The autonomous element En-1 of the maize En/Spm transposable element s
ystem is capable of frequent somatic and germinal excision in the hete
rologous host Arabidopsis thaliana. The pattern of En-homologous trans
cripts generated in transgenic Arabidopsis resembles En transcription
in maize. An excision reporter construct based on NPT-II gene (pKEn2)
can be used reliably for the isolation of En-1 germinal revertants by
seed germination on kanamycin-containing medium. Re-insertion after ge
rminal excision is apparently frequent. A dSpm receptor element can be
efficiently trans-activated in Arabidopsis either by En-1 or by expre
ssing cDNAs of tnpA and tnpD. Excision and re-insertion of En/Spm take
place with similar characteristics as in maize. This is the first des
cription of En/Spm transposition in Arabidopsis and the parameters ana
lysed here suggest that transposon tagging with En should be feasible
in this species.