Genetic Diversity of Pto-Like Serine/Threonine Kinase Disease Resistance Genes in Cultivated and Wild Strawberries

MARTINEZ ZAMORA, MG.; CASTAGNARO AP.; DIAZ RICCI, J.C.

JOURNAL OF MOLECULAR EVOLUTION

SPRINGER

Año: 2008 vol. 67 p. 211 - 221

0022-2844

Degenerate oligonucleotide primers, designedbased on conserved regions of several serine-threoninekinases (STK) previously cloned in tomato and Arabidopsis,were used to isolate STK candidates in wild andcultivated strawberries. Seven distinct classes of STKswere identified from three related wild species, i.e., Fragariavesca, Fragaria chiloensis, and Potentillatucumanensis, and seven different Fragaria 9 ananassacultivars. Alignment of the deduced amino acid sequencesand the Pto R protein from tomato revealed the presence ofcharacteristic subdomains and conservation of the plantSTK consensus and other residues that are crucial for Ptofunction. Based on identity scores and clustering in phylogenetictrees, five groups were recognized as Pto-likekinases. Strawberry Pto-like clones presented sequencesthat were clearly identified as the activation segmentscontained in the Pto, and some of them showed residuespreviously identified as being required for binding toAvrPto. Some of the non-Pto-like kinases presented a highdegree of identity and grouped together with B-lectinreceptor kinases that are also involved in disease resistance.Statistical studies carried out to evaluate departure from theneutral theory and nonsynonymous/synonymous substitutionssuggest that the evolution of STK-encodingsequences in strawberries is subjected mainly to a purifyingselection process. These results represent the first report ofPto-like STKs in strawberry