Isolation and diversity analysis of resistance gene analogues (RGAs) from cultivated and wild strawberries

MARTÍNEZ ZAMORA, MARTÍN GUSTAVO; CASTAGNARO, ATILIO PEDRO; DIAZ RICCI, JUAN CARLOS

MOLECULAR GENETICS AND GENOMICS

Springer-Verlag

Lugar: Heildelberg; Año: 2004 p. 480 - 487

1617-4615

Degenerate oligonucleotide primers, designed based on conserved regions of Nucleotide Binding Site (NBS) from previously cloned plant resistance genes, were used to isolate Resistance Gene Analogues (RGAs) in wild and cultivated strawberries. Seven distinct families of RGAs of the NBS-LRR type were identified from two wild related species, Fragaria vesca and Fragaria chiloensis, and six different Fragaria x ananassa cultivars. With one exception (GAV-3), deduced amino acid sequences of strawberry RGAs showed strong similarity to TIR (Toll Interleukin I Receptor)-type of R genes from Arabidopsis, tobacco and flax suggesting the existence of common ancestors. GAV-3 seemed to be more related to the nonTIR type. Further studies showed that the recombination level and the non-synonymous to synonymous substitutions ratios within families were low. These data suggest that the evolution of NBS encoding sequences of strawberry RGAs are subjected to a gradual accumulation of mutations leading to a purifying selection rather to a divergent process. These results represent the first report of RGAs in strawberry.