Three new HLA-G alleles and their linkage disequilibria with HLA-A

Three new allelic forms of the HLA-G DNA sequence (HLA-G*II, HLA-G*III, and HLA-G*IV) have been identified. With the HLA-G*I sequence (previously designated HLA 6.0) as a reference, HLA-G*II shows a silent (G A) mutation at the third base of codon 57, HLA-G*III bears a non-synonymous (A T), but conservative, (Thr Ser) substitution at the first base of codon 31, and HLA-G*IV shows two silent substitutions: (A T) at the third base of codon 107 and (G A) at the third base of codon 57. A rapid method of singling out each allele on genomic DNA has been developed by using polymerase chain reaction amplification followed by restriction endonuclease treatment. Also, more or less strong linkage disequilibria has been found between most HLA-A alleles and either HLA-G*I or *II, both being the most prevalent alleles in the population, with a genotypic frequency of 0.55 and 0.38, respectively; HLA-G*III is very rare and HLA-G*IV has a genotypic frequency of 0.07. An evolutive classification of HLA-A alleles results according to their association with either HLA-G*I or HLA-G*II, which does not correlate with the classical serological cross-reacting groups classification. The finding of a strong and selective A/G linkage disequilibria with most HLA-A alleles, together with the existence of less frequent random A/G associations, may suggest that there exist in different haplotypes true and varied A/G genetic distances (and not a recombinational hotspot). It may be inferred from preliminary data that in primates HLA-A/G haplotypes bearing G*II may have appeared later than those bearing G*I.The nucleotide sequence data reported in this paper have been submitted to the GenBank and EMBL nucleotide sequence databases and have been assigned the following accession numbers: EMBL-X60983 (HLA-G*II), GenBank-M99048 (HLA-G*III), and GenBank-L07784 (HLA-G*IV).The contribution to this paper by P. Morales and A. Corell is equal, and the order of authorship is arbitrary. Correspondence to: A. Arnaiz-Villena.     

Phenylacetaldehyde by acetic acid bacteria oxidation of 2-phenylethanol

Summary This paper reports the production of 2-phenylacetaldehyde from 2-phenylethanol by acetic bacteria. Several strains of acetic bacteria were investigated and three were found to be effective for this bioconversion. Different conditions (different C source for the microorganisms, pH, substrate concentration, cell immobilization) were tested with yields ranging from 30 to 52.6%.     

Diphyllobothriids (Cestoda: Pseudophyllidea) from the long-finned pilot whale Globicephala melas (Traill, 1809) off the Faroe Islands,with comments on the taxonomy of Diphyllobothrium Cobbold, 1858 species from cetaceans

The taxonomy of marine species of the genus Diphyllobothrium, particularly those parasitic in cetaceans, is rather confused. During parasitological investigations of long-finned pilot whales Globicephala melas from waters off the Faroe Islands, five diphyllobothriid species were detected: Diphyllobothrium sp. (possibly D. polyrugosum), D. stemmacephalum, Diphyllobothrium sp. A, Diphyllobothrium sp. B and Diphyllobothriidae sp. D. stemmacephalum is reported for the first time from G. melas. The stituation regarding the taxonomy of Diphylobothrium species from cetaceans is briefly reviewed. It is concluded that the recent development of genetic techniques may be of great value in relation to clarifying the taxonomy of this group.     

Plant regeneration from hypocotyl segments of Lupinus luteus cv. L. Aurea

Complete plants of Lupinus luteus L. cv. Aurea that were regenerated from hypocotyl segments, bloomed, produced seeds and were efficiently nodulated by Bradyrhizobium sp. strains. The highest rates of shoot formation were obtained on A medium plus 1.3% agar with 10.0 M 2-isopentenyladenine (2iP) and 0.11 M naphthaleneacetic acid (NAA); the best rooting was achieved on a medium with 0.5 M NAA plus 0.05 M 2iP. Afterward, plantlets were transferred to either perlite or peat-containing pots and irrigated with a N-free nutrient solution until maturity. Direct rooting of hypocotyls could also be obtained on A medium with 1% agar.     

