Quasispecies in retrotransposons: a role for sequence variability in Tnt1 evolution

Retroviral replication is a very error-prone process. Replication of retroviruses gives rise to populations of closely related but different genomes referred to as ‘quasispecies’. This huge swarm of different sequences constitutes a reservoir of potentially useful genomes in case of an environmental change, endowing retroviruses with extreme adaptability. Retrotransposons are mobile genetic elements closely related to retroviruses, and retrotransposition is as error prone as retroviral replication. The Tnt1 retrotransposon is present in hundreds of copies in the genome of tobacco that show a high level of sequence heterogeneity. When Tnt1 is expressed, its RNA is not a single sequence but a population of sequences displaying a quasispecies-like structure. This population structure gives to Tnt1, as in the case of retroviruses, a high sequence plasticity and an adaptive capacity. We propose this adaptivity as the major reason for Tnt1 maintenance in Nicotiana genomes and we discuss in this paper the importance of sequence variability for Tnt1 evolution. This revised version was published online in August 2006 with corrections to the Cover Date.     

Over-expression of Saccharomyces cerevisiae hsp90 enhances the virulence of this yeast in mice

Abstract Saccharomyces cerevisiae , a yeast of low pathogenic potential, is a rare but well-documented cause of invasive infections in humans. The yeast Candida albicans is a much commoner cause of significant and life-threatening infections. In such infections the heat shock protein hsp90 is an immunodominant antigen associated with protective humoral immunity. In this study it was shown that over-expression of S. cerevisiae hsp90, the amino acid sequence of which shows 84% identity to C. albicans hsp90, significantly increased the virulence of a laboratory strain of S. cerevisiae in mice, both in terms of colony counts in the kidney, liver and spleen, and in terms of mortality. This is the first direct evidence that hsp90 is a virulence factor.     

Analysis of fae and fhcD Genes in Mono Lake, California

Genes for two enzymes of the tetrahydromethanopterin-linked C₁ transfer pathway (fae and fhcD) were detected in hypersaline, hyperalkaline Mono Lake (California), via PCR amplification and analysis. Low diversity for fae and fhcD was noted, in contrast to the diversity previously detected in a freshwater lake, Lake Washington (Washington).     

Molecular Probe Data Base (MPDB).

In this paper, the current status of the Molecular Probe Data Base (http://www.biotech.ist.unige.it/interlab/ mpdb.html ) is briefly presented together with a short analysis of its activity during 1997. This has been performed by statistically evaluating the 'logs' of the Internet servers that are used for its distribution with reference to the geographical origin of the requests, the words that were utilized to carry out of the searches and the oligonucleotides that were retrieved. Planned enhancements of this database are also described. They include a revision of its data structure and, even more relevant, of its data management procedures.     

Molecular genetic analysis of theripening-inhibitor andnon-ripening loci of tomato: A first step in genetic map-based cloning of fruit ripening genes

Ripening represents a complex developmental process unique to plants. We are using tomato fruit ripening mutants as tools to understand the regulatory components that control and coordinate the physiological and biochemical changes which collectively confer the ripe phenotype. We have genetically characterized two loci which result in significant inhibition of the ripening process in tomato,ripening-inhibitor (rin), andnon-ripening (nor), as a first step toward isolating genes likely to encode key regulators of this developmental process. A combination of pooled-sample mapping as well as classical restriction fragment length polymorphism (RFLP) analysis has permitted the construction of high-density genetic maps for the regions of chromosomes 5 and 10 spanning therin andnor loci, respectively. To assess the feasibility of initiating a chromosome walk, physical mapping of high molecular weight genomic DNA has been employed to estimate the relationship between physical distance (in kb) and genetic distance (in cM) around the targeted loci. Based on this analysis, the relationship in the region spanning therin locus is estimated to be 200–300 kb/cM, while thenor locus region ratio is approximately 200 kb/1 cM. Using RFLP markers tightly linked torin andnor, chromosome walks have been initiated to both loci in a yeast artificial chromosome (YAC) library of tomato genomic DNA. We have isolated and characterized several YAC clones linked to each of the targeted ripening loci and present genetic evidence that at least one YAC clone contains thenot locus.     

FTY720/Fingolimod Reduces Synucleinopathy and Improves Gut Motility in A53T Mice: CONTRIBUTIONS OF PRO-BRAIN-DERIVED NEUROTROPHIC FACTOR (PRO-BDNF) AND MATURE BDNF*

Patients with Parkinson''s disease (PD) often have aggregated α-synuclein (aSyn) in enteric nervous system (ENS) neurons, which may be associated with the development of constipation. This occurs well before the onset of classic PD motor symptoms. We previously found that aging A53T transgenic (Tg) mice closely model PD-like ENS aSyn pathology, making them appropriate for testing potential PD therapies. Here we show that Tg mice overexpressing mutant human aSyn develop ENS pathology by 4 months. We then evaluated the responses of Tg mice and their WT littermates to the Food and Drug Administration-approved drug FTY720 (fingolimod, Gilenya) or vehicle control solution from 5 months of age. Long term oral FTY720 in Tg mice reduced ENS aSyn aggregation and constipation, enhanced gut motility, and increased levels of brain-derived neurotrophic factor (BDNF) but produced no significant change in WT littermates. A role for BDNF was directly assessed in a cohort of young A53T mice given vehicle, FTY720, the Trk-B receptor inhibitor ANA-12, or FTY720 + ANA-12 from 1 to 4 months of age. ANA-12-treated Tg mice developed more gut aSyn aggregation as well as constipation, whereas FTY720-treated Tg mice had reduced aSyn aggregation and less constipation, occurring in part by increasing both pro-BDNF and mature BDNF levels. The data from young and old Tg mice revealed FTY720-associated neuroprotection and reduced aSyn pathology, suggesting that FTY720 may also benefit PD patients and others with synucleinopathy. Another finding was a loss of tyrosine hydroxylase immunoreactivity in gut neurons with aggregated aSyn, comparable with our prior findings in the CNS.