Several variants of the replacement histone H3 genes from soybean, bar
ley and wheat have been cloned and sequenced. Analysis of segregating
populations in barley and soybean, as well as analysis of clones isola
ted from a soybean genomic library, suggested that these genes are dis
persed throughout the genome. Several genes contain introns located in
similar positions, but of different lengths and sequence. Comparison
of mRNA levels in different tissues revealed that the intron-containin
g and intronless genes have different expression patterns. The distrib
ution of the introns in the histone H3 genes across several plant spec
ies suggests that some of the introns might have been lost during the
evolution of the gene family. Sequence divergence among introns and ge
ne-flanking sequences in cloned gene variants allowed us to use them a
s specific probes for localizing individual gene copies and analyzing
the genomic distribution of these variants across a range of genotypes
.