RESUMO
BACKGROUND: Soil is among the most diverse and complex environments in the world. Soil microorganisms play an essential role in biogeochemical cycles and affect plant growth and crop production. However, our knowledge of the relationship between species-assemblies and soil ecosystem processes is still very limited. The aim of this study was to generate a comprehensive metagenomic survey to evaluate the effect of high-input agricultural practices on soil microbial communities. RESULTS: We collected soil samples from three different areas in the Argentinean Pampean region under three different types of land uses and two soil sources (bulk and rhizospheric). We extracted total DNA from all samples and also synthetized cDNA from rhizospheric samples. Using 454-FLX technology, we generated 112 16S ribosomal DNA and 14 16S ribosomal RNA amplicon libraries totaling 1.3 M reads and 36 shotgun metagenome libraries totaling 17.8 million reads (7.7 GB). Our preliminary results suggested that water availability could be the primary driver that defined microbial assemblages over land use and soil source. However, when water was not a limiting resource (annual precipitation >800 mm) land use was a primary driver. CONCLUSION: This was the first metagenomic study of soil conducted in Argentina and our datasets are among the few large soil datasets publicly available. The detailed analysis of these data will provide a step forward in our understanding of how soil microbiomes respond to high-input agricultural systems, and they will serve as a useful comparison with other soil metagenomic studies worldwide.
RESUMO
There are only a few reported nuclear localization signals (NLS) in trypanosomes despite intensive research on nuclear metabolic processes such as mRNA processing and transcription during the recent past. Moreover, there are only two reports for a monopartite (La protein) and bipartite (H2B histone, ESAG8) NLS in Trypanosoma brucei. We decided to investigate a NLS in Trypanosoma cruzi by selecting p14, a small RNA recognition motif (RRM) containing protein involved in the splicing process in the nucleus. Its small size (117 amino acids), and an optimized streamlined workflow for analysis in T. cruzi, allowed us to define a region of basic amino acids (RRKRRR) located at the C-terminus that is necessary for nuclear localization. However, the NLS for p14 appeared to be more complex since the signature RRKRRR alone is necessary but not sufficient to direct heterologous proteins, such as GFP, to the nucleus. Since p14 interacts strongly with splicing factor SF3b155, a much larger protein, we designed a p14 variant unable to interact with it. The results allowed us to discard the notion that p14 is entering the nucleus, or is retained within, as the sole consequence of being part of a larger complex. Extensive mapping showed that all of the information for nuclear import resides within the small p14 protein in a bipartite NLS composed of the signature RRKRRR and a region of the RRM domain. Thus, NLS definition in T. cruzi is more complex than previously described.
