Frequent Regulatory Neofunctionalization After Gene Duplication in Reproductive Organs of Arabidopsis

Regulatory neofunctionalization occurs when a gene's pattern of expression diverges from the ancestral state. Our analyses of microarray data from Arabidopsis thaliana indicate that it is common for one paralog in a duplicate pair to be broadly expressed while the expression of the other paralog is restricted to reproductive organs (flowers and seeds). We are testing the hypothesis that those paralogs have experienced regulatory neofunctionalization by assaying expression of orthologous genes in outgroup species using RT-PCR of the orthologs in Carica and Vitis. In addition we are performing analyses of sequence rate evolution, to test the hypothesis that genes which diverge from the ancestral expression pattern will have evolved more rapidly. Initial data from several gene pairs support those hypotheses by showing cases where the expression pattern of the paralog after duplication has become restricted to reproductive organs, and in some cases only pollen, as well as having experienced accelerated sequence rate evolution. Together the phenomena are indicative of potential functional divergence between paralogs. Thus it is likely that many genes have undergone functional divergence in reproductive organs after gene duplication.