title: PbSR is synthesized in macrogametocytes and involved in formation of the malaria crystalloids.
abstract: Crystalloids are transient organelles that form in developing malaria ookinetes and disappear after ookinete-to-oocyst transition. Their origins and functions remain poorly understood. The Plasmodium berghei scavenger receptor-like protein PbSR is essential for mosquito-to-host transmission of the parasite: PbSR knockout parasites produce normal numbers of oocysts that fail to form sporozoites, pointing to a role for PbSR in the oocyst during sporogony. Here, using fluorescent protein tagging and targeted gene disruption, we show that PbSR is synthesized in macrogametocytes, gets targeted to the crystalloids of developing ookinetes and is involved in crystalloid formation. While oocyst sporulation rates of PbSR knockout parasites are highly reduced in parasite-infected mosquitoes, sporulation rates in vitro are not adversely affected, supporting the view that mosquito factors could be involved in the PbSR loss-of-function phenotype. These findings are the first to identify a parasite protein involved with the crystalloid organelle, and suggest a novel protein-trafficking mechanism to deliver PbSR to the oocysts.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
authors.forename: Victoria
authors.initials: V
authors.lastname: Carter
authors.forename: Shoichi
authors.initials: S
authors.lastname: Shimizu
authors.forename: Meiji
authors.initials: M
authors.lastname: Arai
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Dessens
mesh_terms: D000818:Animals; D009033:Culicidae / Q000469:parasitology; D022083:Cytoplasmic Structures / Q000378:metabolism*; D008288:Malaria; D033661:Oocysts / Q000254:growth & development / Q000378:metabolism*; D010641:Phenotype; D010962:Plasmodium berghei / Q000166:cytology* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D051116:Receptors, Scavenger / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
chemical_list: D015800:Protozoan Proteins; D051116:Receptors, Scavenger