Explosive avian radiations and multi-directional dispersal across Wallacea: evidence from the Campephagidae and other Crown Corvida (Aves)

The systematic relationships among avian families within Crown Corvida have been poorly studied so far and as such been of limited use for biogeographic interpretations. The group has its origin in Australia and is thought to have colonized Africa and the New World via Asia beginning some 35 Mya when terranes of Australian origin approached Asian landmasses. Recent detailed tectonic mapping of the origin of land masses in the region around Wallace's line have revealed a particularly complex movement of terranes over the last 20-30 Myr. Thus the biogeographic dispersal pattern of Crown Corvida is a particularly exciting case for linking vicariance and dispersal events with Earth history. Here we examine phylogenetic affinities among 72 taxa covering a broad range of genera in the basal radiations within Crown Corvida with an emphasis on Campephagidae and Pachycephalidae. Bayesian analyses of nuclear DNA sequence data identified the family Campephagidae as monophyletic but the large genus Coracina is not. Within the family Pachycephalidae the genera Pachycephala and Colluricincla are paraphyletic with respect to each other. The resulting phylogeny suggests that patterns of dispersal across Wallace's line are complex and began at least 25 Mya. We find evidence of explosive radiations and multi-directional dispersal within the last 10 Myr, and three independent long distance ocean dispersal events between Wallacea and Africa at 10-15 Mya. Furthermore, the study reveals that in the Campephagidae a complex series of dispersal events rather than vicariance is the most likely explanation for the current biogeographic pattern in the region.     

Dynamic association of the mammalian insulator protein CTCF with centrosomes and the midbody

CTCF is a highly conserved, ubiquitously expressed DNA-binding protein that has widespread capabilities in gene regulation. CTCF plays important roles in cell growth regulatory processes and epigenetic functions. Ectopic expression of CTCF results in severe cell growth inhibition at multiple points within the cell cycle, indicating that CTCF levels must be stringently monitored. We have investigated the subcellular localization of CTCF in detail. Interestingly, we observe that CTCF shows a dynamic cell cycle-dependent distribution. Immunofluorescent staining reveals that in interphase CTCF is a nuclear protein, which is mainly excluded from the nucleolus. Strikingly, CTCF is associated with the centrosome during mitosis, especially from metaphase to anaphase. At telophase, CTCF dissociates from the centrosome and localizes to the midbody and the reformed nuclei. The association of CTCF with centrosomes and the midbody is further confirmed by biochemical fractionation. Moreover, subcellular fractions of CTCF show cell cycle and organelle-specific posttranslational modifications, suggesting different roles for CTCF at different stages of the cell cycle.     

Inbreeding levels of two Ustilago maydis populations

Little is known about the population mating behavior of the smut fungus Ustilago maydis DC (Corda). To determine the amount of inbreeding that occurs in local U. maydis populations, two cornfields were sampled, one in North America (NA) at Le Sueur, Minnesota, and one in South America (SA) at Tarariras, Uruguay. These fields were chosen because of their geographic isolation and host management differences. Inbreeding coefficients (F(is)) were calculated using data derived from amplified fragment length polymorphism (AFLP) markers. Mean F(is) values estimated for both the NA (-0.08), and the SA (-0.02) populations statistically are not different from zero. The results of this study demonstrate that the U. maydis population structure in both cornfields results predominately from out-crossing and suggests that teliospores infrequently act as single infection units. The genetic differentiation between populations was high (F(st) = 0.25).     

Exogenous Carbohydrate Utilisation by Explants of Brassica napus Cultured in vitro

In 5; non-coding regions of genes for phytochrome A from horseradish (ArPHYAs) were fused with the 35S promoter of cauliflower mosaic virus in the antisense direction (CaMV35SantiArPHYAs) and introduced into horseradish hairy roots. Phytochrome levels of proximal areas in many hairy roots that had been transformed with CaMV35SantiArPHYAs decreased to levels of about one-half to one-quarter those of control hairy roots. The extent of the light-induced formation of adventitious shoots from hairy roots with less than half of the control level of phytochrome was lower than in the controls and not different between the three ArPHYAs. In contrast, the efficiency of phytochrome on the extent of shoot formation differed in hairy roots transformed with CaMV35SantiArPHYAs when phytochrome levels were more than 0.02 (;(;A) g^–1). The efficiency of ArPHYA3 to initiate shoot formation was greatest and that of ArPHYA2 was smallest. Furthermore, previous reports on hairy roots overexpressing ArPHYAs showed a similar efficiency of phytochrome on shoot formation. These results indicate that the ArphyA1 and/or ArphyA3 play major roles in the light-induced formation of adventitious shoots and that ArphyA2 has a minor role.     

