Fig. 6

Model for the evolution of the EKA family by co-option as effectors by Bgh genome. 1. Genome rearrangements after retrotransposon activity produce degenerate copies of LINE retrotransposons in the Bgh genome. Some of these copies are truncated ORF1s. 2. One truncated ORF1 is co-opted as effector E1 that enhances pathogenicity. 3. Plant host evolves a resistance gene R1 that recognizes the presence of E1. 4. E1 becomes an avirulence gene (Avr1) if it is recognized by R1 in a gene-for-gene interaction. 5. Avr1 mutates to avoid recognition by R1. 6. Bgh co-opts other degenerate copies as effectors that contribute to enhanced pathogenicity if they are not recognized by host R genes. During this process, Bgh genome and EKA copies are evolving, and the copy co-opted at point 6 may not have existed at point 2 and could have come from a different EKA ancestor