Comprehensive analysis of YABBY gene family in foxtail millet (Setaria italica) and functional characterization of SiDL

YABBY genes are plant-specific transcription factors (TFs) that function in plant growth and development. We investigated the functions of the YABBY genes in plants' stress tolerance by analyzing the YABBY genes in foxtail millet (Setaria italica) and studying their functions on plant growth and responses to different stresses. Eight YABBY genes were identified on five chromosomes, which showed strong relationships with YABBY genes in other monocot species. Phylogenetical SiYABs were classified into four clades: FIL/YAB3, YAB2, INO, and CRC. No monocot YABBY member was classified into the YAB5 clade. Four conserved motifs were identified, and motif 1 constituted the YABBY domain, whereas motifs 2 and 3 formed the C2-C2 region. SiYAB genes were highly expressed in reproductive tissues. SiDL, one of the SiYABs, was selected to be overexpressed in Arabidopsis thaliana to check the functions of the YABBY genes. Overexpression of SiDL in A. thaliana caused delayed flowering, leaf curling, and reduced seed size. In addition, SiDL acted as a negative regulator in plant response to salt stress. Our study provides information to assist in studying the YABBY gene functions in S. italica.