Genome-wide characterization of Brassica napus INDETERMINATE DOMAIN genes reveals a negative role for BnA08.IDD7 in plant development

Abstract INDETERMINATE DOMAIN (IDD) transcription factors belong to the most conserved gene family in plants and play crucial roles in growth and development. However, there has been no systemic survey and characterization of IDD genes in Brassica napus. Here, we identified 58 IDD genes in the B. napus genome. Phylogenetic analysis of IDD genes from three Brassica species and Arabidopsis thaliana classified them into six groups. The BnIDD genes displayed functional and structural diversity with respect to gene structure and cis-acting elements in their promoters. The majority of BnIDD genes in Group 1/3/4 were highly expressed in leaves, flowers, and reproductive organs, while those in Group 2/5/6 showed more restricted tissue-specific expression patterns. In addition, BnIDD7 genes showed extremely high expression in all detected tissues, which we confirmed by promoter-GUS staining. Subcellular localization showed that BnA08. IDD7 (BnIDD7–1) is localized to the nucleus. Overexpression of BnA08. IDD7 in Arabidopsis resulted in significant inhibition of multiple traits, such as root elongation, delayed flowering, and reduced plant height and aboveground fresh weight. Our study provides insight into the functional evolution of the IDD gene family in plants, and lays a foundation for discovering the molecular mechanisms underlying the negative role of IDD7 in plant growth and development.