ANALYSIS OF STAGE-SPECIFIC TRANSCRIPTS OF THE PLASMODIUM-FALCIPARUM SERINE REPEAT ANTIGEN (SERA) GENE AND TRANSCRIPTION FROM THE SERA LOCUS

We evaluated the stage-specific transcription and processing of serine repeat antigen (SERA) messenger RNA to further examine mechanisms reg ulating gene expression in Plasmodium falciparum. SERA mRNA was expres sed exclusively in trophozoite and schizont stages. Transcription from the SERA gene was first detected between 24 and 29 h following erythr ocyte invasion. The transcript mapping data revealed heterogeneity of the SERA mRNA 5' and 3' ends. RNA sequencing revealed that SERA transc ripts were not generated by a trans-splicing mechanism. A new SERA gen e, SERA3, was identified 1.8 kb upstream of SERA. The direction of tra nscription of the SERA locus genes, SERA3, SERA, and SERA2, was mapped relative to the location of other chromosome 2 genetic markers. The S ERA locus and the closely linked MSA2 locus were found to be transcrip tionally regulated in a coordinate fashion. Collectively, the results of these experiments show that parallel and coordinately controlled tr anscription units reside on chromosome 2. These results implicate a no vel mechanism of transcriptional control in Plasmodium.