Abstract: To adapt to environmental challenges, plants have evolved extensive gene families through duplication events, generating multiple-copy genes that mediate stress responses. However, the function of these duplicated genes in wheat remains unclear. In this study, we identified ten tandemly duplicated ETHYLENE RESPONSE FACTOR 109 (ERF109) genes in wheat, seven of which showed rapid induction under drought treatment. Overexpressing TaERF109A2 resulted in delayed heading date, increased tiller number, reduced plant height and root length, and enhanced drought resilience. Conversely, the CRISPR/Cas9-generated nonuple Taerf109s mutant showed exacerbated growth inhibition under drought stress. RNA-seq and functional analyses indicated that TaMADS56, functioning as a genetic downstream effector of TaERF109A2, modulates wheat tillering, heading date, and drought recovery responses. TaERF109A2 directly binds to the GCC-box motifs in the promoters of TaIPT8-5B/5D, thereby regulating cytokinin (CK) biosynthesis. Moreover, overexpression of TaERF109A2 enhances nicotianamine (NA) accumulation, which in turn confers tolerance to iron toxicity and drought stress via upregulation of nicotianamine synthase (NAS) genes. Our findings have highlighted the critical role of tandemly duplicated genes in the coordination of stress responses and developmental processes in wheat.

Key words: drought tolerance, ERF109, tandemly duplicatedgenes, wheat