The abundance and genomic organization of six simple sequence repeats, cons
isting of di-, tri-, and tetranucleotide sequence motifs, and a minisatelli
te repeat have been analyzed in different gymnosperms by Southern hybridiza
tion. Within the gymnosperm genomes investigated, the abundance and genomic
organization of micro- and minisatellite repeats largely follows taxonomic
groupings. We found that only particular simple sequence repeat motifs are
amplified in gymnosperm genomes, while others such as (CAC)(5) and (GACA)(
4) are present in only low copy numbers. The variation in abundance of simp
le sequence motifs reflects a similar situation to that found in angiosperm
s. Species of the two- and three-needle pine section Pinus are relatively c
onserved and can be distinguished from Pinus strobus which belongs to the f
ive-needle pine section Strobus. The hybridization pattern of Picea species
, bald cypress and gingko were different from the patterns detected in the
Pinus species. Furthermore, sequences with homology to the plant telomeric
repeat (TTTAGGG)(n) have been analyzed in the same set of gymnosperms. Telo
mere-like repeats are highly amplified within two- and three-needle pine ge
nomes, such as slash pine (Pinus elliotfii Engelm. var. elliottii), compare
d to P. strobus, Picea species, bald cypress and gingko. P. elliotfii var.
elliottii was used as a representative species to investigate the chromosom
al organization of telomere-like sequences by fluorescence in situ hybridiz
ation (FISH). The telomere-like sequences are not restricted to the ends of
chromosomes; they form large intercalary and pericentric blocks showing th
at they are a repeated component of the slash pine genome. Conifers have ge
nomes larger than 20 000 Mbp, and our results clearly demonstrate that repe
ats of low sequence complexity, such to (CA)(8), (CA)(8,) (GGAT)(4) and (GA
TA)(4), and minisatellite- and telomere-like sequences represent a large fr
action of the repetitive DNA of these species. The striking differences in
abundance and genome organization of the various repeat motifs suggest that
these repetitive sequences evolved differently in the gymnosperm genomes i
nvestigated.