Gametocytogenesis and ribosomal rRNA gene organisation in the rodent malarias Plasmodium chabaudi and Plasmodium berghei.

A cloned Plasmodium berghei (ANKA) isolate was syringe passaged repeatedly to generate a line that was non-infective to Anopheles stephensi. Ribosomal gene organisation of this non-infective line was then compared to its infective ancestor. DNA was also prepared from asexual parasites and gametocytes of P. chabaudi and the arrangement of the rRNA genes of this species was studied. Although macrogametocytes have many more ribosomes than microgametocytes, this increase does not appear to stem from an amplification of the rRNA genes, as no differences either in the quantity or the arrangement of the rDNA could be detected. Furthermore, the loss of infectivity of the P. berghei gametocytes does not seem to be due to a reduction or rearrangement of sequences coding for the rRNA genes. P. chabaudi and P. berghei DNA failed to show any homology to a repetitive DNA sequence cloned from P. falciparum. We conclude that this probe, PFH8rep20, is specific for P. falciparum.