Among insects, the genetic regulation of regional identities in the postoral head or gnathal segments (mandibular, maxillary, and labial) is best understood in the fly
Drosophila melanogaster
. In part, normal gnathal development depends on
Deformed (Dfd)
and
Sex combs reduced (Scr)
, genes in the split
Drosophila
homeotic complex. The gnathal segments of
Dfd
and
Scr
mutant larvae are abnormal but not homeotically transformed. In the red flour beetle,
Tribolium castaneum
, we have isolated loss-of-function mutations of the
Deformed
ortholog. Mutant larvae display a strong transformation of mandibular appendages to antennae. The maxillary appendages, normally composed of an endite and a telopodite, develop only the telopodite in mutant larvae. We previously reported that mutations in the beetle
Scr
and
Antennapedia
orthologs cause the labial and thoracic appendages, respectively, to be transformed to antennae. Moreover, a deficiency of most of the beetle homeotic complex causes all gnathal (as well as thoracic and abdominal) segments to develop antennae. These and other observations are consistent with the hypothesis that ancestral insect homeotic gene functions have been modified considerably during the evolution of the highly specialized maggot head. One of the ancestral homeobox genes that arose close to the root of the Eumetazoa appears to have given rise to
Dfd, Scr
, and the Antennapedia homeobox-class homeotic genes. Evidence from both
Tribolium
and
Drosophila
suggests that this ancestral gene served to repress anterior development as well as confer a trunk-specific identity.
The localization of the two major isoforms of protein kinase C (PKC), PKCalpha and PKCgamma, present in normal and galactosemic bovine lens epithelial cells in culture, was determined using PKC isoform-specific antisera and visualized with FITC-conjugated secondary antisera. The results indicated that the localization of PKC changed upon exposure to 40 mM galactose after 1 day. The subcellular distribution of control cells was cytoplasmic and perinuclear for PKCalpha, while, in 40 mM galactose-treated cells, PKCalpha was also localized to nuclei. In contrast, upon exposure to 40 mM galactose the PKCgamma of the lens epithelial cells was observed in nucleoli. These results suggest that the subcellular distribution of the PKC isoforms in bovine lens epithelial cells differs and is altered upon exposure to 40 mM galactose.
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