Gene structure and expression of a tobacco endochitinase gene in suspension-cultured tobacco cells

We have isolated and characterized the genomic clone CHN50 corresponding to tobacco basic endochitinase (E.C.3.2.1.14). DNA sequence and blotting analysis reveal that the coding sequence of the gene present on CHN50 is identical to that of the cDNA clone pCHN50 and, moreover, the CHN50 gene has its origin in the progenitor of tobacco, Nicotiana sylvestris. Tobacco basic chitinases are encoded by a small gene family that consists of at least two members, the CHN50 gene and a closely related CHN17 gene which was characterized previously. By northern blot analysis, it is shown that the CHN50 gene is highly expressed in suspension-cultured tobacco cells and the mRNA accumulates at late logarithmic growth phase. To identify cis-DNA elements involved in the expression of the CHN50 gene in suspensioncultured cells, the chimeric gene consisting of 1.1 kb CHN50 5 upstream region fused to the coding sequence of -glucuronidase (GUS) was introduced by electroporation into protoplasts isolated from suspension-cultured tobacco cells. Transient GUS activity was found to be dependent on the growth phase of the cultured cells, from which protoplasts had been prepared. Functional analysis of 5 deletions suggests that the distal region between -788 and -345 contains sequences that potentiate the high-level expression in tobacco protoplasts and the region (-68 to -47) proximal to the TATA box functions as a putative silencer.     

Requirement of c-kit for development of intestinal pacemaker system.

A discovery that the protooncogene encoding the receptor tyrosine kinase, c-kit, is allelic with the Dominant white spotting (W) locus establishes that c-kit plays a functional role in the development of three cell lineages, melanocyte, germ cell, and hematopoietic cell which are defective in W mutant mice. Recent analyses of c-kit expression in various tissues of mouse, however, have demonstrated that c-kit is expressed in more diverse tissues which are phenotypically normal in W mutant mice. Thus, whether or not c-kit expressed outside the three known cell lineages plays a functional role is one of the important questions needing answering in order to fully elucidate the role of c-kit in the development of the mouse. Here, we report that some of the cells in smooth muscle layers of developing intestine express c-kit. Blockade of its function for a few days postnatally by an antagonistic anti-c-kit monoclonal antibody (mAb) results in a severe anomaly of gut movement, which in BALB/c mice produces a lethal paralytic ileus. Physiological analysis indicates that the mechanisms required for the autonomic pacing of contraction in an isolated gut segment are defective in the anti-c-kit mAb-treated mice, W/Wv mice and even W/+ mice. These findings suggest that c-kit plays a crucial role in the development of a component of the pacemaker system that is required for the generation of autonomic gut motility.     

Application of the tryptophanase promoter to high expression of the tryptophan synthase gene inEscherichia coli

Summary The application of an inducible regulation system using the trytophanase operon promoter (TPase promoter; P_tna) was examined for its high expression of the tryptophan synthase (TS) gene in Escherichia coli. The main problem in the application of P_tna for industrial purposes is catabolite repression by glucose, since glucose is the most abundant carbon source. However, this problem could be avoided by changing glucose to an organic acid, such as succinate, fumarate, malate and acetate, in the course of cultivation after glucose initially added was completely consumed. Under these conditions, l-tryptophan was also used to induce tryptophan synthase. Thus, the specific activity of TS in E. coli strain no. 168 harbouring pBR322F-P_tnaTS was increased 500-fold compared to that of the cultured host strain. About 1 mol l-tryptophan/l reaction mixture was formed from indole and l-serine at 37° C for 3.5 h. Offprint requests to: H. Yukawa     

The formation of myeloid bodies in retinular cells of the pupal compound eyes of silkworm moths (Bombyx mori) exposed to a constant bright light

Summary To study the three-dimensional structure of tight junction fibrils, the epithelia of the jejunum and epididymis of adult mice were examined by the freezefracture technique in unfixed and in aldehyde-fixed specimens. The fibrils have a stronger affinity for the protoplasmic (P) face of the lipid bilayer in fixed material, and for the external (E) face in unfixed and rapidly frozen material. Therefore we can observe the fibrils both from the outside and inside of the cell. Fibrils appearing on the P-face are smoothly contoured ridges and rows of hemispherical particles, while those appearing on the E-face are exclusively rows of hemispherical particles. Based on these observations, we wish to propose a new fibril model for the tight junction. There are two distinctive types of junctional elements. One type is composed of a smooth and continuous strand in the external view of the cell, but is studded with hemispherical bulgings in its internal view. This type will be referred to as the continuous type. The other type is bead-like, and will be referred to as the particle type. The relative proportion of these two types of elements appearing within a tight junction network differs among tissues.     

Antibiotic production by the marine photosynthetic bacterium Chromatium purpuratum NKPB 031704: localization of activity to the chromatophores

Abstract Over 200 strains of marine purple photosynthetic bacteria were isolated. Two strains showed antibiotic activity towards Saccharomyces cerevisiae and were tentatively identified as Chromatium purpuratum . Crude antibiotic, prepared by solvent extraction, showed a broad antimicrobial spectrum. The highest activity was found in the chromatophore fraction. Chromatographic separation of purified light harvesting complex from one strain, NKPB 031704, showed the presence of two separate pigmented compounds which were responsible for antimicrobial activity. Our findings reveal the unexpected ability of photosynthetic bacteria to produce broad spectrum antibiotics. In addition, this is the first example of intracellular localization of antibiotic activity in a marine bacterium.     

Structure of the mouse C-reactive protein gene

A genomic DNA clone corresponding to the mouse C-reactive protein (CRP) has been isolated and characterized. The mouse CRP gene is 1.9-kilobase pairs in length and contains a single intron of 213-base pairs which interrupts the codon for the 2nd amino acid residue of the mature CRP protein. We compared nucleotide sequences of the mouse and human CRP genes and discussed structures of possible regulatory sequences. With this characterization, the isolation and sequence analyses of a set of mouse and human pentraxin genes, i.e. CRP and serum amyloid P component genes is not complete.     

Ab initio molecular orbital study of the mispairing ability of a nucleotide base analogue, N4-aminocytosine

The intrinsic properties of N4-aminocytosine, a base analogue of cytosine, are analyzed by an ab initio molecular orbital method. Relative stabilities of four possible isomeric structures of N4-aminocytosine are shown. The more stable isomer has the smaller dipole moment, so the relative stabilities of the isomers in solutions are subject to solvent polarity. The mutagenicity of this base analogue must arise because it can behave like either cytosine or thymine. It can form a guanine-cytosine-like base pair more easily than cytosine, and an adenine-thymine-like base pair less easily than thymine.