Form follows function: Variable microtubule architecture in the malaria parasite

Abstract

The malaria parasite undergoes a series of extensive morphological changes within its human host and mosquito vector. A scaffold of microtubules beneath a peripheral double membrane establishes and maintains the distinct shapes of all infectious forms, but the underlying structural basis remains unknown. Here we applied in situ electron cryo-tomography after focused ion beam milling to follow changes in the microtubule cytoskeleton throughout the Plasmodium life cycle. This revealed an unexpected level of structural and architectural diversity so far not observed in other organisms. Microtubules in migrating mosquito forms consist of 13 protofilaments reinforced by interrupted luminal helices. Conversely, gametocyte microtubules consist of 13 to 18 protofilaments with doublets, triplets and quadruplets of varying arrangements. We show the microtubule cytoskeleton within the native cellular context, highlighting structurally diverse apical rings which act as microtubule organising centres. This provides a unique view into a relevant human pathogen with an unusual microtubule cytoskeleton.