Genetic analysis of the Drosophila 63F early puff: Characterization of mutations in E63-1 and maggie, a putative Tom22

The 63F early puff in the larval salivary gland polytene chromosomes contai ns the divergently transcribed E63-1 and E63-2 ecdysone-inducible genes. E6 3-1 encodes a member of the EF-hand family of Ca2+-binding proteins, while E63-2 has no apparent open reading frame. To understand the functions of th e E63 genes, we have determined the temporal and spatial patterns of E63-1 protein expression, as well as undertaken a genetic analysis of the 63F puf f. We show that E63-1 is expressed in many embryonic and larval tissues, bu t the third-instar larval salivary gland is the only tissue where increases in protein levels correlate with increases in ecdysone titer. Furthermore, the subcellular distribution of E63-1 protein changes dynamically in the s alivary glands at the onset of metamorphosis. E63-1 and E63-2 null mutation s, however, have no effect on development or fertility. We have characteriz ed 40 kb of the 63F region, defined as the interval between Ubi-p and E63-2 , and have identified three lethal complementation groups that correspond t o the dSc-2, ida, and mg-e genes. We show that mge mutations lead to first- instar larval lethality and that Mge protein is similar to the Tom22 mitoch ondrial import proteins of fungi, suggesting that it has a role in mitochon drial function.