Mutant/mutation
The mutant expresses the yeast FlpL recombinase under the control of the promoter of trap.
The mutant does not contain a selectable marker. This marker (the hdhfr gene) has been removed from the genome by using the Flp/FRT site-specific recombination (SSR) system (see below 'Protein-function'). Removal of the hdhfr gene has been achieved by  transmission of the mutant through mosquitoes, thereby activating expression of the FlpL recombinase that resulted in the excision of the hdhfr gene which was flanked by FRT sequences.

Protein (function)
In the Flp/FRT site-specific recombination (SSR) system of yeast, the Flp recombinase recognizes the 34 bp FRT sites and excises any DNA located between two directly oriented sites (referred to as the FRTed sequence). The activity of FlpL (Low activity) recombinase is greatly reduced at 37°C and above - temperatures in erythrocytic stages in the vertebrate host - and is maintained at 20°C –25°C, temperatures permissive for parasite development in the mosquito.

Phenotype
The phenotype analyses indicate that expression of FlpL is specific for midgut and salivary gland sporozoites. Expression of FlpL did not affect viability of infectivity of the different life cycle stages. By analysis of excision of the FRTed hdhfr selectable marker it was shown that FlpL was only active in the sporozoite stages and that the FlpL/FRT system in sporozoites was efficient in excision of FRTed DNA sequences from the genome.

Additional information
This mutant expressing FlpL can be used for introducing additional DNA sequences (genes) that are flanked by FRT sequences. Subsequently these sequences can be removed by mosquito transmission. This 'conditional mutagenesis' approach allows for the analysis of the effect of removal of genes essential for blood stage development. For an example of using this approach see mutant RMgm-270

Derivatives of the TRAP/FlpL(−) clones expressing bright GFP fluorescence via the constitutive HSP70 promoter are now available as parasite “receivers” of conditional alleles of genes of interest.

See also mutant UIS4/Flp(-)F (RMgm-269) for a mutant expressing Flp under the control of the uis4 promoter that is specifically switched on in sporozoites after salivary gland invasion.

Other mutants
RMgm-269: A mutant expressing Flp under the control of the uis4 promoter that is specifically switched on in sporozoites after salivary gland invasion. In addition it expresses GFP under the control of the constitutive hsp70 promoter.
RMgm-278: A mutant expressing Flp under the control of the uis4 promoter that is specifically switched on in sporozoites after salivary gland invasion. It does not contain a drug-selectable marker and does not express GFP.
RMgm-270: A 'conditional knock-out mutant of MSP-1', generated using the Flp/FRT system.