Mapping and gene cloning of a wheat mutant dsc with dwarf and compacted spikes

Plant height and spikelet density are two important traits for wheat (Triticum aestivum L.) yield. The development of wheat mutants not only provides new genetic resources for wheat improvement but also facilitates our understanding of the molecular regulation of these traits. Previously, we obtained a mutant named dwarf and spike compactness (dsc) from wheat cultivar Guomai301 (wild type, WT) treated with ethyl methane sulphonate. This study investigates the heredity, mutated gene location, and the candidate gene of dsc. Highresolution chromosome painting analysis indicated that there were no visible structural variations in the mutant dsc. Genetic analysis indicated that the phenotype of dsc was controlled by a single dominant gene, named as dsc. The wheat 660 K single-nucleotide polymorphism (SNP) array and simple sequence repeat (SSR) marker assay were employed to map the mutated gene. A total of 984 SNPs were identified between the DNA bulks, among which, 492 SNPs were located on chromosome 5A in 580-680 Mb genomic region, which occupied 50% of the total SNPs. The gene dsc was mapped in a 33.4 Mb (625.7-659.1 Mb) region on chromosome arm 5AL, flanked by SSR markers Xbarc319 and Xgpw2136, where 5AQ is located. Sequences and expression patterns of 5AQ from WTand dsc were compared. The two 5AQs had a SNP (G>A) in the miR172 binding site. A dCAPS marker was developed based on the SNP, and the marker was cosegregated with the mutated phenotypes in a F_2:3 population derived from the cross dsc x Chinese Spring (CS). This result demonstrated that the gene 5AQ was the mutated gene of dsc. The expression levels of 5AQ were significantly higher in roots, stems, leaves and spikes of mutant dsc than those in WT. Our results demonstrated that point mutation in the miR172 binding site of the 5AQ likely increased its transcript level via a reduction in miRNA-dependent degradation, and this resulted in pleiotropic effects on spikelet density and plant height. Obviously, miR172-Q was a key regulation module for wheat growth and spike development. The dCAPS marker could be used to detect the elite allele of Q in wheat breeding. Regulation of miR172-Q module might be an approach for wheat yield breeding.