REDUCED GERMLINE MOBILITY OF A MARINER VECTOR CONTAINING EXOGENOUS DNA - EFFECT OF SIZE OR SITE

Germline mobilization of the transposable element mariner is severely inhibited by the insertion of a 4.5- to 11.9-kb fragment of exogenous DNA into a unique Sad site approximately in the middle of the 1286-bp element. In the presence of transposase driven by the germline-specifi c hsp26-sgs3 promoter, mobilization of the MlwB construct (containing a 11.9-kb insertion) is detected at low frequency. Analysis of a mobil ized MlwB element indicated that mobilization is mediated by the marin er transposase. However, transposed MlwB elements are also defective i n germline mobilization. Rare, transposase-induced germ-line excision events were also recovered for such vectors. The estimated rate of exc ision is <0.1% per chromosome per generation. Excision appears to be a ccompanied by gap repair if a suitable template is available. The data imply that the reduced mobility of mariner vectors with exogenous DNA in the Sad site results from disruption of sequences necessary for ef ficient mobilization. The relative stability may be a valuable propert y in the uses of manner-like elements in genetic engineering of insect s of economic importance.