Micronemal protein 13 contributes to the optimal growth of Toxoplasma gondii under stress conditions
- 131 Downloads
Toxoplasma gondii is a ubiquitous parasitic protozoan infecting humans and a wide variety of animals. Fast-replicating tachyzoites during acute infection and slowly growing bradyzoites during chronic infection are the two basic forms of T. gondii in intermediate hosts. Interconversion between the two contributes to the transmission and pathogenesis of this parasite. Secretory micronemal proteins are thought to mediate interactions with host cells and facilitate parasite invasion, therefore the majority of them are highly expressed in tachyzoites. Micronemal protein 13 (MIC13) is unique in that its expression is low in tachyzoites and is upregulated under bradyzoite-inducing conditions. Previous attempts to disrupt this gene were not successful, implying that it may play critical roles during parasite growth. However, in this study, MIC13 was successfully disrupted in type 1 strain RH and type 2 strain ME49 using CRISPR/Cas9-mediated gene disruption techniques. Consistent with its low expression in tachyzoites and increased expression under stress or bradyzoite-inducing conditions, MIC13-inactivated mutants displayed normal growth, host cell invasion, intracellular replication, and egress, as well as acute virulence at the tachyzoite stage. However, under stress conditions, such as high pH or oxygen limitation, MIC13-disrupted parasites showed significantly slower growth rates compared to the parental strains, suggesting that it is required for optimal parasite growth under bradyzoite-inducing or stress conditions. This is the first micronemal protein reported to have such expression pattern and function modes, which expands our understanding of the diverse functions of micronemal proteins.
KeywordsMIC13 Bradyzoite Stress Toxoplasma gondii Micronemal protein
This work was supported the National Key Research and Development Program of China (Grant no. 2017YFD0500402), the National Basic Science Research Program (973 program) of China (Grant no. 2015CB150300), and the Natural Science Foundation of Hubei Province (Project 2017CFA020). The funders had no role in the study design, data collection and analysis, preparation of the manuscript, or decision to submit the work for publication.
Compliance with ethical standards
All animal experiments were approved by the Ethical Committee of Huazhong Agricultural University (permit no. HZAUMO-2017-023).
The authors declare they have no conflict of interest.
- Friedrich N, Santos JM, Liu Y, Palma AS, Leon E, Saouros S, Kiso M, Blackman MJ, Matthews S, Feizi T, Soldati-Favre D (2010) Members of a novel protein family containing microneme adhesive repeat domains act as sialic acid-binding lectins during host cell invasion by apicomplexan parasites. J Biol Chem 285:2064–2076CrossRefGoogle Scholar
- Krishnamurthy S, Deng B, del Rio R, Buchholz KR, Treeck M, Urban S, Boothroyd J, Lam YW, Ward GE (2016) Not a simple tether: binding of toxoplasma gondii AMA1 to RON2 during invasion protects AMA1 from rhomboid-mediated cleavage and leads to dephosphorylation of its cytosolic tail. mBio 7(5):e00754-16Google Scholar
- Meissner M, Reiss M, Viebig N, Carruthers VB, Toursel C, Tomavo S, Ajioka JW, Soldati D (2002) A family of transmembrane microneme proteins of Toxoplasma gondii contain EGF-like domains and function as escorters. J Cell Sci 115:563–574Google Scholar
- Selseleh M, Modarressi MH, Mohebali M, Shojaee S, Eshragian MR, Selseleh M, Azizi E, Keshavarz H (2012) Real-time RT-PCR on SAG1 and BAG1 gene expression during stage conversion in immunosuppressed mice infected with Toxoplasma gondii Tehran strain. Korean J Parasitol 50:199–205CrossRefGoogle Scholar
- Shen B, Brown KM, Lee TD, Sibley LD (2014) Efficient gene disruption in diverse strains of Toxoplasma gondii using CRISPR/CAS9. Mbio 5:01114–01114Google Scholar