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Female inheritance of malarial lap genes is essential for mosquito transmission.

Raine JD, Ecker A, Mendoza J, Tewari R, Stanway RR, Sinden RE - PLoS Pathog. (2007)

Bottom Line: Sporozoite formation was rescued by a genetic cross with wild-type parasites, which results in the production of heterokaryotic polyploid ookinetes and oocysts, and ultimately infective Deltapblap sporozoites, but not if the individual Deltapblap parasite lines were crossed amongst each other.We conclude that the functions of PbLAPs1, 2, 4, and 6 are critical prior to the expression of the male-derived gene after microgametogenesis, fertilization, and meiosis, possibly in the gametocyte-to-ookinete period of differentiation.This phenotype is not seen in the other dividing forms of the mutant parasite lines in the liver and blood stages.

View Article: PubMed Central - PubMed

Affiliation: Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.

ABSTRACT
Members of the LCCL/lectin adhesive-like protein (LAP) family, a family of six putative secreted proteins with predicted adhesive extracellular domains, have all been detected in the sexual and sporogonic stages of Plasmodium and have previously been predicted to play a role in parasite-mosquito interactions and/or immunomodulation. In this study we have investigated the function of PbLAP1, 2, 4, and 6. Through phenotypic analysis of Plasmodium berghei loss-of-function mutants, we have demonstrated that PbLAP2, 4, and 6, as previously shown for PbLAP1, are critical for oocyst maturation and sporozoite formation, and essential for transmission from mosquitoes to mice. Sporozoite formation was rescued by a genetic cross with wild-type parasites, which results in the production of heterokaryotic polyploid ookinetes and oocysts, and ultimately infective Deltapblap sporozoites, but not if the individual Deltapblap parasite lines were crossed amongst each other. Genetic crosses with female-deficient (Deltapbs47) and male-deficient (Deltapbs48/45) parasites show that the lethal phenotype is only rescued when the wild-type pblap gene is inherited from a female gametocyte, thus explaining the failure to rescue in the crosses between different Deltapblap parasite lines. We conclude that the functions of PbLAPs1, 2, 4, and 6 are critical prior to the expression of the male-derived gene after microgametogenesis, fertilization, and meiosis, possibly in the gametocyte-to-ookinete period of differentiation. The phenotypes detectable by cytological methods in the oocyst some 10 d after the critical period of activity suggests key roles of the LAPs or LAP-dependent processes in the regulation of the cell cycle, possibly in the regulation of cytoplasm-to-nuclear ratio, and, importantly, in the events of cytokinesis at sporozoite formation. This phenotype is not seen in the other dividing forms of the mutant parasite lines in the liver and blood stages.

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Sporozoite Development in Genetic CrossesGraphical summary of salivary gland sporozoite numbers derived from crosses between wt and Δpblap and amongst Δpblap strains. Values given are mean % of wt (± standard error of the mean). In wt crosses, diagnostic PCR on blood stage infection resulting from mosquito bite confirmed transmission of the Δpblap parasites (not shown). Δlap1 as published in [4]. Please refer to Table S5 for individual data.
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ppat-0030030-g004: Sporozoite Development in Genetic CrossesGraphical summary of salivary gland sporozoite numbers derived from crosses between wt and Δpblap and amongst Δpblap strains. Values given are mean % of wt (± standard error of the mean). In wt crosses, diagnostic PCR on blood stage infection resulting from mosquito bite confirmed transmission of the Δpblap parasites (not shown). Δlap1 as published in [4]. Please refer to Table S5 for individual data.

Mentions: In previous studies, crossing Δpblap1 gametocytes (pblap1−) with wt gametocytes (pblap1+) to form heterokaryotic (pblap1+/pblap1−) oocysts rescued the lethal Δpblap1 phenotype, and produced Δpblap1 sporozoites that were infectious to mice [4]. Our crosses between Δpblap1 and wt gametocytes produced similar results. Crosses between Δpblap2, Δpblap4, and Δpblap6 and a wt clone similarly produced wt numbers of salivary gland sporozoites that were infectious to mice (Figure 4; Table S5). Diagnostic PCR analysis revealed that both wt and either Δpblap2 or Δpblap4 or Δpblap6 parasites were present in the blood stage parasites isolated from the infected mice, indicating that Δpblap sporozoites (i.e., sporozoites which lack the respective pblap gene but which may contain some of the corresponding PbLAP protein carried over from the heterokaryotic oocyst in which they were formed) could be transmitted to mice and that PbLAP2, 4, and 6, like PbLAP1, are not essential for liver or blood stage development (unpublished data).


