Researching little-known species: the African bat Otomops martiensseni (Chiroptera: Molossidae)

Listed as 'vulnerable' by the International Union for theConservation of Nature, the molossid bat Otomopsmartiensseni occurs widely in Africa and, according to someauthorities, in Madagascar. Apart from a few known cave roosts, there are fewrecords of O. martiensseni, although around Durban, SouthAfrica, the species is common and roosts in buildings. Originally described asthree species, populations of O. martiensseni differsignificantly in size (length of forearm) between East Africa and Durban orMadagascar, but not between Durban and Madagascar. Seventeen buildings used asroosts by O. martiensseni averaged 34.5 ± 15.8years old. In the Durban area, bats entered roosts by landing andcrawling. Roost populations ranged from 7 to 29 individuals, typicallyconsisting of one adult male, several adult females and young (bats withunossified epiphyses), suggesting a harem social structure. The ratio of adultfemales to young was virtually 1:1, and among young the ratio of males:femalesaveraged 2:1. Radio-tracking showed that individuals used several day and nightroosts, and foraged widely in a landscape dominated by sugarcane and urbandevelopment. The echolocation and many social calls of O.martiensseni are readily audible to human observers, allowing anon-contact, low technology method for monitoring the local distribution andactivity of these bats. Although listed as a species of special concern inKwaZulu Natal, there these bats appear to be candidates for inclusion on a'blue' list of species, ones showing stabilized or increasedabundance. We recommend that O. martiensseni be recognizedas a 'flagship' species in the Durban area, r epresenting theresilience of nature.     

Recombining overlapping BACs into a single larger BAC

Background  

BAC clones containing entire mammalian genes including all the transcribed region and long range controlling elements are very useful for functional analysis. Sequenced BACs are available for most of the human and mouse genomes and in many cases these contain intact genes. However, large genes often span more than one BAC, and single BACs covering the entire region of interest are not available. Here we describe a system for linking two or more overlapping BACs into a single clone by homologous recombination.     

Some physiological comparisons between the resurrection grass, Eragrostis nindensis, and the related desiccation-sensitive species, E. curvula

Both the poikilochlorophyllous resurrection grass, Eragrostisnindensis, and the desiccation sensitive species, E.curvula, dehydrate to a relative water content (RWC) of less than5% in two weeks. On rewatering, most E. nindensisleaves (except the older, outer ones) rehydrate and resume normal metabolicactivity within a few days, whereas E. curvula does notrecover. There is a controlled loss of photosynthetic pigments, paralleled witha gradual shutdown in gas exchange during dehydration of E.nindensis. On rehydration respiration resumes almost immediately butphotosynthesis only restarts at 70% RWC by which time chlorophyll hasbeen resynthesised and anthocyanin content reduced. In contrast, photosyntheticactivity in E. curvula is maintained down to 40%RWC, after which further drying results in a sudden breakdown of thephotosynthetic system and its pigments. At this point, electrolyte leakage andincreases F_V/F_M decreases such that belowca. 40% RWC, metabolism is irreparably damaged.Interestingly, the older outer leaf in most tillers of E.nindensis does not rehydrate. These leaves show signs of membranedamage and curl in an irregular manner similar to those of E.curvula during dehydration.     

Human endothelial cells cultured on microporous filters used for leukocyte transmigration studies form monolayers on both sides of the filter

Summary A growing number of studies on the mechanism of leukocyte transendothelial migration use endothelial cells grown on microporous filters as an in vitro model of endothelium. Ultrastructural examination of such a model system previously demonstrated that human pulmonary artery endothelial cells (HPAEC) formed confluent monolayers on both sides of the 3-μm-pore filter (Mackarel et al., 1999). To determine whether this was a characteristic specific to pulmonary artery endothelial cells, the growth characteristics of a human pulmonary microvascular endothelial cell type (HMVEC-L) and the widely used human umbilical vein endothelial cells (HUVEC) on 3-μm microporous filters were examined by transmission electron microscopy (TEM). Similar to HPAEC, HMVEC-L and HUVEC were also found to grow on both sides of the filter. All three endothelial cell types were capable of migrating through the 3 μm pores of the filter to form a monolayer on the filter underside. The endothelial cells on the underside were orientated in an inverted position with the luminal surface facing away from the filter. Such ‘bilayer’ formation was observed at a range of seeding densities and in different culture media. Despite the presence of a bilayer of endothelial cells, TEM demonstrated that neutrophils migrated successfully across the cell-filter-cell system. Previous transmigration reports in which an in vitro model similar to ours was used have often assumed only one layer of endothelial cells. The observations reported here indicate that while endothelial cells on microporous filters are useful models for examining leukocyte-endothelial interactions, they are not appropriate for studies examining endothelial cell ‘sidedness.’     