Characterization of a series of far-red-absorbing thiobarbituric acid oxonol derivatives as fluorescent probes for biological applications

Chromophores that absorb in the far-red region of the spectrum are increasingly being utilized for applications in the biosciences. We have synthesized and evaluated a novel series of fluorescent oxonols based on thiobarbituric acids containing aryl and heteroaryl substituents. The novel chromophores possess narrow absorption spectra ( approximately 40-nm bandwidths), reasonable Stokes shifts ( approximately 25 nm), and quantum yields of up to 0.67 in organic solvents and 0.3 in aqueous solvents, with absorption wavelength maxima at 620-640 nm. The spectral properties of the compounds are sensitive to base and exhibit a loss of far-red absorbance that is concentration and time dependent. Derivatives have been synthesized that can be used for the labeling of macromolecules such as proteins and DNA. The probes show environment sensitivity and the oligonucleotide conjugates sense the formation of duplex DNA. These novel far-red fluorophores have potential applications in diagnostic and research applications.     

The mitochondrial prohibitin complex is essential for embryonic viability and germline function in Caenorhabditis elegans

Prohibitins in eukaryotes consist of two subunits (PHB1 and PHB2) that together form a high molecular weight complex in the mitochondrial inner membrane. The evolutionary conservation and the ubiquitous expression in mammalian tissues of the prohibitin complex suggest an important function among eukaryotes. The PHB complex has been shown to play a role in the stabilization of newly synthesized subunits of mitochondrial respiratory enzymes in the yeast Saccharomyces cerevisiae. We have used Caenorhabditis elegans as model system to study the role of the PHB complex during development of a multicellular organism. We demonstrate that prohibitins in C. elegans form a high molecular weight complex in the mitochondrial inner membrane similar to that of yeast and humans. By using RNA-mediated gene inactivation, we show that PHB proteins are essential during embryonic development and are required for somatic and germline differentiation in the larval gonad. We further demonstrate that a deficiency in PHB proteins results in altered mitochondrial biogenesis in body wall muscle cells. This paper reports a strong loss of function phenotype for prohibitin gene inactivation in a multicellular organism and shows for the first time that prohibitins serve an essential role in mitochondrial function during organismal development.     

A Gondwanan origin of passerine birds supported by DNA sequences of the endemic New Zealand wrens

Zoogeographic, palaeontological and biochemical data support a Southern Hemisphere origin for passerine birds, while accumulating molecular data suggest that most extant avian orders originated in the mid-Late Cretaceous. We obtained DNA sequence data from the nuclear c-myc and RAG-1 genes of the major passerine groups and here we demonstrate that the endemic New Zealand wrens (Acanthisittidae) are the sister taxon to all other extant passerines, supporting a Gondwanan origin and early radiation of passerines. We propose that (i) the acanthisittids were isolated when New Zealand separated from Gondwana (ca. 82-85 Myr ago), (ii) suboscines, in turn, were derived from an ancestral lineage that inhabited western Gondwana, and (iii) the ancestors of the oscines (songbirds) were subsequently isolated by the separation of Australia from Antarctica. The later spread of passerines into the Northern Hemisphere reflects the northward migration of these former Gondwanan elements.     

Timing and duration of moult in three populations of Purple Sandpipers Calidris maritima with different moult/migration patterns

Timing and duration of primary moult in three populations of Purple Sandpipers Calidris maritima were described and discussed in relation to the birds’ need to complete moult before the onset of winter, when resources are required for survival. We predicted that moult would be completed earlier by birds wintering at higher latitudes. The south Norwegian breeding population, which moults and winters along the coast of east Britain (54–57°N) had a mean starting date of 21 July for primary moult (16 July for females and 24 July for males), a mean duration of 61 days, and completed on 20 September. Resident Icelandic (64–65°N) birds had a mean starting date of 22 July for primary moult (17 July for females and 25 July for males), a mean duration of 51 days, and completed on 11 September. Birds moulting in north Norway (70°N) arrived in north Norway in suspended primary moult or without having started moult, and completed it there. They had a mean completion date of 2 November for primary moult (31 October for females and 3 November for males). Starting date and duration could not be estimated because some suspended moult for an undetermined period, but it was thought that they started in late August. It is likely that most originated from Russia. The onset of moult appears to be set by the end of breeding and there is little overlap in these two events. The earlier start of moult by females in all three populations may be because they abandon the males when the chicks hatch, leaving the males to attend the chicks. Although the duration of primary moult followed the expected trend, being fastest in north Norway and slowest in Britain, the onset of moult was so late in north Norway that they had an unexpectedly late completion date, despite their rapid moult. The late completion of primary moult in north Norway suggests that wintering in the far north may not pose the energetic constraints on Purple Sandpipers that had previously been supposed.