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) 6% 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.
Plasmodium falciparum II3 strain was maintained at 37°C, 5% O2 and 5% CO2 in AB+ human RBCs in RPMI 1640 medium containing Albumax II (Invitrogen) supplemented with 2mM L- glutamine. Culture medium was changed in every two days to avoid providing unknown 24 hour rhythmic cues that might be present in the culture medium. Cultures were routinely monitored by Giemsa’s solution-stained thin blood smears and synchronized by treating the cultures with 5% sorbitol (w/v) to kill any late stage asexual stages. For time-series experiment mature segmented schizonts were isolated by centrifugation over cushions of 70% (v/v) isotonic Percoll (GE healthcare Life Sciences), washed twice with RPMI 1640 without Albumax and allowed to invade fresh RBCs for about two hours in a shaker maintained at 37°C . Following invasion, remaining schizonts were removed from the culture by overlaying the culture over cushions of 70% (v/v) isotonic Precool (GE healthcare Life Sciences). Pellet containing ~ two hours early ring stage infected RBCs and uninfected RBCs was then treated with 5% sorbitol (w/v) to kill the contaminating mature schizonts. Culture containing highly synchronous early ring stage parasites was then split into six-well plates. Over the course of 48 h, 1-2 mL of infected RBC culture was collected every two hours, media was removed by centrifugation for two minutes at 900g, and cells were lysed by adding 1 mL of TRIzol and immediately stored at -80°C deep freezer. The T0 time point was considered to be three hours after addition of Percoll cushion isolated segmented mature schizonts to the fresh RBCs.
Kumar SA, Aidan OD, Abhinay R, Hussein A, Abhinav K, Hifzur AR, Alyaa M, Fathia RB, Osamu K, Richard C, Sarah RE, Arnab P. Malaria parasites regulate intraerythrocytic development duration via serpentine receptor 10 to coordinate with host rhythms. Data accessible through GEO Series accession number GSE144976 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE144976)