Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: DIVERGENCE OF DUPLICATED REGIONS AND LINKAGE CONSERVATION IN
THE SOYBEAN GENOME
DIVERGENCE OF DUPLICATED REGIONS AND LINKAGE CONSERVATION IN
THE SOYBEAN GENOME.
Kayla M. Polzin 1, Eberson S. Calvo 2, Terry C. Olson 1, and
Randy C. Shoemaker 3. 1 Dept. of Agronomy, 2 Dept. of
Zoology/Genetics, and 3 USDA-ARS-FCR, Iowa State University,
Ames, IA 50011.
We have studied the divergence of dispersed and tandem
duplicated regions in the diploidized tetraploid\genome of
soybean. Lambda clones of two loci, A071, an uncharacterized
genomic sequence, and sle, a gene encoding a late embryogenic
protein, were used to analyze sequence and linkage conservation
following duplication events. Five of ten A071 loci and two of
three sle loci where isolated from an EMBL3 genomic library of
Williams 82 DNA. Restriction fragment length polymorphism
mapping revealed that live A071 loci (three cloned) were located
on one end of linkage group N and two (one cloned) were located on
linkage group L of the USDA-ARS soybean genome molecular map. In
contrast, three sle loci were each mapped on different linkage
groups (D1 ,G ,and N). Restriction mapping and cross-
hybridization under low stringency conditions showed that the
A071 clones contained only small regions of homology (<3 kb) while the
sle clones shared slightly larger homologous regions (< 5kb).
The distribution of repetitive vs low copy sequences was also
determined for each clone. The clones consisted primarily of
several kilobases of low copy DNA followed by several kilobases
of repetitive sequence. Only small regions of putative single
copy sequence were observed. Low copy DNA isolated from the
clones was used as probes and polymorphisms detected by these
fragments were mapped. Despite the lack of homology between
regions immediately adjacent to the duplicated regions, linkage
conservation was observed between A071 - and sle-associated
probes. This suggests that the different regions flanking
duplicate soybean loci may be the result of small rearrangements
or accumulation of repetitive sequence rather than simply
sequence divergence. Also, the conservation of linkage suggests
that saturating particular regions of the soybean genome may be
possible using probes derived from duplicated regions.
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