Andrew Lambertsson

The role of su(f) gene function and ecdysterone in transcription of glue polypeptide mRNAs in Drosophila melanogaster

SummaryThe effect of the l(1)su(f)ts67gmutation and ecdysterone on the expression of glue polypeptide genes in Drosophila melanogaster has been studied. Using cloned DNA harboring glue protein genes Sgs3, Sgs4, Sgs7, and Sgs8, and Northern blot hybridization we show that no or extremely reduced accumulation of RNAs from these genes occurs in mutant larvae shifted to 30°C before and through 70 h after oviposition. On the other hand, a shift-up at 75 h or later results in the production of nearly normal amounts of these RNAs 48 h after shift-up. The results indicate functions of the su(f) gene other than suppression of forked bristles, namely that it is essential early in the third instar for the later transcription of the glue polypeptide genes. We also show that administration of exogenous ecdysterone to hormone deficient larvae induces transcription of Sgs3, Sgs4, Sgs7, and Sgs8 RNAs.

The ribosomal proteins of Drosophila melanogaster

SummaryThe ribosomal proteins from nine postembryonic developmental stages of Drosophila melanogaster were analyzed by two-dimensional gel electrophoresis. The ribosomal protein patterns thus obtained constitute reliable control patterns against which any potential mutant can be compared. Furthermore, the results provide increased evidence for a qualitative and quantitative change in the protein composition of the total population of ribosomes which occurs mainly during the third larval instar.Two acidic proteins were found, which may be homologous with rat liver ribosomal proteins L40/L41 and E. coli proteins L7/L12.

Effect of the l(1)su(f)ts67g mutation ofDrosophila melanogaster on glue protein synthesis

SummaryThe l(1)su(f)ts67g mutation has been shown to suppress the developmentally regulated expression of glue protein genes at 30°C. Transferring mutant larvae to the restrictive temperature before the end of the second larval instar results in the absence or extreme reduction of glue protein synthesis while general protein synthesis is unaffected. At the same time, the three glue protein correlated chromosomal regions 3C, 25B, and 68C continue to show prominent puffs. The results suggest that the mutation may be affecting the processing or translatability of specific mRNAs rather than the translational machinery itself.

Content of histone H1 and histone phosphorylation in relation to the higher order structures of chromatin in Drosophila

The amount of histone H1 relative to core histones has been determined in three Drosophila species (D. melanogaster, D. texana and D. virilis) in chromatin from several tissues differing in chromatin structure and genetic activity. Low levels of H1 were found in relatively undifferentiated, early embryos as well as in a line of cultured cells. In late embryos the content of H1 was highest in D. virilis which possesses larger amounts of and a partially more compacted constitutive heterochromatin than the two other species. Polytene chromatin from larval salivary glands showed increased levels of H1 compared with diploid chromatin and the degree of phosphorylation of this histone was relatively low. The degree of phosphorylation of H2A was found to be drastically reduced in polytene as compared with diploid embryonic chromatin, which parallels the extensive underreplication of constitutive heterochromatin. Also, in diploid chromatin a qualitative correlation was observed between the relative amounts of heterochromatin and the levels of H2A phosphorylation. These findings suggest a connection between H2A phosphorylation and heavy compaction of interphase chromatin.

Characterization of a novel Minute -locus in Drosophila melanogaster : a putative ribosomal protein gene

We describe a novel Minute locus, M(1)7C, on the X-chromosome of Drosophila melanogaster. Heterozygous deficient females have most, if not all, of the Minute features (short and fine bristles, rough and somewhat larger eyes, thin-textured wings, missing aristae, affected antennae, delayed development, reduced fertility, and decreased viability). Both Minute and non-Minute adult progeny from Minute mothers suffer from Minute maternal effects such as abdominal segmentation defects, fused tergites, and missing or defective legs and halteres. Using a plasmid clone from region 7C5-9, which harbours the D. melanogaster ribosomal protein gene RPS14, we have found that the accumulation of a single transcript of ∼ 650 b is extremely reduced in Minute larvae in comparison with wild-type. We have localized the RPS14 gene to ∼ 28kbp distal from the singed locus. The results suggest that M(1)1C and RPS14 may be the same gene.

