ABSTRACT Tandemly arranged luciferase genes were previously
reported in two dinoflagellates species, but their intergenic regions
were strikingly different and no canonical promoter sequences were
found. Here, we examined the intergenic regions of the luciferase genes
of five other dinoflagellate species along with those of the earlier
two. In all cases, the genes exist in multiple copies and are arranged
tandemly, coding for proteins of similar sizes and sequences. However,
the 5' untranslated region, 3' untranslated region, and intergenic
regions of the seven genes differ greatly in length and sequence,
except for two stretches that are conserved in the intergenic regions
of two pairs of phylogenetically close species. Microsatellites and
minisatellites were detected in the intergenic sequences of four
species, Alexandrium affine (H. Inoue & Y. Fukuyo) E. Balech, A.
tamarense (Lebour) E. Balech, Protoceratium reticulatum (Claparede
& Lachmann) Butschli, and Pyrocystis lunula (Schutt) Schutt, the
first three of which have unusually high percentages of particular sets
of dinucleotides. Most remarkably, the P. reticulatum intergenic region
is almost exclusively made up of 19 nearly identical repeats of an
11-nucleotide sequence. Dinoflagellate luciferase intergenic regions
bear similarities to ribosomal genes and to some protein-encoding genes
in trypanosomes, both of which are transcribed by RNA polymerase I. It
is possible that the transcription of the dinoflagellate genes are
catalyzed by an RNA polymerase with novel properties.