Celebrity with a neglected taxonomy: molecular systematics of the medicinal leech (genus Hirudo)

The medicinal leech is the most famous representative of the Hirudinea. It is one of few invertebrates widely used in medicine and as a scientific model object. It has recently been given considerable conservation effort. Despite all attention there is confusion regarding the taxonomic status of different morphological forms, with many different species described in the past, but only two generally accepted at present. The results of the phylogenetic analysis of a nuclear (ITS2+5.8S rRNA) and two mitochondrial gene sequences (12S rRNA, COI) suggest that the genus Hirudo is monophyletic. It consists, apart form the type Hirudo medicinalis and the East Asian Hirudo nipponia, of three other, neglected species. All of them have already been described either as species or morphological variety, and can readily be identified by their coloration pattern. The type species is in weakly supported sister relation with Hirudo sp. n. (described as variety orientalis) from Transcaucasia and Iran. Sister to them stands Hirudo verbana from southeastern Europe and Turkey, which is nowadays predominantly bred in leech farms and used as 'medicinal leech.' The North African Hirudo troctina is the sister taxon to this group of Western Eurasian species, whereas the basal split is between H. nipponia and the Western Palaearctic clade.     

Paleogenomics or the search for remnant duplicated copies of the yeast DUP240 gene family in intergenic areas

Duplication, resulting in gene redundancy, is well known to be a driving force of evolutionary change. Gene families are therefore useful targets for approaching genome evolution. To address the gene death process, we examined the fate of the 10-member-large S288C DUP240 family in 15 Saccharomyces cerevisiae strains. Using an original three-step method of analysis reported here, both slightly and highly degenerate DUP240 copies, called pseudo-open reading frames (ORFs) and relics, respectively, were detected in strain S288C. It was concluded that two previously annotated ORFs correspond, in fact, to pseudo-ORFs and three additional relics were identified in intergenic areas. Comparative intraspecies analysis of these degenerate DUP240 loci revealed that the two pseudo-ORFs are present in a nondegenerate state in some other strains. This suggests that within a given gene family different loci are the target of the gene erasure process, which is therefore strain dependent. Besides, the variable positions observed indicate that the relic sequence may diverge faster than the flanking regions. All in all, this study shows that short conserved protein motifs provide a useful tool for detecting and accurately mapping degenerate gene remnants. The present results also highlight the strong contribution of comparative genomics for gene relic detection because the possibility of finding short conserved protein motifs in intergenic regions (IRs) largely depends on the choice of the most closely related paralog or ortholog. By mapping new genetic components in previously annotated IRs, our study constitutes a further refinement step in the crucial stage of genome annotation and provides a strategy for retracing ancient chromosomal reshaping events and, hence, for deciphering genome history.     

Telomere protection and TRF2 expression are enhanced by the canonical Wnt signalling pathway

The DNA‐binding protein TRF2 is essential for telomere protection and chromosome stability in mammals. We show here that TRF2 expression is activated by the Wnt/β‐catenin signalling pathway in human cancer and normal cells as well as in mouse intestinal tissues. Furthermore, β‐catenin binds to TRF2 gene regulatory regions that are functional in a luciferase transactivating assay. Reduced β‐catenin expression in cancer cells triggers a marked increase in telomere dysfunction, which can be reversed by TRF2 overexpression. We conclude that the Wnt/β‐catenin signalling pathway maintains a level of TRF2 critical for telomere protection. This is expected to have an important role during development, adult stem cell function and oncogenesis.     

Within‐generation consequences of postsettlement mortality for trait composition in wild populations: An experimental test

There is a critical need to understand patterns and causes of intraspecific variation in physiological performance in order to predict the distribution and dynamics of wild populations under natural and human‐induced environmental change. However, the usual explanation for trait differences, local adaptation, fails to account for the small‐scale phenotypic and genetic divergence observed in fishes and other species with dispersive early life stages. We tested the hypothesis that local‐scale variation in the strength of selective mortality in early life mediates the trait composition in later life stages. Through in situ experiments, we manipulated exposure to predators in the coral reef damselfish Dascyllus aruanus and examined consequences for subsequent growth performance under common garden conditions. Groups of 20 recently settled D. aruanus were outplanted to experimental coral colonies in Moorea lagoon and either exposed to natural predation mortality (52% mortality in three days) or protected from predators with cages for three days. After postsettlement mortality, predator‐exposed groups were shorter than predator‐protected ones, while groups with lower survival were in better condition, suggesting that predators removed the longer, thinner individuals. Growth of both treatment groups was subsequently compared under common conditions. We did not detect consequences of predator exposure for subsequent growth performance: Growth over the following 37 days was not affected by the prior predator treatment or survival. Genotyping at 10 microsatellite loci did indicate, however, that predator exposure significantly influenced the genetic composition of groups. We conclude that postsettlement mortality did not have carryover effects on the subsequent growth performance of cohorts in this instance, despite evidence for directional selection during the initial mortality phase.     

