Identification and molecular characterization of mutant line deficiency in three waxy proteins of common wheat (Triticum aestivum L.) [post]

2019 unpublished
Starch is the main component of wheat (Triticum aestivum L.) grain and a key factor in determining wheat processing quality. The Wx gene encodes the granule bound starch synthase I (GBSS I) and is the sole gene responsible for amylose synthesis. Results: A waxy mutant (Wx-null) was isolated by screening M3 seeds derived from 1.0% EMS mutagenized materials with I2-KI staining of endosperm starch. SDS-PAGE electrophoresis confirmed that the Wx-null line lacked all three waxy proteins. DNA
more » ... oteins. DNA sequencing revealed three SNPs and a 3-bp InDel in the first exon, and a 16-bp InDel at the junction region of the first Wx-A1 intron from the Wxnull line. Six SNPs were identified in Wx-B1 gene of Wx-null line compared to the wild-type Gao 8901, including four missense mutations. One nonsense mutation was found at position 857 in the fourth exon, which resulted in a premature stop codon. Expression levels of Wx genes were dramatically reduced in the Wx-null line. Nonsense-mediated mRNA decay (NMD) may be triggered to degrade the non-functional Wx mRNA. There were no detectable differences in granule size and morphology between Wx-null and wild-type, but the Wx-null line contained a larger proportion of B-type starch granules. The amylose content of the Wx-null line (0.22%) was remarkably lower compared to the wild-type Gao 8901 (20.82%). Total starch is also lower in the Wx-null line. Conclusions: All three waxy proteins were non-functional in the Wx-null line. NMD may be the cause for reduced expression levels of Wx genes in the Wx-null line. The Wx-null line exhibited more B-type starch granules, dramatically lower amylose content, and decreased total starch. The Wx-null line may provide a potential waxy material with high agronomic performance in wheat breeding programs. Background Wheat (Triticum aestivum L.) is one of the most important crops worldwide. Starch is the main component of wheat grain and accounts for 65-75% of seed dry mass [1]. Wheat starch consists of two molecular types of glucose polymers: amylose and amylopectin. Amylose consists of long linear chains of D-glucopyranose units joined by α (1-4) glycosidic bonds, while amylopectin is highly branched and contains both α (1-4) and α (1-6) linkages of D-glucopyranose units [2]. Amylopectin molecules are significantly larger than amylose. Based on the content of amylose and amylopectin in
doi:10.21203/rs.2.18059/v1 fatcat:4ndai4qoxrfhfgj2332ffxsjau