A Gain-of-Function Mutant of IAA7 Inhibits Stem Elongation by Transcriptional Repression of Genes in .

Plant height is one of the most important agronomic traits of rapeseeds. In this study, we characterized a dwarf mutant, named , obtained from fast neutrons and DES mutagenesis. Based on BSA-Seq and genetic properties, we identified causal mutations with a time-saving approach. The mutation was identified on chromosome A03 and can result in an amino acid substitution in the conserved degron motif (GWPPV to EWPPV) of the Auxin/indole-3-acetic acid protein 7 (BnaA03.IAA7) encoded by the causative gene. Aux/IAA protein is one of the core components of the auxin signaling pathway, which regulates many growth and development processes. However, the molecular mechanism of auxin signal regulating plant height is still not well understood. In the following work, we identified that BnaARF6 and BnaARF8 as interactors of BnaA03.IAA7 and as a target of BnaARF6 and BnaARF8. The three genes , and were highly expressed in stem, suggesting that these genes were involved in stem development. The overexpression of results in larger rosettes leaves and longer inflorescence stems in . Our results indicate that BnaA03.IAA7- and BnaARF6/8-dependent auxin signal control stem elongation and plant height by regulating the transcription of gene, which is one of the targets of this signal.