Complex interference in the eye developmental pathway by Drosophila NF-YA

The CCAAT motif-binding factor NF-Y consists of three different subunits, NF-YA, NF-YB, and NF-YC, all of which are required for formation of the NF-Y complex and DNA-binding. NF-YA contains a DNA binding domain in its C-terminal region. We established transgenic fly lines carrying the UAS-HA-dNF-YA or UAS-dNF-YAIR and showed over-expression or knockdown with various GAL4 drivers to be lethal at various developmental stages, suggesting that dNF-YA participate in various gene regulatory pathways during Drosophila development. Expression of dNF-YA with eyeless-GAL4 mainly resulted in lethality with a headless phenotype in pharate-adults. Reduction of the eyeless gene dose enhanced the dNF-YA-induced phenotype, while reduction of the Distal-less gene dose suppressed the phenotype. On the other hand, crossing the dNF-YA over-expressing flies with Notch mutant resulted in no apparent effect on the phenotype. These results suggest that dNF-YA can disturb eye disc specification, but not eye disc growth.     

Headless flies produced by mutations in the paralogous Pax6 genes eyeless and twin of eyeless

The two Pax6 gene homologs eyeless and twin of eyeless play decisive early roles in Drosophila eye development. Strong mutants of twin of eyeless or of eyeless are headless, which suggests that they are required for the development of all structures derived from eye-antennal discs. The activity of these genes is crucial at the very beginning of eye-antennal development in the primordia of eye-antennal discs when eyeless is first activated by the twin of eyeless gene product. This activation does not strictly depend on the Twin of eyeless protein, but is temperature-dependent in its absence. Twin of eyeless acts also in parallel to the eyeless gene and exerts functions that are partially redundant with those of Eyeless, while Eyeless is mainly required to prevent early cell death and promote eye development in eye-antennal discs.     

Trypanosome hybrids generated in tsetse flies by nuclear fusion.

Genetic exchange may occur between two particular Trypanosoma brucei clones simultaneously transmitted by the same tsetse fly. We report here that this exchange takes place in the fly, through nuclear fusion. The resulting hybrids appear to be sub-tetraploid, some particular DNA sequences from one of the parental stocks being lost before enough cloned hybrid trypanosomes could be harvested for DNA analysis. A further reduction of the DNA content of these hybrids occurs gradually upon growth and yields near diploid value in a major part of the population. This mode of hybrid generation is different from the fusion of haploid gametes, which is thought to occur normally upon inoculation of metacyclic trypanosomes in their mammalian host. In this respect, the sub-tetraploid hybrids appear to undergo meiosis in the fly, generating sub-diploid metacyclic forms, then fusion in the mammalian blood.     

Tobamovirus-resistant tobacco generated by RNA interference directed against host genes

Two homologous Nicotiana tabacum genes NtTOM1 and NtTOM3 have been identified. These genes encode polypeptides with amino acid sequence similarity to Arabidopsis thaliana TOM1 and TOM3, which function in parallel to support tobamovirus multiplication. Simultaneous RNA interference against NtTOM1 and NtTOM3 in N. tabacum resulted in nearly complete inhibition of the multiplication of Tomato mosaic virus and other tobamoviruses, but did not affect plant growth or the ability of Cucumber mosaic virus to multiply. As TOM1 and TOM3 homologues are present in a variety of plant species, their inhibition via RNA interference should constitute a useful method for generating tobamovirus-resistant plants.     

家蝇工程及其开发前景

以蝇蛆为例 ,就工程蝇的初步概念、家蝇的营养价值分析、养殖的基本要求和经济效益、开发利用研究的热点和市场展望等方面进行了较全面概括 ,针对其未来发展提出个人建议     

Functional analysis of proteoglycan galactosyltransferase II RNA interference mutant flies

Heparan sulfate proteoglycan plays an important role in developmental processes by modulating the distribution and stability of the morphogens Wingless, Hedgehog, and Decapentaplegic. Heparan and chondroitin sulfates share a common linkage tetrasaccharide structure, GlcAbeta1,3Galbeta1,3Galbeta1,4Xylbeta-O-Ser. In the present study, we identified Drosophila proteoglycan galactosyltransferase II (dbeta3GalTII), determined its substrate specificity, and performed its functional analysis by using RNA interference (RNAi) mutant flies. The enzyme transferred a galactose to Galbeta1,4Xyl-pMph, confirming that it is the Drosophila ortholog of human proteoglycan galactosyltransferase II. Real-time PCR analyses revealed that dbeta3GalTII is expressed in various tissues and throughout development. The dbeta3GalTII RNAi mutant flies showed decreased amounts of heparan sulfate proteoglycans. A genetic interaction of dbeta3GalTII with Drosophila beta1,4-galactoslyltransferase 7 (dbeta4GalT7) or with six genes that encode enzymes contributing to the synthesis of glycosaminoglycans indicated that dbeta3GalTII is involved in heparan sulfate synthesis for wing and eye development. Moreover, dbeta3GalTII knock-down caused a decrease in extracellular Wingless in the wing imaginal disc of the third instar larvae. These results demonstrated that dbeta3GalTII contributes to heparan sulfate proteoglycan synthesis in vitro and in vivo and also modulates Wingless distribution.     

