title: The stripe rust fungal effector PEC6 suppresses pattern-triggered immunity in a host species-independent manner and interacts with adenosine kinases.
abstract: We identified a wheat stripe rust (Puccinia striiformis) effector candidate (PEC6) with pattern-triggered immunity (PTI) suppression function and its corresponding host target. PEC6 compromised PTI host species-independently. In Nicotiana benthamiana, it hampers reactive oxygen species (ROS) accumulation and callose deposition induced by Pseudomonas fluorescens. In Arabidopsis, plants expressing PEC6 were more susceptible to Pseudomonas syringae pv. tomato (Pto) DC3000 ΔAvrPto/ΔAvrPtoB. In wheat, PEC6-suppression of P. fluorescens-elicited PTI was revealed by the fact that it allowed activation of effector-triggered immunity by Pto DC3000. Knocking down of PEC6 expression by virus-mediated host-induced gene silencing decreased the number of rust pustules, uncovering PEC6 as an important pathogenicity factor. PEC6, overexpressed in plant cells without its signal peptide, was localized to the nucleus and cytoplasm. A yeast two-hybrid assay showed that PEC6 interacts with both wheat and Arabidopsis adenosine kinases (ADKs). Knocking down wheat ADK expression by virus-induced gene silencing reduced leaf growth and enhanced the number of rust pustules, indicating that ADK is important in plant development and defence. ADK plays essential roles in regulating metabolism, cytokinin interconversion and methyl transfer reactions, and our data propose a model where PEC6 may affect one of these processes by targeting ADK to favour fungal growth.
authors.affiliation: Section for Plant and Soil Science, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark.
authors.forename: Changhai
authors.initials: C
authors.lastname: Liu
authors.affiliation: Section for Plant and Soil Science, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark.
authors.forename: Carsten
authors.initials: C
authors.lastname: Pedersen
authors.affiliation: Section for Plant and Soil Science, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark.
authors.forename: Torsten
authors.initials: T
authors.lastname: Schultz-Larsen
authors.affiliation: Section for Plant and Soil Science, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark.
authors.forename: Geziel B
authors.initials: GB
authors.lastname: Aguilar
authors.affiliation: Section for Plant and Soil Science, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Madriz-Ordeñana
authors.affiliation: Department of Agroecology, Aarhus University, Forsøgsvej 1, Slagelse, DK-4200, Denmark.
authors.forename: Mogens S
authors.initials: MS
authors.lastname: Hovmøller
authors.affiliation: Section for Plant and Soil Science, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Thordal-Christensen
keywords: adenosine kinase; effector; pattern-triggered immunity; stripe rust; wheat (Triticum aestivum)