organelles: the plasma membrane (Sso1p and the closely MRC Laboratory of Molecular Biology, Hills Road, related Sso2p), an endosomal/pre-vacuolar compartment Cambridge CB2 2QH, UK (Pep12p), the cis-Golgi (Sed5p) and the endoplasmic 1 Corresponding author reticulum (ER) (Ufe1p) (Hardwick and Pelham, 1992;Aalto et al., 1993;Becherer et al., 1996; Lewis and Sorting of membrane proteins between compartments Pelham, 1996). t-SNAREs in different compartments are of the secretory pathway is mediated in part by their not highly conserved at the primary sequence level, transmembrane domains (TMDs). In animal cells, although they share common secondary structural features: TMD length is a major factor in Golgi retention. In they are C-terminally anchored, with the bulk of the yeast, the role of TMD signals is less clear; it has been protein being in the cytosol, and they contain three proposed that membrane proteins travel by default to stretches of heptad repeats which could form coiledthe vacuole, and are prevented from doing so by coil domains, the longest stretch being close to the cytoplasmic signals. We have investigated the targeting transmembrane domain (TMD). This region has been of the yeast endoplasmic reticulum (ER) t-SNARE shown to be crucial for the interaction of syntaxin with Ufe1p. We show that the amino acid sequence of the the incoming v-SNARE, synaptobrevin (Calakos et al., Ufe1p TMD is important for both function and ER 1994; Kee et al., 1995). targeting, and that the requirements for each areThe t-SNAREs, which 'define' a given compartment in distinct. Targeting is independent of Rer1p, the only that they determine which vesicles are able to fuse with candidate sorting receptor for TMD sequences curit, must be localized correctly in order to prevent aberrant rently known. Lengthening the Ufe1p TMD allows fusion of vesicles with the wrong compartment. They thus transport along the secretory pathway to the vacuole provide a model system for studying protein sorting, i.e. or plasma membrane. The choice between these desthey are a family of similar proteins which are targeted tinations is determined by the length and composition to diverse locations. t-SNAREs lack well-characterized of the TMD, but not by its precise sequence. A longer sorting signals, although we have shown previously that TMD is required to reach the plasma membrane in the localization of the Golgi t-SNARE, Sed5p, is influenced yeast than in animal cells, and shorter TMDs direct both by its TMD and by the cytoplasmic portion of the proteins to the vacuole. TMD-based sorting is therefore protein (Banfield et al., 1994). a general feature of the yeast secretory pathway, butThis study focuses on the ER t-SNARE, Ufe1p. In occurs by different mechanisms at different points. particular, we have investigated the importance of the

Background: Plasmodium parasites undergo several major developmental transitions during their complex lifecycle, which are enabled by precisely ordered gene expression programs. Transcriptomes from the 48-h blood stages of the major human malaria parasite Plasmodium falciparum have been described using cDNA microarrays and RNA-seq, but these assays have not always performed well within non-coding regions, where the AT-content is often 90-95%. Results: We developed a directional, amplification-free RNA-seq protocol (DAFT-seq) to reduce bias against AT-rich cDNA, which we have applied to three strains of P. falciparum (3D7, HB3 and IT). While strain-specific differences were detected, overall there is strong conservation between the transcriptional profiles. For the 3D7 reference strain, transcription was detected from 89% of the genome, with over 78% of the genome transcribed into mRNAs. We also find that transcription from bidirectional promoters frequently results in non-coding, antisense transcripts. These datasets allowed us to refine the 5′ and 3′ untranslated regions (UTRs), which can be variable, long (> 1000 nt), and often overlap those of adjacent transcripts. Conclusions: The approaches applied in this study allow a refined description of the transcriptional landscape of P. falciparum and demonstrate that very little of the densely packed P. falciparum genome is inactive or redundant. By capturing the 5′ and 3′ ends of mRNAs, we reveal both constant and dynamic use of transcriptional start sites across the intraerythrocytic developmental cycle that will be useful in guiding the definition of regulatory regions for use in future experimental gene expression studies.

Both malaria and intestinal helminths are endemic in sub-Saharan Africa, and their co-infection occurs commonly. This cross-sectional study assessed the prevalence of malaria and intestinal helminth co-infection in a sample of > 700 pregnant women in Ghana and identified risk factors for co-infection. The prevalence of malaria infection, intestinal helminth infection(s), and co-infection was 36.3%, 25.7%, and 16.6%, respectively. Women with intestinal helminth infection(s) were 4.8 times more likely to have malaria infection. Young age, low income, being single, and being primigravid were each associated with increased odds of co-infection. These associations were present when assessed separately for primi- and multigravid women, but the strength of associations varied considerably for the two groups of women. Young age had the strongest association among both primigravid (odds ratio = 5.2) and multigravid (odds ratio = 3.2) women. This study shows relatively high prevalence rates of malaria, intestinal helminths, and co-infection in pregnant women in Ghana.

Malaria has had a major effect on the human genome, many protective polymorphisms such as sickle cell trait having been selected to high frequencies in malaria endemic regions 1 , 2 . Recently, it was shown that the blood group variant Dantu provides 74% protection against all forms of severe malaria in homozygous individuals 3 – 5 . This is a similar degree of protection to sickle cell trait and considerably greater than the best malaria vaccine, but until now the protective mechanism has been unknown. Here, we demonstrate a significant impact of Dantu on Plasmodium falciparum-merozoite RBC invasion. Dantu was associated with extensive changes to the RBC surface protein repertoire, but unexpectedly, inhibition did not correlate with specific RBC-parasite receptor-ligand interactions. By following invasion using video microscopy, we found a strong link between RBC tension and merozoite invasion and identified a tension threshold above which invasion rarely occurred, even in non-Dantu RBCs. Dantu RBCs had higher average tension, meaning that a greater proportion resisted invasion. These findings provide both an explanation for the malaria-protective effect of Dantu, and fresh insights into why the efficiency of P. falciparum invasion might vary across the heterogenous populations of RBCs both within and between individuals.