plasmodesmata and punctate cytosolic structures. Altogether, our analysis suggests that rust fungal candidate effectors target distinct cellular components in host cells to promote parasitic growth.

Plain Language Summary

This study suggests that a group of specialized proteins (effectors) produced by the European poplar rust fungus attack specific host cell components in order to facilitate the fungus’s proliferation.

As with numerous fungal diseases, the European poplar rust fungus injects effectors into the cells of its host in order to weaken its defence mechanisms and divert resources to its own use. The purpose of this study was to assess the ability of certain effectors produced by the rust fungus to promote its own proliferation, thereby increasing its virulence in poplar.

Studying these effectors makes it possible to gain a better understanding of the interactive mechanisms existing between trees and microbes, taking the poplar as a model system to better assess potential damage that may be caused by exotic pests.