Dosage response to reduced height‐1 (Rht‐1) loss‐of‐function mutations and characterization of slender phenotype in hexaploid wheat

Abstract

AbstractThe reduced height (Rht‐1) genes in wheat (Triticum aestivum L.) are integral in controlling plant height. Previous studies in other plant species have demonstrated that loss‐of‐function mutations in their orthologous Rht‐1 genes results in plants with a slender phenotype illustrated by increased plant heights, sterility, and a constitutive gibberellic acid (GA3) response; however, this phenotype has not been described in wheat. In this study, nonsense alleles occurring in the GRAS domain of Rht‐A1, B1, and D1 were combined to create single, double, and triple Rht‐1 mutants. Homozygous lines possessing none, one, two, or three Rht‐1 stop mutations were grown in replicated field trials in three environments to assess agronomic traits. Germination tests to measure GA3 responsiveness and gene expression analysis via RNA‐seq were also performed. Rht‐1 triple mutants exhibited a slender phenotype characterized by rapid growth, elongated coleoptiles and internodes, elongated spikes, decreased tiller and spikelet number, and sterile heads. The presence of a single functional Rht‐1 gene resulted in a normal phenotype. Differences in plant height among the Rht‐1 double mutants, Rht‐1 single mutants, and Rht‐1 all wild‐type dosages trended toward increased plant height with increased Rht‐1 stop mutation dosage. Differences in Rht‐1 homeolog gene expression did not equate to differences in plant height between the different Rht‐1 stop mutations.