Potential impacts of climate change on the environmental services of humid tropical alpine regions

Aim Humid tropical alpine environments are crucial ecosystems that sustain biodiversity, biological processes, carbon storage and surface water provision. They are identified as one of the terrestrial ecosystems most vulnerable to global environmental change. Despite their vulnerability, and the importance for regional biodiversity conservation and socio‐economic development, they are among the least studied and described ecosystems in the world. This paper reviews the state of knowledge about tropical alpine environments, and provides an integrated assessment of the potential threats of global climate change on the major ecosystem processes. Location Humid tropical alpine regions occur between the upper forest line and the perennial snow border in the upper regions of the Andes, the Afroalpine belt and Indonesia and Papua New Guinea. Results and main conclusions Climate change will displace ecosystem boundaries and strongly reduce the total area of tropical alpine regions. Displacement and increased isolation of the remaining patches will induce species extinction and biodiversity loss. Drier and warmer soil conditions will cause a faster organic carbon turnover, decreasing the below‐ground organic carbon storage. Since most of the organic carbon is currently stored in the soils, it is unlikely that an increase in above‐ground biomass will be able to offset soil carbon loss at an ecosystem level. Therefore a net release of carbon to the atmosphere is expected. Changes in precipitation patterns, increased evapotranspiration and alterations of the soil properties will have a major impact on water supply. Many regions are in danger of a significantly reduced or less reliable stream flow. The magnitude and even the trend of most of these effects depend strongly on local climatic, hydrological and ecological conditions. The extreme spatial gradients in these conditions put the sustainability of ecosystem management at risk.     

The genetic characterization of Pseudomonas syringae pv. tagetis based on the 16S–23S rDNA intergenic spacer regions

Pseudomonas syringae pv. tagetis, a plant pathogen being considered as a biological control agent of Canada thistle (Cirsium arvense), produces tagetitoxin, an inhibitor of RNA polymerase which results in chlorosis of developing shoot tissues. Although the bacterium is known to affect several plant species in the Asteraceae and has been reported in several countries, little is known of its genetic diversity. The genetic relatedness of 24 strains of P. syringae pv. tagetis with respect to each other and to other P. syringae and Pseudomonas savastanoi pathovars was examined using 16S–23S rDNA intergenic spacer (ITS) sequence analysis. The size of the 16S–23S rDNA ITS regions ranged from 508 to 548 bp in length for all 17 P. syringae and P. savastanoi pathovars examined. The size of the 16S–23S rDNA ITS regions for all the P. syringae pv. helianthi and all the P. syringae pv. tagetis strains examined were 526 bp in length. Furthermore, the 16S–23S rDNA ITS regions of both P. syringae pv. tagetis and P. syringae pv. helianthi had DNA signatures at specific nucleotides that distinguished them from the 15 other P. syringae and P. savastanoi pathovars examined. These results provide strong evidence that P. syringae pv. helianthi is a nontoxigenic form of P. syringae pv. tagetis. The results also demonstrated that there is little genetic diversity among the known strains of P. syringae pv. tagetis. The genetic differences that do exist were not correlated with differences in host plant, geographical origin, or the ability to produce toxin.     

A bioinformatics-based update on microRNAs and their targets in rainbow trout (Oncorhynchus mykiss)

MicroRNAs (miRNAs) participate in various vitally biological processes via controlling target genes activity and thousands of miRNAs have been identified in many species to date, including 18,698 known animal miRNA in miRBase. However, there are only limited studies reported in rainbow trout (Oncorhynchus mykiss) especially via the computational-based approaches. In present study, we systematically investigated the miRNAs in rainbow trout using a well-developed comparative genome-based homologue search. A total of 196 potential miRNAs, belonging to 124 miRNA families, were identified, most of which were firstly reported in rainbow trout. The length of miRNAs ranged from 17 to 24 nt with an average of 20 nt while the length of their precursors varied from 47 to 152 nt with an average of 85 nt. The identified miRNAs were not evenly distributed in each miRNA family, with only one member per family for a majority, and multiple members were also identified for several families. Nucleotide U was dominant in the pre-miRNAs with a percentage of 30.04%. The rainbow trout pre-miRNAs had relatively high negative minimal folding free energy (MFE) and adjusted MFE (AMFE). Not only the mature miRNAs but their precursor sequences are conserved among the living organisms. About 2466 O. mykiss genes were predicted as potential targets for 189 miRNAs. Gene Ontology (GO) analysis showed that nearly 2093, 2107, and 2081 target genes are involved in cellular component, molecular function, and biological processes respectively. KEGG pathway enrichment analysis illuminated that these miRNAs targets might regulate 105 metabolic pathways, including those of purine metabolism, nitrogen metabolism, and oxidative phosphorylation. This study has provided an update on rainbow trout miRNAs and their targets, which represents a foundation for future studies.     

