PLASMODIUM-FALCIPARUM - PARASITES DEFECTIVE IN EARLY STAGES OF GAMETOCYTOGENESIS

Some molecular characteristics of Plasmodium falciparum lines which do not produce gametocytes are described. Parasites carrying a subtelome rically deleted chromosome 9 cannot form even the earliest forms of ga metocytes, detectable with antibodies against the gametocyte-specific antigen Pfg27, In a parasite culture of clone HB3, in which both intac t and deleted forms of chromosome 9 are present, full-length chromosom e 9 molecules are retained mainly in gametocytes. These data suggest t hat the subtelomeric portion of chromosome 9 is required at an early s tage of gametocytogenesis. Parasite subclones derived from gametocyte producing clone 3D7, which completely lost ability to produce gametocy tes, are also described. Unlike the previous gametocyteless lines, the se parasites stably maintain a full-length chromosome 9 and the abilit y to cytoadhere to C32 melanoma cells after prolonged asexual propagat ion, Their defect in sexual development is therefore genetically and f unctionally distinct from that of parasites carrying a deleted chromos ome 9. Gametocyteless subclones derived from 3D7 do not produce any Pf g27 mRNA, while this gene is anomalously expressed in asexual stage pa rasites of two lines of a different genetic background, 1776se18 and C 10, one able and the other unable to produce gametocytes. (C) 1995 Aca demic Press, Inc.