Identification and Crystallization of a Protease-Resistant Core of Calnexin That Retains Biological Activity

Calnexin is a molecular chaperone that facilitates folding of glycoproteins in the endoplasmic reticulum (ER). The cloned lumenal domain of canine calnexin, cnxΔTMC, retains its biological activity without the transmembrane and cytosolic region. For the purpose of structure determination we generated a crystallizable core by mild proteolysis and identified its termini by N-terminal sequencing and molecular mass determination. A truncated gene was cloned accordingly. Its product, cnxΔN25C15, was purified to apparent homogeneity and crystallized. This truncated variant remains biologically active as shown by its binding to monoglucosylated oligosaccharides and functional interaction with ERp57. A heavy atom derivative was identified.     

Diversity of β-Globin Mutations in Israeli Ethnic Groups Reflects Recent Historic Events

We characterized nearly 500 β-thalassemia genes from the Israeli population representing a variety of ethnic subgroups. We found 28 different mutations in the β-globin gene, including three mutations (β^S, β^C, and β^O-Arab) causing hemoglobinopathies. Marked genetic heterogeneity was observed in both the Arab (20 mutations) and Jewish (17 mutations) populations. On the other hand, two ethnic isolates—Druze and Samaritans—had a single mutation each. Fifteen of the β-thalassemia alleles are Mediterranean in type, 5 originated in Kurdistan, 2 are of Indian origin, and 2 sporadic alleles came from Europe. Only one mutant allele—nonsense codon 37—appears to be indigenous to Israel. While human habitation in Israel dates back to early prehistory, the present-day spectrum of β-globin mutations can be largely explained by migration events that occurred in the past millennium.     

Isolation, fractionation and some properties of polysaccharides produced in a bound form by Azospirillum brasilense and their possible involvement in Azospirillum-wheat root interactions

Abstract It was shown that Azospirillum brasilense strains Sp7, Sp107, Sp245, and S17 when cultivated in a liquid synthetic malate medium to the end of the exponential phase of growth, produced at least two complex polysaccharide-containing components. The components were arbitrarily called lipopolysaccharide-protein complex and polysaccharide-lipid complex. These complexes were shown to interact with a wheat germ agglutinin. From polysaccharide-lipid complexes, acidic polysaccharides were isolated and their specific rotation, molecular masses, affinity for wheat germ agglutinin, and monosaccharide composition were determined. The polysaccharides of all strains contained rhamnose, galacturonic acid, and glucosamine, while the polysaccharides of strains Sp7 and S17 included additional fucose and mannose, respectively, and both had galactose. It is suggested that lipopolysaccharide-protein complexes, polysaccharide-lipid complexes, and polysaccharides may be involved in the process of interaction of azospirilla with wheat root surfaces.     

Identification,characterisation and clinical applications of cosmids from the telomeric and centromeric regions of the long arm of chromosome 22

Using human telomeric repeats and centromeric alpha repeats, we have identified adjacent single copy cosmid clones from human chromosome 22 cosmid libraries. These single copy cosmids were mapped to chromosome 22 by fluorescence in situ hybridisation (FISH). Based on these cosmids, we established contigs that included part of the telomeric and subtelomeric regions, and part of the centromeric and pericentromeric regions of the long arm of human chromosome 22. Each of the two cosmid contigs consisted of five consecutive steps and spanned approximately 100–150 kb at both extreme ends of 22q. Moreover, highly informative polymorphic markers were identified in the telomeric region. Our results suggest that the telomere specific repeat (TTAGGG) _n encompasses a region that is larger than 40 kb. The cosmid contigs and restriction fragment length polymorphism markers described here are useful tools for physical and genetic mapping of chromosome 22, and constitute the basis of further studies of the structure of the subtelomeric and pericentromeric regions of 22q. We also demonstrate the use of these clones in clinical diagnosis of different chromosome 22 aberrations by FISH.     

