To date, few mutations in wheat have been characterized at the molecular level. In this study, the mutations in the three waxy alleles in waxy wheat (Wx-A1b,Wx-B1b and Wx-D1b) were characterized, and waxy gene expression was compared in several wheat lines, including hexaploid and tetraploid waxy lines of wheat. Southern analysis showed that the Wx-B1b allele had sustained a deletion which included the entire coding region of the Wx-B1 gene. DNA homologous to waxy gene sequences was still present in the Wx-A1b and Wx-D1b alleles of the hexaploid waxy mutant. Transcripts of waxy alleles were also detected in both hexaploid and tetraploid mutants at 10 days post-anthesis, but the transcript level was dramatically reduced compared to that found in non-waxy lines. Isolation of cDNAs showed that transcripts were produced by both the Wx-A1b and Wx-D1b alleles. A 23-bp deletion sustained by the Wx-A1b 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-A1b cDNA lacks 39 amino acids, including the putative ADP-glucose binding site and a portion of the transit peptide. The C-terminal region of the deduced protein encoded by the Wx-D1b cDNA lacks the last 30 amino acids. Comparison of the genomic sequences of the null and wild-type Wx-D1 alleles indicated that 588 bp were deleted in the Wx-D1b mutation, and that the last 261 bp of the Wx-D1b cDNA originated from the normally non-transcribed 3′ flanking region. Like several deletion mutations characterized in other plant species, both Wx-A1b and Wx-D1b alleles contain small DNA insertions, or filler DNA, between the deletion end-points.
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Received: 16 November 1998 / Accepted: 8 January 1999
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Vrinten, P., Nakamura, T. & Yamamori, M. Molecular characterization of waxy mutations in wheat. Mol Gen Genet 261, 463–471 (1999). https://doi.org/10.1007/s004380050989
- Key words Granule-bound starch synthase