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Front. Plant Sci. | doi: 10.3389/fpls.2018.00265

A suppressor/avirulence gene combination in Hyaloperonospora arabidopsidis determines race specificity in Arabidopsis thaliana.

  • 1Institute of Science and the Environment, University of Worcester, United Kingdom
  • 2College of Life and Environmental Sciences, University of Exeter, United Kingdom
  • 3Department of Biology and Biochemistry, University of Bath, United Kingdom
  • 4School of Life Sciences, University of Warwick, United Kingdom

The pathosystem of Arabidopsis thaliana and diploid biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa) has been a model for investigating the molecular basis of Flor’s gene-for-gene hypothesis. The isolates Hpa-Noks1 and Hpa-Cala2 are virulent on Arabidopsis accession RMX-A02 whilst an F1 generated from a cross between these two isolates was avirulent. The F2 progeny segregated 3,1 (avirulent, virulent), indicating a single major effect AVR locus in this pathogen. SNP-based linkage mapping confirmed a single AVR locus within a 14kb map interval containing two genes encoding putative effectors. The Hpa-Cala2 allele of one gene, designated H. arabidopsidis cryptic1 (HAC1), encodes a protein with a signal peptide and an RxLR/dEER motif, and triggers a defence response in RMX-A02. The second gene is heterozygous in Hpa-Cala2. One allele, designated Suppressor of HAC1Cala2 (S-HAC1Cala2) encodes a protein with a signal peptide and a dKEE motif with no RxLR motif; the other allele (s-hac1 Cala2) encodes a protein with a signal peptide, a dEEE motif and is divergent in sequence from the S-HAC1Cala2 allele. In selfed progeny from Hpa-Cala2, dominant S-HAC1Cala2 allele carrying progeny correlates with virulence in RMX-A02, whereas homozygous recessive s-hac1Cala2 carrying progeny were avirulent. Genetic investigations suggested other heterozygous suppressor loci might exist in the Hpa-Cala2 genome.

Keywords: effector, avirulence inhibitor, suppressor, oomycete, Arabidopsis, Downy mildew, heterozygosity.

Received: 15 Dec 2017; Accepted: 14 Feb 2018.

Edited by:

Xin Li, University of British Columbia, Canada

Reviewed by:

Daolong Dou, Nanjing Agricultural University, China
Hugo Germain, Université du Québec à Trois-Rivières, Canada  

Copyright: © 2018 Tor, Studholme, Cevik, Telli, Holub and Tör. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Mahmut Tör, University of Worcester, Institute of Science and the Environment, NPARU, University of Worcester, Henwick Grove, Worcester, WR2 6AJ, Worcestershire, United Kingdom, m.tor@worc.ac.uk