To date, few mutations in wheat have been characterized at the molecular le
vel. In this study, the mutations in the three waxy alleles in waxy wheat (
Wx-Alb, Wx-Blb and Wx-Dlb) were characterized, and waxy gene expression was
compared in several wheat lines, including hexaploid and tetraploid waxy l
ines of wheat. Southern analysis showed that the Wx-Blb allele had sustaine
d a deletion which included the entire coding region of the Wx-Bl gene. DNA
homologous to waxy gene sequences was still present in the Wx-Alb and Wx-D
lb alleles of the hexaploid waxy mutant. Transcripts of waxy alleles were a
lso detected in both hexaploid and tetraploid mutants at 10 days post-anthe
sis. but the transcript level was dramatically reduced compared to that fou
nd in non-waxy lines. Isolation of cDNAs showed that transcripts were produ
ced by both the Wx-Alb and Wx-Dlb alleles. A 23-bp deletion sustained by th
e Wx-Alb allele at an exon-intron junction results in the use of a cryptic
splice site during mRNA processing. The deduced translation product encoded
by the Wx-Alb cDNA lacks 39 amino acids, including the putative ADP-glucos
e binding site and a portion of the transit peptide. The C-terminal region
of the deduced protein encoded by the Wx-Dlb cDNA lacks the last 30 amino a
cids. Comparison of the genomic sequences of the null and wild-type Wx-Dl a
lleles indicated that 588 bp were deleted in the Wx-Dlb mutation, and that
the last 261 bp of the Wx-Dlb cDNA originated from the normally non-transcr
ibed 3' flanking region. Like several deletion mutations characterized in o
ther plant species, both Wx-Alb and Wx-Dlb alleles contain small DNA insert
ions, or filler DNA, between the deletion end-points.