Size-polymorphism of mini-exon gene-bearing chromosomes among natural populations of Leishmania, subgenus Viannia

In order to explore genomic plasticity at the level of the mini-exon gene-b earing chromosome in natural populations of Leishmania, the molecular karyo type of 84 Leishmania stocks belonging to subgenus Viannia, originating mos tly from Peru and Bolivia, and differing according to eco-geographical and clinical parameters, was resolved and hybridised with a mini-exon probe. Th e results suggest that size variation of the mini-exon gene-bearing chromos ome is frequent and important (up to 245-kb size-difference), and partially involves variation (up to 50%) in copy number of mini-exon genes. There is no significant size-difference between mini-exon-bearing chromosomes of Pe ruvian and Bolivian populations of cutaneous and mucosal isolates of Leishm ania (Viannia) braziliensis, but there is between eco-geographical populati ons of Leishmania (Viannia) peruviana. Leishmania (V.) peruviana presented a significantly smaller mini-exon-bearing chromosome than the other species of subgenus Viannia. The contrast between the general chromosome size hete rogeneity and the homogeneity observed in some Peruvian Andean areas is dis cussed in terms of selective pressure. (C) 1999 Australian Society for Para sitology Inc. Published by Elsevier Science Ltd. All rights reserved.