Genome evolution in polyploids

Polyploidy is a prominent process in plants and has been significant in the evolutionary history of vertebrates and other eukaryotes. In plants, inter disciplinary approaches combining phylogenetic and molecular genetic perspe ctives have enhanced our awareness of the myriad genetic interactions made possible by polyploidy. Here, processes and mechanisms of gene and genome e volution in polyploids are reviewed. Genes duplicated by polyploidy may ret ain their original or similar function, undergo diversification in protein function or regulation, or one copy may become silenced through mutational or epigenetic means. Duplicated genes also may interact through inter-locus recombination, gene conversion, or concerted evolution. Recent experiments have illuminated important processes in polyploids that operate above the organizational level of duplicated genes. These include inter-genomic chrom osomal exchanges, saltational, non-Mendelian genomic evolution in nascent p olyploids, inter-genomic invasion, and cytonuclear stabilization. Notwithst anding many recent insights, much remains to be learned about many aspects of polyploid evolution, including: the role of transposable elements in str uctural and regulatory gene evolution; processes and significance of epigen etic silencing; underlying controls of chromosome pairing; mechanisms and f unctional significance of rapid genome changes; cytonuclear accommodation; and coordination of regulatory factors contributed by two, sometimes diverg ent progenitor genomes. Continued application of molecular genetic approach es to questions of polyploid genome evolution holds promise for producing l asting insight into processes by which novel genotypes are generated and ul timately into how polyploidy facilitates evolution and adaptation.