SEXUAL-STAGE-SPECIFIC RNA EXPRESSION OF A NEW PLASMODIUM-FALCIPARUM GENE DETECTED BY IN-SITU HYBRIDIZATION

A gene, Pf77, transcribed in the sexual stages of Plasmodium falciparu m was isolated from a genomic expression library with a polyclonal ant ibody raised to gametocyte proteins. The entire coding region was obta ined from a series of overlapping genomic and cDNA clones (from gameto cyte RNA). A single open reading frame is present with no introns and no tandem repeat sequences. A Pf77 probe hybridised to a single transc ript present in RNA prepared from purified gametocytes and could not b e detected in RNA prepared from asexual blood stages. In situ hybridis ation studies confirmed that the expression of Pf77 mRNA is sexual-sta ge-specific and in addition, showed that Pf77 mRNA is present only in female gametocytes during the vertebrate stages of the parasite's deve lopment.