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Title: Molecular evolution of an Avirulence Homolog (Avh) gene subfamily in Phytophthora ramorum

Author: GossErica M.,; Press, Caroline M.; Grünwald, Niklaus J.;

Date: 2008

Source: In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. p. 361

Publication Series: General Technical Report (GTR)

   Note: This article is part of a larger document. View the larger document

Description: Pathogen effectors can serve a virulence function on behalf of the pathogen or trigger a rapid defense response in resistant hosts. Sequencing of the Phytophthora ramorum genome and subsequent analysis identified a diverse superfamily of approximately 350 genes that are homologous to the four known avirulence genes in plant pathogenic oomycetes and share with them two protein motifs (RxLR and dEER). These have been termed Avh (avirulence homolog) genes. While as a whole the genes in this superfamily exhibit modest sequence similarity, small groups of closely related genes can be identified. We have investigated the molecular evolution of one such group of seven Avh genes. Microarray data suggests that four of these genes are expressed in isolate Pr-102 whose genome was sequenced. We sequenced the full coding region (approximately 400 bp) and flanking noncoding regions of each gene in the three clonal lineages of P. ramorum. The umber of polymorphic sites within P. ramorum genes ranges from 0 to 35, suggesting different evolutionary pressures among genes. Analysis indicates that these genes contain both codons under purifying selection (e.g. in the signal peptide and RxLR and dEER motifs) and under positive selection. We have also been able to obtain the sequence of homologous Avh genes in the sister taxa P. hibernalis, P. lateralis, and P. foliorum allowing for examination of the evolution of these genes across species.

Keywords: Phytophthora ramorum, Phytophthora lateralis, Phytophthora hibernalis effector, RXLR motif

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GossErica M.; Press, Caroline M.; Grünwald, Niklaus J. 2008. Molecular evolution of an Avirulence Homolog (Avh) gene subfamily in Phytophthora ramorum. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. p. 361

 


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