Novel Genetic Variants of GA-Insensitive <i>Rht-1</i> Genes in Hexaploid Wheat and Their Potential Agronomic Value

This study has found numerous novel genetic variants of GA-insensitive dwarfing genes with potential agricultural value for crop improvement. The cultivar, Spica is a tall genotype and possesses the wild-type genes of Rht-A1a, Rht-B1a and Rht-D1a. The cultivar Quarrion possesses a null mutant in the DELLA motif in each of the 3 genomes. This is a first report of a null mutant of Rht-A1. In addition, novel null mutants which differ from reported null alleles of Rht-B1b, Rht-B1e and Rht-D1b have been found in Quarrion, Carnamah and Whistler. The accession, Aus1408 has an allele of Rht-B1 with a mutation in the conserved ‘TVHYNP’ N-terminal signal binding domain with possible implications on its sensitivity to GA. Mutations in the conserved C-terminal GRAS domain of Rht-A1 alleles with possible effects on expression have been found in WW1842, Quarrion and Drysdale. Genetic variants with putative spliceosomal introns in the GRAS domain have been found in all accessions except Spica. Genome-specific cis-sequences about 124 bp upstream of the start codon of the Rht-1 gene have been identified for each of the three genomes.本研究发现了多个赤霉素不敏感型矮化基因的新型遗传变异，其具备用于作物遗传改良的潜在农业应用价值。品种Spica为高秆基因型，携带Rht-A1a、Rht-B1a与Rht-D1a的野生型等位基因。品种Quarrion的3个基因组中，每个基因组的DELLA结构域均存在无效突变体，这是首次报道Rht-A1的无效突变体。此外，在Quarrion、Carnamah与Whistler中发现了不同于已报道的Rht-B1b、Rht-B1e及Rht-D1b无效等位基因的新型无效突变体。种质材料Aus1408的Rht-B1等位基因存在保守"TVHYNP"N端信号结合结构域的突变，该突变可能影响其对赤霉素的敏感性。在WW1842、Quarrion与Drysdale的Rht-A1等位基因中，发现了位于保守C端GRAS结构域的突变，该突变可能对基因表达产生影响。除Spica外，所有供试材料均发现了GRAS结构域中带有推定剪接体内含子的遗传变异。研究人员在三个基因组各自的Rht-1基因起始密码子上游约124 bp处，鉴定到了基因组特异性顺式作用序列。