Key Importance of Small RNA Binding for the Activity of a Glycine-Tryptophan (GW) Motif-containing Viral Suppressor of RNA Silencing

Viruses express viral suppressors of RNA silencing (VSRs) to counteract RNA silencing-based host defenses. Although virtually all stages of the antiviral silencing pathway can be inhibited by VSRs, small RNAs (sRNAs) and Argonaute (AGO) proteins seem to be the most frequent targets. Recently, GW/WG motifs of some VSRs have been proposed to dictate their suppressor function by mediating interaction with AGO(s). Here we have studied the VSR encoded by Pelargonium line pattern virus (family Tombusviridae). The results show that p37, the viral coat protein, blocks RNA silencing. Site-directed mutagenesis of some p37 sequence traits, including a conserved GW motif, allowed generation of suppressor-competent and -incompetent molecules and uncoupling of the VSR and particle assembly capacities. The engineered mutants were used to assess the importance of p37 functions for viral infection and the relative contribution of diverse molecular interactions to suppressor activity. Two main conclusions can be drawn: (i) the silencing suppression and encapsidation functions of p37 are both required for systemic Pelargonium line pattern virus infection, and (ii) the suppressor activity of p37 relies on the ability to bind sRNAs rather than on interaction with AGOs. The data also caution against potential misinterpretations of results due to overlap of sequence signals related to distinct protein properties. This is well illustrated by mutation of the GW motif in p37 that concurrently affects nucleolar localization, efficient interaction with AGO1, and sRNA binding capability. These concomitant effects could have been overlooked in other GW motif-containing suppressors, as we exemplify with the orthologous p38 of turnip crinkle virus.     

Comparison of impact of EMCV replication on the nuclear apparatus of NIH 3T3 and HEp-2 cells

We have investigated differences between the actions of encephalomyocarditis virus (EMCV) on cytometric indices in cultured NIH 3T3 and HEp-2 cells, which are characterized by different levels of transformation. HEp-2 cells surviving 48 h after EMCV infection showed lower nuclear ploidy, reduced nuclear area, fewer nucleoli and a higher percentage of euploid cells. There was a significant increase of nucleolar/nuclear DNA 6-24 h after EMCV infection. However, EMCV had markedly different effects on NIH 3T3 cells: there was a consistent increase in population ploidy, but the average number of nucleoli and the number of euploid cells in the population remained constant. The nucleolar/nuclear DNA ratio was almost unchanged. These different viral effects might be explained by the contrasting levels of differentiation of the cultured cell lines. The number of nucleoli does not depend on the amount of nuclear DNA in either viral-infected or intact cells but on the euploidy-to-aneuploidy ratio. The ratio of the sums of the nucleolar perimeters to the nuclear perimeter increases linearly with the number of nucleoli per nucleus in both intact and virus-infected cells. In both cell lines, the amount of DNA per nucleolus decreases as the number of nucleoli increases.     

