Promoter Mutation of the bZIP Transcription Factor BdABF Accelerates Flowering in Brachypodium distachyon

Flowering time plays an important role in crop regional adaptation, yield and reproductive success. ABRE BINDING FACTORs (ABFs) are bZIP transcription factors that participate in various plant biological processes. However, only a few ABFs have been reported to function in controlling flowering time. Here, we identified and characterized the function of the Brachypodium bZIP transcription factor BdABF in controlling flowering time. The results showed that Bdabf mutation in the promoter region promoted early flowering time in Bdabf T-DNA mutants compared with wild-type (WT) plants. Transcriptomic analysis showed that, compared with WT plants, 447 differentially expressed genes (DEGs) (266 upregulated and 181 downregulated) were identified in circadian rhythm, ABA signaling, IAA signaling, and flavonoid biosynthesis pathways in Bdabf mutants. Quantitative reverse transcription–polymerase chain reaction (qRT–PCR) results showed that the expression profiles of these genes in various pathways were consistent with the RNA-seq-based transcriptome dataset. The TF binding element analysis of these genes involved in different pathways in the promoter region showed that bHLH, bZIP, NF-Y, TIFY, and WRKY transcription factors were enriched. Taken together, our results showed that BdABF was involved in controlling flowering time by activating various metabolic pathways and provided new insights into ABFs controlling flowering time in Brachypodium.