Narrow species concepts in the Frullania dilatata–appalachiana–eboracensis complex (Porellales, Jungermanniopsida): evidence from nuclear and chloroplast DNA markers

We investigated the phylogeny of a Holarctic-Asian group of Frullania species, the Frullania dilatata–F. appalachiana–F. eboracensis complex, using multiple accessions of morphologically circumscribed taxa and three molecular markers (nrITS region, cp DNA trnL-F and atpB-rbcL regions). Maximum parsimony and likelihood analyses indicated monophyly of morphologically defined taxa. Our phylogenies support a species rather than a subspecies concept within the complex, with four species in North America (F. appalachiana, F. eboracensis, F. parvistipula and F. virginica), and two species in Europe (F. dilatata and F. parvistipula). Accessions of F. dilatata from Southeast Europe and Asia are separated from other European accessions, indicating a former disjunct range of the species.     

Specificity of Staphyloferrin B Recognition by the SirA Receptor from Staphylococcus aureus

Many organisms use sophisticated systems to acquire growth-limiting iron. Iron limitation is especially apparent in bacterial pathogens of mammalian hosts where free iron concentrations are physiologically negligible. A common strategy is to secrete low molecular weight iron chelators, termed siderophores, and express high affinity receptors for the siderophore-iron complex. Staphylococcus aureus, a widespread pathogen, produces two siderophores, staphyloferrin A (SA) and staphyloferrin B (SB). We have determined the crystal structure of the staphyloferrin B receptor, SirA, at high resolution in both the apo and Fe(III)-SB (FeSB)-bound forms. SirA, a member of the class III binding protein family of metal receptors, has N- and C-terminal domains, each composed of mainly a β-stranded core and α-helical periphery. The domains are bridged by a single α-helix and together form the FeSB binding site. SB coordinates Fe(III) through five oxygen atoms and one nitrogen atom in distorted octahedral geometry. SirA undergoes conformational change upon siderophore binding, largely securing two loops from the C-terminal domain to enclose FeSB with a low nanomolar dissociation constant. The staphyloferrin A receptor, HtsA, homologous to SirA, also encloses its cognate siderophore (FeSA); however, the largest conformational rearrangements involve a different region of the C-terminal domain. FeSB is uniquely situated in the binding pocket of SirA with few of the contacting residues being conserved with those of HtsA interacting with FeSA. Although both SirA and HtsA bind siderophores from the same α-hydroxycarboxylate class, the unique structural features of each receptor provides an explanation for their distinct specificity.     

Exclusive conservation of mitochondrial group II intron nad4i548 among liverworts and its use for phylogenetic studies in this ancient plant clade

Liverworts occupy a pivotal position in land plant (embryophyte) phylogeny as the presumed earliest-branching major clade, sister to all other land plants, including the mosses, hornworts, lycophytes, monilophytes and seed plants. Molecular support for this earliest dichotomy in land plant phylogeny comes from strikingly different occurrences of introns in mitochondrial genes distinguishing liverworts from all other embryophytes. Exceptionally, however, the nad5 gene--the mitochondrial locus hitherto used most widely to elucidate early land plant phylogeny--carries a group I type intron that is shared between liverworts and mosses. We here explored whether a group II intron, the other major type of organellar intron, would similarly be conserved in position across the entire diversity of extant liverworts and could be of use for phylogenetic analyses in this supposedly most ancient embryophyte clade. To this end, we investigated the nad4 gene as a candidate locus possibly featuring different introns in liverworts as opposed to the non-liverwort embryophyte (NLE) lineage. We indeed found group II intron nad4i548 universally conserved in a wide phylogenetic sampling of 55 liverwort taxa, confirming clade specificity and surprising evolutionary stability of plant mitochondrial introns. As expected, intron nad4i548g2 carries phylogenetic information in its variable sequences, which confirms and extends previous cladistic insights on liverwort evolution. We integrate the new nad4 data with those of the previously established mitochondrial nad5 and the chloroplast rbcL and rps4 genes and present a phylogeny based on the fused datasets. Notably, the phylogenetic analyses suggest a reconsideration of previous phylogenetic and taxonomic assignments for the genera Calycularia and Mylia and resolve a sister group relationship of Ptilidiales and Porellales.     

