Hypothesis: selection of imprinted genes is driven by silencing deleterious gene activity in somatic tissues

In mammals and plants, parental genomic imprinting restricts expression of certain loci to one parental allele. In mammals, imprinted genes affect various aspects of maternal care and nutrition of offspring from embryogenesis until adulthood. In plants, the expression of imprinted genes is mostly restricted to the endosperm, which nurtures the embryo. Although this restricted domain of expression suggests that the selection of imprinted genes is related to their role in endosperm, supporting evidence is still limited. In contrast, our literature survey supports a significant impact of ectopic expression of imprinted genes on vegetative tissues that affects plant fitness. We propose that silencing of gene function in vegetative tissue is the primary cause of selection of imprinted genes that may be followed by acquisition of major roles in seed development.