Multiple resistances to bacterial and fungal pathogens due to Pto-type serine/threonine kinase (STK) has made this protein a promising candidate for resistance breeding and provided motivation to identify functional Pto-type genes from other plant species. In our present paper, eight classes of STKs were isolated from the cucumber (Cucumis sativus L.) introgressed line 5211S that shows downy mildew resistance. Phylogenetic analysis revealed six classes of cucumber Pto-type resistance gene analogues (RGAs). Multiple sequence alignment of deduced amino acid sequences from these Pto-type RGAs and Pto showed the typical structure of a Pto protein. Non-synonymous to synonymous nucleotide substitution (Ka : Ks) ratios for these Pto-type RGAs were less than 1, indicating that purifying selection played an important role in the evolutionary process. The Pto-type RGAs identified in this study will permit further genetic characterisation that may lead to the development of specific or even broad-spectrum pathogen resistance in 5211S.
Gene Duplication and Hypermutation of the Pathogen Resistance Gene SNC1 in the Arabidopsis bal Variant
