Perturbation of parent-specific gene expression during interspecific hybridization

Interspecific hybridization often induces epigenetic remodeling that leads to transposon activation, gene expression changes, and loss of imprinting. These genomic changes can be deleterious and lead to postzygotic hybrid incompatibility. In Arabidopsis, loss of genomic imprinting of PHERES1 and presumed failure of Polycomb Repressive Complex is partially responsible for seed inviability observed in A. thaliana X A. arenosa interspecific hybrids. We used this species pair to further analyze the relationship between parent-specific gene expression and postzygotic hybrid incompatibility using two A. thaliana ecotypes, Col-0 and C24, with differential seed survival. We found that maternal imprinting was perturbed for PHERES1, HDG3, and six other genes in both A. thaliana hybrids and paternal imprinting was lost for MEDEA as observed previously. Three classes of retroelements; Sadhu, Athila, and Copia, maintained proper repression patterns suggesting some regulatory mechanisms are not disrupted early in development. We propose that early genome remodeling and loss of imprinting of seed development genes induces lethality in both compatible and incompatible hybrids. Overall design: We examined gene expression in A. thaliana intraspecific hybrid crosses to determine normal patterns of maternal and paternal expression early in seed development.