Heme binding in the NEAT domains of IsdA and IsdC of Staphylococcus aureus

Absorption, magnetic circular dichroism (MCD), and electrospray mass spectral (ESI-MS) data are reported for the heme binding NEAr iron Transporter (NEAT) domains of IsdA and IsdC, two proteins involved in heme scavenging by Staphylococcus aureus. The mass spectrometry data show that the NEAT domains are globular in structure and efficiently bind a single heme molecule. In this work, the IsdA NEAT domain is referred to as NEAT-A, the IsdC NEAT domain is referred to as NEAT-C, heme-free NEAT-C is NEAT-A and NEAT-C are inaccessible to small anionic ligands. Reduction of the high-spin Fe(III) heme iron to 5-coordinate high-spin Fe(II) in NEAT-A results in coordination by histidine and opens access, allowing for CO axial ligation, yielding 6-coordinate low-spin Fe(II) heme. In contrast, reduction of the high-spin Fe(III) heme iron to 5-coordinate high-spin Fe(II) in NEAT-C results in loss of the heme from the binding site of the protein due to the absence of a proximal histidine. The absorption and MCD data for NEAT-A closely match those previously reported for the whole IsdA protein, providing evidence that heme binding is primarily a property of the NEAT domain.     

Phylogenetic relationships in the Lejeuneaceae (Hepaticae) inferred using ITS sequences of nuclear ribosomal DNA

Sequences of the ITS1–5.8S–ITS2 region of nuclear ribosomal DNA were generated for 12 species from 9 genera of Lejeuneaceae and a single species of Jubulaceae (outgroup). The taxon sampling of Lejeuneaceae included representatives of the two widely recognized subfamilies, Lejeuneoideae and Ptychanthoideae. The molecular dataset was analysed independently and in combination with a morphological dataset. The nrITS dataset and the combined dataset resulted in identical topologies. The genus Bryopteris, sometimes treated as a separate family Bryopteridaceae, is nested within the Lejeuneaceae subfamily Ptychanthoideae. Lejeuneaceae subfamily Lejeuneoideae proved to be paraphyletic with the tribe Lejeuneeae sister to Ptychanthoideae, albeit without significant bootstrap support. The tribes Brachiolejeuneeae and Cheilolejeuneeae of Lejeuneoideae, established recently based on morphological evidence, are well supported in bootstrap analyses both of the ITS and the combined molecular–morphological datasets. The results support classifications of Lejeuneaceae based on morphological data and demonstrate the usefulness of the ITS region for phylogenetic studies within or among closely related genera of Lejeuneaceae.     

Frequency distribution of DNA in blood and bone marrow cells of children with acute non-lymphatic leukemia using impulse cytophotometry

1. As compared with the peripheral blood lymphocytes of healthy subjects the cells in the mononuclear fraction of peripheral blood and in the bone marrow of children with ANLL show a significant higher S- and G2 + M-phase. 2. A high proliferative activity correlate with a bad prognosis or with reaching no haematological remission. 3. Frequently, aneuploid cell populations will occur in the morphological subtypes M 4 and M 5.     

Correlation of stable oxygen isotope temperature record with light attenuation profiles in reef-dwellingTridacna shells

Molluscs are known to record environmental changes in their carbonate shells in detail. This paper reports the findings of a high-resolution analysis of stable oxygen isotopic compositions and light transmission properties of a shell of the reef-dwelling Pacific giant clamTridacna gigas. Our findings reveal that the annual growth rates and the longevity ofTridacna specimens can be readily determined by measuring the annual light attenuation pattern within the shell. Annual seasonal changes in water temperature are reflected with high resolution in the stable oxygen isotope ratios and in the light attenuation values of the aragonite shell. The inner shell ofT. gigas deposited below the pallial line revealing undisturbed shell accretion with high growth rates shows the maximum seasonal oxygen isotope range and the highest resolution in light attenuation changes. We suggest that this is the best part of the shell to reconstruct former seasonal surface water temperatures in tropical environments. Scanning electron microscopy (SEM) studies suggest that the annual growth patterns observed in transmitted light are generated by a complex pattern of daily growth increments with varying sizes of skeletal crystallites and varying amounts of organic carbon.     

Plagiochila virginica A.Evans rather than P. dubia Lindenb. & Gottsche occurs in Macaronesia; placement in sect. Contiguae Carl is supported by ITS sequences of nuclear ribosomal DNA

 Plagiochila dubia Lindenb. & Gottsche is reduced to a synonym of the Neotropical P. patula (Sw.) Lindenb. Specimens from the Canary Islands and Madeira proved to belong to the eastern North American P. virginica A.Evans, new to Europe. Phylogenetic analyses of the internal transcribed spacer regions (ITS1-5.8S-ITS2) of nuclear ribosomal DNA of ten Plagiochila species produced four independent lineages that are well supported by all bootstrap analyses (maximum likelihood, maximum parsimony, and distance). These lineages correspond with the Plagiochila sections Arrectae, Contiguae, Cucullatae and Glaucescentes. Spruce's “Ramiflorae” and “Cauliflorae” may no longer be regarded as monophyletic units of Plagiochila. Received August 19, 2001 Accepted October 11, 2001