When Mrtf^{ΔN.H.Scer\UAS} is expressed under the control of both Scer\GAL4^twi.PG and Scer\GAL4^how-24B together, excessive migration of the mesoderm is seen in developing embryos. This results in disruption of the segmentally distributed muscle pattern in stage 14 embryos; large groups of muscle cells are clustered and located more dorsally than normal, and there are obvious gaps in the ventral lateral region. In stage 16 embryos, the cardiac cells are misaligned and they do not form a heart tube. Expression of Mrtf^{ΔN.H.Scer\UAS} under the control of Scer\GAL4^btl.PS results in defects in the tracheal system in embryos; abnormally long dorsal branches are often seen on the dorsal side of the embryo, whereas the extension of the ganglionic branches is undirectional and enhanced. Expression of Mrtf^{ΔN.H.Scer\UAS} under the control of Scer\GAL4^da.G32 in embryos results in a disruption of the patterning of the tracheal system associated with excessive and unpatterned branches. Defects in mesoderm migration are also seen in these embryos.