Molecular chaperones and the biogenesis of mitochondria and peroxisomes

Summary— A review of the proteinaceous machinery involved in protein sorting pathways and protein folding and assembly in mitochondria and peroxisomes is presented. After considering the various sorting pathways and targeting signals of mitochondrial and peroxisomal proteins, we make a comparative dissection of the protein factors involved in: i) the stabilization of cytosolic precursor proteins in a translocation competent conformation; ii) the membrane import apparatus of mitochondria and peroxisomes; iii) the processing of mitochondrial precursor proteins, and the eventual processing of certain peroxisomal precursor, in the interior of the organelles; and iv) the requirement of molecular chaperones for appropriate folding and assembly of imported proteins in the matrix of both organelles. Those aspects of mitochondrial biogenesis that have developed rapidly during the last few years, such as the requirement of molecular chaperones, are stressed in order to stimulate further parallel investigations aimed to understand the origin, biochemistry, molecular biology and pathology of peroxisomes. In this regard, a brief review of findings from our group and others is presented in which the role of the F₁-ATPase α-subunit is pointed out as a molecular chaperone of mitochondria and chloroplasts. In addition, data are presented that could question our previous indication that the immunoreactive protein found in the rat liver peroxisomes is due to the presence of the F₁-ATPase α-subunit.     

Distribution of microtubules during the growth of tobacco pollen tubes

Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α-, β- and tyrosinated α-tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer-assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes.     

Biomass structure and dry matter dynamics of subtropical alluvial and exotic Ligustrum forests at the Río de la Plata,Argentina

Biomass, litterfall, litter standing crop, and decomposition was studied in a native subtropical alluvial forest locally known as Selva Marginal (SM) and an exotic Ligustrum lucidum forest (LF) at the Reserva Integral de Punta Lara, Buenos Aires Province, 34°47S and 58°1W. The alluvial forest site was at the southern limit of distribution of subtropical forests in South America. The Ligustrum forest was invading disturbed areas. Total biomass was 147.7 Mg/ha (86% aboveground and 14% belowground) in the SM, and 71.4 Mg/ha (93% and 7%, respectively) in the LF. Litterfall was 10.3 Mg/ha·yr and 13.8 Mg/ha·yr respectively. Annual leaf decomposition rate was greater for Ligustrum (k=4.07) than for SM species (k=1.48). The mean residence time of aboveground biomass was 12 yr for the SM and 5 yr for the LF. The k₁ values (litterfall/standing crop) were 1.9 and 2.0 for SM and LF respectively. The influence of coastal road and wall in the hydroperiod, native forested wetland ecosystem survival and exotic forest invasion is discussed.     

Thermostable β-Glycosidase from Sulfolobus Solfataricus

The Sulfolobus solfataricus β-glycosidase (Sβgly) is a thermostable and thermophilic glycosyl-hydrolase with broad substrate specificity. The enzyme hydrolizes β-D-gluco-, fuco-, and galactosides, and a large number of /Winked glycoside dimers and oligomers, linked β1-3, β1-4, and β1-6, It is able to hydrolize oligosaccharides with up to 5 glucose residues. Furthermore, it is also able to promote transglycosylation reactions. The corresponding gene has been cloned and overexpressed both in yeast and Escherichia coli. Based on sequence and functional data, the Sβgly has been assigned to the so-called BGA family of glycosyl-hydrolases, including β-glycosidases, β-galactosidases and phosho-β-galactosidases from mesophilic and thermophilic organisms of the three domains. The Sβgly has been crystallized and the resolution of its structure is in progress. Because of its special properties, the enzymes has considerable biotechnological potential.     

Characterization of the length polymorphism in the A+T-rich region of the Drosophila obscura group species

Summary In the twelve Drosophila obscura group species studied, belonging to the affinis, obscura, and pseudoobscura subgroups, the mitochondrial DNA length ranges from 15.8 to 17.2 kb. This length polymorphism is mainly due to insertions/deletions in the variable region of the A+T-rich region. In addition, one species (D. tristis) possess a tandem duplication of a 470-bp fragment that contains the replication origin.The same duplication has occurred at least twice in the Drosophila evolutionary history due to the fact that the repetition is analogous to repetitions found in the four species of the D. melanogaster complex.By comparing the nucleotide sequence of the conserved region in D. ambigua, D. obscura, D. yakuba, D. teissieri, and D. virilis, we show the presence of a secondary structure, likely implied in the replication origin, which could favor the generation of this kind of duplications.Finally, we propose that the high A and T content in the variable region of the A + T-rich region favors the formation of less-stable secondary structures, which could explain the generation of minor insertion/deletions found in this region.Offprint requests to: A. Latorre