In
collaboration with colleagues in China and Saudi Arabia, the Malaria Unit at Nekken present a landmark new publication; the genomes of
Plasmodium malariae and Plasmodium ovale published for the first time. These two species of
malaria parasite are responsible for a large burden of disease throughout the
tropics. Despite their importance as human pathogens their genomes have not
been available until now, due to difficulties in obtaining sufficient
quantities of DNA. The publication of these genomes will aid with the
development of new drugs and vaccines against these neglected tropical
pathogens. Genome-scale
comparison of expanded gene families in Plasmodium ovale
wallikeri and Plasmodium ovale
curtisi with Plasmodium malariae
and with other Plasmodium species Abstract Malaria
in humans is caused by six species of Plasmodium parasites, of which the
nuclear genome sequences for the two Plasmodium ovale
spp., P. ovale curtisi and
P. ovale wallikeri, and
Plasmodium malariae have not yet been analyzed. Here
we present an analysis of the nuclear genome sequences of these three
parasites, and describe gene family expansions therein. Plasmodium ovale curtisi and P. ovale wallikeri are genetically
distinct but morphologically indistinguishable and have sympatric ranges
through the tropics of Africa, Asia and Oceania. Both P. ovale
spp. show expansion of the surfin variant gene
family, and an amplification of the Plasmodium interspersed repeat (pir) superfamily which results in an approximately 30%
increase in genome size. For comparison, we have also analyzed the draft
nuclear genome of P. malariae, a malaria parasite
causing mild malaria symptoms with a quartan life
cycle, long-term chronic infections, and wide geographic distribution.
Plasmodium malariae shows only a moderate level of
expansion of pir genes, and unique expansions of a
highly diverged transmembrane protein family with over 550 members and the
gamete P25/27 gene family. The observed diversity in the P. ovale
wallikeri and P. ovale curtisi surface antigens, combined with their phylogenetic
separation, supports consideration that the two parasites be given species
status. |