Structure of the used donor plasmids and expression cassettes. A: Scheme of the basis donor plasmid (linear structure) with its modular structure. The cassette allows the simple substitution of promoter, signal peptide (sp) gene of interest and terminator DNA sequences without loosing the flanking loxP sites due to unique restriction sites. B: "Floxed" (flanked by loxP) expression modules were used that encode an expression cassette for the MSP1 C-terminus gene (top) and the blasticidin resistance (bsdR, bottom) gene, respectively. All expression cassettes are flanked by a histone promoter (H4-1) and a beta tubulin terminator (BTU2).