Epigenetic interactions among three dTph1 transposons in two homologous chromosomes activate a new excision-repair mechanism in petunia.
Unstable anthocyanin3 (an3) alleles of petunia with insertions of the Activator/Dissociation-like transposon dTph1 fall into two classes that differ in their genetic behavior. Excision of the (single) dTph1 insertion from class 1 an3 alleles results in the formation of a footprint, similar to the "classical" mechanism observed for excisions of maize and snapdragon transposons. By contrast, dTph1 excision and gap repair in class 2 an3 alleles occurs via a newly discovered mechanism that does not generate a footprint at the empty donor site. This novel mechanism depends on the presence of two additional dTph1 elements: one located in cis, 30 bp upstream of the an3 translation start in the same an3 allele, and a homologous copy, which is located in trans in the homologous an3 allele. Absence of the latter dTph1 element causes a heritable suppression of dTph1 excision-repair from the homologous an3 allele by the novel mechanism, which to some extent resembles paramutation. Thus, an epigenetic interaction among three dTph1 copies activates a novel recombination mechanism that eliminates a transposon insertion.
van Houwelingen
A
A
Department of Genetics, Institute for Molecular Biological Sciences, Vrije Universiteit, BioCentrum Amsterdam, de Boelelaan 1087, 1081 HV, Amsterdam, The Netherlands.
Souer
E
E
Mol
J
J
Koes
R
R
D000483:Alleles; D001483:Base Sequence; D002875:Chromosomes; D004260:DNA Repair; D004251:DNA Transposable Elements; D018744:DNA, Plant; D019657:Solanaceae / Q000235:genetics*
D004251:DNA Transposable Elements; D018744:DNA, Plant