Roberts, A. B. | Search bioRxiv

bioRxiv2021

Regulators of male and female sexual development critical for transmission of a malaria parasite

The transmission of malaria parasites from vertebrate host to mosquito vector requires a developmental switch in asexually dividing blood-stage parasites to sexual reproduction. In Plasmodium berghei the transcription factor AP2-G is required and sufficient for this switch, but how a particular sex is determined in a haploid parasite remains unknown. Using a global screen of barcoded mutants, we here identify ten genes essential for the formation of either male or female sexual forms and validate their importance for transmission. High-resolution single-cell transcriptomics of wild-type and mutant parasites portrays the developmental bifurcation and reveals a regulatory cascade of putative gene functions in determination and subsequent differentiation of each sex. A male-determining gene with a LOTUS/OST-HTH domain points towards unexpected conservation of molecular mechanisms of gametogenesis in animals and a distantly related eukaryotic parasite.

genomics↗

bioRxiv2019

Experimentally engineered mutations in a ubiquitin hydrolase, UBP-1, modulate in vivo resistance to artemisinin and chloroquine in Plasmodium berghei.

As resistance to artemisinins (current frontline drugs in malaria treatment) emerges in south East Asia (SEA), there is an urgent need to identify the genetic determinants and understand the molecular mechanisms underpinning such resistance. Such insights could lead to prospective interventions to contain resistance and prevent the eventual spread to other malaria endemic regions. Artemisinin reduced susceptibility in SEA has been primarily linked to mutations in P. falciparum Kelch13, which is currently widely recognised as a molecular marker of artemisinin resistance. However, 2 mutations in a ubiquitin hydrolase, UBP-1, have been previously associated with artemisinin resistance in a rodent model of malaria and some cases of UBP-1 mutation variants associating with artemisinin treatment failure have been reported in Africa and SEA. Here, CRISPR-Cas9 genome editing and pre-emptive drug pressures was used to test these artemisinin resistance associated mutations in UBP-1 in P. berghei sensitive lines in vivo. The data demonstrate that the V2721F UBP-1 mutation results in artemisinin resistance and some low-level resistance to chloroquine, while the V2752F mutation results in high-level resistance to chloroquine and moderate resistance to artemisinins. Genetic reversal of the V2752F mutation restored chloroquine sensitivity in these mutant lines while simultaneous introduction of both mutations could not be achieved and appears to be lethal. Interestingly, these mutations carry a detrimental growth defect, which would possibly explain their lack of expansion in natural infection settings. This is the first independent, direct experimental evidence on the role of UBP-1 in artemisinin and chloroquine resistance under in vivo conditions.

microbiology↗