To establish the relationships of the lizard- and mammal-infecting
Leishmania
, we characterized the intergenic spacer region of ribosomal RNA genes from
L. tarentolae
and
L. hoogstraali
. The organization of these regions is similar to those of other eukaryotes.
The intergenic spacer region was approximately 4 kb in
L. tarentolae
and 5.5 kb in
L. hoogstraali
. The size difference was due to a greater number of 63-bp repetitive elements
in the latter species. This region also contained another element, repeated
twice, that had an inverted octanucleotide with the potential to form a
stem-loop structure that could be involved in transcription termination
or processing events. The ribosomal RNA gene localization showed a distinct
pattern with one chromosomal band (2.2 Mb) for
L. tarentolae
and two (1.5 and 1.3 Mb) for
L. hoogstraali
. The study also showed sequence differences in the external transcribed
region that could be used to distinguish lizard
Leishmania
from the mammalian
Leishmania
. The intergenic spacer region structure features found among Leishmania
species indicated that lizard and mammalian
Leishmania
are closely related and support the inclusion of lizard-infecting species
into the subgenus
Sauroleishmania
proposed by Saf'janova in 1982.