Synthesis and evaluation of the quorum sensing inhibitory effect of substituted triazolyldihydrofuranones

Acylhomoserine lactone (AHL) analogues in which the amide function is replaced by a triazole group were synthesized and evaluated for their effect on quorum sensing (QS) and biofilm formation in Burkholderia cenocepacia and Pseudomonas aeruginosa. In addition, the influence of the length of the acyl-mimicking chain was investigated. The compounds showed selectivity between two different AHL QS systems. 3-(1H-1,2,3-Triazol-1-yl)dihydrofuran-2(3H)-ones, in which the 4-substituent best resembled the acyl chain of the native AHL molecule exhibited significant QS agonistic and antagonistic activities. Replacing this aliphatic substituent by a phenyl-containing moiety resulted in active inhibitors of QS. The most active compounds showed biofilm inhibitory as well as biofilm eradicating activities in both test organisms.     

Biodegradation of gasoline and BTEX in a microaerophilic biobarrier

Continuous bioremediation of gasoline-contaminatedwater in a packed-bed biobarrier system underoxygen-limited conditions is discussed. This studywas part of an extensive effort to develop analternative technology for the in situbioremediation of hydrocarbons where there is alimited supply of oxygen. Protruded stainless steelpieces and granulated peat moss were used as packingmaterial to support microbial growth in twobiobarriers. The inoculum was an enrichment culture ofan indigenous microbial population from a soil sample.The biobarriers' inlet gasoline concentrations and thelinear liquid velocities were similar to thosecommonly found at in situ conditions. Gasolineremoval efficiencies ranged from 94% to 99.9% in thestainless steel-packed biobarrier, and from 86.6% to99.6% in the peat moss-packed biobarrier. Effluentgasoline concentrations below 0.03 mg/l were obtainedat gasoline loading rates less than 27.5 mg/l.d in thestainless steel-packed biobarrier. The remainingfraction of gasoline in the effluent consisted mainlyof three aliphatic compounds and not the aromaticcompounds. Both biobarrier packings supported nearcomplete removal of the most soluble aromatichydrocarbons of gasoline (BTEX) under all theconditions examined. The consumption of sulfate andthe presence of sulfate-reducing microorganismssuggested the presence of anaerobic metabolism duringthe degradation of gasoline. Up to 92% gasoline wasremoved during the first 3 cm of the biobarriers'length.     

Angiotensin II induces tyrosine nitration and activation of ERK1/2 in vascular smooth muscle cells

Angiotensin II (Ang II) induces a prominent and sustained nitration and activation of ERK1/2 in rat vascular smooth muscle cells, both mediated via AT1 receptor. Nitration and activation was also shown for recombinant non-activated extracellular signal-regulated kinase (ERK) and MEK. Nitration and phosphorylation of ERK1/2 by Ang II was significantly inhibited by NAD(P)H inhibitors and scavengers of oxygen and nitrogen reactive species and completely blocked by a selective inducible nitric-oxide synthase inhibitor. MEK inhibitor U0126 did not affect ERK nitration but completely blocked activation. These data indicate that Ang II nitrates and activates ERK1/2 via a reactive species-sensitive pathway.     

A Genetic Analysis of Mancozeb Resistance in Typhlodromus Pyri (Acari: Phytoseiidae)

A field population of Typhlodromus pyri (Acari: Phytoseiidae) tolerant to mancozeb was selected in the laboratory. After 10 mancozeb selections the LC₅₀ value for mancozeb was 73 times higher in the selected-10 strain compared to the standard susceptible strain. A genetic analysis using reciprocal crosses and backcrosses of female F₁ progeny found no maternal effect. Resistance in the selected-10 strain was codominant in expression, dominance value was about −0.1. Backcrosses between F₁ females and the susceptible strain indicate that the resistance to mancozeb could be principally conferred by a predominant gene, but additional factors would also be involved.