The powdery mildew resistance gene Pm8 derived from rye is suppressed by its wheat ortholog Pm3. (23rd July 2014)

• Record Type: Journal Article
• Authors: Hurni, Severine; Brunner, Susanne; Stirnweis, Daniel; Herren, Gerhard; Peditto, David; McIntosh, Robert A.; Keller, Beat
• Is Part Of: Plant journal. Volume 79:Number 6(2014:Sep.)
• Page Start: 904
• Page End: 913
• Publication Date: 2014-07-23
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12593
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12593-abs-0001"> <title>Summary</title> <p>The powdery mildew resistance gene <italic>Pm8</italic> derived from rye is located on a 1BL.1RS chromosome translocation in wheat. However, some wheat lines with this translocation do not show resistance to isolates of the wheat powdery mildew pathogen avirulent to <italic>Pm8</italic> due to an unknown genetically dominant suppression mechanism. Here we show that lines with suppressed <italic>Pm8</italic> activity contain an intact and expressed <italic>Pm8</italic> gene. Therefore, the absence of <italic>Pm8</italic> function in certain 1BL.1RS‐containing wheat lines is not the result of gene loss or mutation but is based on suppression. The wheat gene <italic>Pm3</italic>, an ortholog of rye <italic>Pm8</italic>, suppressed <italic>Pm8</italic>‐mediated powdery mildew resistance in lines containing <italic>Pm8</italic> in a transient single‐cell expression assay. This result was further confirmed in transgenic lines with combined <italic>Pm8</italic> and <italic>Pm3</italic> transgenes. Expression analysis revealed that suppression is not the result of gene silencing, either in wheat 1BL.1RS translocation lines carrying <italic>Pm8</italic> or in transgenic genotypes with both <italic>Pm8</italic> and <italic>Pm3</italic> alleles. In addition, a similar abundance of the PM8 and PM3 proteins in single or double homozygous transgenic lines suggested that a post‐translational mechanism is involved in suppression of <italic>Pm8</italic>. Co‐expression of <italic>Pm8</italic> and <italic>Pm3</italic> genes in <italic>Nicotiana benthamiana</italic> leaves followed by co‐immunoprecipitation analysis showed that the two proteins interact. Therefore, the formation of a heteromeric protein complex might result in inefficient or absent signal transmission for the defense reaction. These data provide a molecular explanation for the suppression of resistance genes in certain genetic backgrounds and suggest ways to circumvent it in future plant breeding.</p> </abstract>