Requirements for zygotic gene activity during gastrulation in XXXX .

@entity73366 @entity238 @entity56680
Mutations at the folded gastrulation ( @entity56680 ) and twisted gastrulation ( @entity73366 ) loci interfere with early morphogenetic movements in @entity238 . @entity56680 embryos do not form a normal posterior midgut and although their germbands do elongate, they do not extend dorsally. As a result, when normal embryos have fully extended germbands, the germbands in mutant embryos are folded into the interior on the ventral side of the embryo. @entity73366 embryos have abnormally deep dorsal folds during early gastrulation, associated with the failure of dorsal cells to slip laterally to make way for the expanding germband. Both @entity56680 and @entity73366 embryos continue to develop, but form disorganized first instar larvae. @entity56680 and @entity73366 are zygotically active genes expressed at least by 10 and 20 min after the onset of gastrulation. Both mutations are viable in homozygous germ cells and the wild-type genes need not be expressed during oogenesis for survival of heterozygous progeny. Elimination of @entity56680 + gene product from maternal germ cells does, however, affect the extent of folding observed during gastrulation in viable heterozygotes. Analysis of @entity56680 adult and larval gynandromorphs indicates that normal folded gastrulation gene function is only required at the posterior region of the embryo, most probably in the cells giving rise to the posterior midgut or proctodeum. The relative survival of @entity56680 mosaics suggests that embryos with mosaic "lethal foci" also die during embryogenesis, although the typical @entity56680 phenotype is only produced when the entire focus is mutant. In contrast to the @entity56680 focus, no particular cell must be wild type in @entity73366 mosaics for survival. Wild-type cells on the dorsal side of the embryo, however, are most effective in rescuing the embryo. This indicates that normal @entity73366 gene product may be required only on the dorsal side of the embryo, potentially in the region which gives rise to the amnion serosa.
