Multiprotein expression systems for pest control

The application describes a polycistronic expression cassette comprising two or more coding sequences each separated by a coding sequence encoding a self-cleaving peptides sequence. Self-cleaving peptides cause a ribsosomal skipping event allowing a polycistronic translation of two or more coding sequences under the control of a single promoter element. One or more of said coding sequences encode one or more lethal gene product(s) making this expression cassette a lethality system. The expression cassette is under the control of a single repressible promoter. The application also describes an expression construct, which further comprises a second expression cassette. The second expression cassette optionally encodes one or more male determining gene(s). Also, the application describes a transgenic insect comprising this polycistronic expression cassette or expression construct. The transgenic insect is a crop pest insect or a disease transmitting insect. The application also describes the use of a transgenic insect according to the invention for controlling reproduction in an insect population of interest. Furthermore, the application provides a method of controlling reproduction in an insect population of interest.