Generation of Novel NF135 and NF54 Lines Expressing Fluorescent Reporter Proteins Under the Control of Strong and Constitutive Promoters.

Transgenic reporter lines of malaria parasites that express fluorescent or luminescent proteins are valuable tools for drug and vaccine screening assays as well as to interrogate parasite gene function. Different ( ) reporter lines exist, however nearly all have been created in the African NF54/3D7 laboratory strain. Here we describe the generation of novel reporter lines, using CRISPR/Cas9 gene modification, both in the standard NF54 background and in a recently described Cambodian NF135.C10 line. Sporozoites of this line show more effective hepatocyte invasion and enhanced liver merozoite development compared to NF54. We first generated NF54 reporter parasites to analyze two novel promoters for constitutive and high expression of mCherry-luciferase and GFP in blood and mosquito stages. The promoter sequences were selected based on available transcriptome data and are derived from two housekeeping genes, i.e., translation initiation factor SUI1, putative (, PF3D7_1243600) and 40S ribosomal protein S30 (, PF3D7_0219200). We then generated and characterized reporter lines in the NF135.C10 line which express GFP driven by the and promoters as well as by the previously used α promoter (α, ). The reporter line showed strongest GFP expression in liver stages as compared to the other two lines. The strength of reporter expression by the promoter throughout the complete life cycle, including liver stages, makes transgenic lines expressing reporters by the promoter valuable novel tools for analyses of .