Mitotic Evolution of Plasmodium falciparum Shows a Stable Core Genome but Recombination in Antigen Families
Figure 1
Generation of atovaquone (ATQ)-resistant parasites.
A. Selection schematic. An initial parasite clone (3D7) was split into three lines after 55 days, and 20 nM or 50 nM ATQ pressure was applied to lines R4 and R5, respectively. The parental line was kept drug-free. After 24 days, the parental line was split again into four lines, and 2 nM ATQ pressure was applied to three lines (R1, R2, and R3) while line S1 was kept drug free. R2 was again split after 74 days, and 20 nM ATQ was applied repeatedly to line R2b. After the indicated time in culture, all lines were cloned by limiting dilution. Four ATQ-resistant clones were kept in culture (Generation 1 (G1): R1a and b G1 and R2a and b G1) and recloned, resulting in a second generation of clones (Generation 2 (G2): R1a and b G2 and R2a and b G2). The number of days (d) in culture between splits is indicated above each flask. B. ATQ structure and growth inhibition assay. EC50 values for 3D7 parent, the sensitive clones, and the ATQ-resistant clones are the means ± SD of three independent experiments performed in quadruplicate. Statistically significant differences between EC50 values of the parental 3D7 line and the ATQ-resistant clones were calculated by a one-way ANOVA followed by a Dunnett posttest (*, p<0.0001).