Mutant/mutation
The mutant expresses GFP fused to a minitransgene containing the N-terminus with the HT-motif (host-targeting motif) of the histidine-rich protein II of P. falciparum (HRPIIminhis.HT.GFP) .
In the paper a second (control) mutant is described expressing GFP fused to a minitransgene containing an alanine-rich replacement HT-motif (HRPIIminhis.Δ.GFP).

Protein (function)
The host-targeting motif (HT-motif) has been identified as an 11-amino acid signal required for the secretion of proteins from the P. falciparum vacuole to the human erythrocyte ((Hiller, N.L. (2004) Science 306:1934-37). The truncated HRPII-proteins were previously used to define minimal soluble reporters needed to detect and establish HT-mediated export of GFP in P. falciparum  ( Lopez-Estrano C. et al (2003) Proc Natl Acad Sci U S A 100: 12402-12407).
The full-length PfHRPII protein (histidine rich protein) contains an N-terminal SS and HT motif, followed by a sequence rich in histidine-repeats that extends to the C terminus. In contrast, the minitransgene contains the HRPII N terminus with either the wildtype HT motif (HRPIIminhis.HT.GFP) or an alanine-rich replacement HT-motif (HRPIIminhis.Δ.GFP) followed by a single monomeric repeat of the histidine rich region fused to GFP.

Phenotype
HRPIIminhis.HT.GFP, green fluorescence was readily detected in the host erythrocyte. Green fluorescence was also detected in cytoplasm of the parasite, presumably because the constitutive eefia promoter is used to drive transgene expression.
In the mutant in which the HT-motif was replaced (HRPIIminhis.Δ.GFP) with an alanine-rich sequence the release of GFP into the erythrocyte cytoplasm was blocked. GFP was detected in the body of the parasite as well as tubular extensions connected to vesicular elements at the periphery of the erythrocyte.
These analyses indicate that the HT-motif can be utilized by P. berghei in exporting proteins to the erythrocyte cytoplasm and suggests that the machinery for HT-dependent export is conserved throughout the genus Plasmodium. They also indicate the presence of tubovesicular connections that extend between the vacuolar parasite and the periphery of the host erythrocyte, as detected in live cells.

Additional information

Other mutants