STRUCTURE AND POLYMORPHISM OF THE UPSTREAM REGION OF THE PFGZ7 25 GENE, TRANSCRIPTIONALLY REGULATED IN GAMETOCYTOGENESIS OF PLASMODIUM-FALCIPARUM/

Transcription of the early gametocyte-specific gene pfg27/25, and geno mic structure and polymorphism of its upstream region were studied in the human malaria parasite Plasmodium falciparum. The upstream genomic sequence of the pfg27/25 gene is characterised by a repetitive region that contains five direct and one inverted repeats of a unit constitu ted by a perfectly conserved sequence flanked by a poly-dT and a poly- d(AT) tract. Sequences further upstream from the repetitive region are polymorphic in distantly;elated parasite lines, Nuclear 'run off' exp eriments indicated that transcription of pfg27/25 is developmentally r egulated. Transcription of the gene, undetectable in asexual parasites , is activated at the onset of gametocytogenesis. The gene is transcri bed in a 2.5 kb mature mRNA for the first 2-3 days of sexual different iation, while transcription is down-regulated in more mature gametocyt es.