Mutant/mutation
The mutant lacks expression of FAP20. In addition, it expresses GFP under control of a male gametocyte specific promoter and RFP under the control of a female gametocyte specific' promoter (and the mutant does not contain a drug-selectable marker cassette that has been removed by negative selection).

Published in: bioRxiv preprint doi: https://doi.org/10.1101/2023.10.19.562943

Protein (function)
Male gametocytes undergo three rounds of rapid genome replication via closed mitosis and coordinate the formation of eight axonemes with genome multiplication and separation. From a bipartite microtubule organizing center (MTOC) that bridges the nuclear envelope, mitotic spindles form within the nucleus, and axonemes form at the cytosolic face of the MTOC. Plasmodium axonemes usually feature a classic 9+2 microtubule array with two central microtubules being surrounded by 9 doublets. Yet, often axonemes with deviating arrays are formed. Parasites that cannot form axonemes or form non-motile axonemes are infertile and cannot establish an infection in the mosquito. Whether Plasmodium axoneme assembly, stability or function depends on Microtubule inner proteins (MIPs) has not been studied so far.
Microtubule inner proteins, MIPs, are microtubule associated proteins that bind to tubulin from the luminal side. Most MIPs so far were found in axonemes with over 60 MIPs being revealed in sperm axonemes. To investigate if there are MIPs in Plasmodium axonemes we searched for orthologs to known MIPs from other organisms using PlasmoDB. Blasting known axoneme associated MIPs), we identified orthologues to the two flagellar associated proteins FAP20 and FAP52. P. berghei and P. falciparum FAP52 orthologues were less well preserved (compared to FAP20 on a sequence level), but their structure, consisting of two WD40 domains, was highly similar to that of human or Chlamydomonas FAP52.

Phenotype
No phenotype different from wild type was detected throughout the complete life cycle (although a (slightly) lower number of salivary gland sporozoites compared to wildtype).

See also mutant RMgm-5434 (fab20/fap52(-)) lacking expression of both FAP20 and FAB52: this mutant showed strongly reduced male gamete formation (and ookinete/oocyst formation). Evidence is presented that axonemes are formed during male gamete formation of mutant fab20/fap52(-) but that in the microtubule doublets often a small gap exists between the protofilaments that link the B-tubule to the A-tubule

Additional information
 From the paper: 'Microtubule inner proteins, MIPs, are microtubule associated proteins that bind to tubulin from the luminal side. Here we investigate the role of four MIPs in a rodent malaria parasite for their role in transmission to and from the mosquito. We show by single and double gene deletions that SPM1 and TrxL1, MIPs associated with the subpellicular microtubules are dispensable for transmission from the vertebrate host to the mosquito and back. In contrast, FAP20 and FAP52, MIPs associated with the axonemes of gametes, are essential for transmission to mosquitoes but only if both genes are deleted. In the absence of both, FAP20 and FAP52 the B-tubule of the axoneme partly detaches from the A-tubule resulting in the deficiency of axonemal beating and hence gamete formation and egress. Our data suggest that a high level of redundancy ensures microtubule stability in the transmissive stages of Plasmodium'.

Other mutants