AUTHOR=Woods-Tör Alison , Studholme David J. , Cevik Volkan , Telli Osman , Holub Eric B. , Tör Mahmut 

TITLE=A Suppressor/Avirulence Gene Combination in Hyaloperonospora arabidopsidis Determines Race Specificity in Arabidopsis thaliana

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00265

DOI=10.3389/fpls.2018.00265

ISSN=1664-462X

ABSTRACT=<p>The pathosystem of <italic>Arabidopsis thaliana</italic> and diploid biotrophic oomycete <italic>Hyaloperonospora arabidopsidis</italic> (<italic>Hpa</italic>) has been a model for investigating the molecular basis of Flor's gene-for-gene hypothesis. The isolates <italic>Hpa</italic>-Noks1 and <italic>Hpa</italic>-Cala2 are virulent on <italic>Arabidopsis</italic> accession RMX-A02 whilst an F<sub>1</sub> generated from a cross between these two isolates was avirulent. The F<sub>2</sub> progeny segregated 3,1 (avirulent, virulent), indicating a single major effect <italic>AVR</italic> locus in this pathogen. SNP-based linkage mapping confirmed a single <italic>AVR</italic> locus within a 14 kb map interval containing two genes encoding putative effectors. The <italic>Hpa</italic>-Cala2 allele of one gene, designated <underline><italic>H</italic></underline>. <underline><italic>a</italic></underline><italic>rabidopsidis</italic><underline><italic>c</italic></underline><italic>ryptic1</italic> (<italic>HAC1</italic>), encodes a protein with a signal peptide and an RxLR/dEER motif, and triggers a defense response in RMX-A02. The second gene is heterozygous in <italic>Hpa</italic>-Cala2. One allele, designated <underline><italic>S</italic></underline><italic>uppressor of</italic><underline><italic>HAC1</italic></underline><sup><italic>Cala2</italic></sup> (<italic>S-HAC1</italic><sup><italic>Cala2</italic></sup>) encodes a protein with a signal peptide and a dKEE motif with no RxLR motif; the other allele (<italic>s-hac1</italic><sup><italic>Cala2</italic></sup>) encodes a protein with a signal peptide, a dEEE motif and is divergent in sequence from the <italic>S-HAC1</italic><sup><italic>Cala2</italic></sup> allele. In selfed progeny from <italic>Hpa</italic>-Cala2, dominant <italic>S-HAC1</italic><sup><italic>Cala2</italic></sup> allele carrying progeny correlates with virulence in RMX-A02, whereas homozygous recessive <italic>s-hac1</italic><sup><italic>Cala2</italic></sup> carrying progeny were avirulent. Genetic investigations suggested other heterozygous suppressor loci might exist in the <italic>Hpa</italic>-Cala2 genome.</p>