A MOTILITY FUNCTION FOR THE PARAFLAGELLAR ROD OF LEISHMANIA PARASITESREVEALED BY PFR-2 GENE KNOCKOUTS

We demonstrate a functional role for the paraflagellar rod (PFR) in mo tility of Leishmania mexicana. The PFR is a complex cytoskeletal struc ture running parallel to the axoneme in the flagella of kinetoplastid protozoa. The PFR is composed of a latticework of protein filaments wh ose major constituents are two related proteins (PFR-1 and PFR-2 in Le ishmania). The molecular details of their assembly into PFR filaments are unknown as is the biological function of the PFR. As an approach t o understanding the structure and function of the PFR in Leishmania, w e made L. mexicana null mutants of PFR-2. PFR-2 minus parasites grow a nd divide normally in culture and still express the PFR-1 protein. The y lack most of the PFR structure demonstrating that the PFR-2 protein is an essential constituent of the PFR. Detailed ultrastructural analy sis of the PFR-2 null mutant reveals the presence of a residual inner substructure of the PFR which contains PFR-1 protein, indicating that PFR-1 can polymerize in the absence of PFR-2. The PFR-2 null mutant di splays pronounced changes in flagellar beat waveform and forward swimm ing velocity, compared to wild type parasites consistent with decrease d internal elastic bending resistance in PFR-lacking flagella, and ind icating a functional role for the PFR in the motility of Leishmania. ( C) 1997 Elsevier Science B.V.