Mutant/mutation
The mutant lacks expression of  a transcription factor with AP2 domain(s) (AP2-O, AP2 in ookinetes)

Protein (function)
AP2-O belongs to the Apetala2 (AP2) family which encode transcription factors (TFs). The AP2 family TFs were first identified in plants. Plant AP2 family TFs are named for their possession of at least one common DNA-binding domain of approximately 60 amino acids, the AP2 domain. Bioinformatic analyses have revealed the presence of 26 AP2-related genes in the Plasmodium genome. The predicted Plasmodium AP2-related genes encode proteins with one to four AP2 domains. AP2-O has two conserved regions which include the AP2 domain near the C-terminus.

Phenotype
The phenotype analyses indicate an essential role of AP2-O during ookinete development. The phenotype analyses as described in 'Additional information' indicate that AP2-O is a transcription factor that binds to promoter regions of genes that are expressed during ookinete development and activates expression of genes, including genes involved in mosquito midgut invasion.

Additional information
In wild type parasites ap2-0 transcripts are present in both gametocytes and ookinetes. Protein expression was analysed using a mutant expressing a GFP-tagged form of AP2-O (RMgm-208). No expression was observed in the gametocyte stage indicating translational repression of the ap2-o transcripts in gametocytes. Weak GFP fluorescent signals were observed in retort-form ookinetes, beginning at 8h after fertilization. The signals were localized in the nucleus and signal intensities increased with ookinete development.

Cross-fertilization experiments mating mutant gametes with either fertile wild type female or fertile wild type male gametes indicated that the AP2-O defect is inherited from the female line. Mutant females when fertilized with wild type males produced deformed ookinetes. However, wild type females when fertilized by mutant males produced normal ookinetes. These results suggest that AP2-O transcripts in zygotes/ookinetes are derived from female gametocytes and are essential for zygote development into normal infective ookinetes.

Micro-array analysis of mutant retort-form ookinetes at 12h after fertilization showed decreased levels of transcripts of ookinete specific proteins. Evidence is presented that AP2-O binds to a six base sequence (TAGCTA) in the upstream promoter region of the genes whose transcripts are decreased in the absence of AP2-O. Evidence is presented that the TAGCTA sequence is a cis-acting element in the ookinete stage.

Other mutants:
RMgm-208: a mutant expressing a GFP-tagged form of AP2-O
RMgm-399: a mutant lacking expression of AP2-Sp (AP2 in sporozoites; PBANKA_132980;PF14_0633)
RMgm-398: a mutant expressing a GFP-tagged form of AP2-Sp (PBANKA_132980;PF14_0633)
RMgm-400: a mutant expressing a mutated form of AP2-O (PBANKA_090590; PF11_0442) whose AP2 domain had been swapped with that of AP2-Sp (PBANKA_132980;PF14_0633)