Mutant/mutation
In the 'promoter swap mutant': the promoter of pp1 has been replaced with the asexual blood stage promoter ama1 (PBANKA_0915000). This promoter is active in asexual blood stages but not in gametocytes.

Protein (function)
PP1 is a serine/threonine protein phosphatase

Phenotype
To investigate the function of PP1 during cell division in male gametogenesis, we used a promoter trap double homologous recombination (PTD) approach to downregulate gene expression at this stage by placing the pp1 gene under the control of the AMA1 promoter. AMA1 is known to be highly expressed in asexual blood stages, but not during sexual differentiation.

PP1 is expressed both in asexual blood stages and (male) gametocytes. Knock-out of the pp1 gene is not possible since it has an essential role in asexual blood stages. In the promoter swap mutant PP1 is expressed in asexual blood stages but is down-regulated in (male) gametocytes.

The PP1PTD parasites grew slower than the WT-GFP controls in the asexual blood stage but produced normal numbers of gametocytes in mice.
Reduced numbers of exflagellation (male gamete formation). Strongly reduced ookinete formation. No oocyst formation.

Additional information
Evidence is presented that:
- Ultrastructure analysis of PP1PTD male gametocytes shows defects in nuclear pole and axoneme assembly after activation. The development of PP1PTD male gametocytes was severely retarded, although axoneme growth increased.

From the Abstract:
'Using real-time live-cell and ultrastructural imaging, conditional gene knockdown, RNA-seq and proteomic approaches, we show that Plasmodium PP1 is implicated in both mitotic exit and, potentially, establishing cell polarity during zygote development in the mosquito midgut'.

From the paper: 'we used an auxin-inducible degron (AID) system to try and study the effect of rapid PP1 degradation in gametocytes. We tagged the endogenous pp1 gene with an AID/HA epitope tag to degrade the fusion protein in presence of auxin (Philip and Waters, 2015), and successfully generated pp1- AID parasite lines as shown by integration PCR but could not deplete kinesin-13 protein by auxin treatment'.

Other mutants