Genetic diversity of Pto-like serine/threonine kinase disease resistance genes in cultivated and wild strawberries

MARTINEZ ZAMORA, GUSTAVO; CASTAGNARO, ATILIO P; DÍAZ RICCI, JUAN C.

JOURNAL OF MOLECULAR EVOLUTION

Springer

Lugar: Heidelberg; Año: 2008 vol. 67 p. 211 - 221

0022-2844

Degenerate oligonucleotide primers, designed based on conserved regions of several serine-threonine kinases (STK) previously cloned in tomato and Arabidopsis, were used to isolate STK candidates in wild and cultivated strawberries. Seven distinct classes of STKs were identified from three wild related species, e.g. Fragaria vesca, Fragaria chiloensis, and Potentilla tucumanensis and seven different Fragaria x ananassa cultivars. Alignment of the deduced amino acid sequences and the Pto R protein from tomato revealed the presence of characteristic subdomains, the conservation of the plant STK consensus and other residues that are crucial for Pto function. Based on identity scores and clustering in phylogenetic trees, five groups were designated as Pto-like kinases. Strawberry Pto-like clones preset sequences that were clearly identified as the activation segments contained in the Pto sequences, and some of them show residues previously identified as required for binding to AvrPto. Some of the non Pto-like kinases presented high levels of identity and group together with B-lectin receptor kinases that are also involved in disease resistance. Two statistics test failed to detect departures from the neutral theory and studies of non-synonymous and synonymous substitutions showed that the evolution of STK encoding sequences in strawberries is subjected to a purifying rather than to a divergent selection process. These results represent the first report of STKs in strawberry.