An integrated approach reveals how lipo‐chitooligosaccharides interact with the lysin motif receptor‐like kinase MtLYR3

N‐acetylglucosamine containing compounds acting as pathogenic or symbiotic signals are perceived by plant‐specific Lysin Motif Receptor‐Like Kinases (LysM‐RLKs). The molecular mechanisms of this perception are not fully understood, notably those of lipo‐chitooligosaccharides (LCOs) produced during root endosymbioses with nitrogen‐fixing bacteria or arbuscular mycorrhizal fungi. In Medicago truncatula, we previously identified the LysM‐RLK LYR3 (MtLYR3) as a specific LCO‐binding protein. We also showed that the absence of LCO binding to LYR3 of the non‐mycorrhizal Lupinus angustifolius, (LanLYR3), was related to LysM3, which differs from that of MtLYR3 by several amino acids and, particularly, by a critical tyrosine residue absent in LanLYR3. Here, we aimed to define the LCO binding site of MtLYR3 by using molecular modelling and simulation approaches, combined with site‐directed mutagenesis and LCO binding experiments. 3D models of MtLYR3 and LanLYR3 ectodomains were built, and homology modelling and molecular dynamics (MD) simulations were performed. Molecular docking and MD simulation on the LysM3 identified potential key residues for LCO binding. We highlighted by steered MD simulations that in addition to the critical tyrosine, two other residues were important for LCO binding in MtLYR3. Substitution of these residues in LanLYR3‐LysM3 by those of MtLYR3‐LysM3 allowed the recovery of high‐affinity LCO binding in experimental radioligand‐binding assays. An analysis of selective constraints revealed that the critical tyrosine has experienced positive selection pressure and is absent in some LYR3 proteins. These findings now pave the way to uncover the functional significance of this specific evolutionary pattern.     

Lineage diversity within a widespread endemic Australian skink to better inform conservation in response to regional‐scale disturbance

Much attention is paid in conservation planning to the concept of a species, to ensure comparability across studies and regions when classifying taxa against criteria of endangerment and setting priorities for action. However, various jurisdictions now allow taxonomic ranks below the level of species and nontaxonomic intraspecific divisions to be factored into conservation planning—subspecies, key populations, evolutionarily significant units, or designatable units. Understanding patterns of genetic diversity and its distribution across the landscape is a key component in the identification of species boundaries and determination of substantial geographic structure within species. A total of 12,532 reliable polymorphic SNP loci were generated from 63 populations (286 individuals) covering the distribution of the Australian eastern three‐lined skink, Bassiana duperreyi, to assess genetic population structure in the form of diagnosable lineages and their distribution across the landscape, with particular reference to the recent catastrophic bushfires of eastern Australia. Five well‐supported diagnosable operational taxonomic units (OTUs) existed within B. duperreyi. Low levels of divergence of B. duperreyi between mainland Australia and Tasmania (no fixed allelic differences) support the notion of episodic exchange of alleles across Bass Strait (ca 60 m, 25 Kya) during periods of low sea level during the Upper Pleistocene rather than the much longer period of isolation (1.7 My) indicated by earlier studies using mitochondrial sequence variation. Our study provides foundational work for the detailed taxonomic re‐evaluation of this species complex and the need for biodiversity assessment to include an examination of cryptic species and/or cryptic diversity below the level of species. Such information on lineage diversity within species and its distribution in the context of disturbance at a regional scale can be factored into conservation planning regardless of whether a decision is made to formally diagnose new species taxonomically and nomenclaturally.     

Leptin treatment increases suppressors of cytokine signaling in central and peripheral tissues.

Leptin concentrations are elevated in the majority of obese individuals raising the possibility that leptin resistance contributes to their obesity. Peripheral leptin administration for 48 h caused a several-fold increase in mRNA encoding the suppressors of cytokine signaling SOCS-3 and CIS in hypothalamus and peripheral tissues. Paradoxically, CIS and SOCS-3 mRNAs are also elevated in the leptin-deficient ob/ob mouse. Forced expression of CIS in insulinoma cells prevented transactivation mediated by leptin. Thus tissues continuously exposed to leptin and/or other factors associated with obesity accumulate excessive amounts of SOCS-3 and CIS which could provide a potential mechanism for leptin resistance.