Female inheritance of malarial lap genes is essential for mosquito transmission.

Raine JD, Ecker A, Mendoza J, Tewari R, Stanway RR, Sinden RE - PLoS Pathog. (2007)

Sporozoite Development in Genetic CrossesGraphical summary of salivary gland sporozoite numbers derived from crosses between wt and Δpblap and amongst Δpblap strains. Values given are mean % of wt (± standard error of the mean). In wt crosses, diagnostic PCR on blood stage infection resulting from mosquito bite confirmed transmission of the Δpblap parasites (not shown). Δlap1 as published in [4]. Please refer to Table S5 for individual data.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1808070&req=5

ppat-0030030-g004: Sporozoite Development in Genetic CrossesGraphical summary of salivary gland sporozoite numbers derived from crosses between wt and Δpblap and amongst Δpblap strains. Values given are mean % of wt (± standard error of the mean). In wt crosses, diagnostic PCR on blood stage infection resulting from mosquito bite confirmed transmission of the Δpblap parasites (not shown). Δlap1 as published in [4]. Please refer to Table S5 for individual data.
Mentions: In previous studies, crossing Δpblap1 gametocytes (pblap1−) with wt gametocytes (pblap1+) to form heterokaryotic (pblap1+/pblap1−) oocysts rescued the lethal Δpblap1 phenotype, and produced Δpblap1 sporozoites that were infectious to mice [4]. Our crosses between Δpblap1 and wt gametocytes produced similar results. Crosses between Δpblap2, Δpblap4, and Δpblap6 and a wt clone similarly produced wt numbers of salivary gland sporozoites that were infectious to mice (Figure 4; Table S5). Diagnostic PCR analysis revealed that both wt and either Δpblap2 or Δpblap4 or Δpblap6 parasites were present in the blood stage parasites isolated from the infected mice, indicating that Δpblap sporozoites (i.e., sporozoites which lack the respective pblap gene but which may contain some of the corresponding PbLAP protein carried over from the heterokaryotic oocyst in which they were formed) could be transmitted to mice and that PbLAP2, 4, and 6, like PbLAP1, are not essential for liver or blood stage development (unpublished data).

Bottom Line: Sporozoite formation was rescued by a genetic cross with wild-type parasites, which results in the production of heterokaryotic polyploid ookinetes and oocysts, and ultimately infective Deltapblap sporozoites, but not if the individual Deltapblap parasite lines were crossed amongst each other.We conclude that the functions of PbLAPs1, 2, 4, and 6 are critical prior to the expression of the male-derived gene after microgametogenesis, fertilization, and meiosis, possibly in the gametocyte-to-ookinete period of differentiation.This phenotype is not seen in the other dividing forms of the mutant parasite lines in the liver and blood stages.

View Article: PubMed Central - PubMed

Affiliation: Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.

ABSTRACT
Members of the LCCL/lectin adhesive-like protein (LAP) family, a family of six putative secreted proteins with predicted adhesive extracellular domains, have all been detected in the sexual and sporogonic stages of Plasmodium and have previously been predicted to play a role in parasite-mosquito interactions and/or immunomodulation. In this study we have investigated the function of PbLAP1, 2, 4, and 6. Through phenotypic analysis of Plasmodium berghei loss-of-function mutants, we have demonstrated that PbLAP2, 4, and 6, as previously shown for PbLAP1, are critical for oocyst maturation and sporozoite formation, and essential for transmission from mosquitoes to mice. Sporozoite formation was rescued by a genetic cross with wild-type parasites, which results in the production of heterokaryotic polyploid ookinetes and oocysts, and ultimately infective Deltapblap sporozoites, but not if the individual Deltapblap parasite lines were crossed amongst each other. Genetic crosses with female-deficient (Deltapbs47) and male-deficient (Deltapbs48/45) parasites show that the lethal phenotype is only rescued when the wild-type pblap gene is inherited from a female gametocyte, thus explaining the failure to rescue in the crosses between different Deltapblap parasite lines. We conclude that the functions of PbLAPs1, 2, 4, and 6 are critical prior to the expression of the male-derived gene after microgametogenesis, fertilization, and meiosis, possibly in the gametocyte-to-ookinete period of differentiation. The phenotypes detectable by cytological methods in the oocyst some 10 d after the critical period of activity suggests key roles of the LAPs or LAP-dependent processes in the regulation of the cell cycle, possibly in the regulation of cytoplasm-to-nuclear ratio, and, importantly, in the events of cytokinesis at sporozoite formation. This phenotype is not seen in the other dividing forms of the mutant parasite lines in the liver and blood stages.

Show MeSH
Related in: MedlinePlus