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The powdery mildew resistance gene Pm8 derived from rye is suppressed by its wheat ortholog Pm3
Author(s) -
Hurni Severine,
Brunner Susanne,
Stirnweis Daniel,
Herren Gerhard,
Peditto David,
McIntosh Robert A.,
Keller Beat
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12593
Subject(s) - powdery mildew , gene , chemistry , transgene , chromosomal translocation , common wheat , microbiology and biotechnology , blumeria graminis , genetics , plant disease resistance , biology , botany , chromosome , biochemistry
Summary The powdery mildew resistance gene Pm8 derived from rye is located on a 1 BL .1 RS 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 Pm8 due to an unknown genetically dominant suppression mechanism. Here we show that lines with suppressed Pm8 activity contain an intact and expressed Pm8 gene. Therefore, the absence of Pm8 function in certain 1 BL .1 RS ‐containing wheat lines is not the result of gene loss or mutation but is based on suppression. The wheat gene Pm3 , an ortholog of rye Pm8 , suppressed Pm8 ‐mediated powdery mildew resistance in lines containing Pm8 in a transient single‐cell expression assay. This result was further confirmed in transgenic lines with combined Pm8 and Pm3 transgenes. Expression analysis revealed that suppression is not the result of gene silencing, either in wheat 1 BL .1 RS translocation lines carrying Pm8 or in transgenic genotypes with both Pm8 and Pm3 alleles. In addition, a similar abundance of the PM 8 and PM 3 proteins in single or double homozygous transgenic lines suggested that a post‐translational mechanism is involved in suppression of Pm8 . Co‐expression of Pm8 and Pm3 genes in Nicotiana benthamiana 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.