A transcriptional network associated with natural variation in Drosophila aggressive behavior

Background  

Aggressive behavior is an important component of fitness in most animals. Aggressive behavior is genetically complex, with natural variation attributable to multiple segregating loci with allelic effects that are sensitive to the physical and social environment. However, we know little about the genes and genetic networks affecting natural variation in aggressive behavior. Populations of Drosophila melanogaster harbor quantitative genetic variation in aggressive behavior, providing an excellent model system for dissecting the genetic basis of naturally occurring variation in aggression.     

Binding protein-independent histidine permease mutants. Uncoupling of ATP hydrolysis from transmembrane signaling

Periplasmic permeases consist of a substrate-binding receptor, located in the periplasm, and a membrane-bound complex composed of two integral membrane proteins and two nucleotide-binding proteins. The receptor interacts with the membrane-bound complex, which, upon receiving this signal, is postulated to hydrolyze ATP and translocate the substrate. We show that a class of mutations in the membrane-bound complex of the histidine permease, which allow transport in the absence of the substrate-binding protein, hydrolyze ATP independently from any signal. The data are compatible with the notion that cross-membrane signaling between the liganded periplasmic receptor and the cytoplasmic ATP-binding sites initiates conformational changes leading to ATP hydrolysis and substrate translocation.     

Hormonal regulation of genetic tumor induction: Cytokinin and abscisic acid

Young seedlings of the tumor-prone amphiploid Nicotiana suaveolens? N. langsdorjfii were grown aseptically on nutrient mediumin a controlled environment chamber. At regular intervals theincidence of tumor formation was scored and plants were harvested.Total cytokinin activity was determined by means of the cucumbercotyledon bioassay, while ABA activity was measured by radioimmunoassay.A close correlation between onset of tumor formation and elevationin endogenous cytokinin activity was demonstrated, but no correlationwas observed between onset of tumorigenesis and change in thelevel of ABA. In addition, exposure of plants to exogenous ABAdid not alter therate of tumor formation. These results arediscussed in relation to the trigger mechanism for tumor inductionin the Nicotiana system. ¹A preliminary report of some of this work was presented atthe American Society of Plant Physiologists meeting in June1978. ³Present address: Department of Biology, West Virginia University,Morgantown, West Virginia 26506, U.S.A. (Received March 10, 1979; )     

Aging in the post-genomic era: simple or complex?

A report on the Third Genetic Effects on Aging Meeting, The Jackson Laboratory, Bar Harbor, Maine, August 4-8, 2000.     

The amyloid precursor protein of Alzheimer's disease is released by human platelets

Western blots of normal human platelets, employing a monoclonal antibody raised against the full-length amyloid precursor protein of Alzheimer's disease (APP695), revealed major bands of 100-110 and 120-130 kDa in both cytosolic, membrane, and released fractions. These species were similar in size to forms seen in brain preparations and in plasma. There was no difference in Western blots of platelet preparations from Alzheimer patients compared with controls. Purified platelet amyloid precursor proteins were sequenced and shown to be amino terminally homogeneous. Immunohistochemistry localized the antigen to the platelet and megakaryocyte and demonstrated weak immunostaining of some lymphocytes. Immunoprecipitation of material released from platelets demonstrated that sedimentable full-length APP with the carboxyl-terminal epitope, and soluble APP lacking the carboxyl-terminal epitope, may exist in the circulation. Western blots and carboxyl-terminal and amino-terminal APP radioimmunoassay of material released by platelets in response to stimulation revealed that platelets release APP during degranulation. The function of platelet APP is yet to be determined, but the present studies suggest a role in regulation of the coagulation cascade or in platelet aggregation.     

A mutational hot-spot in the hisM gene of the histidine transport operon in Salmonella typhimurium is due to deletion of repeated sequences and results in an altered specificity of transport

Summary Duplicated sequences within hisM, a gene coding for a membrane-bound component of histidine transport, result in frequent deletions which, being in frame, allow production of an altered protein with aparent changed specificity of transport. While the wild-type transport system does not transport L-histidinol but does transport L-histidine and several of its analogs, the hisM deletion mutants do not transport the latter compounds but do transport L-histidinol. These results are interpreted as supporting the hypothesis (Ames and Higgins 1983) that transport through periplasmic systems involves binding of the substrate by the cytoplasmic membrane-bound components.     

Methylation segments are not required for chemotactic signalling by cytoplasmic fragments of Tsr, the methyl-accepting serine chemoreceptor of Escherichia coli

The serine chemoreceptor Tsr and other methyl-accepting chemotaxis proteins (MCPs) control the swimming behaviour of Escherichia coli by generating signals that influence the direction of flagellar rotation. MCPs produce clockwise (CW) signals by stimulating the autophosphorylation activity of CheA, a cytoplasmic histidine kinase, and counter-clockwise signals by inhibiting CheA. CheW couples CheA to chemoreceptor control by promoting formation of MCP/CheW/CheA ternary complexes. To identify MCP structural determinants essential for CheA stimulation, we inserted fragments of the tsr coding region into an inducible expression vector and used a swimming contest called 'pseudotaxis' to select for transformant cells carrying CW-signalling plasmids. The shortest active fragment we found, Tsr (350–470), stimulated CheA in a CheW-dependent manner, as full-length Tsr molecules do. It spans a highly conserved 'core' (370–420) that probably specifies the CheA and CheW contact sites and other determinants needed for stimulatory control of CheA. Tsr (350–470) also carries portions of the left and right arms flanking the core, which probably play roles in regulating MCP signalling state. However, this Tsr fragment lacks all of the methylation sites characteristic of MCP molecules, indicating that methylation segments are not essential for generating receptor output signals.