Circadian Biology in Parasites: Beyond Known Mechanisms

Circadian rhythms play a fundamental role in regulating biological processes across the tree of life. While these 24-h cycles are well-characterized in model organisms, their role in parasitic organisms has remained largely unexplored until recently. Here, we review emerging evidence that parasites possess intrinsic timekeeping abilities, focusing particularly on the malaria parasite Plasmodium. We examine two principal paradigms of biological timing: transcriptional-translational feedback loops and posttranscriptional feedback loops. Despite lacking canonical clock genes found in other eukaryotes, Plasmodium employs sophisticated regulatory machinery, including ApiAP2 transcription factors, chromatin regulators, and noncoding RNAs, that could form novel timing circuits. We discuss how these mechanisms might enable parasites to synchronize with host rhythms and optimize their development and transmission. Understanding these temporal regulatory networks could reveal new therapeutic strategies and expand our knowledge of biological timing mechanisms across evolution.