GENOME-WIDE IDENTIFICATION AND CHARACTERIZATION OF SAUR1 GENES IN BRASSICA SPECIES AND SEEDLING GROWTH

Abstract

Auxin controls plant growth and development, and the small auxin-up RNA (SAUR) family is the largest group of auxin-responsive genes. SAUR genes are rapidly induced by auxin and regulate cell growth, but their repertoire and activity in Brassica species have not been examined. Here we carried out a genome-wide identification and characterization of SAUR1 genes in six Brassica species (B. rapa, B. nigra, B. oleracea, B. juncea, B. napus and B. carinata). Sixteen SAUR1 genes were identified and analyzed for sequence features, gene structure, conserved motifs and chromosomal location. All of them lacked introns and carried highly conserved motifs, which suggests evolutionary stability. Subcellular localization analysis predicted that SAUR1 proteins are targeted mainly to chloroplasts and mitochondria. Phylogenetic analysis showed strong homology with Arabidopsis SAURs and lineage-specific diversification. Promoter analysis detected multiple auxin- and stress-related cis-elements, which points to roles in development and adaptation. The species differed significantly in root length, shoot length, and fresh and dry biomass (ANOVA), indicating species-specific growth responses. This is the first comprehensive characterization of SAUR1 genes in Brassica, and it gives a basis for studying auxin signaling and growth regulation in the genus.