Toxoplasma gondii chromatin remodeler SWI/SNF controls parasite division and gene expression.

Toxoplasma gondii is a zoonotic apicomplexan parasite that relies on highly orchestrated gene expression programs to coordinate its cell cycle progression. Although epigenetic mechanisms are recognized as pivotal drivers of developmental gene regulation in parasitic life cycles, the contributions of chromatin remodeling complexes to these processes remain largely unexplored. In this study, we focus on two core ATPase subunits of the SWI/SNF chromatin remodeling complex and investigate their roles in parasite biology and gene regulation. Our findings reveal that these SWI/SNF ATPases work coordinately, occupying the promoters of many tachyzoite-specific genes. Their deletion causes diminished chromatin accessibility and transcriptional reprogramming, downregulating tachyzoite-specific genes and unlocking certain transcripts normally confined to merozoite stage. Loss of these genes severely impairs parasite fitness and causes division defects, with incomplete endopolygeny accompanied by starch accumulation. TgSNF2b also interacts with the MORC remodeler to modulate chromatin architecture and gene expression. These findings provide new insights into the epigenetic regulation of gene expression and cell division in T. gondii and open new avenues for innovative strategies in toxoplasmosis control.