Figure 2.

The PfCRT L272F mutation causes an increase in the DV volume and exerts a fitness cost. (a) Average DV volumes of the pfcrt-modified Dd2^{Dd2 L272F} (green), Dd2^Dd2 (red) and Dd2^GC03 (dark orange) lines over a 36-hour time course. DV volumes are represented as the means ± SEM of 15 independent experiments. (b) Changes in allele frequencies over time, as derived from head-to-head in vitro competition assays between Dd2^Dd2 and Dd2^{Dd2 L272F}. Dd2^Dd2 and Dd2^{Dd2 L272F} were seeded at a 1:4 ratio and monitored every 2 days for 40 days (i.e. 20 generations). After 4 generations, cultures were split into two replicates. Observed allele frequencies (shown as means ± SEM beginning on the 5^th generation, i.e., day 10) were fitted using a computer model of the Plasmodium life cycle (solid lines, yielding a very close correlation with r² = 0.992). Results indicated a 20 ± 1% fitness difference and 4.0 ± 0.2 hour increase in the cell cycle duration in the Dd2^{Dd2 L272F} line. D lc h, difference in the intra-erythrocytic life cycle in hours; D r, difference in relative fitness.