The mini-exon genes of three Phytomonas isolates that differ in plant tissue tropism

The tandem mini-exon gene repeat is an ideal diagnostic target for trypanosomatids because it includes sequences that are conserved absolutely coupled with regions of extreme variability. We have exploited these features and the polymerase chain reaction to differentiate Phytomonas strains isolated from phloem, fruit or latex of various host plants. While the transcribed regions are nearly identical, the intergenic sequences are variable in size and content (130-332 base pairs). The mini-exon genes of these phytomonads can therefore be distinguished from each other and from the corresponding genes in insect trypanosomes, with which they are oft confused.