The apicomplexan protozoan Toxoplasma gondii, the causative agent of toxoplasmosis, harbors an apicoplast, a plastid-like organelle with essential metabolic functions. Although the FASII fatty acid biosynthesis pathway located in the apicoplast is essential for parasite survival, the cellular effects of FASII disruption in T. gondii had not been examined in detail. Here, we combined light and electron microscopy techniques – including focused ion beam scanning electron microscopy (FIB-SEM) – to characterize the effect of FASII disruption in T. gondii, by treatment with the FASII inhibitor triclosan or by inducible knockdown of the FASII component acyl carrier protein. Morphological analyses showed that FASII disruption prevented cytokinesis completion in T. gondii tachyzoites, leading to the formation of large masses of ‘tethered’ daughter cells. FIB-SEM showed that tethered daughters had a mature basal complex, but a defect in new membrane addition between daughters resulted in incomplete pellicle formation. Addition of exogenous fatty acids to medium suppressed the formation of tethered daughter cells and supports the notion that FASII is essential to generate lipid substrates required for the final step of parasite division.
The authors declare no competing or financial interests.
E.S.M.-D., R.C.V., N.S. and W.d.S. contributed to the study design. E.S.M.-D. and M.C. performed the experiments. R.C.V. helped with the experiments. E.S.M.-D. performed data analysis and interpretation. E.S.M.-D. and W.d.S. wrote the article.
This work was supported by the Indo-Brazil Collaborative Programme, sponsored by the Department of Science and Technology, Ministry of Science and Technology (India) [grant number DST/ INT/ BRAZIL RPO-01/2009/P-1] and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) [grant number 490440/2009-6]; and also by fellowships and grants from CNPq, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ).
Supplementary information available online at http://jcs.biologists.org/lookup/doi/10.1242/jcs.185223.supplemental
- Received December 21, 2015.
- Accepted July 19, 2016.
- © 2016. Published by The Company of Biologists Ltd