FIGURE 1.

Bidirectional promoter activity of var introns. Promoter activity of var introns was measured in transient transfection assays using the reporter construct pHLIRH (A), containing the reporter genes firefly and Renilla luciferase. Parasites were transfected and luciferase activity (firefly, light gray; Renilla dark gray) was measured from 2.5 mL cultures after ∼68 h (ring stage, light-colored columns) and ∼92 h (schizonts, dark columns), respectively (B). Luminescence values were standardized to 1% parasitemia. Genomic loci and upstream promoter types of var genes corresponding to the chosen var introns (grouping of var5′ promoter types according to Lavstsen et al. [2003]) (C).