<em>Plasmodium berghei</em> High-Throughput (PbHiT): a CRISPR-Cas9 System to Study Genes at Scale

Genetic modification is essential for understanding parasite biology, yet it remains challenging in <i>Plasmodium.</i> This is partially due to the parasite's low genetic tractability and reliance on homologous recombination, since the parasites lack the canonical non-homologous end-joining pathway. Existing approaches, such as the <i>Plasmo</i>GEM project, enable genome-wide knockouts but remain limited in coverage and flexibility. Here, we present the <i>Plasmodium berghei</i> high-throughput (PbHiT) system, a scalable CRISPR-Cas9 protocol for efficient genome editing in rodent malaria parasites. The PbHiT method uses a single cloning step to generate vectors in which a guide RNA (gRNA) is physically linked to short (100 bp) homology arms, enabling precise integration at the target locus upon transfection. The gRNA also serves as a unique barcode, allowing pooled vector transfections and identification of mutants by downstream gRNA sequencing. The PbHiT system reliably recapitulates known mutant growth phenotypes and supports both knockout and tagging strategies. This protocol provides a reproducible and scalable tool for genome editing in <i>P. berghei</i>, enabling both targeted functional studies and high-throughput genetic screens. Additionally, we provide an online resource covering the entire <i>P. berghei</i> protein-coding genome and describe a step-by-step pooled ligation approach for large-scale vector production. Key features • PbHiT provides a high-throughput CRISPR-Cas9 genome editing platform optimised for <i>Plasmodium berghei</i> experimental infections in rodents. • This protocol enables efficient and reproducible generation of knockout and tagged parasite lines using short homology arms. • This protocol is supported by a free online resource for <i>P. berghei</i> gene construct design and requires basic knowledge of cloning. • Transfection of <i>Plasmodium berghei</i> requires experience in handling mice/rats, an ethical permit, and an animal facility.