SNPs and an insertion sequence in five Wx-A1 alleles as factors for variant Wx-A1 protein in wheat
2013
Yamamori, Makoto | Guzmán, Carlos
The waxy (Wx) gene encodes a granule-bound starch synthase (also called Wx protein) that is involved in synthesizing amylose in the starch grains of cereals, including common wheat (Triticum aestivum L.). Because amylose content affects the quality of food products made from wheat flour, Wx alleles affecting amylose content are of interest. Five wheat Wx alleles (Wx-A1c, -A1d, -A1e, -A1i and -A1j) that produce polymorphic Wx proteins on electrophoretic gels were investigated in terms of amylose content in starch and DNA sequences. Measurement and electrophoresis of gelled starch showed that apparent amylose contents of the genotypes were as follows: Wx-A1e, 2.9% (= waxy phenotype) < -A1i, 8.0% < -A1c, 16.8% < -A1j, 22.6% = level of wild type allele -A1a. DNA sequencing of the five alleles identified single nucleotide polymorphisms (SNPs) and insertion/deletion variations compared to Wx-A1a. A particular SNP causing amino acid changes in Wx-A1e and -A1c was identified as the factor responsible for decreased amylose. A SNP in Wx-A1d should cause an amino acid change and be responsible for an altered Wx-A1d protein. A transposable-like element of 376 bp present in the 3′ untranslated region (UTR) of Wx-A1i most likely lowered the levels of Wx protein and amylose through aberrant mRNA. The fifth allele, Wx-A1j, possessed four SNPs, two of which altered amino acids in the Wx-A1j protein and should cause polymorphism in the Wx protein. Based on the DNA sequences, functional markers for Wx-A1c, -A1d, -A1e and -A1i were developed. © Springer Science+Business Media Dordrecht 2012.
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