Plant Genome III Conference Plant Genome III Conference
We have begun detailed investigations and comparisons of several different 50 kb to 500 kb regions of grass genomes, both to characterize the composition of such chromosomal domains and to determine how they have evolved. The most advanced of these studies is centered on the pollen-specific Adh genes of maize and sorghum. In previous work, we have shown that a 280 kb region surrounding the maize Adh1 gene is composed of short stretches of single-copy, gene-like DNA bounded by relatively long (10 kb to >90 kb) blocks of mixed classes of repetitive DNA [Springer et al., Proc. Natl. Acad.Sci. USA 21, 863(1994)], a pattern that is common to most other regions of the maize genome (Bennetzen et al., Genome 37, 565 (1994)]. Within the Adhl region, we have identify scaffold/matrix attachment sites and sequences within homology to transcribed sequences found in cDNA libraries and in nuclear run-off experiments. Analysis of the homeologous region of the sorghum genome has indicated that the pollen-specific Adh genes are duplicated, but are found within a large region of low copy-number DNA.