Whole Genome Resequencing Reveals Natural Target Site Preferences of Transposable Elements in Drosophila melanogaster

Transposable elements are mobile DNA sequences that integrate into host genomes using diverse mechanisms with varying degrees of target site specificity. While the target site preferences of some engineered transposable elements are well studied, the natural target preferences of most transposable elements are poorly characterized. Using population genomic resequencing data from 166 strains of Drosophila melanogaster, we identified over 8,000 new insertion sites not present in the reference genome sequence that we used to decode the natural target preferences of 22 families of transposable element in this species. We found that terminal inverted repeat transposon and long terminal repeat retrotransposon families present clade-specific target site duplications and target site sequence motifs. Additionally, we found that the sequence motifs at transposable element target sites are always palindromes that extend beyond the target site duplication. Our results demonstrate the utility of population genomics data for high-throughput inference of transposable element targeting preferences in the wild and establish general rules for terminal inverted repeat transposon and long terminal repeat retrotransposon target site selection in eukaryotic genomes

Large and Small Business in Russian Agriculture: Adaptation to Market

Russian farms are classified into large and small agricultural businesses depending on both their volume of operations and organisational form. The article examines the development of these two groups of farms during the transition and their adaptation to the new market conditions. The effect of regional factors and agricultural policies on the changing farm structure is analysed. Government support policies are shown to have a pronounced large farm bias, which is inconsistent with a market economy. The relationship between large corporate farms and rural household plots is quantified. The partial productivity of land and labour is compared between corporate and individual farms. Comparative Economic Studies (2005) 47, 85–100. doi:10.1057/palgrave.ces.8100078