Large herbivore grazing and invertebrates in an alpine ecosystem

The literature on how plants respond to grazing and other disturbance factors have advanced greatly in recent decades, but studies of invertebrates are comparably few. We here quantify the effects of 3 levels of sheep grazing on selected invertebrates in an alpine ecosystem in Norway. We tested the hypothesis that invertebrates are more sensitive to grazing than plants (responding mainly at high density), and that primary consumers (herbivorous beetles) are more sensitive than predatory species (beetles and spiders). We captured 1218 specimens belonging to 44 beetle species and 6672 specimens belonging to 66 species of spiders. The community was dominated by few species: 5 beetle and 3 spider species made up 53.0% and 37.4% of the catch, respectively. At the local (plot) scale, most negative responses were only recorded at high sheep density, and invertebrates were thus not more responsive than the plant community. Two dominant herbivorous beetles responded to grazing while 3 dominant species of predatory beetles did not (one marginally). Spider species richness and frequency of occurrence of 2 dominant species were negatively affected by sheep grazing, suggesting variation between different taxonomic groups of predators. Further functional details than simple classification like herbivorous, predatory and litter-dwelling invertebrates seem to be required before a framework to predict responses to disturbance are robust.     

CorrXpression--identification of significant groups of genes and experiments by means of correspondence analysis and ratio analysis

CorrXpression is a stand-alone desktop application for the identification of significant genes within collections of microarrays. The software combines three methods in two steps of analysis: correspondence analysis (CA), ratio analysis and correlation analysis. The graphical interface of CorrXpression visualizes the result of the CA with a biplot and the expression of selected genes in dependency of the experiments as bar diagrams. The CA-plot is an excellent tool for visualization and evaluation of data and results of ratio analysis and correlation analysis. The input data are selected from a database or from appropriate ASCII files.     

ELOVL3 is an important component for early onset of lipid recruitment in brown adipose tissue

During the recruitment process of brown adipose tissue, the mRNA level of the fatty acyl chain elongase Elovl3 is elevated more than 200-fold in cold-stressed mice. We have obtained Elovl3-ablated mice and report here that, although cold-acclimated Elovl3-ablated mice experienced an increased heat loss due to impaired skin barrier, they were unable to hyperrecruit their brown adipose tissue. Instead, they used muscle shivering in order to maintain body temperature. Lack of Elovl3 resulted in a transient decrease in the capacity to elongate saturated fatty acyl-CoAs into very long chain fatty acids, concomitantly with the occurrence of reduced levels of arachidic acid (C20:0) and behenic acid (C22:0) in brown adipose tissue during the initial cold stress. This effect on very long chain fatty acid synthesis could be illustrated as a decrease in the condensation activity of the elongation enzyme. In addition, warm-acclimated Elovl3-ablated mice showed diminished ability to accumulate fat and reduced metabolic capacity within the brown fat cells. This points to ELOVL3 as an important regulator of endogenous synthesis of saturated very long chain fatty acids and triglyceride formation in brown adipose tissue during the early phase of the tissue recruitment.     

Lineage-specific expansions provide genomic complexity among sea urchin GTPases

In every organism, GTP-binding proteins control many aspects of cell signaling. Here, we examine in silico several GTPase families from the Strongylocentrotus purpuratus genome: the monomeric Ras superfamily, the heterotrimeric G proteins, the dynamin superfamily, the SRP/SR family, and the "protein biosynthesis" translational GTPases. Identified were 174 GTPases, of which over 90% are expressed in the embryo as shown by tiling array and expressed sequence tag data. Phylogenomic comparisons restricted to Drosophila, Ciona, and humans (protostomes, urochordates, and vertebrates, respectively) revealed both common and unique elements in the expected composition of these families. Galpha and dynamin families contain vertebrate expansions, consistent with whole genome duplications, whereas SRP/SR and translational GTPases are highly conserved. Unexpectedly, Ras superfamily analyses revealed several large (5+) lineage-specific expansions in the sea urchin. For Rho, Rab, Arf, and Ras subfamilies, comparing total human gene numbers to the number of sea urchin genes with vertebrate orthologs suggests reduced genomic complexity in the sea urchin. However, gene duplications in the sea urchin increase overall numbers such that total sea urchin gene numbers approximate vertebrate gene numbers for each monomeric GTPase family. These findings suggest that lineage-specific expansions may be an important component of genomic evolution in signal transduction.     

