Mutant/mutation
The mutant lacks expression of gcβ (deleted the first three exons of gcβ causing frame shift mutation) AND lacks expression of cdc50a.
In the paper several additional mutants are described expressing mutated forms of gcβ (see also below)

Protein (function)

Phenotype
Wild type gametocyte production, ookinete production and morphology, Ookinetes lost gliding motility. No oocyst production and sporozoite production

Additional information
This study describes a large number of mutants expressing tagged (mutated) versions of different proteins, gene-deletion mutants and mutants with mutated genes (see link).

genes tagged:
gcβ (PY17X_1138200), gcα (PY17X_0911700), pdeδ (PY17X_1338400), pkg (PY17X_1009800), cdc50a (PY17X_0619700), cdc50b (PY17X_0916600); imc1 (f,g,i,j,k,l,m), alvX (PY17X_1240600), isp1 (PY17X_1212600), isp3 (PY17X_1328100),

mtip (PY17X_1462100); ara1 (PY17X_1412750); myosinb (PY17X_0931400); soap (PY17X_1040200); dhhc10 (PY17X_0513100), mpodd (PY17X_1225400)

genes deleted:
gcβ (PY17X_1138200), cdc50a (PY17X_0619700), cdc50b (PY17X_0916600); cdpk3 (PY17X_0410700), pdeδ (PY17X_1338400), Δisp1 (PY17X_1212600)

P28M/Δcdc50a, Δcdc50a/Δgcβ, Δcdpk3/Δgcβ, Δcdpk3/Δcdc50a, Δpdeδ/Δgcβ, Δpdeδ/Δcdc50a,

Mutated GCβ
5 mutants

Analyses of these mutants showed the following (from the Abstract):
'Using real-time imaging to visualize Plasmodium yoelii guanylate cyclase β (GCβ), we show that cytoplasmic GCβ translocates and polarizes to the parasite plasma membrane at ‘‘ookinete extrados site’’ (OES) during zygote-to-ookinete differentiation. The polarization of enzymatic active GCβ at OES initiates gliding of matured ookinete. Both the P4-ATPase-like domain and guanylate cyclase domain are required for GCβ polarization and ookinete gliding. CDC50A, a co-factor of P4-ATPase, binds to and stabilizes GCβ during ookinete development. Screening of inner membrane complex proteins identifies ISP1 as a key molecule that anchors GCβ/CDC50A complex at the OES of mature ookinetes.'

From the paper:
'3'–5'-cyclic guanosine monophosphate (cGMP), cGMP-dependent protein kinase G (PKG), phosphodiesterase delta (PDEδ), and guanylate cyclase beta (GCβ) have been shown to be crucial for ookinete motility in the rodent malaria parasite Plasmodium berghei. Coordinated activities of GCβ (synthesizes cGMP) and PDEδ (hydrolyzes cGMP) regulate cGMP levels that activate PKG, leading to phospholipase C (PLC)/inositol triphosphate (IP3)-mediated Ca2+ release, phosphorylation of multiple proteins in the glideosome, and initiation of ookinete gliding.
The Plasmodium yoelii parasite encodes two large guanylate cyclases (GCα, 3,850 amino acids [aas] and GCβ, 3,015 aas that contain 22 transmembrane (TM) helixes spanning an N-terminal P4-ATPase-like domain (ALD) and a C-terminal guanylate cyclase domain (GCD). The GC enzymes possessing this ALD/GCD structure are observed in many protozoan species.'

From the paper:
'To test whether cGMP synthesis activity of polarized GCb at OES is required for ookinete gliding, we generated GCb mutant parasites that maintained GCb OES polarization but lost the ability to synthesize cGMP. Sequences analysis reveal the conserved residues Asn-Thr-Ala-Ser-Arg (NTASR) in the a4 helix of catalytic domain 1 (C1) of GC, which are likely critical for the cyclase to bind its substrate guanosine triphosphate (GTP), and mutations in these residues may reduce or abolish the cyclase activity (Figure S3H). Accordingly, we introduced mutations by replacing ‘‘NTASR’’ with ‘‘NKASR’’ or ‘‘AKASA’’ in the gcβ::6HA parasite, generating GCDm1 and GCDm2 parasites, respectively. Both mutants showed normal GCβ polarization and expression levels similar to that of gcβ::6HA parasite but had severely impaired ookinete motility, resembling the phenotype of gcβ disruption.'

From the paper:
'The ALD of GCβ is structurally related to the P4-ATPase proteins, which function as flippase translocating phospholipids, such as phosphatidylserine (PS) from exofacial to cytofacial leaflets of membranes in eukaryotic cells. However, sequence analysis revealed that ALD contains mutations in several conserved functional motifs, including the critical DKTGT motif, suggesting a pseudo P4-ATPase.
P4-ATPase interacts with the co-factor protein, CDC50, which is required for trafficking of the complex from ER to plasma membrane and for flippase activity. A search of the Plasmodium genomes identified three paralogs of cdc50 genes: cdc50a (PY17X_0619700); cdc50b (PY17X_0916600); and cdc50c (PY17X_0514500). To determine which CDC50 associates with GCb, we generated parasites with individual CDC50 protein tagged with 6HA: cdc50a::6HA; cdc50b::6HA; and cdc50c::6HA. Of the three proteins, only CDC50A has polarization at OES similar to GCβ in mature ookinetes. Notably, CDC50A is exclusively expressed in gametocytes, zygotes, and ookinetes during the parasite life cycle and, similar to GCβ, polarized at OES during zygote to ookinete development. Results from immunoprecipitation using anti-HA antibody indicate that GCβ binds to CDC50A in ookinetes lysate of the gcβ::6HA/cdc50a::mCherry parasite. These data demonstrate that CDC50A colocalizes and binds to GCβ during ookinete development.'

Other mutants
This study describes a large number of mutants expressing tagged (mutated) versions of different proteins, gene-deletion mutants and mutants with mutated genes (see link)..

In the paper several additional mutants are described expressing mutated forms of gcβ (see also above).