Genetic Manipulation Toolkits in Apicomplexan Parasites

Apicomplexan parasites are a group of intracellular pathogens of great medical and veterinary importance, including Toxoplasma gondii and Plasmodium, which cause toxoplasmosis and malaria, respectively. Efficient and accurate manipulation of their genomes is essential to dissect their complex biology and to design new interventions. Over the past several decades, scientists have continually optimized the methods for genetic engineering in these organisms, and tremendous progress has been made. Here, we review the genetic manipulation tools currently used in several apicomplexan parasites, and discuss their advantages and limitations. The widely used CRISPR/Cas9 genome editing technique has been adapted in several apicomplexans and shown promising efficiency. In contrast, conditional gene regulation is available in only a limited number of organisms, mainly Plasmodium and Toxoplasma, thus posing a research bottleneck for other parasites. Conditional gene regulation can be achieved with tools that regulate gene expression at the DNA, RNA or protein level. However, a universal tool to address all needs of conditional gene manipulation remains lacking. Understanding the scope of application is key to selecting the proper method for gene manipulation.