adult midgut (with lab14)
embryonic tritocerebrum (with lab9)
Homozygotes show mild perturbation of postorbital bristles. Temperature-dependent effects on larval midgut acidification and viability are seen. lab2/lab14 flies show a strong head phenotype; duplication and disarray of the postorbital bristles is seen. lab2/lab14 larvae lack midgut acidification at all temperatures. However, lab2/lab14 adults show no significant difference in midgut acidification compared to wild-type adults raised at the same temperature at 18, 25 or 31oC. Viability at 31oC is only 2-4%. The lab2/lab14 adults retain a full complement of copper cells at 31oC and the invaginated morphology of the copper cells is normal. Staining for Ank reveals that the characteristic ring-shaped profiles of the copper cells is still present, but the normal progression from large, thin rings in the anterior to smaller, thicker rings in the posterior is not seen.
Homozygous embryos raised at the restrictive temperature have a weak brain phenotype. lab2/lab9 embryos raised at the restrictive temperature (for lab2) show a loss of the tritocerebral commissure and thinning of the longitudinal connectives. These embryos do not show a mutant brain phenotype when raised at the permissive temperature. When raised at the restrictive temperature, except for 1 hour at the permissive temperature at embryonic stage 11, these embryos show complete rescue of the brain phenotype.
At the permissive temperature (18oC) adults develop, but at the restrictive temperature, 31oC, flies die during the first larval instar.
Hemizygous animals die at the embryonic/first larval instar border. A variable cuticle phenotype is seen, with the severity of the defects correlating with the degree of failure of head involution. The frontal sac appears collapsed, and the pharynx occupies a more anterior position than normal. The salivary glands are missing. Transheterozygous combinations of lab2 with other lab alleles produces some adult flies at 18oC. These flies have a mutant phenotype in the head, with the central postorbital region consistently showing a duplication of bristles, one or both maxillary palps are missing, and a spiracle-like structure is sometimes present in the central postgenal region.
temperature-sensitive allele
Kaufman.
T. Kaufman.
Temperature shift experiments show that lab function is required from approximately 3-4 hours until 16-18 hours of embryogenesis.
There is some residual function at 31oC. Temperature shift experiments show that the requirement for lab in making and maintaining the copper cells is continuous after 3hrs of development.