Genetic,cytological, and ultrastructural characterization of a temperature-sensitive lethal in Drosophila melanogaster

Genetic analysis of a strain of Drosophila melanogaster revealed that a recessive mutation [l(1)ER^ts] causing temperature-sensitive embryonic lethality is located in the distal region of the X chromosome approximately at map position 18. At 22–25°C mutant embryos exhibit normal viability, and all eggs arrest prior to gastrulation if they are reared at 29°C. The mutant is biphasic, exhibiting a maternal effect which is expressed throughout the first 8 hr of development as well as a second temperature-sensitive period (TSP) during the first 3 days of larval life. Larvae exposed to the restrictive temperature (RT) during the second TSP must also spend the remainder of larval and pupal life and the time of normal eclosion at RT to die as fully developed pupae which fail to eclose. Light and electron microscopy of arrested embryos reveal disturbances in the distribution of nuclei, cytoplasm, and yolk and abnormal configurations of rough endoplasmic reticulum. The cause of pupal death during the second lethal period is unknown.     

果蝇早老素基因的研究进展

果蝇早老素(Drosophila presenilin,DPS)是一种具有天冬氨酸水解酶活性的蛋白,在果蝇生长发育的各阶段都有表达,对果蝇的生长发育和调节胞内Ca2+平衡具有重要的作用。果蝇早老素功能的缺失能够导致Notch信号下降、神经元凋亡和胞质钙浓度上升,最终造成果蝇长时程记忆损伤和认识丧失。果蝇早老素的这些功能使之成为研究果蝇阿尔茨海默病(Alzheimer’s disease,AD)模型最重要的着手点之一,为阐明AD的病理提供了大量有价值的信息。文章概述了DPS基因与AD相关的功能。     

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.     

Genetic and molecular characterization of a variegating hsp70-acZ fusion gene in the euchromatic 31 B region of Drosophila melanogaster.

A hsp70-lacZ fusion gene introduced into Drosophila melanogaster at the euchromatic 31B region by Pelement transformation displayed a variegated expression with respect to the lacZ fusion protein in the salivary gland cells under heat-shock conditions. The variegation is also reflected by the chromosome puffing pattern. Subsequent transposition of the 31B P element to other euchromatic positions restored wild-type activity, that is, a nonvariegated phenotype. A lower developmental temperature reduced the amount of expression under heat-shock conditions, similar to genes undergoing position-effect variegation (PEV). However, other modifiers of PEV did not affect the expression pattern of the gene. These results show a novel euchromatic tissue-specific variegation that is not associated with classical heterochromatic PEV.     

Genetic and molecular variation in the RpII215 region of Drosophila melanogaster

Molecular Genetics and Genomics - The RpII215 region of the X chromosome of Drosophila melanogaster was investigated to identify genetic functions and correlate these with the known molecular...     

Genetic characterization of the Drosophila melanogaster Suppressor of deltex gene: A regulator of notch signaling.

The Notch receptor signaling pathway regulates cell differentiation during the development of multicellular organisms. A number of genes are known to be components of the pathway or regulators of the Notch signal. One candidate for a modifier of Notch function is the Drosophila Suppressor of deltex gene [Su(dx)]. We have isolated four new alleles of Su(dx) and mapped the gene between 22B4 and 22C2. Loss-of-function Su(dx) mutations were found to suppress phenotypes resulting from loss-of-function of Notch signaling and to enhance gain-of-function Notch mutations. Hairless, a mutation in a known negative regulator of the Notch pathway, was also enhanced by Su(dx). Phenotypes were identified for Su(dx) in wing vein development, and a role was demonstrated for the gene between 20 and 30 hr after puparium formation. This corresponds to the period when the Notch protein is involved in refining the vein competent territories. Taken together, our data indicate a role for Su(dx) as a negative regulator of Notch function.     

Genetic and developmental characterization of the aldox-2 locus of Drosophila melanogaster

The aldox-2 locus in Drosophila melanogaster has been shown to affect differentially three molybdoenzymes, aldehyde oxidase, pyridoxal oxidase, and xanthine dehydrogenase. These effects are most obvious at times surrounding the pupal-adult boundary, when the normal organism accumulates large amounts of these enzymes in their active form. This locus has been more precisely mapped genetically to 2-82.9 +/- 2.1, with complete concordance between the effects of all recombinant chromosomes on all three enzymes. The cytogenetic location has also been determined to be between 52E and 54E8, with the likelihood that it lies within the region 54B1-54E8. The aldox-2 mutant allele has no visible phenotype and is completely recessive for enzyme effects at all stages tested. Segmental duplication of this region, including the aldox-2+ allele, has no apparent effect on the visible phenotype or the enzymatic activity. The mutant aldox-2 allele has no effect on the developmental expression of two unrelated enzymes, 6-phosphogluconate dehydrogenase and NADP+-dependent isocitrate dehydrogenase. The effects of this locus on aldehyde oxidase, xanthine dehydrogenase, and pyridoxal oxidase suggest that this locus may code for a product involved in the synthesis of the molybdenum cofactor common to these enzymes.     

Genetic analysis of the X-chromosomal region 1E-2A of Drosophila melanogaster

Reversion mutagenesis of three single P elements located in the cytogenetic interval 1E-2A at the tip of the X chromosome of Drosophila melanogaster was used to recover new deletions in this chromosomal region. The deletions obtained include small aberrations within region 2A and larger lesions extending from 2A into 1E and 1B. All three screens also yielded terminal deficiencies. The new deficiencies, together with previously characterized rearrangements, were analyzed for their complementation behaviour with the maternal effect locus fs(1)Nasrat and lethal loci in the region. These analyses provide an overall genetic map of the interval 1E-2A. In addition, the smaller deletions were physically mapped within cloned genomic DNA of the 2A region.     

