Notch signaling: cell fate control and signal integration in development

Notch signaling defines an evolutionarily ancient cell interaction mechanism, which plays a fundamental role in metazoan development. Signals exchanged between neighboring cells through the Notch receptor can amplify and consolidate molecular differences, which eventually dictate cell fates. Thus, Notch signals control how cells respond to intrinsic or extrinsic developmental cues that are necessary to unfold specific developmental programs. Notch activity affects the implementation of differentiation, proliferation, and apoptotic programs, providing a general developmental tool to influence organ formation and morphogenesis.     

Malaria parasite development in a Drosophila model

Malaria is a devastating public health menace, killing over one million people every year and infecting about half a billion. Here it is shown that the protozoan Plasmodium gallinaceum, a close relative of the human malaria parasite Plasmodium falciparum, can develop in the fruit fly Drosophila melanogaster. Plasmodium gallinaceum ookinetes injected into the fly developed into sporozoites infectious to the vertebrate host with similar kinetics as seen in the mosquito host Aedes aegypti. In the fly, a component of the insect's innate immune system, the macrophage, can destroy Plasmodia. These experiments suggest that Drosophila can be used as a surrogate mosquito for defining the genetic pathways involved in both vector competence and part of the parasite sexual cycle.     

Association between potassium concentration and serological type of sheep red blood cells

When red blood cells from 115 sheep were classified for the presence or absence of antigenic factor M and for high (as opposed to low) potassium concentration levels, the cells of the 22 M-negative sheep were low in potassium.     

微生物与土壤矿物相互作用的研究进展

微生物体吸附于矿物表面后,其活性将发生改变,从而影响到土壤中与生物和生物分子相关的一系列土壤过程,如矿物形成与演化、土壤结构体稳定性、土壤养分有效性、土壤污染物质的毒性以及污染土壤的生物修复等。因此,研究土壤矿物、微生物相互作用,不仅有助于深入了解土壤微生物过程,而且对评估和预测土壤体系中有机污染物降解和转化的特点与动态,进而提高污染物的修复效率等有着重要的实际意义。     

Effects of helpers on juvenile development and survival in meerkats

Although breeding success is known to increase with group size in several cooperative mammals, the mechanisms underlying these relationships are uncertain. We show that in wild groups of cooperative meerkats, Suricata suricatta, reductions in the ratio of helpers to pups depress the daily weight gain and growth of pups and the daily weight gain of helpers. Increases in the daily weight gain of pups are associated with heavier weights at independence and at 1 year of age, as well as with improved foraging success as juveniles and higher survival rates through the first year of life. These results suggest that the effects of helpers on the fitness of pups extend beyond weaning and that helpers may gain direct as well as indirect benefits by feeding pups.     

Site-specific recombination between homologous chromosomes in Drosophila

The ability to mark a cell and its descendants genetically so that the resulting cell clone can be distinguished from neighboring cells facilitates studies in animal biology and development. A method of generating clones by inducing homologous mitotic recombination in Drosophila with a site-specific yeast recombinase is described. This method allows for frequent mosaicism after mitotic exchange is induced at predefined sites in the genome.     

Crossmodal interactions between olfactory and visual learning in Drosophila

Different modalities of sensation interact in a synergistic or antagonistic manner during sensory perception, but whether there is also interaction during memory acquisition is largely unknown. In Drosophila reinforcement learning, we found that conditioning with concurrent visual and olfactory cues reduced the threshold for unimodal memory retrieval. Furthermore, bimodal preconditioning followed by unimodal conditioning with either a visual or olfactory cue led to crossmodal memory transfer. Crossmodal memory acquisition in Drosophila may contribute significantly to learning in a natural environment.     

Genome-wide RNAi analysis of growth and viability in Drosophila cells

A crucial aim upon completion of whole genome sequences is the functional analysis of all predicted genes. We have applied a high-throughput RNA-interference (RNAi) screen of 19,470 double-stranded (ds) RNAs in cultured cells to characterize the function of nearly all (91%) predicted Drosophila genes in cell growth and viability. We found 438 dsRNAs that identified essential genes, among which 80% lacked mutant alleles. A quantitative assay of cell number was applied to identify genes of known and uncharacterized functions. In particular, we demonstrate a role for the homolog of a mammalian acute myeloid leukemia gene (AML1) in cell survival. Such a systematic screen for cell phenotypes, such as cell viability, can thus be effective in characterizing functionally related genes on a genome-wide scale.     

