Xenopus TACC3/maskin is not required for microtubule stability but is required for anchoring microtubules at the centrosome

Members of the transforming acidic coiled coil (TACC) protein family are emerging as important mitotic spindle assembly proteins in a variety of organisms. The molecular details of how TACC proteins function are unknown, but TACC proteins have been proposed to recruit microtubule-stabilizing proteins of the tumor overexpressed gene (TOG) family to the centrosome and to facilitate their loading onto newly emerging microtubules. Using Xenopus egg extracts and in vitro assays, we show that the Xenopus TACC protein maskin is required for centrosome function beyond recruiting the Xenopus TOG protein XMAP215. The conserved C-terminal TACC domain of maskin is both necessary and sufficient to restore centrosome function in maskin-depleted extracts, and we provide evidence that the N terminus of maskin inhibits the function of the TACC domain. Time-lapse video microscopy reveals that microtubule dynamics in Xenopus egg extracts are unaffected by maskin depletion. Our results provide direct experimental evidence of a role for maskin in centrosome function and suggest that maskin is required for microtubule anchoring at the centrosome.     

Multilocus genotyping and molecular phylogenetics resolve a novel head blight pathogen within the Fusarium graminearum species complex from Ethiopia

A survey of Fusarium head blight (FHB)-contaminated wheat in Ethiopia recovered 31 isolates resembling members of the Fusarium graminearum species complex. Results of a multilocus genotyping (MLGT) assay for FHB species and trichothecene chemotype determination suggested that 22 of these isolates might represent a new species within the Fg complex. Phylogenetic analyses of multilocus DNA sequence data resolved the 22 Ethiopian isolates as a novel, phylogenetically distinct species. The new species also appears to be novel in that MLGT probe data and sequence analysis of both ends of the TRI-cluster identified 15ADON and NIV recombination blocks, documenting inter-chemotype recombination involving the chemotype-determining genes near the ends of the TRI-cluster. Results of pathogenicity experiments and analyses of trichothecene mycotoxins demonstrated that this novel Fg complex species could induce FHB on wheat and elaborate 15ADON in planta. Herein the FHB pathogen from Ethiopia is formally described as a novel species.     

Comparison of three organelle markers for phylogeographic inference in Batrachospermum helminthosum (Batrachospermales, Rhodophyta) from North America

Phylogeographic signal provided by the newly developed 23S plastid rRNA marker (universal plastid amplicon, UPA) and the cytochrome oxidase subunit I gene marker (COI) in the freshwater red alga Batrachospermum helminthosum, throughout its range in North America, was investigated. These markers were compared in individuals from a previous study using the cytochrome oxidase 2–3 spacer region ( cox 2–3), which has yielded the most useful data to date with 13 haplotypes among geographic locations. Five haplotypes were resolved for the UPA, differing by only one to two base pairs (bp), and we conclude that this marker may be more appropriate for studying interspecific variation. In contrast, the COI gene revealed 16 haplotypes, differing from one to 44 base pairs or up to 6.6% sequence variation. The intraspecific variation of COI in this taxon is much greater than that reported thus far for marine red algae (generally <5 bp). The intraspecific variation within B. helminthosum is in accord with levels shown in Batrachospermum macrosporum (48 bp within distant locations in Brazil). The COI gene is comparable to the cox 2–3 spacer for phylogeographic studies as the haplotype networks were similar and showed the same geographic patterns. To our knowledge, this is the first comparison of these three regions for phylogeographic research in the red algae.     