Genetic localization of a follicle cell protein locus in Drosophila melanogaster

SummaryThree variant forms of a “novel” set of follicle cell proteins (Fc) were found when screening geographic wild-type strains of Drosophila melanogaster by SDS-polyacrylamide gel electrophoresis of 35S-methionine labelled ovaries. These variant forms were used to establish X chromosomal linkage and for further genetic localization by both recombinant analysis and by cytogenetical mapping. A locus involved in the synthesis of Fc proteins was localized to the 7C1-9 region, i.e. very close to the singed locus (21.0 cM). The number of Fc proteins, their variation and possible function is discussed.

Ecdysterone responsive functions in the mutantl(1)su(f)ts67g ofDrosophila melanogaster

SummaryTransferring the temperature sensitive mutantl(1)su(f)ts67g from 25° C to 30° C before or early in the third larval instar blocks the increase in the ecdysterone titer that normally occurs at the end of the larval period. Feeding exogenous ecdysterone to these hormone-deficient larvae results in the formation of pseudopupae. The mutant was used to study ecdysterone-inducible functions in late larval salivary glands by preparing three animal samples with different hormone titers: the titer was low in one sample because of an earlier temperature shift, high in a second sample because the larvae were subsequently transferred to ecdysterone-supplemented food, and also high in a third sample that was kept at 25°C, providing a control for normal development. The effect of the different hormone conditions was studied by35S-methionine labeling of the salivary gland proteins during the larval to prepupal transition and the prepupal period. The results indicate that synthesis of several of the proteins normally appearing during the transition and prepupal period is induced by exogenous ecdysterone.

Stage specific synthesis of some follicle cell proteins inDrosophila melanogaster

SummaryOvarian protein synthesis in the temperature-sensitive mutantl(1)su(f)ts67g was analysed at the permissive and non-permissive temperature by SDS-polyacrylamide gel electrophoresis of35S-methionine labelled ovaries. The synthesis of yolk and three other ovarian proteins of approximative molecular weights of 92K, 82K and 76K, respectively, were affected by the shift to the restrictive temperature. Examination of protein synthesis pattern in staged egg chambers revealed that these three proteins were synthesized at stage 10. Analysis of separated cell types present at stage 10 demonstrate that the three proteins were follicle cell products. We have been unable to identify these proteins as any previously described follicle cell proteins.

Imaginal disc ribosomal proteins of D. melanogaster

SummaryThe ribosomal proteins from undifferentiated imaginal discs of Drosophila melanogaster were analyzed by two-dimensional gel electrophoresis and compared with the ribosomal protein pattern of adult flies. It is shown that the ribosomal proteins from these discs are qualitatively identical with those of adult flies except that two acidic proteins are missing in the discs. This heterogeneity is discussed in terms of the functional roles these two proteins may carry in connection with disc differentiation.

Correlation between a female sterile mutation and a set of follicle cell proteins in Drosophila melanogaster

SummaryIn order to correlate the synthesis of a previously described set of follicel cell (Fc) proteins with a known mutation that affects female fertility, three female sterile mutations, fs(1)384, fs(1)508 and fs(1)1501, mapping in the same region as the Fc locus (7C1-9), were analysed with respect to Fc synthesis. The fs(1)508 strain displayed a normal Fc protein pattern, while in fs(1)384 no Fc protein synthesis could be detected. The fs(1)1501 pattern of Fc polypeptide synthesis was totally different from that of any previously analysed strain, displaying a set of proteins that were much larger than the standard Fc variant form. Two of the female sterile mutations, fs(1)384 and fs(1)1501, were combined in rans with two wild-type strains displaying two different electrophoretic variant forms of the Fc proteins. The combinations were then analysed for Fc protein synthesis, using the fact that females heterozygous for two of the Fc variant forms display both parental forms. The results indicate that the fs(1)384 mutation is directly involved in the synthesis of the Fc proteins, as the trans heterozygotes only synthesize the Fc form derived from the wild-type parent. We also suggest that the large proteins synthesized by the fs(1)1501 mutant are a defective Fc variant form. The nature of the two mutations is also discussed.