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Correlation analysis between starch properties and single nucleotide polymorphisms of waxy genes in common rye (Secale cereale L.)

Author(s): M. Meng, X. Gao, L.J. Han, X.Y. Li, D. Wu, H.Z. Li and Q.J. Chen

To understand the relationships between single nucleotide polymorphisms (SNPs) in the waxy gene and starch parameters in common rye, we performed sequence characterization, enzyme activity testing, amylopectin/amylose ratio evaluation, starch property testing, and correlation analysis. Specific primers were used to clone waxy from 20 rye cultivars. Sequence analysis showed that waxy was 2852 bp, including 11 exons, and sequence similarity across the 20 cultivars was over 98%. The Waxy protein showed >95% similarity with those from wheat, rice, and barley, the closest genetic relationship being with wheat Wx-A type. Waxy had multiple SNPs, most of which were located in the exons. Amino acid variants were found to be mainly distributed in the catalytic domain in an imbalanced state. Multi-factor correlation analysis revealed significant correlation among starch pasting parameters in rye flour. The Waxy protein activity was significantly negatively correlated with the amylose content and amylopectin/amylose ratio. However, pasting parameters, Waxy enzyme activity, and amylopectin/amylose content ratio were not correlated. The correlation of SNPs, the key catalytic site of Waxy, with starch parameters and enzyme activity suggested that both starch pasting parameters and Waxy protein activity were influenced by No. 260 amino acid (aa). Further, the 141 and 152 aa loci were found in the enzyme-catalyzing domain of Waxy. Interestingly, Waxy enzyme activity was also influenced by the 363 aa locus in the pliable region. These results provide important theoretical regarding the high-throughput quality identification of noodle starch, functional studies, directional selection, and molecular markers of wheat Wx subunits