The role of intraflagellar transport during the disassembly of the Leishmania mexicana flagellum
The ability of the Leishmania parasites to remodel its flagellum is important for its survival as it navigates through multiple host environments during its lifecycle. The most striking remodelling step is during the differentiation from the long, motile flagellum of promastigotes to the short, sensory flagellum of amastigotes. Previous work has suggested a large reduction in the intraflagellar transport (IFT) system can lead to flagellum disassembly in Leishmania. However, it is not clear how or when the IFT system changes during this disassembly process. Here, we show that the flagellum disassembly is associated with a large drop in IFT numbers and a slight decrease in IFT velocity. This drop occurs within 30 minutes of differentiation suggesting the ‘shock’ of the change in environmental conditions is the likely trigger of the IFT reduction. The potential role of post-translational modifications in regulating IFT was investigated but no major changes in modification patterns were observed. We also looked at a previously documented naturally occurring Leishmania mutant, known as the dysflagellar mutant. It had a very short but otherwise normal axoneme but a large mass of unorganised material at the exit of the flagellar pocket, which created a bulge. The underlying cause of this mutant was hypothesised to be a defect in IFT. However, analyses showed that a large 27 kb deletion, containing four genes, on chromosome 35 was present. We found when the deletion of a serine kinase was replicated it led to a similar phenotype as the dysflagellar mutant. This could be rescued when the serine kinase was reintroduced. Overall, we have provided initial observations regarding flagellum remodelling of Leishmania that can be used to address unanswered questions such as what is controlling flagellum (dis)assembly.
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