Plum pox virus (PPV), which causes Sharka disease, is one of the main
limiting factors for apricot production. In apricot (Prunus armeniaca L.),
the major PPV resistance locus (PPVres) has been mapped to the upper part of
linkage group 1. Elena Zuriaga and her colleagues from Instituto Valenciano
de Investigaciones Agrarias in Spain predicted that meprin and TRAF-C
homology domain (MATHd)-containing genes as PPV resistance candidate genes.

The team characterized the global apricot transcriptome response to PPV-D
infection and identified six PPVres locus genes, ParP-1, -2, -3, -4, -5 and
-6, differentially expressed in resistant and susceptible cultivars. Two of
these, ParP-3 and ParP-4, encoding MATHd proteins, were found to be
downregulated in resistant cultivars.

ParP-3 and ParP-4, termed Prunus armeniaca PPVres MATHd-containing genes
(ParPMC), are the only 2 genes having allelic variants linked to PPV
resistance. Resistant cultivars carrying the ParPMC2 mutated allele showed
lack of expression in both ParPMC2 and especially ParPMC1.

The results show that ParPMC1 and/or ParPMC2 as host susceptibility genes
required for PPV infection and silencing these may confer PPV resistance
trait.



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