Patterns and drivers of Araucaria araucana forest growth along a biophysical gradient in the northern Patagonian Andes: Linking tree rings with satellite observations of soil moisture

Araucaria araucana (Araucaria) is a long‐lived conifer growing along a sharp west–east biophysical gradient in the Patagonian Andes. The patterns and climate drivers of Araucaria growth have typically been documented on the driest part of the gradient relying on correlations with meteorological records, but the lack of in situ soil moisture observations has precluded an assessment of the growth responses to soil moisture variability. Here, we use a network of 21 tree‐ring width chronologies to investigate the spatiotemporal patterns of tree growth through the entire gradient and evaluate their linkages with regional climate and satellite‐observed surface soil moisture variability. We found that temporal variations in tree growth are remarkably similar throughout the gradient and largely driven by soil moisture variability. The regional spatiotemporal pattern of tree growth was positively correlated with precipitation (r = 0.35 for January 1920–1974; P < 0.01) and predominantly negatively correlated with temperature (r = ?0.38 for January–March 1920–1974; P < 0.01) during the previous growing season. These correlations suggest a temporally lagged growth response to summer moisture that could be associated with known physiological carry‐over processes in conifers and to a response to moisture variability at deeper layers of the rooting zone. Notably, satellite observations revealed a previously unobserved response of Araucaria growth to summer surface soil moisture during the current rather than the previous growing season (r = 0.65 for 1979–2000; P < 0.05). This new response has a large spatial footprint across the mid‐latitudes of the South American continent (35°–45°S) and highlights the potential of Araucaria tree rings for palaeoclimatic applications. The strong moisture constraint on tree growth revealed by satellite observations suggests that projected summer drying during the coming decades may result in regional growth declines in Araucaria forests and other water‐limited ecosystems in the Patagonian Andes.     

Are dendrites in Drosophila homologous to vertebrate dendrites?

Dendrites represent arborising neurites in both vertebrates and invertebrates. However, in vertebrates, dendrites develop on neuronal cell bodies, whereas in higher invertebrates, they arise from very different neuronal structures, the primary neurites, which also form the axons. Is this anatomical difference paralleled by principal developmental and/or physiological differences? We address this question by focussing on one cellular model, motorneurons of Drosophila and characterise the compartmentalisation of these cells. We find that motorneuronal dendrites of Drosophila share with typical vertebrate dendrites that they lack presynaptic but harbour postsynaptic proteins, display calcium elevation upon excitation, have distinct cytoskeletal features, develop later than axons and are preceded by restricted localisation of Par6-complex proteins. Furthermore, we demonstrate in situ and culture that Drosophila dendrites can be shifted from the primary neurite to their soma, i.e. into vertebrate-like positions. Integrating these different lines of argumentation, we propose that dendrites in vertebrates and higher invertebrates have a common origin, and differences in dendrite location can be explained through translocation of neuronal cell bodies introduced during the evolutionary process by which arthropods and vertebrates diverged from a common urbilaterian ancestor. Implications of these findings for studies of dendrite development, neuronal polarity, transport and evolution are discussed.     

Oceanimonas smirnovii sp. nov., a novel organism isolated from the Black Sea

A slightly creamy, melanogenic, gram-negative, aerobic bacterium was isolated from seawater sample collected in the Karadag Natural Reserve of the Eastern Crimea, the Black Sea. The novel organism was chemoorganotrophic, had no obligate requirement in NaCl, tolerated to 12% NaCl, grew between 10 and 45 degrees C, was slightly alkaliphilic, and was not able to degrade starch, gelatin, agar, and Tween 80. 16S rRNA gene sequence-based analyses of the new organism revealed that Oceanimonas doudoroffii ATCC 27123T, Oceanimonas baumanii ATCC 700832T, and Oceanisphaera litoralis DSM 15406T were the closest relatives (similarity around 97%-96%). The G + C content of the DNA of the strain 31-13T was 55.5mol%. Phosphatidylethanolamine (49.0%), phosphatidylglycerol (41.8%), and diphosphatidylglycerol (9.2%) were the predominant phospholipids. The major fatty acids were 16:0 (24.1%), 16:1omega7 (40.3%), and 18:1omega7 (29.2%). On the basis of the significant differences demonstrated in the phenotypic and chemotaxonomic characteristics, it is suggested that the bacterium be classified as a novel species; the name Oceanimonas smirnovii sp. nov. is proposed. The type strain is 31-13T (UCM B-11076T = LMG 22147T = ATCC BAA-899T).     

Spatial changes in carbon and nitrogen stable isotopes of the plankton food web in a saline lake ecosystem

We investigated spatial changes in the isotope ratios of the plankton food web in Lake Chany, Siberia, Russia, especially at an estuarine transition zone of the lake. The δ¹³C values of particulate organic matter (POM) varied among the sampling sites, and increased with increasing pH of the lake water. This may reflect a shift by phytoplankton from using CO₂ to using bicarbonate for photosynthesis with increasing pH. The δ¹³C values of zooplankton community also changed at each site along with those of the POM. This was indicative of carbon isotope changes of plankton food webs between the stations along an environmental gradient.     

