Mutations in the UBIAD1 gene, encoding a potential prenyltransferase, are causal for Schnyder crystalline corneal dystrophy

Schnyder crystalline corneal dystrophy (SCCD, MIM 121800) is a rare autosomal dominant disease characterized by progressive opacification of the cornea resulting from the local accumulation of lipids, and associated in some cases with systemic dyslipidemia. Although previous studies of the genetics of SCCD have localized the defective gene to a 1.58 Mbp interval on chromosome 1p, exhaustive sequencing of positional candidate genes has thus far failed to reveal causal mutations. We have ascertained a large multigenerational family in Nova Scotia affected with SCCD in which we have confirmed linkage to the same general area of chromosome 1. Intensive fine mapping in our family revealed a 1.3 Mbp candidate interval overlapping that previously reported. Sequencing of genes in our interval led to the identification of five putative causal mutations in gene UBIAD1, in our family as well as in four other small families of various geographic origins. UBIAD1 encodes a potential prenyltransferase, and is reported to interact physically with apolipoprotein E. UBIAD1 may play a direct role in intracellular cholesterol biochemistry, or may prenylate other proteins regulating cholesterol transport and storage.     

Conjugative junctions in RP4-mediated mating of Escherichia coli

The physical association of bacteria during conjugation mediated by the IncPalpha plasmid RP4 was investigated. Escherichia coli mating aggregates prepared on semisolid medium were ultrarapidly frozen using copper block freezing, followed by freeze substitution, thin sectioning, and transmission electron microscopy. In matings where the donor bacteria contained conjugative plasmids, distinctive junctions were observed between the outer membranes of the aggregates of mating cells. An electron-dense layer linked the stiffly parallel outer membranes in the junction zone, but there were no cytoplasmic bridges nor apparent breaks in the cell walls or membranes. In control experiments where the donors lacked conjugative plasmids, junctions were not observed. Previous studies have shown that plasmid RP4 carries operons for both plasmid DNA processing (Tra1) and mating pair formation (Tra2). In matings where donor strains carried Tra2 only or Tra2 plus the pilin-processing protease TraF, junctions were found but they were shorter and more interrupted than the wild type. If the donor strain had the pilin gene knocked out (trbC), junctions were still found. Thus, it appears that the electron-dense layer between the outer membranes of the conjugating cells is not composed of pilin.     

Successful pollination of the Neotropical crop Solanum quitoense by Bombus terrestris: behaviour,efficiency and yield

The South American lulo (Solanum quitoense Lam.) is a crop plant of the Andes of Ecuador and Colombia, pollinated by South American bumblebees, such as, Bombus atratus Franklin. The cultivation of lulo outside of its native range, for example in European glasshouses, requires the presence of efficient pollinators to enable high fruit set and yield. Until now, the suitability of Bombus terrestris L., native to Europe and commonly used in agriculture, has been untested for this purpose. In this study, the pollen‐collecting behaviour of B. terrestris when visiting lulo flowers was investigated. It was shown that B. terrestris adopted the lulo as a pollen source, and on average visited three flowers per minute, had five buzzing events per stay and foraged for 15 s on a single flower, independently of the previous number of visits and level of bruising to the anthers. The pollination efficiency of five different treatments was evaluated: (i) exclusion of bees, (ii) single and (iii) multiple visits of B. terrestris, (iv) self‐ and (v) cross‐pollination by hand. The results clearly demonstrated that, for fruit set, pollination is crucial. It was also found that lulo flowers can be successfully self‐pollinated, but give 25% fewer fruit set compared with pollination via multiple bumblebee visits, or cross‐pollination by hand. Fruit set, seed set and fruit size were as high with pollination by B. terrestris as with cross‐pollination by hand, indicating that this bumblebee is an appropriate pollinator for lulo. However, B. terrestris was conspicuously less effective when a flower was visited only once. Therefore, when growing lulos commercially, multiple bumblebee visits should be encouraged, but it is likely that the behaviour of B. terrestris would ensure this anyway. Our results indicate that B. terrestris is a suitable and efficient pollinator for the production of lulo fruits.     

Multilocus phylogenetic structure within the Trichoderma harzianum/Hypocrea lixii complex

Trichoderma harzianum is a ubiquitous species in the environment and is effective in the biological control of plant-pathogenic fungi. T. harzianum has not been linked unequivocally to its sexual state nor has its phylogeny been studied in detail. It has been suggested that T. harzianum is a species complex based on the phenotypic and genotypic variability encountered. On the basis of morphological and cultural characters and DNA sequence data analysis of four genes (ITS rDNA, translation elongation factor 1-alpha, calmodulin, and alpha-actin), Hypocrea lixii was found to be the sexual state of T. harzianum. Both the asexual and sexual states of this species have wide geographic distributions. Phylogenetic analysis of four genes showed that T. harzianum/H. lixii is a cohesive group that is supported by bootstrap values higher than 95%. Principles of genealogical concordance indicated that T. harzianum/H. lixii is a complex of independent monophyletic lineages, but no diagnostic morphological distinctions were identified that justify formal taxonomic recognition for the different lineages.     

The structure of a cytochrome oxidase-lipid model membrane

The structure of “membranous cytochrome oxidase” has been investigated by X-ray diffraction, optical polarization spectroscopy and EPR spectroscopy. These studies indicate that the cytochrome oxidase molecules are oriented asymmetrically in the membrane profile with a significant portion of their mass occurring within the extravesicular surface of the membrane; the oxidase molecultes span the membrane profile; the distribution of the oxidase molecules over the plane of these membranes is non-crystalline; the oxidase molecules contain bundles of α-helical polypeptide chain segments where the average orientation of the helices is normal to the membrane plane; and the average heme orientation within the oxidase molecules is such that the normal to the heme plane lies in the plane of the membrane.     

MALDI-TOF MS of <Emphasis Type="Italic">Trichoderma</Emphasis>: a model system for the identification of microfungi

This investigation aimed to assess whether MALDI-TOF MS analysis of the proteome could be applied to the study of Trichoderma, a fungal genus selected because it includes many species and is phylogenetically well defined. We also investigated whether MALDI-TOF MS analysis of peptide mass fingerprints would reveal apomorphies that could be useful in diagnosing species in this genus. One hundred and twenty nine morphologically and genetically well-characterized strains of Hypocrea and Trichoderma, belonging to 25 species in 8 phylogenetic clades, were analyzed by MALDI-TOF MS mass spectrometry. The resulting peak lists of individual samples were submitted to single-linkage cluster analysis to produce a taxonomic tree and were compared to ITS and tef1 sequences from GenBank. SuperSpectra™ for the 13 most relevant species of Trichoderma were computed. The results confirmed roughly previously defined clades and sections. With the exceptions of T. saturnisporum (Longibrachiatum Clade) and T. harzianum (Harzianum Clade), strains of individual species clustered very closely. T. polysporum clustered distantly from all other groups. The MALDI-TOF MS analysis accurately reflected the phylogenetic classification reported in recent publications, and, in most cases, strains identified by DNA sequence analysis clustered together by MALDI-TOF MS. The resolution of MALDI-TOF MS, as performed here, was roughly equivalent to ITS rDNA. The MALDI-TOF MS technique analyzes peptides and represents a rough equivalent to sequencing, making this method a useful adjunct for determination of species limits. It also allows simple, reliable, and quick species identification, thus representing a valid alternative to gene sequencing for species diagnosis of Trichoderma and other fungal taxa.