SRA

The intra-erythrocytic developmental cycle (IDC) of malaria parasites is synchronized with the time-of-day hosts feed, but the mechanism underpinning this coordination is unknown. Combining in vivo and in vitro approaches using rodent and human malaria parasites, we reveal that: (i) 57% of P. chabaudi genes exhibit 24 h “circadian” periodicity in expression; (ii) 58% of these genes lose rhythmicity when the IDC is out-of-synchrony with host rhythms; (iii) 9% of P. falciparum genes show circadian expression under free-running conditions; (iv) Serpentine receptor 10 (SR10) is circadian and disrupting it in rodent models shortens the IDC by 2-3 hours; (v) diverse processes, including DNA replication, the ubiquitin and proteasome pathways, are affected by disruption of SR10 and loss of coordination with host rhythms. Our results reveal that malaria parasites are at least in part responsible for scheduling their IDC, explaining the fitness benefits of coordination with host rhythms. Overall design: Ring stage sr10KO (clone A and B) and wild type P. chabaudi parasites were sub-inoculated into groups of four CBA mice each (1 x 106 parasitized RBCs per mouse) by intravenous injection at 20:30 hrs, day 0. Starting at 20:30 hrs on day 2 post-infection, blood smears were taken for both groups every three hours for 48 hrs producing a total of 17 time points. 20µl of blood were also collected via tail snip at these time points, washed in PBS and immediately treated with 500 uL TRIzol reagent and stored shortly at 4°C and for long term at -80°C. Total RNA was isolated from TRIzol treated samples according to the manufacturer's instructions (Life Technologies). Strand-specific mRNA libraries were prepared from total RNA using TruSeq Stranded mRNA Sample Prep Kit LS (Illumina) according to the manufacturer's instructions. Briefly, at least 100ng of total RNA was used as starting material to prepare the libraries. PolyA+ mRNA molecules were purified from total RNA using oligo-T attached magnetic beads. First strand synthesis was performed using random primers followed by second strand synthesis where dUTP were incorporated in place of dTTP to achieve strand-specificity. Ends of the double stranded cDNA molecules were adaptor ligated and the libraries amplified by PCR for 15 cycles. Libraries were sequenced on Illumina HiSeq 4000 platform with paired-end 100/150bp read chemistry according to manufacturer's instructions. Data from 14 timepoints were anlyzed further