Singles engage the RNA interference pathway

Single-stranded RNAs interact with components of the RNA interference pathway to reduce the expression of target mRNAs. Now, Lima et?al. and Yu et?al. show that, with extensive chemical modifications, small single-stranded RNAs can robustly induce gene silencing with efficacy similar to their double-stranded counterparts.     

Silencing of Toll pathway components by direct injection of double-stranded RNA into Drosophila adult flies

Double-stranded RNA (dsRNA) gene interference is an efficient method to silence gene expression in a sequence-specific manner. Here we show that the direct injection of dsRNA can be used in adult Drosophila flies to disrupt function of endogenous genes in vivo. As a proof of principle, we have used this method to silence components of a major signaling cascade, the Toll pathway, which controls fruit fly resistance to fungal and Gram-positive bacterial infections. We demonstrate that the knockout is efficient only if dsRNA is injected in 4- or more day-old flies and that it lasts for at least 1 week. Furthermore, we report dsRNA-based epistatic gene analysis via injection of a mixture of two dsRNAs and propose that injection of dsRNA represents a powerful method for rapid functional analysis of genes in Drosophila melanogaster adults, particularly of those whose mutations are lethal during development.     

Effect of dimethoate on the developmental rate of forensic importance Calliphoridae flies

Forensic entomotoxicology has grown to impact judicial systems in developed countries. Where the use of insects and maggots as samples in death investigations as an alternative technique, especially following degradation or loss of the conventionally used samples. Carrion flies feed on dead bodies and may ingest toxic substances found in the dead body, especially when the body was poisoned before death. The knowledge of how the chemicals interact with the insect following ingestion is crucial to forensic entomotoxicologists. The study investigated the impact of dimethoate on the life cycle of four species of Calliphoridae flies, namely Chrysomya megacephala, Chrysomya saffranea, Chrysomya rufifacies and Chrysomya indiana. Various concentrations of dimethoate (1 ppm, 2 ppm, 3 ppm and 4 ppm) were utilized in the study. The rate of development of the carrion flies showed a negative correlation with the concentration of the chemical. This paper glares at the impact of the chemicals may pose to the insects, and how analysis of such impacts can guide forensic investigations of poisoning and help the investigators to solve the crime puzzle.     

Evolutionary trade-offs between thermal tolerance and locomotor and developmental performance in drosophilid flies

Cold-tolerant ectothermal animals are generally absent from warmer regions, suggesting that the acquisition of cold tolerance is associated with the loss of adaptation to warmer environments. In the present study, we compared thermal tolerance, walking speed (WS) and pupal development (PD) for 28 drosophilid species from cool-temperate, warm-temperate, and subtropical regions by the phylogenetically-based method and the conventional regression to understand trade-offs between these traits. A significant negative relationship was observed between cold tolerance and the rate of PD in both sexes and between cold tolerance and WS in the male in the phylogenetically-based analysis. Similar results were obtained in the conventional regression analysis, although the level of significance somewhat differed. Thus, cold tolerant species are assumed to have lost abilities to develop and walk fast. Subsequently, they may become more vulnerable to predators, parasitoids or infectious microorganisms and may have become extinct in warmer regions through enemy-mediated interactions and/or resource competition with cold susceptible species with faster development and quicker locomotion. In the present study, no significant relationship was observed between heat tolerance and WS or the rate of PD in the phylogenetically-based analysis, although heat tolerance was significantly related with the rate of PD in the conventional regression analysis. Thus, trade-offs associated with heat tolerance were not apparent.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 375–380.     

Human developmental disorders and the Sonic hedgehog pathway

Sonic hedgehog (Shh) is a morphogen that is crucial for normal development of a variety of organ systems, including the brain and spinal cord, the eye, craniofacial structures, and the limbs. Mutations in the human SHH gene and genes that encode its downstream intracellular signaling pathway cause several clinical disorders. These include holoprosencephaly (HPE, the most common anomaly of the developing forebrain), nevoid basal cell carcinoma syndrome, sporadic tumors, including basal cell carcinomas, and three distinct congenital disorders: Greig syndrome Pallister–Hall syndrome, and isolated postaxial polydactyly. These conditions caused by abnormalities in the SHH pathway demonstrate the crucial role of SHH in complex developmental processes, and molecular analyses of these disorders provide insight into the normal function of the SHH pathway in human development.