A P-element mutation in the Hsp60C gene was generated through mobilising the protein trap transposon inserted at 25E6 cytological position (a recessive lethal mutation, G262, of Morin et al., 2001), using Δ2-3 transposase. The P-element is inserted 251bp upstream of the transcription start site in the promoter region.
Hsp60C1 flies display reduced viability with only approximately 10-12% surviving to adult stage. Homozygous Hsp60C1 embryos hatch later than their heterozygous siblings and they produce smaller and slower moving first instar larvae compared to heterozygotes. The mean length of newly hatched Hsp60C1 homozygous larvae is 0.63mm compared to 1.13mm in heterozygous Hsp60C1 larvae. Hsp60C1 homozygotes display defects in the tracheal system, with liquid, present during development, failing to be cleared from parts of the tracheal system upon hatching. In a few larvae, one of the two dorsal tracheal trunks can fail to have any liquid clearance. In most of the mutant larvae the main dorsal trunks are highly convoluted and/or asymmetrically organised, while in some the lateral branches are very thin and/or abnormally developed. In a few cases, one or both of the dorsal trunks does not extend the entire larval length but exhibits an unusual midway block and bifurication. Nearly 90% of the Hsp60C1 homozygous larvae die as first instar, the other 10% survive on to adulthood. The escapee Hsp60C1 homozygous flies display poor viability and sterility of males as well as females. The escapee mutant flies are weak and poor fliers, most die within 10 days with none surviving beyond 15 days. The homozygous flies also exhibit roughening of the eyes, with black patches in some cases, abnormal antennae and defects in bristle arrangements. The Hsp60C1 heterozygotes do not exhibit any of the other above defects. Hsp60C1 homozygous males exhibit testes and seminal vesicles that are much smaller than in wild-type and are devoid of sperm bundles. The accessory glands, vas deferens and ejaculatory duct, however, appear similar to wild-type. The number of primary and secondary spermatocytes is much less in mutant testes despite the packaging and initial growth of the existing germ cells appearing normal in the mutant testes up to the 16-cell stage. Most of the later-stage testes exhibit extensive degeneration. Unlike wild-type, no individualised and motile sperms are seen in Hsp60C1 homozygous testes. Instead, a few abnormal sperm bundles, a large amount of needle-shaped debris, and degraded fragments of spermatid tails are visible.
