Several species of Plasmodium have been shown to contain a circular 
extrachromosomal DNA molecule which is widely supposed to be mitochondrial DNA. 
However, it has recently been shown to have a number of features in common with 
chloroplast DNA. Here, a phylogenetic analysis of RNA polymerase coding 
sequences from the Plasmodium molecule has been carried out using distance 
matrix, maximum likelihood, parsimony and operator invariant methods. The 
analysis indicates that the molecule is in fact derived from an oxygenic 
photosynthetic organism and should be regarded as plastid DNA. This suggests 
that Plasmodium originated from a phototroph that has lost the capacity to 
photosynthesize.