BackgroundThe post-genomic era of malaria research provided unprecedented insights into the biology of Plasmodium parasites. Due to the large evolutionary distance to model eukaryotes, however, we lack a profound understanding of many processes in Plasmodium biology. One example is the cell nucleus, which controls the parasite genome in a development- and cell cycle-specific manner through mostly unknown mechanisms. To study this important organelle in detail, we conducted an integrative analysis of the P. falciparum nuclear proteome.ResultsWe combined high accuracy mass spectrometry and bioinformatic approaches to present for the first time an experimentally determined core nuclear proteome for P. falciparum. Besides a large number of factors implicated in known nuclear processes, one-third of all detected proteins carry no functional annotation, including many phylum- or genus-specific factors. Importantly, extensive experimental validation using 30 transgenic cell lines confirmed the high specificity of this inventory, and revealed distinct nuclear localization patterns of hitherto uncharacterized proteins. Further, our detailed analysis identified novel protein domains potentially implicated in gene transcription pathways, and sheds important new light on nuclear compartments and processes including regulatory complexes, the nucleolus, nuclear pores, and nuclear import pathways.ConclusionOur study provides comprehensive new insight into the biology of the Plasmodium nucleus and will serve as an important platform for dissecting general and parasite-specific nuclear processes in malaria parasites. Moreover, as the first nuclear proteome characterized in any protist organism, it will provide an important resource for studying evolutionary aspects of nuclear biology.

SummaryCentromeres are essential for the faithful transmission of chromosomes to the next generation, therefore being essential in all eukaryotic organisms. The centromeres of Plasmodium falciparum, the causative agent of the most severe form of malaria, have been broadly mapped on most chromosomes, but their epigenetic composition remained undefined. Here, we reveal that the centromeric histone variant PfCENH3 occupies a 4-4.5 kb region on each P. falciparum chromosome, which is devoid of pericentric heterochromatin but harbours another histone variant, PfH2A.Z. These CENH3 covered regions pinpoint the exact position of the centromere on all chromosomes and revealed that all centromeric regions have similar size and sequence composition. Immunofluorescence assay of PfCENH3 strongly suggests that P. falciparum centromeres cluster to a single nuclear location prior to and during mitosis and cytokinesis but dissociate soon after invasion. In summary, we reveal a dynamic association of Plasmodium centromeres, which bear a unique epigenetic signature and conform to a strict structure. These findings suggest that DNA-associated and epigenetic elements play an important role in centromere establishment in this important human pathogen.

Background: Recruitment of peripheral proteins to the inner membrane complex (IMC) of the malaria parasite can be mediated by N-terminal acylation. Results: Characterization of substrate determinants and identification of an IMC-localized palmitoyl acyltransferase PfDHHC1. Conclusion: Residues close to palmitoylation sites interfere with specific IMC recruitment. PfDHHC1 represents an apicomplexan-specific PAT. Significance: Dissection of palmitoylation for protein recruitment to the inner membrane complex in P. falciparum.

Background:In several plant species, sticky chromosomes are a consequence of genetic mutations or environmental effects on mitosis and meiosis. Sticky chromosomes result in an unequal distribution of genetic material in daughter cells. This unequal distribution is hypothesized to result in an increase in the coefficient of variation (CV) of the G1 peak of dividing cells. Methods: The st 1 mutant and a nonmutant line in the same genetic background of maize (Zea mays L.) were planted in a soilless mix. A wheat (Triticum aestivum L. em thell.) line was grown in both low and high aluminumsaturated soil. Both plant species were assessed for sticky chromosomes by Feulgen-stained mitotic analysis and flow cytometric analysis of propidium iodide (PI)-stained G1 nuclei.