Targeted knock-down of miR21 primary transcripts using snoMEN vectors induces apoptosis in human cancer cell lines

We have previously reported an antisense technology, 'snoMEN vectors', for targeted knock-down of protein coding mRNAs using human snoRNAs manipulated to contain short regions of sequence complementarity with the mRNA target. Here we characterise the use of snoMEN vectors to target the knock-down of micro RNA primary transcripts. We document the specific knock-down of miR21 in HeLa cells using plasmid vectors expressing miR21-targeted snoMEN RNAs and show this induces apoptosis. Knock-down is dependent on the presence of complementary sequences in the snoMEN vector and the induction of apoptosis can be suppressed by over-expression of miR21. Furthermore, we have also developed lentiviral vectors for delivery of snoMEN RNAs and show this increases the efficiency of vector transduction in many human cell lines that are difficult to transfect with plasmid vectors. Transduction of lentiviral vectors expressing snoMEN targeted to pri-miR21 induces apoptosis in human lung adenocarcinoma cells, which express high levels of miR21, but not in human primary cells. We show that snoMEN-mediated suppression of miRNA expression is prevented by siRNA knock-down of Ago2, but not by knock-down of Ago1 or Upf1. snoMEN RNAs colocalise with Ago2 in cell nuclei and nucleoli and can be co-immunoprecipitated from nuclear extracts by antibodies specific for Ago2

Communities of ground-living spiders in deciduous forests: Does tree species diversity matter?

Schuldt A, Fahrenholz N, Brauns M, Migge-Kleian S, Platner C, Schaefer M. Communities of ground-living spiders in deciduous forests: Does tree species diversity matter? BIODIVERSITY AND CONSERVATION. 2008;17(5):1267-1284.The relationships between species diversity and ecosystem functions are in the focus of recent ecological research. However, until now the influence of species diversity on ecosystem processes such as decomposition or mineral cycling is not well understood. In deciduous forests, spiders are an integral part of the forest floor food web. In the present study, patterns of spider diversity and community structure are related to diversity of deciduous forest stands in the Hainich National Park (Thuringia). In 2005, pitfall trapping and quantitative forest floor sampling were conducted in nine plots of forest stands with one (Diversity Level 1), three (DL 2) and five (DL 3) major deciduous tree species. Species richness, measured with both methods, as well as spider abundance in forest floor samples were highest in stands with medium diversity (DL 2) and lowest in pure beech stands (DL 1). The Shannon-Wiener index and spider numbers in pitfall traps decreased from DL 1 to DL 3, while the Shannon-Wiener index in forest floor samples increased in the opposite direction. Spider community composition differed more strongly between single plots than between diversity levels. Altogether, no general relationship between increasing tree species diversity and patterns of diversity and abundance in spider communities was found. It appears that there is a strong influence of single tree species dominating a forest stand and modifying structural habitat characteristics such as litter depth and herb cover which are important for ground-living spiders

Spider–Plant Interactions: An Ecological Approach

Spiders are among the most common animals in diverse terrestrial environments, and display a variety of lifestyles and foraging modes. This chapter represents an overview of our knowledge of spider–plant interactions. Spiders are strongly influenced by plant architecture, rather than being randomly distributed in the vegetation; structures such as rosette-shaped clusters of leaves or glandular trichomes are particularly common in plants that have associations with spiders. Spiders derive benefits from plants such as shelter and access to insect prey. In turn, they can protect plants against herbivory. However, they may also consume or deter pollinators, imposing a cost that can exceed their benefit to the plant. Specific spider–plant associations are mutualistic if spiders provide protective or nutritional benefits, thus improving plant fitness, and if plants provide shelter and suitable foraging sites to spiders. We examine several case studies of spiders living in association with plants, and describe spatial/temporal adaptations in spider–plant relationships