Retinoid X Receptor Agonists Upregulate Genes Responsible for the Biosynthesis of All-Trans-Retinoic Acid in Human Epidermis

UAB30 is an RXR selective agonist that has been shown to have potential cancer chemopreventive properties. Due to high efficacy and low toxicity, it is currently being evaluated in human Phase I clinical trials by the National Cancer Institute. While UAB30 shows promise as a low toxicity chemopreventive drug, the mechanism of its action is not well understood. In this study, we investigated the effects of UAB30 on gene expression in human organotypic skin raft cultures and mouse epidermis. The results of this study indicate that treatment with UAB30 results in upregulation of genes responsible for the uptake and metabolism of all-trans-retinol to all-trans-retinoic acid (ATRA), the natural agonist of RAR nuclear receptors. Consistent with the increased expression of these genes, the steady-state levels of ATRA are elevated in human skin rafts. In ultraviolet B (UVB) irradiated mouse skin, the expression of ATRA target genes is found to be reduced. A reduced expression of ATRA sensitive genes is also observed in epidermis of mouse models of UVB-induced squamous cell carcinoma and basal cell carcinomas. However, treatment of mouse skin with UAB30 prior to UVB irradiation prevents the UVB-induced decrease in expression of some of the ATRA-responsive genes. Considering its positive effects on ATRA signaling in the epidermis and its low toxicity, UAB30 could be used as a chemoprophylactic agent in the treatment of non-melanoma skin cancer, particularly in organ transplant recipients and other high risk populations.     

Tau,XMAP215/Msps and Eb1 co-operate interdependently to regulate microtubule polymerisation and bundle formation in axons

The formation and maintenance of microtubules requires their polymerisation, but little is known about how this polymerisation is regulated in cells. Focussing on the essential microtubule bundles in axons of Drosophila and Xenopus neurons, we show that the plus-end scaffold Eb1, the polymerase XMAP215/Msps and the lattice-binder Tau co-operate interdependently to promote microtubule polymerisation and bundle organisation during axon development and maintenance. Eb1 and XMAP215/Msps promote each other’s localisation at polymerising microtubule plus-ends. Tau outcompetes Eb1-binding along microtubule lattices, thus preventing depletion of Eb1 tip pools. The three factors genetically interact and show shared mutant phenotypes: reductions in axon growth, comet sizes, comet numbers and comet velocities, as well as prominent deterioration of parallel microtubule bundles into disorganised curled conformations. This microtubule curling is caused by Eb1 plus-end depletion which impairs spectraplakin-mediated guidance of extending microtubules into parallel bundles. Our demonstration that Eb1, XMAP215/Msps and Tau co-operate during the regulation of microtubule polymerisation and bundle organisation, offers new conceptual explanations for developmental and degenerative axon pathologies.     

On the origin of the Norwegian lemming

The Pleistocene glacial cycles resulted in significant changes in species distributions, and it has been discussed whether this caused increased rates of population divergence and speciation. One species that is likely to have evolved during the Pleistocene is the Norwegian lemming (Lemmus lemmus). However, the origin of this species, both in terms of when and from what ancestral taxon it evolved, has been difficult to ascertain. Here, we use ancient DNA recovered from lemming remains from a series of Late Pleistocene and Holocene sites to explore the species' evolutionary history. The results revealed considerable genetic differentiation between glacial and contemporary samples. Moreover, the analyses provided strong support for a divergence time prior to the Last Glacial Maximum (LGM), therefore likely ruling out a postglacial colonization of Scandinavia. Consequently, it appears that the Norwegian lemming evolved from a small population that survived the LGM in an ice‐free Scandinavian refugium.     

Rapid identification and interpretation of gene–environment associations using the new R.SamBada landscape genomics pipeline

sam βada is a genome–environment association software, designed to search for signatures of local adaptation. However, pre‐ and postprocessing of data can be labour‐intensive, preventing wider uptake of the method. We have now developed R.SamBada, an r ‐package providing a pipeline for landscape genomic analysis based on sam βada , spanning from the retrieval of environmental conditions at sampling locations to gene annotation using the Ensembl genome browser. As a result, R.SamBada standardizes the landscape genomics pipeline and eases the search for candidate genes of local adaptation, enhancing reproducibility of landscape genomic studies. The efficiency and power of the pipeline is illustrated using two examples: sheep populations from Morocco with no evident population structure and Lidia cattle from Spain displaying population substructuring. In both cases, R.SamBada enabled rapid identification and interpretation of candidate genes, which are further discussed in the light of local adaptation. The package is available in the r CRAN package repository and on GitHub (github.com/SolangeD/R.SamBada).     

Genetic diversity and geographic distribution of Bemisia tabaci and Trialeurodes vaporariorum in Costa Rica

The tobacco whitefly Bemisia tabaci (Gennadius) cryptic species complex and of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) are extensively reported as destructive pests in vegetable crops worldwide. A survey was conducted in 2011 and 2012 to determine the occurrence and genetic diversity present in the populations of these whiteflies in the major vegetable production areas of Costa Rica. Insect samples were collected from sweet pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), common bean (Phaseolus vulgaris L.) and weeds present in commercial crops either in open field or greenhouse conditions. PCR‐RFLP analysis of mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI) sequences of 621 whitefly individuals confirmed the presence of the Mediterranean (MED) type of the B. tabaci and of T. vaporariorum in most sampled regions. Also, individuals of the Middle East‐Asia Minor 1 (MEAM1) type of the B. tabaci were observed in low numbers. Contingency analyses based on type of crop, geographical region, whitefly species, year of collection and production system confirmed that T. vaporariorum was the most frequent species in vegetable production areas in Costa Rica, both in greenhouses and in open fields. B. tabaci MED is likely spreading to new areas of the country, whereas B. tabaci MEAM1 was mostly absent or rarely found. Comparisons of mtCOI sequences from B. tabaci individuals revealed the presence of four B. tabaci sequence haplotypes (named MED‐i, MED‐ii, MEAM1‐i, MEAM1‐xviii) in Costa Rica, three of them identical to B. tabaci haplotypes previously reported in the Western Hemisphere and other parts of the world. Analysis of sequences of T. vaporariorum individuals revealed a more complex population with the presence of 11 haplotypes, two of which were identical to T. vaporariorum sequences reported from other countries.