Plant Defense Response to Fungal Pathogens (Activation of Host-Plasma Membrane H+-ATPase by Elicitor-Induced Enzyme Dephosphorylation)

Elicitor preparations containing the avr5 gene products from race 4 of Cladosporium fulvum and tomato (Lycopersicon esculentum L.) cells near isogenic for the resistance gene Cf5 were used to investigate events following the treatment of host plasma membranes with elicitor. A 4-fold increase in H+-ATPase activity, coincident with the acidification of the extracellular medium, was detected immediately after elicitor treatment. The elicitor-induced stimulation of the plasma membrane H+-ATPase was inhibited by okadaic acid but not by staurosporine, suggesting that protein dephosphorylation was required for increased H+-ATPase activity. This observation was confirmed by [gamma]-32P labeling and immunodetection of the plasma membrane H+-ATPase. Effects of guanidine nucleotide analogs and mastoparan on the ATPase activity suggested the role of GTP-binding proteins in mediating the putative elicitor-receptor binding, resulting in activation of a phosphatase(s), which in turn stimulates the plasma membrane H+-ATPase by dephosphorylation.     

Regulation of spvR, the positive regulatory gene of Salmonella plasmid virulence genes

Abstract The regulation of the spvR promoter from the Salmonella dublin virulence plasmid was monitored using proter-reporter gene fusion constructs. Activity was dependent upon the presence of the spv region and was affected by the number of copies of the spv region present with the cell. Activity remained constant throughout exponential growth, and increased rapidly with the onset of stationary phase, under both aerobic and anaerobic conditions. Additionally, the level of spvR expression was controlled by the availability of iron, activity being greatest under low iron conditions in stationary phase. The spvA gene product negatively regulated spvR expression in a dose-dependent manner, indicating that SpvA provides a negative feedback mechanism for this operon.     

Axial filament formation in Bacillus subtilis: induction of nucleoids of increasing length after addition of chloramphenicol to exponential-phase cultures approaching stationary phase.

When chloramphenicol was added to a culture of Bacillus subtilis in early exponential growth, microscopic observation of cells stained by 4',6-diamidino-2-phenylindole showed nucleoids that had changed in appearance from irregular spheres and dumbbells to large, brightly stained spheres and ovals. In contrast, the addition of chloramphenicol to cultures in mid- and late exponential growth showed cells with elongated nucleoids whose frequency and length increased as the culture approached stationary phase. The kinetics of nucleoid elongation after the addition of chloramphenicol to exponential-phase cultures was complex. Immediately after treatment, the rate of nucleoid elongation was very rapid. The nucleoid then elongated steadily for about 4 min, after which the rate of elongation decreased considerably. Nucleoids of cells treated with 6-(p-hydroxyphenylazo)-uracil (an inhibitor of DNA synthesis) exhibited the immediate rapid elongation upon chloramphenicol treatment but not the subsequent changes. These observations suggest that axial filament formation during stationary phase (stage I of sporulation) in the absence of chloramphenicol results from changes in nucleoid structure that are initiated earlier, during exponential growth.     

X chromosome linkage studies in familial Rett syndrome

Four families, each with two individuals affectecd by Rett Syndrome (RS), were analysed using restriction fragment lenght polymorphisms and microsatellite markers from the X chromosome. In two of the families, X-linked dominant inheritance of the RS defect from a germinally mosaic mother could be assumed. Therefore, maternal X chromosome markers showing discordant inheritance were used to exclude regions of the X chromosome as locations of the RS gene. Much of the short arm could be excluded, including regions containing three candidate genes, OTC, synapsin 1 and synaptophysin. Although most of the long arm was inherited in common it was possible to exclude a centromeric region. Inheritance of X chromosome markers is also presented for two families with affected aunt-niece pairs, one of which has not been previously studied at the DNA level.     

New Zealand machair vegetation

Abstract. Machair vegetation is reported for the first time from New Zealand. The habitat is similar to that of British machairs in climate, topography and generally in soil. pH and CaCO₃ content are much lower through most of the sequence, though this difference may partly reflect the greater disturbance of British machair. Sea machair is present, predominantly comprising native species. This grades into machair proper, which contains many species found also in British machair. The machair includes Ammophila-occupied hillocks, a feature typical of British machair. Machair marsh is also present.     

ExbB acts as a chaperone-like protein to stabilize TonB in the cytoplasm

The TonB protein is required to transduce energy from the cytoplasmic membrane to outer membrane transport proteins of Gram-negative bacteria. Two accessory proteins, ExbB and ExbD, are required for TonB function and it has been suggested that TonB and ExbBD form a complex in the membrane. In this paper we demonstrate that there are two spatially distinct, functional interactions between ExbBD and TonB. First, there is an interaction between ExbBD and the N-terminal signal-like peptide of TonB, probabiy the formation of a stable complex in the membrane. Second, ExbB interacts with TonB in the cytoplasm. This interaction involves the domain of TonB that is normally periplasmic. Thus, this is a transient interaction which occurs during the synthesis and/or localization of TonB, implying a chaperone-like role for ExbB. The transmembrane topology of ExbB was shown to be consistent with this role.     

Crystallization and preliminary X-ray analysis of nonglycosylated tissue inhibitor of metalloproteinases-1, N30QN78Q TIMP-1

A nonglycosylated (N₃₀QN₇₈Q) form of the human tissue inhibitor of metalloproteinases, TIMP-1, has been prepared and crystallized in a form suitable for X-ray diffraction analysis. Small single crystals have been grown using sodium tartrate as a precipitant. The crystals are in space group P2₁, with cell dimensions a = 35.28, b = 53.95, c = 48.56, and β = 96.0°. There is a single molecule of TIMP-1 in the asymmetric unit. The crystals diffract to at least 2.3 Å resolution. Complete data have been collected to 2.9 Å and a search for heavymetal derivatives is in progress. © 1993 Wiley-Liss, Inc.     

Transforming growth factor-beta 1 acts cooperatively with sodium n-butyrate to induce differentiation of normal human keratinocytes.

Growth factors with established biological activity toward cultured normal human epidermal keratinocytes (NHEKs) (e.g., transforming growth factor-beta, TGF-beta; retinoic acid, RA) initiate programmed changes in cellular maturation which differ with regard to the specific differentiation pathway (normal or abnormal) analyzed. Sodium butyrate (NaB) initiates one form of epidermal differentiation leading to enhanced cornified envelope (CE) formation which involves abrogation of the normally inhibitory effect of RA on NHEK maturation. NaB also induces TGF-beta mRNA in the maturing suprabasal compartment, suggesting that TGF-beta may play a role in NaB-initiated NHEK differentiation. Treatment with TGF-beta 1 alone, however, only marginally increased (by twofold) the number of detergent-resistant CEs compared to control NHEKs and did not alter the prevalence of fully mature enucleated CEs. TGF-beta 1 was quite effective in inducing significant levels of CE expression when used simultaneously with suboptimal concentrations of NaB. The cooperative action of suboptimal NaB and TGF-beta 1 generated numbers of CEs which, in fact, exceeded the incidence of mature CEs formed in response to optimal levels of NaB alone. Neutralizing antibodies to TGF-beta, moreover, effectively reduced the incidence of CE formation in cultures treated with optimal NaB concentrations, further implicating endogenous TGF-beta activity in the NaB-initiated NHEK differentiation model. It is suggested, therefore, that within the NaB-induced pathway of NHEK differentiation, TGF-beta can positively modulate expression of the differentiated phenotype but alone is insufficient for generation of mature CEs.