Mutant/mutation
In the 'promoter-swap' mutant the promoter of myosin A is replaced by an 'asexual blood stage’ promoter that is silent (or has a strongly reduced activity) in ookinetes (the promoter of ama1, PBANKA_091500). Expression of MyoA was absent in mutant ookinetes whereas wild type ookinetes express MyoA.

Protein (function)
Myosin A is the founding member of unconventional class XIV myosins. These myosins are remarkably small, essentially composed of the actin-interacting ATPase domain, followed by a very short tail domain. Class XIV myosins are exclusively found in the Alveolata branch of eukaryotic organisms, including the Apicomplexa. Plasmodium Myosin A is considered vital for merozoite invasion of erythrocytes. Myosin A is a component of the glideosome of apicomplexan parasites, which is an actin- and myosin-based machine located at the pellicle, between the plasma membrane (PM) and inner membrane complex (IMC), that powers parasite motility, migration, and host cell invasion and egress. It is composed of myosin A, its light chain MLC1, and two gliding-associated proteins, GAP50 and GAP45

Phenotype
Myosin A is considered vital for blood stage development/multiplication (merozoite invasion of erythrocytes).

In the 'promoter-swap' mutant the promoter of myosin A is replaced by an 'asexual blood stage’ promoter that is silent (or has a strongly reduced activity) in ookinetes (the promoter of ama1, PBANKA_091500). Expression of MyoA was absent in mutant ookinetes whereas wild type ookinetes express MyoA.

Phenotype analyses of the promoter swap mutant indicates that Myosin A has an essential role in ookinete motility (and subsequent oocyst development)

Additional information
Oocysts of the promoter mutant produced normal numbers of sporozoites which invaded salivary glands. These sporozoites produced Myosin A and were motile. Mutant oocysts were obtained by micro-injection of cultured, mature ookinetes into the haemocoel/thorax of mosquitoes.

Other mutants