Glen E. Collier

Cytoplasmic and mitochondrial arginine kinases inDrosophila: Evidence for a single gene

Mitochondrial and cytoplasmic isozymes of arginine kinase have been identified inDrosophila melanogaster. On the basis of their immunological similarity, parallel dosage responses, and cosegregation of electrophoretic mobility differences, it is concluded that both isozymes are the product of a single gene. The consequences of this in relation to the regulation and evolution of this unusual gene-enzyme system are discussed. It is inferred that the origin of the phosphagen shuttle must predate the divergence of invertebrates and vertebrates.

Phylogeography of the genus Epiplatys (Aplocheiloidea: Cyprinodontiformes)

There are six major genera of aplocheiloid killifishes endemic to West Africa. Five of these are largely restricted to the two major blocks of rainforest. Two are found within the Eastern rainforest block (Nigeria to the central Congo) while three are found within the Western rainforest block (Sierra Leone to Togo). The sixth genus (Epiplatys) has a range that exceeds that of the combined area of the other five genera. Phylogenetically this genus is related to the Western rainforest taxa. Phylogeographic analysis of this genus suggests that it escaped the confines of the Western block by first expanding into lowland habitats exposed after a sea level drop and then dispersed along coastal habitats to the east. One lineage managed to penetrate the interior of the Eastern rainforest block and one derivative of this lineage penetrated the Congo basin. A second route out of the Western rainforest block was to the north through what is now savannah habitat. The greater phylogeographic range of Epiplatys is hypothesized to be due to retention of ancestral morphology related to a greater adaptability compared to the other five genera.

Low specific activity of rare allozymes of |[alpha]|-glycerophosphate dehydrogenase in Drosophila

ELECTROPHORETIC surveys of Drosophila species1 show that many gene–enzyme systems are essentially monomorphic. Very often, however, one or more populations may contain rare alleles, that is, at frequencies less than 5%. Are these alleles selectively neutral and rare because of historical accidents2 or are they deleterious and maintained in populations only through mutation? The dimeric enzyme α-glycerophosphate dehydrogenase (αGPDH) is a good example of an essentially monomorphic Drosophila gene–enzyme system. Out of the 101 species of Drosophila surveyed thus far for electrophoretic variation of αGPDH (refs 3–5), only D. melanogaster is polymorphic. This polymorphism seems to be maintained by selection with temperature being, or strongly correlated with, the selective agent6–8. Microcomplement fixation experiments indicate that this enzyme is evolving slowly among Drosophila species and has accepted relatively few changes in its structure9. We propose that the rare alleles of the αGPDH locus found in some species (see ref. 5) may be at low frequencies because the products of these alleles (allozymes) are catalytically less efficient than their ‘wild-type’ counterparts.

Hormonally regulated expression of arginine kinase in Drosophila melanogaster

SummaryArginine kinase (AK) is present throughout the life cycle of Drosophila melanogaster, but there is a sharp, transient peak of AK activity during the prepupal period and a second period of elevated activity at the time of eclosion of the adult. Imaginal discs show the greatest increase in AK activity at the prepupal stage of those tissues assayed. The prepupal peak is not seen when the temperature-sensitive ecdysoneless mutant ecd-1 is shifted to 29° C at mid-third instar larval stage. The peak in activity reappears when ecd-1 is either shifted back to 20° C after 60 h at 29° C or is fed 20-hydroxyecdysone. At the restrictive temperature, imaginal discs from ecd-1 larvae progressively lose AK activity, whereas discs from 20-hydroxyecdysone-fed larvae have a marked increase in AK activity at stage P3 of the prepupal period. These data suggest that the prepupal peak is regulated by the hormone 20-hydroxyecdysone.

Developmental and biochemical differentiation of glycerolphosphate dehydrogenase isozymes in Mormoniella vitripennis (Hymenoptera:Pteromalidae)

Abstract The two major isozymes of glycerolphosphate dehydrogenase in adult Mormoniella vitripennis (Hymenoptera:Pteromalidae) differ in electrophoretic mobility, heat stability, pH optima, tissue distribution, K m and expression during development. The major adult isozyme is localized to the thorax, is heat stable, has a pH optimum of 5.9 and is not expressed until pupation. The minor adult isozyme is localized in the abdomen, is heat labile, has a pH optimum of 7.2 and is the predominant form expressed in larvae. The abdominal isozyme has lower K m values for dihydroxyacetone phosphate, NADH and α-glycerolphosphate than the thoracic isozyme. Both isozymes have similar K m values for NAD + . The molecular weight of each isozyme is about 60,000 as estimated by gel filtration. The differences between the properties of these isozymes are similar to the differences between the isozymes of glycerolphosphate dehydrogenase from Drosophila melanogaster (Diptera:Drosophilidae).

Sequential Florivory/Saproflorivory of Anaxagorea crassipetala (Annonaceae) by Diathoneura tessellata (Drosophilidae)

ABSTRACT Diathoneura tessellata Duda, 1925 (Diptera: Drosophilidae) uniquely and effectively uses the fleshy tepals of Anaxagorea crassipetala (Annonaceae), a small, understory tree of the primary lowland rain forest of Costa Rica, as a larval substrate and pupation site. This study is the first to document 1) the brood substrate for larvae of this species and the 2) use of flowers in the Annonaceae as a drosophilid larval substrate. Oviposition into the tough, immature flower buds is made possible by an enlarged oviscape. This relationship is unique in that these flowers support two sequential cohorts of larvae, one cohort mining the living tepals of immature and mature flowers and the second cohort consuming the fallen, postanthesis tepals. We refer to this phenomenon as sequential florivory/saproflorivory. The first cohort consists of fewer, larger larvae, whereas the second cohort consists of more numerous, smaller larvae. Both cohorts exhibit a female skewed sex ratio.

Evolutionary Relationships of Enzymes in the Genus Drosophila

While basking in the dawn of the age of DNA sequence data, this is an opportune time for us, as Drosophila evolutionary biologists, to take both a retrospective and prospective look at what the now traditional analyses of protein evolution have told us, and still can tell us, about the history of our favorite genus. The genus Drosophila is an extraordinarily rich testing ground for the evolutionary potential of molecular data. It is old enough so the evolutionary rates of change of conserved molecules can be measured, yet many speci-ation events are comparatively recent. Hence, the more ephemeral events involved in genome reorganization can be traced as well. This chapter will summarize and expand on the the conclusions of an earlier effort (MacIntyre and Collier, 1986), and, present new data on the evolutionary rates of change of several enzymes. In addition, we will examine in more detail the remarkable correspondence between allozyme and chromosome based phylogenies of several species groups.

Genetic and biochemical characterization of phosphofructokinase from Drosophila melanogaster

Phosphofructokinase (PFK; EC 2.7.1.11) activity in Drosophila melanogaster is controlled by a single dosage-sensitive region of the genome between 45F and 47E of chromosome IIR. Only a single form of PFK was detected electrophoretically in both adults and larvae. Nearly 90% of the PFK activity in adults is localized to the thorax. Purification of the enzyme was hampered by the extreme lability of Drosophila PFK; however, a 36-fold partial purification was achieved.