Genome-Wide Identification of the ARF Gene Family in Safflower (Carthamus tinctorius L.) and Their Response Patterns...

Auxin response factors (ARFs) are a class of transcription factors widely present in plants. As an important economic crop, research on the effects of safflower ARFs on endogenous auxin and effective components is relatively limited. In this study, a total of 23 ARF genes were identified from the safflower genome. Sequence alignment and domain analysis indicated the presence of conserved B3 and Auxin_resp domains in these ARFs. Phylogenetic analysis indicated that CtARF could be classified into five subfamilies, a conclusion also supported by gene structure, consensus motifs, and domain compositions. Transcriptome data showed that ARFs are expressed in all flower colors, but the expression levels of ARF family members vary among different flower colors. CtARF19 had relatively higher expression in deep red flowers, CtARF3 had higher expression in white flowers, CtARF2/12 had higher expression in yellow flowers, and CtARF21/22 had higher expression in light red flowers. Protein-protein interaction network analysis indicated that ARF family members (CtARF2/3/4/5/15/18/19/22) are located within the interaction network. Cis-acting element analysis suggested that CtARF genes may be regulated by hormone treatment (AuxRR-core) and abiotic stress, and the results of qRT-PCR also confirmed this. Additionally, the content of endogenous auxin and active components in safflower with different flower colors significantly changed upon treatment with hormones that affect IAA content. In summary, our study provides valuable insights into the biological functions of CtARF genes under exogenous hormone conditions and their effects on active components.