Twisted Sister1: an agravitropic mutant of bread wheat (Triticum aestivum) with altered root and shoot architectures

Abstract

AbstractWe identified a mutant of hexaploid wheat (Triticum aestivum) with impaired responses to gravity. The mutant namedTwisted Sister1(TS1) had agravitropic roots that were often twisted along with altered shoot phenotypes. Roots ofTS1were insensitive of externally applied auxin with the genetics and physiology suggestive of a mutatedAUX/IAAtranscription factor gene. Hexaploid wheat possesses over eightyAUX/IAAgenes and sequence information did not identify an obvious candidate. Bulked segregant analysis of an F2population mapped the mutation to chromosome 5A and subsequent mapping located the mutation to a 41 Mbp region. RNA-seq identified theTraesCS5A03G0149800gene encoding a TaAUX/IAA protein to be mutated in the highly conserved domain II motif. We confirmedTraesCS5A03G0149800as underlying the mutant phenotype by generating transgenicArabidopsis thaliana. Analysis of RNA-seq data suggested broad similarities between Arabidopsis and wheat for the role ofAUX/IAAgenes in gravity responses. Here we show that the sequenced wheat genome along with previous knowledge largely from the model species Arabidopsis, gene mapping, RNA-seq and expression in Arabidopsis have enabled cloning of a key wheat gene defining plant architecture.