Kori bustard (Ardeotis kori struthiunculus) occurrence in the Serengeti grass plains,northern Tanzania

The kori bustard (Ardeotis kori struthiunculus) is indigenous to grasslands and lightly wooded savannahs of southern and eastern Africa. The species is categorized as near threatened in its entire range due to anthropogenic factors and low reproductive rates. The aim of this study was to analyse the impact of grass colour, grass height, season and location on the density/occurrence of this bird species in the Serengeti grass plains, Tanzania. Data were collected from January 2014 to June 2015 using transect counts in four seasons: (i) short dry, (ii) long rain, (iii) long dry and (iv) short rain seasons, respectively. The mean density of kori bustard in the grass plains was 0.25 ± 1.01 per 0.2 km² with near‐significant differences among the study sites. The occurrence of kori bustard was high in the medium height (11–30 cm) during the long rain and short dry seasons. The kori bustard density is relatively low, and the distribution varies with grass height and season. We suggest that conservation efforts should be directed at preventing its local extinction by protecting the habitat from excessive human activities, such as livestock grazing and illegal offtake.     

Visualization of PtdIns3P dynamics in living plant cells

To investigate PtdIns3P localization and function in plants, a fluorescent PtdIns3P-specific biosensor (YFP-2xFYVE) was created. On lipid dot blots it bound specifically and with high affinity to PtdIns3P. Transient expression in cowpea protoplasts labelled vacuolar membranes and highly motile structures undergoing fusion and fission. Stable expression in tobacco BY-2 cells labelled similar motile structures, but labelled vacuolar membranes hardly at all. YFP-2xFYVE fluorescence strongly co-localized with the pre-vacuolar marker AtRABF2b, partially co-localized with the endosomal tracer FM4-64, but showed no overlap with the Golgi marker STtmd-CFP. Treatment of cells with wortmannin, a PI3 kinase inhibitor, caused the YFP-2xFYVE fluorescence to redistribute into the cytosol and nucleus within 15 min. BY-2 cells expressing YFP-2xFYVE contained twice as much PtdIns3P as YFP-transformed cells, but this had no effect on cell-growth or stress-induced phospholipid signalling responses. Upon treatment with wortmannin, PtdIns3P levels were reduced by approximately 40% within 15 min in both cell lines. Stable expression of YFP-2xFYVE in Arabidopsis plants labelled different subcellular structures in root compared with shoot tissues. In addition labelling the motile structures common to all cells, YFP-2xFYVE strongly labelled the vacuolar membrane in leaf epidermal and guard cells, suggesting that cell differentiation alters the distribution of PtdIns3P. In dividing BY-2 cells, YFP-2xFYVE-labelled vesicles surrounded the newly formed cell plate, suggesting a role for PtdIns3P in cytokinesis. Together, these data show that YFP-2xFYVE may be used as a biosensor to specifically visualize PtdIns3P in living plant cells.     

Primary mesenchyme cells of the sea urchin embryo require an autonomously produced, nonfibrillar collagen for spiculogenesis

A collagen molecule in the sea urchin embryo was characterized by analysis of a 2.7-kb cDNA clone. This clone, Spcoll, was obtained by screening a gastrula stage Strongylocentrotus purpuratus cDNA library with a 237-bp genomic clone encoding a collagen-like sequence previously isolated by Venkatesan et al. (1986). DNA sequence analysis of the cDNA clone demonstrated the nonfibrillar nature of the encoded molecule--13 interruptions of the Gly-X-Y repeat motif were found in the 85-kDa open reading frame. The mRNA of approximately 9 kb accumulated specifically in mesenchyme cells of the embryo through development to the pluteus larva. Polyclonal antibodies generated against a Spcoll-beta-galactosidase fusion protein were utilized to identify and localize the native Spcoll. This collagen molecule of approximately 210 kDa was deposited into the blastocoel by the primary mesenchyme cells. When primary mesenchyme cells were cultured in vitro, Spcoll was secreted into the media and accumulated at sites of cell-substrate interaction. Addition of anti-Spcoll antibodies to primary mesenchyme cell cultures selectively inhibited spiculogenesis, whereas other antibodies had no inhibitory effect. Since collagen is not a component of the organic matrix of spicules (Benson et al., 1986), these results suggest that the autonomous production of Spcoll by differentiating mesenchyme cells in turn influences the point in differentiation at which these cell initiate biomineralization.