Cytogenetic analysis of the X-chromosome region 2B1-2-2B9-10 of Drosophila melanogaster: V. Puffing disturbances carried by lethal mutants of the gene dor are due to ecdysterone deficiency

A dual function for Deep orange in programmed autophagy in the Drosophila melanogaster fat body

Lysosomal degradation of cytoplasm by way of autophagy is essential for cellular amino acid homeostasis and for tissue remodeling. In insects such as Drosophila, autophagy is developmentally upregulated in the larval fat body prior to metamorphosis. Here, autophagy is induced by the hormone ecdysone through down-regulation of the autophagy-suppressive phosphoinositide 3-kinase (PI3K) signaling pathway. In yeast, Vps18 and other members of the HOPS complex have been found essential for autophagic degradation. In Drosophila, the Vps18 homologue Deep orange (Dor) has previously been shown to mediate fusion of multivesicular endosomes with lysosomes. A requirement of Dor for ecdysone-mediated chromosome puffing has also been reported. In the present report, we have tested the hypothesis that Dor may control programmed autophagy at the level of ecdysone signaling as well as by mediating autophagosome-to-lysosome fusion. We show that dor mutants are defective in programmed autophagy and provide evidence that autophagy is blocked at two levels. First, PI3K activity was not down-regulated correctly in dor larvae, which correlated with a decrease in ecdysone reporter activity. The down-regulation of PI3K activity was restored by feeding ecdysone to the mutant larvae. Second, neither exogenous ecdysone nor overexpression of PTEN, a silencer of PI3K signaling, restored fusion of autophagosomes with lysosomes in the fat body of dor mutants. These results indicate that Dor controls autophagy indirectly, via ecdysone signaling, as well as directly, via autolysosomal fusion.

The acquisition of competence to respond to ecdysone in Drosophila is transcript specific

The steroid hormone ecdysone induces a precise sequence of gene activity in Drosophila melanogaster salivary glands in late third larval instar larvae. The acquisition of competence for this response does not result from a single event or pathway but requires factors that accumulate throughout the instar. Individual transcripts become competent to respond at different times and their expression is differentially affected in ecd1, dor22 and BR-C mutants. The induction of early-late transcripts, originally assumed to necessarily follow early transcripts, is partially independent of early transcript activation. Attempts to inhibit the synthesis of regulatory proteins reveal transcript-specific superinduction effects. Furthermore these inhibitors lead to the induction of betaFTZ-F1 and E93 transcripts at levels normally found in prepupal glands. These studies reveal the complexity of the processes underlying the establishment of a hormonal response.

Not just pretty eyes: Drosophila eye-colour mutations and lysosomal delivery

Analysis of Drosophila eye-colour mutations has made seminal contributions to the fields of genetics and biochemistry. Recent findings suggest that a subset of eye-colour genes is crucial for vesicular transport of proteins to pigment granules, specialized lysosomes of eye-pigment cells. Thus, classical work describing more than 85 eye-colour mutations and their genetic interactions offers a remarkable, untapped resource for the genetic analysis of protein delivery to lysosomes.

Ecdysone and insect immunity: the maturation of the inducibility of the diptericin gene in Drosophila larvae

The developmental analysis of the inducibility of the Drosophila diptericin gene promoter as a response to septic injury shows an important increase in the response during the third larval instar leading to a maximum in late larvae and early prepupae. This increase, or maturation, is temporally correlated with known ecdysone induced events of the salivary gland and we now present evidence, using wild type and mutant larvae, that it does indeed depend upon ecdysone. The response remains minimal in larvae carrying either the temperature sensitive ecdysone deficient late larval lethal allele ecd1, or l(1)t187, a deep orange allele known to be deficient in the ecdysone response. However, experiments with the late larval lethal Broad-Complex mutant l(1)t435 show that the regulation of this response is distinct from the developmental ecdysone regulated hierarchies.

Localization of genes ecs, dor and swi in eight Drosophila species

A cluster of genes corresponding to the early ecdysone stimulated puff 2B of the Drosophila melanogaster X chromosome has been localized using in situ hybridization in eight Drosophila species. Genes ecs, dor and swi from this cluster have been mapped in D. funebris, D. virilis, D. hydei, D. repleta, D. mercatorum and D. paranaensis to the telomeric region of the X chromosome, in D. kanekoi to the distal region, and in D. pseudoobscura, to the proximal region of the X chromosome. It is assumed that organization of this cluster in these species is conserved. In D. hydei, multiple hybridization sites of certain DNA probes from this region were found.

Chromomeric organization of polytene chromosomes

This is a review summarizing work carried out at the Laboratory of Molecular Cytogenetics in recent years. Problems of genetic organization of bands, interbands and puffs as well as intercalary heterochromatin and position effect variegation are discussed from the point of view of the dynamic model of polytene chromosome organization.

Polytene chromosomes from ovarian pseudonurse cells of the Drosophila melanogaster otu mutant. I. Photographic map of chromosome 3

Certain mutant alleles of the otu locus in Drosophila melanogaster produce abnormal nurse cells in the ovaries. These cells are called pseudonurse cells (PNC), since they generate polytene chromosomes instead of endopolyploid ones and do not normally have an oocyte to nurse. The banding pattern of polytene chromosome 3 from the salivary glands (SG) and from PNCs of homozygous otu1 females was compared and a detailed photomap of PNC chromosomes with different degrees of polyteny is presented. The banding pattern was found to be strikingly similiar in the two tissues. The puffing pattern of the PNC chromosomes is discussed. No constrictions or breaks were found in the PNC chromosomes which seems to indicate that these sites, which are known to be underreplicated in the SG chromosomes, are equally replicated along with the rest of the chromosomes in the PNC nuclei.

Larval fat body-specific gene expression in D. melanogaster

The Pl gene, together with the LSP-1 alpha, -1 beta, and -1 gamma, LSP-2, and P6 genes, is expressed exclusively in the larval fat body of D. melanogaster during the third instar. In vivo mapping of the cis-acting regulatory sequences of the P1 gene was carried out using hybrid constructs with three different reporter genes and a combination of transient and germline transformation assays. This revealed that regulatory elements involved in the setting up of the temporal and spatial specificities of transcription of the P1 gene are located in a short DNA region immediately upstream of the mRNA transcription start. This region includes an element that behaves as a fat-body transcriptional enhancer and element(s) required for ecdysone inducibility of transcription of the P1 gene.

Digitonin treatment activates specific genes including the heat-shock genes in salivary glands of Drosophila melanogaster

A large number of chromosomal sites were found to form puffs in Drosophila salivary glands after treatment with the mild detergent digitonin and incubation in a defined medium for 2 hr. The cytological locations of these puffs were determined, and the puff size was measured at 43 loci in both digitonin-treated salivary glands and intact glands. On the basis of comparisons of puffing between digitonin-treated and intact salivary glands, the puffs were classified into three categories: (1) digitonin-unaffected preexisting puffs (8 sites), (2) digitonin-activated preexisting puffs (6 sites), and (3) digitonin-induced new puffs ("digitonin puffs", 29 sites). The digitonin puffs included some of the developmentally regulated puffs and all the heat-shock puffs known in Drosophila melanogaster. The activation of the specific loci by digitonin treatment suggests that gene expression at these loci is suppressed in salivary glands by a mechanism(s) sensitive to digitonin.