The Effect of Cauda Equina Constriction on Nitric Oxide Synthase Activity

Nitric oxide synthase (NOS) activity was studied in the gray and white matter regions of the spinal cord 2 and 5 days after multiple cauda equina constrictions of the central processes of L7-Co5 dorsal root ganglia neurons. The results show considerable differences in enzyme activity in the thoracic, upper lumbar, lower lumbar, and sacral segments. Increased NOS activity was observed at 2 days after multiple cauda equina constrictions in the dorsal, lateral, and ventral columns of the lower lumbar segments and in the ventral column of the upper lumbar segments. The values returned to control levels within 5 postconstriction days. In the lateral columns of thoracic segments taken 2 and 5 days after surgery, NOS activity was enhanced by 54% and 55% and in the upper lumbar segments by 130% and 163%, respectively. Multiple cauda equina constrictions performed surgically for 2 and 5 days caused a significant increase in NOS activity predominantly in the gray matter regions of thoracic segments. A quite different response was found 5 days postconstriction in the upper lumbar segments, where the enzyme activity was significantly decreased in the dorsal horn, intermediate zone, and ventral horn. No such extreme differences could be seen in the lower lumbar segments, where NOS activity was significantly enhanced only in the ventral horn. The data correspond with a higher number of NOS immunoreactive somata, quantitatively evaluated in the ventral horn of the lower lumbar segments at 5 days after multiple cauda equina constrictions. While the great region-dependent heterogeneity in NOS activity seen 2 and 5 days after multiple cauda equina constrictions is quite apparent and suggestive of an active role played by nitric oxide in neuroprotective or neurotoxic processes occurring in the gray and white matter of the spinal cord, the extent of damage or the degree of neuroprotection caused by nitric oxide in compartmentalized gray and white matter in this experimental paradigm would be possible only using longer postconstriction periods.     

中国干旱地区啮齿动物物种分布的区域分异

搜集整理我国干旱地区啮齿动物地理分布数据,通过生境分析,确定啮齿动物分布区。基于GIS技术,以面积约为6470km^2的766个栅格收集我国干旱地区啮齿动物的二元分布数据,采用多元分析的分层聚类方法,依据欧氏距离平方值,将地理分布单元划分为若干个组。结果表明,当欧氏距离平方值分别为11．379,17．068,22．758和28．447时,766个地理分布单元依次可分为30,9,5和3个组。分布单元组的物种组成比较和生态型分析表明;（1）在我国干旱地区的海拔较低地带,景观自东向西由草原,荒漠草原过渡到荒漠,地理分布单元组亦呈现相应的分布格局,喜湿的物种逐渐减少,耐旱的种类增加;（2) 藏高原,帕米尔高原寒漠与蒙新温性和暖温性荒漠啮齿动物物种数和组成相近,物种多样性近;（3）阿尔泰山地及南麓平原啮齿动物组成较为特殊,寒湿啮齿动物成份最高;（4）东祁连山地及其北麓以及分犁谷地,额敏谷地,伊犁天山,准噶尔界山及东麓山前平均的啮齿动物成份较为复杂,物种多样性较高。我国干旱地区东部啮齿动物的物种密度和多样性高于西部,但在东部草原和西部荒漠之间的过渡区物种密度较高,表现出的种生态地理分布的边缘效应,体现干旱区啮齿动物物种分布与生物群落地带性分布以及山地和高原等特殊环境非地带性分布的适应关系。蒙新温性荒漠区和青藏高原寒漠区的啮齿动物在区系组成上有一定的历史渊源。     

Chromosomal location of rDNA in Allium: in situ hybridization using biotin- and fluorescein-labelled probe

Summary A biotin- and fluorescein-labelled probe of Helianthus argophyllus has been used to map specific repeated rDNA sequences by in situ hybridization on mitotic chromosomes of Alliwn cepa, Allium fistulosum, a diploid interspecific (Allium fistulosum x Allium cepa) F₁ hybrid, and a triploid interspecific (2 x = A. cepa, 1 x = A. fistulosum) shallot. Hybridization sites were restricted to satellited and smallest pairs of chromosomes in both A. cepa and A. fistulosum. The number, size, and position of the hybridization sites distinguish homologous chromosomes and identify the individual chromosomes carrying the nucleolus organizing region (NOR) at the secondary constriction, as well as the individual chromosomes carrying an additional NOR. This in situ hybridization technique is the first reported in a plant species and offers new cytogenetic markers in Allium.     

Gold Toning Improves the Visualization of Nucleolar Organizer Regions in Paraffin Embedded Tissues

A modification of the silver colloid technique for staining nucleolar organizer regions in paraffin embedded tissues is described. This modification involves the application of a gold toning step with subsequent gold reduction, if necessary, following incubation of sections in the standard silver colloid solution. Silver stained nucleolar organizer regions (AgNORs) in toned sections are more sharply delineated when compared to untoned controls. in high grade tumors the addition of the toning step results in significantly higher AgNOR counts due to the ability to discriminate more easily individual AgNORs in argyrophilic aggregates within the nucleus. It is recommended, because of enhanced visualization, that this modification of the silver colloid technique be used in studies involving quantification of AgNORs in tissue sections.