EXTRACHROMOSOMAL PLASMID DNA TRANSMISSION AND AMPLIFICATION IN METASEIULUS-OCCIDENTALIS (ACARI, PHYTOSEIIDAE) TRANSFORMANTS GENERATED BY MATERNAL MICROINJECTION

The plasmid pJKP2 (12.5 kb) was injected into Metaseiulus occidentalis females using a maternal microinjection procedure (Presnail and Hoy 1 992). DNA transmission to their progenies was followed by the polymera se chain reaction (PCR) for several generations. After selecting and r etaining individuals that tested positive by the PCR for 5 generations . individual females were used. to initiate 12 separate transgenic lin es (T1-T12). Southern blot analysis performed 10 generations after inj ection indicated that in at least 8 lines the plasmid DNA was transmit ted extrachromosomally, and in 5 of these lines the extrachromosomal plasmid DNA was highly amplified with an estimated 10 million copies p er female. The longevity, fecundity, immature mortality, and sex ratio of these transgenic lines were not different from the wild-type contr ol under laboratory conditions. However, after 20 generations, few tra nsformants tested positive by the PCR and Southern blot analysis indic ated no distinct banding pattern. Results from Southern blot analysis and the PCR indicated the extrachromosomal plasmid DNA was completely lost after 30 generations, suggesting a fitness cost did occur. Matern al microinjection delivers DNA efficiently to M. occidentalis and coul d be used for testing selectable markers or to deliver transposable-el ement vectors to obtain high rates of chromosomal integrations.