Extinction patterns in the avifauna of the Hawaiian islands

Through the continuing accumulation of fossil evidence, it is clear that the avifauna of the Hawaiian Islands underwent a large‐scale extinction event around the time of Polynesian arrival. A second wave of extinctions since European colonization has further altered this unique avifauna. Here I present the first systematic analysis of the factors characterizing the species that went extinct in each time period and those that survived in order to provide a clearer picture of the possible causal mechanisms. These analyses were based on mean body size, dietary and ecological information and phylogenetic lineage of all known indigenous, non‐migratory land and freshwater bird species of the five largest Hawaiian Islands. Extinct species were divided into ‘prehistoric’ and ‘historic’ extinction categories based on the timing of their last occurrence. A model of fossil preservation bias was also incorporated. I used regression trees to predict probability of prehistoric and historic extinction based on ecological variables. Prehistoric extinctions showed a strong bias toward larger body sizes and flightless, ground‐nesting species, even after accounting for preservation bias. Many small, specialized species, mostly granivores and frugivores, also disappeared, implicating a wide suite of human impacts including destruction of dry forest habitat. In contrast, the highest extinction rates in the historic period were in medium‐sized nectarivorous and insectivorous species. These differences result from different causal mechanisms underlying the two waves of extinction.     

Campylobacter infection of broiler chickens in a free-range environment

Campylobacter jejuni is the most common cause of bacterial gastroenteritis worldwide, with contaminated chicken meat considered to represent a major source of human infection. Biosecurity measures can reduce C. jejuni shedding rates of housed chickens, but the increasing popularity of free-range and organic meat raises the question of whether the welfare benefits of extensive production are compatible with food safety. The widespread assumption that the free-range environment contaminates extensively reared chickens has not been rigorously tested. A year-long survey of 64 free-range broiler flocks reared on two sites in Oxfordshire, UK, combining high-resolution genotyping with behavioural and environmental observations revealed: (i) no evidence of colonization of succeeding flocks by the C. jejuni genotypes shed by preceding flocks, (ii) a high degree of similarity between C. jejuni genotypes from both farm sites, (iii) no association of ranging behaviour with likelihood of Campylobacter shedding, and (iv) higher genetic differentiation between C. jejuni populations from chickens and wild birds on the same farm than between the chicken samples, human disease isolates from the same region and national samples of C. jejuni from chicken meat.     

Quantitative genetic analysis of life-history traits of <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis> in stressful environments

Background  

Organisms live in environments that vary. For life-history traits that vary across environments, fitness will be maximised when the phenotype is appropriately matched to the environmental conditions. For the free-living nematode Caenorhabditis elegans, we have investigated how two major life-history traits, (i) the development of environmentally resistant dauer larvae and (ii) reproduction, respond to environmental stress (high population density and low food availability), and how these traits vary between lines and the genetic basis of this variation.     

The association of split hand foot malformation (SHFM) and congenital heart defects

BACKGROUND: Split hand foot malformation (SHFM) (cleft hand, central ray deficiency) is a highly variable malformation that shows genetic heterogeneity with at least five loci mapped to date. SHFM occurs as an isolated finding or in association with other anomalies, including congenital heart defects (CHDs). METHODS: In total 48 SHFM1, 52 SHFM3, 48 SHFM4, 21 SHFM5, and four chromosome 8 patients were evaluated. In addition, we performed a literature review to identify “unmapped” SHFM patients with CHD to evaluate the various etiologies of this combination of findings. The London Dysmorphology Database also served as a resource to identify syndromes with this combination of phenotypic findings. Only patients presenting with both SHFM and CHD were included in the analysis. Classification of CHD among mapped and unmapped SHFM patients was performed utilizing the revised Clark classification. A closer inspection of the types of CHD found in this patient group was performed in order to investigate possible pathogenetic mechanisms. RESULTS: CHDs were found in 10% of SHFM1 patients, 47% of SHFM5 patients, but were not reported in SHFM2, SHFM4 patients, or patients mapped to chromosome 8. Forty‐two syndromic cases and 15 cases of unrecognized syndromes were identified. CONCLUSIONS: The higher frequency of heart defects seen in SHFM1 and SHFM5 of the mapped patient group raises the question as to whether common mechanisms/genetic players are involved. Candidate genes for SHFM1 and SHFM5 include members of the DLX homeobox gene family. Birth Defects Research (Part A), 2008. © 2008 Wiley‐Liss, Inc.