Topological analysis of the fusion process between cellular and subcellular compartments

The study presents an application of the theory of homeomorphic transformations of topological manifolds and the operation of the connected sum of manifolds for topological analysis of membrane transformations during the fusion process between cellular and subcellular compartments. The biological cell and the subcellular structures in the form of vesicles are modelled by an arrangement of two concentric spheres corresponding to the inner and outer layer of the membrane bounding the vesicles. The analysis shows eight succeeding topological stages of membrane transformations during the fusion process and these stages are characterized. It is concluded that there is a vectorial translocation of lipid molecules from the outer layers of the membranes before the fusion process to the internal layer of the membrane bounding the vesicle after the fusion process and there is no lipid translocation in the reverse direction.     

A new Catasetum species (Catasetinae,Orchidaceae) from Goiás,Brazil

A new Catasetum species from Brazil,Catasetum confusum, is described and illustrated. This widely cultivated species had been referred previously toCatasetum ornithoides Pabst.     

Resistance to the cereal cyst nematode (Heterodera avenae Woll.) transferred from the wild grassAegilops ventricosa to hexaploid wheat by a “stepping-stone” procedure

Transfer of resistance toHeterodera avenae, the cereal cyst nematode (CCN), by a stepping-stone procedure from the wild grassAegilops ventricosa to hexaploid wheat has been demonstrated. The number of nematodes per plant was lower, and reached a plateau much earlier, in the resistant introgression line H93-8 (1–2 nematodes per plant) than in the recipient H10-15 wheat (14–16 nematodes per plant). Necrosis (hypersensitive reaction) near the nematode, little cell fusion, and few, often degraded syncytia were observed in infested H93-8 roots, while abundant, well-formed syncytia were present in the susceptible H10-15 wheat. Line H93-8 was highly resistant to the two Spanish populations tested, as well as the four French races (Fr1-Fr4), and the British pathotype Hall, but was susceptible to the Swedish pathotypes HgI and HgIII. Resistance was inherited as though determined by a single quasi-dominant factor in the F₂ generations resulting from crosses of H93-8 with H10-15 and with Loros, a resistant wheat carrying the geneCre1 (syn.Ccn1). The resistance gene in H93-8 (Cre2 orCcn2) is not allelic with respect to that in Loros. RFLPs and other markers, together with the cytogenetical evidence, indicate that theCre2 gene has been integrated into a wheat chromosome without affecting its meiotic pairing ability. Introduction ofCre2 by backcrossing into a commercial wheat backgroud increases grain yield when under challenge by the nematode and is not detrimental in the absence of infestation.     

Chromosomal localization of four human zinc finger cDNAs

cDNA clones encoding zinc finger motifs were isolated by screening human placenta and T-cell (Peer) cDNA libraries with zinc finger (ZNF) consensus sequences. Unique cDNA clones were mapped in the human genome by rodent-human somatic cell hybrid analysis and in some cases in situ chromosomal hybridization. ZNF 80 mapped to 3p12-3qter, ZNF 7 was previously mapped to 8q24 and is here shown by in situ hybridization and use of appropriate hybrids to map telomeric to the MYC locus. ZNF 79 mapped to 9q34 centromeric to the ABL gene and between a constitutional chromosomal translocation on the centromeric side and the CML specific ABL translocation on the telomeric side. ZNF77 mapped to 19p while ZNF 78L1 (pT3) mapped to 19q. Chromosome 19 carries many ZNF loci and other genes with zinc finger encoding motifs; the pT3 clone additionally detected a locus designated ZNF 78L2, which mapped to chromosome region 1p, most likely in the region 1p32 where the MYCL and JUN loci map.     

Ecosystem-level effects of re-oligotrophication and N:P imbalances in rivers and estuaries on a global scale

Trends and ecological consequences of phosphorus (P) decline and increasing nitrogen (N) to phosphorus (N:P) ratios in rivers and estuaries are reviewed and discussed. Results suggest that re-oligotrophication is a dominant trend in rivers and estuaries of high-income countries in the last two–three decades, while in low-income countries widespread eutrophication occurs. The decline in P is well documented in hundreds of rivers of United States and the European Union, but the biotic response of rivers and estuaries besides phytoplankton decline such as trends in phytoplankton composition, changes in primary production, ecosystem shifts, cascading effects, changes in ecosystem metabolism, etc., have not been sufficiently monitored and investigated, neither the effects of N:P imbalance. N:P imbalance has significant ecological effects that need to be further investigated. There is a growing number of cases in which phytoplankton biomass have been shown to decrease due to re-oligotrophication, but the potential regime shift from phytoplankton to macrophyte dominance described in shallow lakes has been documented only in a few rivers and estuaries yet. The main reasons why regime shifts are rarely described in rivers and estuaries are, from one hand the scarcity of data on macrophyte cover trends, and from the other hand physical factors such as peak flows or high turbidity that could prevent a general spread of submerged macrophytes as observed in shallow lakes. Moreover, re-oligotrophication effects on rivers may be different compared to lakes (e.g., lower dominance of macrophytes) or estuaries (e.g., limitation of primary production by N instead of P) or may be dependent on river/estuary type. We conclude that river and estuary re-oligotrophication effects are complex, diverse and still little known, and in some cases are equivalent to those described in shallow lakes, but the regime shift is more likely to occur in mid to high-order rivers and shallow estuaries.     

Towards an ethical and legal framework in archeogenomics: A local case in the Atlantic coast of central Patagonia

Ethical discussions around ancient DNA (aDNA) research predate the technological breakthroughs that led to the accelerated generation of ancient genomic data, revealing a long-due need to address these aspects in the field. Given the diverse conflicts that genomics has raised towards the communities associated with the Non-living Human Ancestors under study, it has been suggested that the ethical and legal implications of genetically studying present-day and ancient human populations should be considered case-by-case. Nevertheless, the discussions have focused on US and European perspectives. To contribute from a local and Latin American position to the problem, we present the history of consensus and disagreement of the relationships between scientists and Indigenous communities of the Atlantic coast of the central Argentinian Patagonia. We describe how these relationships resulted in the approval of a groundbreaking provincial law that acknowledges the Indigenous community's right to be involved in decision-making concerning their Ancestors. In addition, we emphasize how these established relationships allowed the development of aDNA studies. With this background, we address the main ethical concerns of genomic studies of Ancestors identified in the reference literature and commit to applying some of the recommendations suggested in those ethical guidelines. Then, we reflect on possible negative consequences of ongoing research and propose some suggestions based on personal experiences that will contribute to moving the ethical field towards a more contextualized science with a local perspective.     

In vivo species specificity of DNA polymerase α

The DNA polymerase a enzymes from human, and budding (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe) are homologous proteins involved in initiation and replication of chromosomal DNA. Sequence comparision of human DNA polymerase α with that of S. cerevisiae and S. pombe shows overall levels of amino acid sequence identity of 32% and 34%, respectively. We report here that, despite the sequence conservation among these three enzymes, functionally active human DNA polymerase a fails to rescue several different conditional lethal alleles of the budding yeast POL1 gene at nonpermissive temperature. Furthermore, human DNA polymerase α cannot complement a null allele of budding yeast POL1 either in germinating spores or in vegetatively growing cells. In fission yeast, functionally active human DNA polymerase α is also unable to complement the disrupted polα::ura4 ⁺ allele in germinating spores. Thus, in vivo, DNA polymerase α has stringent species specificity for initiation and replication of chromosomal DNA.