Structured illumination microscopy reveals actin I localization in discreet foci in Plasmodium berghei gametocytes

•Actin I was detected in discreet ∼130 nm foci in P. berghei gametocytes.•Treatment with jasplakinolide did not modify the length of the structures.•Sedimentation of actin I at 100 000 × g confirms filamentous actin in gametocytes.

Actin has important roles in Plasmodium parasites but its exact function in different life stages is not yet fully elucidated. Here we report the localization of ubiquitous actin I in gametocytes of the rodent model parasite P. berghei. Using an antibody specifically recognizing F-actin and deconvolution microscopy we detected actin I in a punctate pattern in gametocytes. 3D-Structured Illumination Microscopy which allows sub-diffraction limit imaging resolved the signal into structures of less than 130 nm length. A portion of actin I was soluble, but the protein was also found complexed in a stabilized form which could only be completely solubilized by treatment with SDS. An additional population of actin was pelleted at 100 000 × g, consistent with F-actin. Our results suggest that actin in this non-motile form of the parasite is present in short filaments cross-linked to other structures in a cytoskeleton.

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