Proposed model for the evolution of the ancient two-haplotype SRK system. The duplication and diversification of the common ancestor of Brassicaceae SRKs, A_SRK, generated two tandem duplicate genes A_SRKI and A_SRKII. Random sub-/neo-functionalization of A_SRKI and A_SRKII produced the postulated two-haplotype system of two ancient SRK haplotypes SRKI and SRKII.
Xing et al. BMC Evolutionary Biology 2013 13:69 doi:10.1186/1471-2148-13-69