Mutant/mutation
The mutant expresses a C-terminal cmyc-tagged version of ron3, PBANKA_1464900

Protein (function)
From the Abstract:

Recently we demonstrated that rhoptry neck protein 2 (RON2), which is crucial for tight junction formation in merozoites, is also important for sporozoite invasion of both target cells. With the aim of comprehensively describing the mechanisms of sporozoite invasion, the expression and localization profiles of rhoptry proteins were investigated in Plasmodium berghei sporozoites. Of 12 genes representing merozoite rhoptry molecules, nine are transcribed in oocyst-derived sporozoites at a similar or higher level compared to those in blood-stage schizonts. Immuno-electron microscopy demonstrates that eight proteins, namely RON2, RON4, RON5, ASP/RON1, RALP1, RON3, RAP1, and RAMA, localize to rhoptries in sporozoites. It is noteworthy that most rhoptry neck proteins in merozoites are localized throughout rhoptries in sporozoites. This study demonstrates that most rhoptry proteins, except components of the high-molecular mass rhoptry protein complex (rhoph1a, PBANKA_1400600; rhoph2, BANKA_0830200; rhoph3, PBANKA_0416000), are commonly expressed in merozoites and sporozoites in Plasmodium spp., which suggests that components of the invasion mechanisms are basically conserved between infective forms independently of their target cells

Phenotype
Ten mutants expressing 10 different c-myc tagged rhoptry proteins were analysed. Immuno-electron microscopy (IEM) analysis showed:
In P. berghei merozoites, RON2, RON4, RON5, RALP1, and ASP/RON1, which are categorized as rhoptry neck proteins in Pf merozoites, were confirmed to localize to the rhoptry neck region. In addition, RAP1, RON3, RhopH1A, RhopH2, and RhopH3 are observed in the rhoptry bulb region, as reported for Pf merozoites. RAMA is observed on the rhoptry membrane at the bulb region. RON6 could not be detected by anti-c-Myc antibodies, possibly because its protein amount in merozoites is not sufficient to be observed by IEM.

In sporozoites formed inside oocysts, it was confirmed that three components for the RhopH complex do not accumulate in rhoptries, as expected from the observation of far less amounts of transcripts and proteins in sporozoites compared to merozoites. Other than the RhopH complex, all proteins examined are localized to rhoptries in sporozoites as well as in merozoites. However, most proteins are distributed throughout rhoptries in sporozoites, despite their sub-localization in merozoites, suggesting that sub-compartmentation in rhoptries might be different between merozoites and sporozoites.

In salivary gland sporozoites RON2, RON4, RON5, RALP1 and RAP1 were detected in rhoptries of sporozoites residing in salivary glands, indicating that rhoptry proteins reside in rhoptries after sporozoite invasion of salivary glands, presumably available for subsequent invasion of hepatocytes in mammalian hosts. RON3 could not be detected, which might due to less target or c-Myc tagged protein amounts in salivary gland sporozoites.

Additional information
ron2, PBANKA_1315700;
ron4, PBANKA_0932000;
ron5, PBANKA_0713100;
ron6, PBANKA_0311700;
ralp1, PBANKA_0619700;
asp/ron1, PBANKA_1003600; (not tagged with c-myc) 
rap1, PBANKA_1032100;
ron3, PBANKA_1464900;
rama, PBANKA_0804500; (not tagged with c-myc)
rhoph1a, PBANKA_1400600;
rhoph2, PBANKA_0830200;
rhoph3, PBANKA_0416000.

Transcript analysis showed:
Six molecules categorized as encoding rhoptry neck proteins in merozoites (ron2, ron4, ron5, ron6, rhoptry-associated leucine zipper-like protein 1 (ralp1), and apical sushi protein (asp)/ron1) are also transcribed in sporozoites. Among six genes encoding rhoptry proteins localized to the bulb region in merozoites, rhoptry-associated protein 1 (rap1), ron3, and rhoptry associated membrane antigen (rama) are also transcribed in sporozoites; while the other three, encoding the components of the high-molecular mass rhoptry protein complex (RhopH complex), are transcribed far less in sporozoites than in schizonts. This data raises the possibility that RhopH1A, RhopH2, and RhopH3 may play roles predominantly in merozoites. In contrast, ron5, ron6, asp/ron1, and ron3 are predominantly transcribed in sporozoites vs. schizonts. The transcripts of rhoptry molecules expressed in sporozoites increase during sporozoite maturation in oocysts. After sporozoite invasion of salivary glands, the transcript amounts of ron2, ron4, rap1, ron3, and rama are significantly decreased, while transcripts of ron5, ron6, ralp1, and asp1/ron1 remain high or increase. In salivary gland sporozoites, ron5 and ron6 are the highest transcribed among rhoptry molecules; however, their amounts remain ∼200-fold less than that of a micronemal molecule, sporozoite protein essential for cell traversal 2 (spect2), whose transcription is strongly enhanced after sporozoites invade salivary glands.

Other mutants