The ability to bind albumin is correlated with nitric oxide sensitivity in Moraxella catarrhalis

Moraxella catarrhalis is sensitive to NO generators e.g. S -nitroso- N -acetylpenicillamine (SNAP) and sodium nitroprusside (SNP), but can spontaneously develop higher SNP tolerance. Using SDS-PAGE of outer membrane proteins and immunoblotting for serum albumin, we found that the wild strain bound more blood-medium-derived albumin than the SNP-resistant variant did. There was a negative correlation between NO tolerance and the presence of serum albumin in the medium. We suggest that M. catarrhalis can change its surface properties to avoid binding albumin and thereby increase its resistance to NO. Growth of Moraxella is affected by iron, and that may have influenced our results. Using chrome azurol S plates as an indicator, we noted that both albumin and SNP have a strong affinity for iron(III).     

Physical mapping of rDNA loci in Brassica species.

The number of major rDNA loci (the genes coding for 18S-5.8S-26S rRNA) was investigated in the economically important Brassica species and their wild relatives by in situ hybridization of an rDNA probe to metaphase chromosomes and interphase nuclei. The diploid species B. nigra (B genome) has two major pairs of rDNA loci, B. oleracea (C genome) has two major pairs and one minor pair of loci, while B. campestris (A genome) has five pairs of loci. Among the three tetraploid species arising from these three diploid ancestors, B. carinata (BBCC genomes) has four loci, B. juncea (AABB genomes) has five major pairs and one minor pair of loci, and B. napus (AACC genomes) has six pairs of loci, indicating that the number of loci has been reduced during evolution. The complexity of the known rDNA restriction fragment length polymorphism patterns gave little indication of number of rDNA loci. It is probable that chromosome rearrangements have occurred during evolution of the amphidiploid species. The data will be useful for physical mapping of genes relative to rDNA loci, micro- and macro-evolutionary studies and analysis of aneuploids including addition and substitution lines used in Brassica breeding programs.     

Localization of tandemly repeated DMA sequences in Arabidopsis thaliana

In-situ hybridization to interphase nuclei and chromosomes of Arabidopsis thaliana (2n= 10) shows that there are four sites of rDNA in a diploid nucleus. The sites are located on chromosomes 2 and 4, and the strength of hybridization indicates that copy number is similar at both pairs of sites. Hybridization to trisomic line 4 revealed five hybridization sites. Silver staining of nucleoli demonstrates that all four loci can be active in diploid interphase nuclei. The tandemly repeated probe pAL1 hybridizes near to the centromeres of all five chromosome pairs. In diploid interphase nuclei, 10 sites of hybridization are detected, while 15 are seen in triploid nuclei. The sites of hybridization co-localize with the centromeric heterochromatin visualized by staining DNA with the fluorochrome DAPI. The results demonstrate that molecular cytogenetics can be applied to A. thaliana and high resolution physical chromosome maps can be generated. Both probes may be useful for interphase cytogenetics, where they enable chromosome number and aneuploidy to be examined in tissues without divisions. The physical localization of these hybridization sites provides a starting point for linking RFLP and physical chromosome maps.     

Cytological events in explants of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> during early callogenesis

Leaf explants of diploid (2n = 2x = 10) and autotetraploid (2n = 4x = 20) plants of Arabidopsis thaliana ecotype Columbia were cytologically and cytogenetically analysed to determine the time and the mechanisms of the process of polyploidization. The first polyploid cells were observed after the third day of culture in both genotypes of explants. Polyploid cells were the result of pre-existing mixoploidy in explants of A. thaliana. Other factors such as endoreduplication, endomitosis, abnormal microtubules arrangement and DNA damage may have induced polyploidization during early stages of callogenesis.     

The crystal structure of 2-deoxy-β-d-arabino-hexopyranose at −150°

2-Deoxy-β-d-arabino-hexopyranose, C₆H₁₂O₅, is orthorhombic, P2₁2₁2₁, with cell dimensions at ?150° [20°], a = 6.484(2) [6.510(3)], b = 10.364(2) [10.427(4)], c = 11.134(3) [11.153(5)] Å, V = 748.2 [757.1] ų, Z = 4, D_x = 1.457 [1.440], and D_m = [1.455] g.cm^?3. The intensities of 1269 reflections were measured by using MoKα radiation. The structure was solved by direct methods, and refined by full-matrix least-squares, with anisotropic, thermal parameters for the carbon and oxygen atoms, and isotropic parameters for the hydrogen atoms. The pyranose has the ⁴C₁(d) conformation, with puckering parameters Q = 0.563 Å, θ = 3.9°, and ? = 350.3°. The departure from ideality is very small, and less than that in β-d-glucopyranose, Q = 0.584 Å and θ = 6.9°. The β-glycosidic, CO bond is short, 1.383(4) Å, and the OCOH torsion angle is ?87°, consistent with the anomeric effect. The hydrogen-bonding scheme consists of infinite chains, with side chains terminating at a ring-oxygen atom.     

Chromosomal localization of a novel repetitive sequence in theChenopodium quinoa genome

In this study, a novel repetitive sequence pTaq10 was isolated from theTaq I digest of the genomic DNA of the pseudocerealChenopodium quinoa. Sequence analysis indicated that this 286-bp monomer is not homologous to any known retroelement sequence. FISH and Southern blot analysis showed that this sequence is characterized by an interspersed genomic organization. After FISH, hybridization signals were observed as small dots spread throughout all of the chromosomes. pTaq hybridization signals were excluded from 45S rRNA gene loci, but they partly overlapped with 5S rDNA loci. pTaq10 is not a species-specific sequence, as it was also detected inC. berlandieri.