Comparative transcription map of the wobbler critical region on mouse chromosome 11 and the homologous region on human chromosome 2p13-14

Background  

To support the positional cloning of the mouse mutation wobbler (wr ) the corresponding regions on human Chr2p13-14 and mouse Chr11 were analyzed in detail and compared with respect to gene content, order, and orientation.     

K+ channels of stomatal guard cells: bimodal control of the K+ inward-rectifier evoked by auxin

The influence of the auxins indole-3-acetic acid (IAA) and 1-napthylene acetic acid (NAA) on K⁺ channels and their control was examined in stomatal guard cells of Vicia faba L. Intact guard cells were impaled with multibarrelled microelectrodes to record membrane potentials and to monitor K⁺ channel currents under voltage clamp during exposures to 0.1–100 µM IAA and NAA. Following impalements, challenge with either IAA or NAA in the presence of 10 mM KCl resulted in the concerted modulation of at least four different currents with distinct kinetic characteristics and concentration dependencies. Equivalent concentrations of benzoic acid were wholly without effect. Most striking, current carried by inward-rectifying K⁺ channels (I_K,in) exhibited a bimodal response to both IAA and NAA which was reversed on washing the auxins from the bathing medium. The steady-state current was augmented 1.3- to 2-fold at concentrations between 0.1 and 10 µM and antagonized at concentrations near 30 µM and above. Auxin agonism of I_K,in was time- and voltage-independent. By contrast, I_K,in inactivation at the higher auxin concentrations was marked by a voltage-dependence and slowing of the kinetics for current activation. Inactivation of I_K,in by the auxins was relieved when cytoplasmic pH (pH_i) was clamped near 7.0 in the presence of 30 mM Na⁺-butyrate. In addition to the control of I_K,in, current carried by a second class of (outward-rectifying) K⁺ channels rose in a monotonic and largely voltage-independent manner with auxin concentrations about 10 µM and above, and IAA and NAA also activated an inward-going current with a voltage dependence characteristic of guard cell anion channels. Further changes in background current were consistent with a limited activation of the H⁺-ATPase. Over the concentration range examined, the auxins evoked membrane hyperpolarizations and depolarizations of up to ±12–19 mV, depending on the free-running membrane potential prevailing before auxin additions. Prolonging exposures to 100 µM auxin beyond 3–5 min frequently elicited rapid transitions to voltages near E_K as well as regenerative action potentials. However, in every case the voltage response was a predictable consequence of auxin action on the K⁺ channels and, at 100 µM auxin, on the anion current. These results demonstrate a control of K⁺ channel activity by auxin, consistent with the roles of these channels in mediating K⁺ flux for stomatal movements; the data associate a bimodal characteristic with the activity of I_K,in, implicating pH_i as a putative intermediate in its control, and offer strong evidence for a multiplicity of signal cascades evoked by auxin; finally, they highlight a coordinate modulation of transport activities by auxin, thereby drawing a close analogy to the pattern of stimulus-response coupling in abscisic acid.     

Pathogenesis of mucosal disease: a cytopathogenic pestivirus generated by an internal deletion.

Cytopathogenic bovine viral diarrhea virus (BVDV) arises by RNA recombination in animals persistently infected with noncytopathogenic BVDV. Such animals develop fatal mucosal disease. In this report, the genome of a cytopathogenic BVDV isolate, termed CP9, is characterized. CP9-infected cells contained not only viral genomic RNA of 12.3 kb but also a BVDV-specific RNA of 8 kb. cDNA cloning and sequencing revealed that the 8-kb RNA is a BVDV genome with an internal deletion of 4.3 kb. The 8-kb RNA represents the genome of a typical defective interfering particle (DI), since its replication was strictly dependent on the presence of a helper virus and strongly interfered with the replication of the helper. Cell culture experiments demonstrated that the CP9 virus stock contains two viruses, namely, a helper virus and DI9. While the helper virus alone was noncytopathogenic, the presence of the DI conferred cytopathogenicity. Expression experiments demonstrated that p80, the marker protein of cytopathogenic BVDV, is translated from the defective genome. The occurrence of this cytopathogenic DI is linked to a fatal disease in cattle.     

Formation of Siderite in Microbial Microcosms Derived from a Marine Sediment

Abstract

Exceptionally well-preserved fossils are frequently encased by carbonate concretions. The initial steps of their formation in marine and freshwater sediments are induced by microbial activity. The role of the involved microbial communities, however, is not well understood. In this study, siderite (FeCO₃) formation in microbial microcosms is observed, with various fatty acyl compounds (lipids, surfactants) as substrates and Wadden Sea sediment samples as inocula. In actively growing microcosms, sulfate-reducing bacteria (the genus Desulfofrigus in particular) dominate the microbial community and submicroscopic siderite precipitates on bacterial cell surfaces were identified. We suggest that these biologically induced mineralization processes may, in the natural environment, initiate the formation of large concretions under suboxic conditions in coastal sediments.     

Incorporation of 1-[1-(13)C]Deoxy-D-xylulose in chamomile sesquiterpenes.

Incorporation of synthetically prepared 1-[1-(13)C]deoxy-d-xylulose into chamomile sesquiterpenes has been achieved by injecting an aqueous solution into the anthodia of the plant. The analysis of labeling patterns and absolute (13)C abundances of the isolated sesquiterpenes bisabololoxide A (1), bisabololoxide B (2), and chamazulene (3) using quantitative (13)C NMR spectroscopy showed that 1-[1-(13)C]deoxy-d-xylulose was efficiently incorporated in all three isoprene building blocks of the sesquiterpenes. A significantly lower (13)C abundance of the labeled carbon atom in the biogenetically terminal isoprene unit confirms the mixed biosynthesis of this unit, involving both the mevalonic acid pathway and the methylerythritol phosphate pathway.     

Biochemical analyses of the cement float of the goose barnacle Dosima fascicularis – a preliminary study

The goose barnacle Dosima fascicularis produces an excessive amount of adhesive (cement), which has a double function, being used for attachment to various substrata and also as a float (buoy). This paper focuses on the chemical composition of the cement, which has a water content of 92%. Scanning electron microscopy with EDX was used to measure the organic elements C, O and N in the foam-like cement. Vibrational spectroscopy (FTIR, Raman) provided further information about the overall secondary structure, which tended towards a β-sheet. Disulphide bonds could not be detected by Raman spectroscopy. The cystine, methionine, histidine and tryptophan contents were each below 1% in the cement. Analyses of the cement revealed a protein content of 84% and a total carbohydrate content of 1.5% in the dry cement. The amino acid composition, 1D/2D-PAGE and MS/MS sequence analysis revealed a de novo set of peptides/proteins with low homologies with other proteins such as the barnacle cement proteins, largely with an acidic pI between 3.5 and 6.0. The biochemical composition of the cement of D. fascicularis is similar to that of other barnacles, but it shows interesting variations.