Putative E74B mutation, 14bp deletion from position +1118 to +1131 relative to the E74B transcriptional start site. The deletion alters the reading frame such that a stop codon is introduced 114bp downstream of the deletion prematurely terminating the open reading frame in the middle of the first exon.
At the onset of pupation, as staged by head eversion, Eip74EFDL-1/Df(3L)81k19 mutant animals exhibit the following phenotypes: 1. Mutant larval midguts are extremely condensed and the adult and larval epithelia have separated such that a defined adult lumen exists. These mutants also form an adult midgut epithelium, and the larval proventriculus and gastric caeca are destroyed. Thus, Eip74EFneo24/Df(3L)81k19 larval midguts appear to be arrested at a stage of destruction that is similar to the midgut of wild-type animals 6-12 h following puparium formation. 2. DNA fragmentation is detected in all larval midgut cells of mutant animals 3. Mutant larval midgut cells appear to die normally and have numerous autophagic structures, including mitochondria in vacuoles, crystalline inclusions, and myelin-like membrane swirls. Between the white prepua stage and head eversion, Eip74EFDL-1/Df(3L)81k19 mutant midguts decrease in length by an average of 73% in length compared to 85% in the wild-type.
Homozygous mutant γ neurons (generated in the brain as somatic clones) exhibit no detectable abnormalities in larval or adult stages.
Lethal when carried as a transheterozygote with other Eip74EF mutations, hemizygotes are pupal lethal. Some hemizygous progeny arrest prior to pupation, they have a gas bubble and have partially undergone larval-pupal apolysis. Others undertake but fail to complete pupariation, the gas bubble is expelled into the posterior end, but fails to translocate the gas pocket anteriorly so the gas remains trapped between the hypodermis and pupal case. Remaining hemizygous pupae fail to completely evert their anterior spiracles and cephalic complexes and they retain their long segmented larval shapes, tanning proceeds normally but the darkened cuticle is soft. A few succeed in everting the cephalic complex but do not display further head development, the microcephalic phenotype.
Eip74EFDL-1, br2Bc-2 has lethal | recessive | prepupal stage phenotype
Eip74EFDL-1, br5 has lethal | recessive | larval stage phenotype
Eip74EFDL-1 is a non-enhancer of phenotype of zipEbr
Double heterozygotes with brrbp-5, br5 or br2Bc-2 show no effect on development. Proportion of Eip74EFDL-1 flies showing either a prepupal or pharate lethal phenotype is unchanged as the effective dose of br+ is reduced. All br5, Eip74EFDL-1 double mutants arrest development at the larval/prepupal transition, whereas Eip74EFDL-1 mutants show a range of lethal phases from prepupal to pharate adult. In double mutants with br2Bc-2 the lethal phase shifts earlier to the prepupal stage, and the puparium is extremely curved.
Burtis, 1990.
Puffs normally active at puparium formation are prematurely induced in hemizygous white prepupae.
Retains little or no E74B function while leaving the E74A function unaffected.