We investigated the expression of several mRNAs in exoerythrocytic and eryt
hrocytic stages of Plasmodium yoelii in infected mice, focusing our attenti
on on genes thought to be involved in signal transduction (like pypka and p
ymap-1, encoding homologues of cAMP-dependent and mitogen-activated protein
kinases, respectively) and cell cycle progression (those encoding the cdc2
-related kinases Pycrk-1, Pycrk-3 and Pymrk). Messengers coding for-enzymes
involved in general processes such as DNA replication and RNA transcriptio
n (both subunits of the ribonucleotide reductase (Pymr1, Pyrnr2) and RNA po
lymerase II) as well as a messenger coding for Pys21, a sexual stage-specif
ic protein, were also investigated. Total RNA was prepared from livers of i
nfected mice at different times post sporozoite inoculation. In contrast to
the pys21 transcript, which was observed only in infected erythrocytes, al
l messenger species could be detected in the liver by RT-PCR, peaking at 43
h post infection, a time when parasite burden was maximum, and decreasing
markedly thereafter to become hardly visible at 168 h. Some transcripts (py
pka, pymap-1, pymr1 and pyrnr2) could be detected 12 h after infection, whi
le others (pymrk and pyrnapolII) did not become detectable until 24 h. In a
ddition, we characterised all these messengers by Northern blot of total RN
As extracted from infected erythrocytes. Taken together, these data suggest
that a similar set of regulatory genes is expressed during both exoerythro
cytic and erythrocytic schizogony. (C) 2000 Elsevier Science B.V. All right
s reserved.