A genetic analysis of the cytological region 46C-F containing the Drosophila melanogaster homolog of the jun proto-oncogene

The cytogenetic region 46C-F on the right arm of Drosophila chromosome 2, which contains the homolog of the human jun proto-oncogene, has been genetically mapped and characterized. This project led to the identification and characterization of a Jra (jun-related antigen) mutation, which has been described in detail elsewhere. Three mutagens, EMS, DEB and gamma-rays, were used to isolate 126 lethal lines for this interval. Complementation analysis of the 126 lethal lines identified 29 lethal complementation groups in the region; nine of which have now been correlated with known genes or phenotypes. The region has been subdivided into ten intervals using various small deletions, seven intervals in 46C/D and three intervals in 46E/F. Sixteen P-element lines have been mapped to this interval and are allelic to eight of our complementation groups. The remaining unidentified complementation groups have been analyzed for critical phase, which is when the first observable defect arises and/or when death occurs. There are twelve embryonic lethal groups and seven larval lethal groups. Three lines show visible abnormalities in gut and tracheal development prior to death.     

Genetic organization of the ci-M-pan region on chromosome IV in Drosophila melanogaster.

The genes cubitus interruptus (ci), ribosomal protein S3A (RpS3A), and pangolin (pan) are localized within 73 kb in the cytological region 101F-102A on chromosome IV in Drosophila melanogaster. A region of 13 kb harbours the regulatory regions of both ci and pan, transcribed in opposite directions, and a 1.1-kb gene encoding RpS3A. This dense clustering gives rise to very complicated complementation patterns between different alleles in these loci. We investigated this region genetically and molecularly by use of an enhancer trap line (IA5), where the P-element was found to be inserted into the first intron of pan. Screens for imprecise excisions of the P-element were performed, and complementations between new and old established mutant lines were investigated. We found that when mutated or deleted the RpS3A gene gives rise to a Minute phenotype, and we conclude that M(4)101 encodes the ribosomal protein S3A.     

Genetic analyses of essential genes in cytological region 61D1-2 to 61F1-2 of Drosophila melanogaster

We performed a systematic mutagenesis screen for lethals in the genomic region 61D1-2 to 61F1-2 on chromosomal arm 3L of Drosophila melanogaster. Our genetic analyses revealed that this region contains eight essential complementation groups including trio, Glut1 and extra macrochaetae (emc). For the trio locus, 22 mutant alleles were identified, and all of the alleles analyzed resulted in defects in the central nervous system of embryos, indicating that trio functions in the control of axon extension or guidance. Western analysis showed that at least three proteins are derived from trio and also suggested that a polypeptide of over 200 kDa plays a crucial role in embryonic or larval development. In addition, a newly identified emc allele was associated with several defects in embryonic morphogenesis, including abnormalities in head involution, gut formation and dorsal closure, thus revealing multiple roles for emc in embryonic development. We also performed preliminary phenotypic analyses on stocks bearing mutations belonging to the other lethal complementation groups. These genes function in essential biological events, but the mutations do not result in gross morphological changes during embryonic stages. The present study extends our knowledge of the Drosophila gene set, by identifying most of the essential genes in the chromosomal region 61D1-2 to 61F1-2.     

Analysis of the shortvein cis-regulatory region of the decapentaplegic gene of Drosophila melanogaster

In mammals, the Transforming Growth Factor-beta (TGF-beta) superfamily controls a variety of developmental processes. In Drosophila, by contrast, a single member of the superfamily, decapentaplegic (dpp) performs most TGF-beta developmental functions. The complexity of dpp functions is reflected in the complex cis-regulatory sequences that flank the gene. Dpp is divided into three regions: Hin, including the protein-coding exons; disk, including 3' cis-regulatory sequences; and shortvein (shv), including noncoding exons and 5' cis-regulatory sequences. We analyzed the cis-regulatory structure of the shortvein region using a nested series of rearrangement breakpoints and rescue constructs. We delimit the molecular regions responsible for three mutant phenotypes: larval lethality, wing venation defects, and head capsule defects. Multiple overlapping elements are responsible for larval lethality and wing venation defects. However, the area regulating head capsule formation is distinct, and resides 5' to these elements. We have demonstrated this by isolating and describing two novel dpp alleles, which affect only the adult head capsule.     

Genetic,functional and evolutionary characterization of scox,the Drosophila melanogaster ortholog of the human SCO1 gene

SCO proteins are copper-donor chaperones involved in the assembly of mitochondrial cytochrome c oxidase (COX). Mutations in the two human SCO-encoding genes, SCO1 and SCO2, produce tissue-specific COX deficiencies associated with distinct clinical phenotypes. Here, we report the identification and characterization of scox, the single Drosophila melanogaster SCO-encoding gene. Null mutations of the scox gene are associated with larval lethality, while mutations in its 5′UTR are associated with motor dysfunction and female sterile phenotypes. All mutant phenotypes may be rescued by a transgene encompassing wild-type scox. The analysis of the phenotypes associated with the D. melanogaster scox mutations shows that unimpaired COX assembly and activity is required for biological processes that specifically depend on an adequate energy supply. Finally, we identified the SCO1 orthologs in 39 eukaryotic species informative for a tentative reconstruction of the evolutionary history of the SCO function. Comparison of the exon/intron structure and other key features suggest that eukaryotic SCO genes descend from an intron-rich ancestral gene already present in the last common ancestor of lineages that diverged as early as metazoans and flowering plants.