Dominant negative mutant of P lasmodium R ad51 causes reduced parasite burden in host by abrogating DNA double‐strand break repair

Summary Malaria parasites survive through repairing a plethora of DNA double‐stranded breaks ( DSB s) experienced during their asexual growth. In P lasmodium   R ad51 mediated homologous recombination ( HR ) mechanism and homology‐independent alternative end‐joining mechanism have been identified. Here we address whether loss of HR activity can be compensated by other DSB repair mechanisms. Creating a transgenic P lasmodium line defective in HR function, we demonstrate that HR is the most important DSB repair pathway in malarial parasite. Using mouse malaria model we have characterized the dominant negative effect of P f R ad51 K143R mutant on P lasmodium   DSB repair and host–parasite interaction. Our work illustrates that P lasmodium berghei harbouring the mutant protein ( P f R ad51 K143R ) failed to repair DSB s as evidenced by hypersensitivity to DNA ‐damaging agent. Mice infected with mutant parasites lived significantly longer with markedly reduced parasite burden. To better understand the effect of mutant P f R ad51 K143R on HR , we used yeast as a surrogate model and established that the presence of P f R ad51 K143R completely inhibited DNA repair, gene conversion and gene targeting. Biochemical experiment confirmed that very low level of mutant protein was sufficient for complete disruption of wild‐type P f R ad51 activity. Hence our work provides evidence that HR pathway of P lasmodium could be efficiently targeted to curb malaria.