Mariner (Mos1) transposase and genomic integration of foreign gene sequences in Bombyx mori cells

Widespread occurrence in insects and the capacity to transpose in the absen ce of host-derived factors means that mariner-like elements are considered to be attractive candidates for the development of a universal insect genet ic transformation system. Here we show that the Mos1 mariner element of Dro sophila mauritiana is capable of mediating excision and transposition event s in a silkmoth (Bombyx mori) derived tissue culture cell line (Bm5 cells). Plasmid rescue assays, in combination with Southern hybridization and poly merase chain reaction (PCR) analyses, confirm that the Mos1 transposase can mediate excision of DNA sequences, inserted between terminally repeated se quences recognized by the transposase, and integration into the chromosomal DNA of the Bm5 cells. In addition to chromosomal integration events, inter - and intraplasmid transposition and target element excision events were al so detected. Approximately 50% of the plasmids recovered from plasmid rescu e assays were found to contain the 'signature' of Mos1-specific excision an d/or integration events, indicating that the mariner transposase functions efficiently in the Bombyx cells. Because mariner-induced excision and integ ration events are strictly dependent on the presence of a co-transfected Mo s1 transposase expression vector, it is clear that the multiple copies of e ndogenous mariner-like elements (Bmmar1) that exist in the Bombyx genome ar e neither functional nor do they interfere with the efficiency of the trans position process. Thus, the Mos1 element and, probably, mariner elements, i n general, hold great promise for the development of genetic transformation systems for lepidopteran insects.