Transient expression of homologous genes in Drosophila cells

A cloned Drosophila heat shock protein 22 gene was transfected into two independently established Drosophila cell lines. Each line carried a different heat shock protein 22 allele, distinguishable by electrophoresis of the protein. The transfected gene was not expressed at 25 degrees C but could be induced at 36 degrees C. In one line, two heat shock protein 22 electromorphs were synthesized.     

Glycosylation restores survival of chilled blood platelets

Cooling of blood platelets clusters the von Willebrand factor receptor complex. Macrophage alphaMbeta2 integrins bind to the GPIbalpha subunit of the clustered complex, resulting in rapid clearance of transfused, cooled platelets. This precludes refrigeration of platelets for transfusion, but the current practice of room temperature storage has major drawbacks. We document that alphaMbeta2 is a lectin that recognizes exposed beta-N-acetylglucosamine residues of N-linked glycans on GPIbalpha. Enzymatic galactosylation of chilled platelets blocks alphaMbeta2 recognition, prolonging the circulation of functional cooled platelets. Platelet-associated galactosyltransferase produces efficient galactosylation when uridine diphosphate-galactose is added, affording a potentially simple method for storing platelets in the cold.     

Requirement for RORgamma in thymocyte survival and lymphoid organ development

Most developing thymocytes undergo apoptosis because they cannot interact productively with molecules encoded by the major histocompatibility complex. Here, we show that mice lacking the orphan nuclear hormone receptor RORgamma lose thymic expression of the anti-apoptotic factor Bcl-xL. RORgamma thus regulates the survival of CD4+8+ thymocytes and may control the temporal window during which thymocytes can undergo positive selection. RORgamma was also required for development of lymph nodes and Peyer's patches, but not splenic follicles. In its absence, there was loss of a population of CD3-CD4+CD45+ cells that normally express RORgamma and that are likely early progenitors of lymphoid organs. Hence, RORgamma has critical functions in T cell repertoire selection and lymphoid organogenesis.     

农村创新中农民与正式部门的互动案例分析

对1885个农民创新者的案例进行了分析,探讨了中国农村创新中农民与正式部门的互动现状及存在的问题.结果表明:1)农村创新中农民与正式部门间存在一定程度的互动,但是互动不足;2)互动较多地发生在创新成果推广阶段;3)政府和农民都在积极寻求互动,但是企业、科研机构缺乏主动性;4)互动形式多样,有助于促进创新的产生与成果扩散...     

植物与病原菌相互作用的研究

从植物与病原微生物相互作用的角度来阐明植物抗病的分子机制,为农作物有效地抵抗病原菌提供参考。     

Regulation of JNK by Src during Drosophila development

In Drosophila, the Jun amino-terminal kinase (JNK) homolog Basket (Bsk) is required for epidermal closure. Mutants for Src42A, a Drosophila c-src protooncogene homolog, are described. Src42A functions in epidermal closure during both embryogenesis and metamorphosis. The severity of the epidermal closure defect in the Src42A mutant depended on the amount of Bsk activity, and the amount of Bsk activity depended on the amount of Src42A. Thus, activation of the Bsk pathway is required downstream of Src42A in epidermal closure. This work confirms mammalian studies that demonstrated a physiological link between Src and JNK.     

Drosophila Sex lethal gene initiates female development in germline progenitors

Sex determination in the Drosophila germ line is regulated by both the sex of the surrounding soma and cell-autonomous cues. How primordial germ cells (PGCs) initiate sexual development via cell-autonomous mechanisms is unclear. Here, we demonstrate that, in Drosophila, the Sex lethal (Sxl) gene acts autonomously in PGCs to induce female development. Sxl is transiently expressed in PGCs during their migration to the gonads; this expression, which was detected only in XX PGCs, is necessary for PGCs to assume a female fate. Ectopic expression of Sxl in XY PGCs was sufficient to induce them to enter oogenesis and produce functional eggs when transplanted into an XX host. Our data provide powerful evidence that Sxl initiates female germline fate during sexual development.