Inducible developmental reprogramming redefines commitment to sexual development in the malaria parasite Plasmodium berghei
Authors: Robyn S Kent
Nisha Philip
Oliver Billker
Andrew P Waters
Rachael Cameron
Katarzyna K Modrzynska
Journal: Nature microbiology (2018)
Discipline: MICROBIOLOGY
Keywords: malaria infection; Plasmodium spp.; red blood cells; developmental pathways; asexual replication
Affiliations: Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK., Department of Microbiology and molecular genetics, University of Vermont, Burlington, VT, USA., Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK. ., Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK. ., Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, UK.

Abstract:  During malaria infection, Plasmodium spp. parasites cyclically invade red blood cells and can follow two different developmental pathways. They can either replicate asexually to sustain the infection, or differentiate into gametocytes, the sexual stage that can be taken up by mosquitoes, ultimately leading to disease transmission. Despite its importance for malaria control, the process of gametocytogenesis remains poorly understood, partially due to the difficulty of generating high numbers of sexually committed parasites in laboratory conditions1. Recently, an apicomplexa-specific transcription factor (AP2-G) was identified as necessary for gametocyte production in multiple Plasmodium species2,3, and suggested to be an epigenetically regulated master switch that initiates gametocytogenesis4,5. Here we show that in a rodent malaria parasite, Plasmodium berghei, conditional overexpression of AP2-G can be used to synchronously convert the great majority of the population into fertile gametocytes. This discovery allowed us to redefine the time frame of sexual commitment, identify a number of putative AP2-G targets and chart the sequence of transcriptional changes through gametocyte development, including the observation that gender-specific transcription occurred within 6 h of induction. These data provide entry points for further detailed characterization of the key process required for malaria transmission. 

Retracted: No

PubPeer comments:
 This is a cool paper with a great new tool for studying gametocytes. I want to draw attention to a potential discrepency between figures 2 and 4 however. The former figure shows that the un-induced *Plasmodium berghei* modified strain gives a 0.14 percentage of gametocytes captured by FACS of infected cells. In figure 4 the 820 line (I m not sure if this is the parental line of the modified strain or if it is the modified strain itself) gives total gametocyte percentage of around 14%. I can t find in the manuscript why there would be such differences between these two figures which are meant to show the background signal of gametocytes compared to induction knock-out. Does the former figure include uninfected red blood cells while the latter is only of infected cells? , 
 Thanks for sharing your appreciation for our paper! The difference between the data in the two panels is because they do not show the same thing, i.e. you are correct to observe that the uninduced PBGAMi mutant does not behave like the parental 820 line. There is some relevant biology behind this and I am sorry we skipped over this in the paper, leading to confusion. In Fig. 2c the two FACS plots both show the PBGAMi mutant line without and with induction by rapamycin (shown as R- and R+ on the axis label). You are right to note that in the uninduced control gametocytes are virtually absent (only 0.14% of all infected erythrocytes fall within the gates; upper panel). This led us to conclude that this line behaves not like wild type, but like an ap2g knockout. We were not too surprised and did not dwell on it in the paper, since in this line the 5u2019 upstream region in the endogenous ap2g locus is replaced with an hsp70 promoter that remains inverted until the split Cre protein is activated by rapamycin (Fig. 1f). It seems the inverted promoter cannot drive ap2g expression well enough to maintain wild type levels of gametocyte production. No big surprise, but we should obviously have spelled it out to avoid confusion. Panel 2b is more informative, since it shows additional biological replicates and includes the parental 820 line. The behaviour of the parental line is intermediate between the R+ and R- condition of the PBGAMi mutant, as you expected. In Fig. 4b we show a different type of experiment, where the parental line in the left panel serves as a control for the mutant in the right panel. Gametocyte numbers in the parental 820 line, which is wild type with respect to both the ap2g locus and PBANKA_0312700 are within the typical range of a wild type infection. Here the parental line is the appropriate control to reveal the loss of males observed in the mutant. ,