Alarmone (p)ppGpp regulates the transition from pathogenicity to mutualism in Photorhabdus luminescens

The enteric gamma‐proteobacterium Photorhabdus luminescens kills a wide range of insects, whilst also maintaining a mutualistic relationship with soil nematodes from the family Heterorhabditis. Pathogenicity is associated with bacterial exponential growth, whilst mutualism is associated with post‐exponential (stationary) phase. During post‐exponential growth, P. luminescens also elaborates an extensive secondary metabolism, including production of bioluminescence, antibiotics and pigment. However, the regulatory network that controls the expression of this secondary metabolism is not well understood. The stringent response is a well‐described global regulatory system in bacteria and mediated by the alarmone (p)ppGpp. In this study, we disrupted the genes relA and spoT, encoding the two predicted (p)ppGpp synthases of P. luminescens TTO1, and we showed that (p)ppGpp is required for secondary metabolism. Moreover, we found the (p)ppGpp is not required for pathogenicity of P. luminescens, but is required for bacterial survival within the insect cadaver. Finally, we showed that (p)ppGpp is required for P. luminescens to support normal nematode growth and development. Therefore, the regulatory network that controls the transition from pathogenicity to mutualism in P. luminescens requires (p)ppGpp. This is the first report outlining a role for (p)ppGpp in controlling the outcome of an interaction between a bacteria and its host.     

Trophic structure of shallow-water benthic communities in the sub-Antarctic Strait of Magellan

Trophic structure is among the most fundamental characteristics of an ecosystem since it is a useful way to determine the main energy flow at the ecosystem level. In the Magellan Strait, the local spatial heterogeneity at the shallow-waters ecosystems may have a great variety of potential food sources; however, knowledge about their biological communities and their structure is still unclear. We examined the trophic structure of shallow-water-mixed bottom communities at two sites in the sub-Antarctic Magellan Strait based on carbon (δ ¹³C) and nitrogen (δ ¹⁵N) stable isotope ratios. The benthic communities were composed of 46 species from 20 major taxa at Bahía Laredo (BL) and 55 species from 18 major taxa at Punta Santa Ana (PSA). Benthic macroalgae and organic matter associated with sediment are the major primary food sources at both sites. Although both sites are quite similar in their food sources and in their vertical trophic structure (≥three trophic levels), the food web structure varied distinctly. Functionally, predators and grazers dominated both communities, but top predators were shorebirds, carnivore anemones and predatory nemerteans at BL, and sea stars, shorebirds, crabs and fishes at PSA. The distinct differences in the trophic structure at BL and PSA highlight the important variability of δ ¹⁵N at the base of the benthic food web, the role of local environmental conditions and community dynamics in structuring shallow-water communities.

     

Aspects of reproductive biology of wild-caught polar cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) from Svalbard waters

Polar cod (Boreogadus saida) is considered a key species in the Arctic marine ecosystems. Yet detailed or even basic knowledge regarding its biology and adaptations, especially during the polar night, is in many cases poor. Data are presently unavailable in Western literature on the gonad development of polar cod and its reproductive biology in wild specimens. Accordingly, gonad development of wild-caught polar cod from fjords of the Svalbard archipelago was studied across seasons (April, August, September, November and January). Histological analyses of polar cod showed strong indication of a group-synchronous oocyte development with determinate fecundity and iteroparity. Females started gonadal development prior to April and had not yet reached the final stage of maturation in January. Testes matured more rapidly, with males ready to spawn in January. Furthermore, our data show that polar cod were able to reach sexual maturity at age 1+. Based on our data and previous reports, we hypothesise that polar cod is a total spawner.     

New insights into the history of domesticated and wild apricots and its contribution to Plum pox virus resistance

Studying domesticated species and their wild relatives allows understanding of the mechanisms of population divergence and adaptation, and identifying valuable genetic resources. Apricot is an important fruit in the Northern hemisphere, where it is threatened by the Plum pox virus (PPV), causing the sharka disease. The histories of apricot domestication and of its resistance to sharka are however still poorly understood. We used 18 microsatellite markers to genotype a collection of 230 wild trees from Central Asia and 142 cultivated apricots as representatives of the worldwide cultivated apricot germplasm; we also performed experimental PPV inoculation tests. The genetic markers revealed highest levels of diversity in Central Asian and Chinese wild and cultivated apricots, confirming an origin in this region. In cultivated apricots, Chinese accessions were differentiated from more Western accessions, while cultivated apricots were differentiated from wild apricots. An approximate Bayesian approach indicated that apricots likely underwent two independent domestication events, with bottlenecks, from the same wild population. Central Asian native apricots exhibited genetic subdivision and high frequency of resistance to sharka. Altogether, our results contribute to the understanding of the domestication history of cultivated apricot and point to valuable genetic diversity in the extant genetic resources of wild apricots.