The drought-responsive factor MdDREB2A affects root development by directly regulating the transcription of MdARF6

Drought is one of the most common abiotic stresses, which affects plant growth and root system architecture. Auxin is a key phytohormone in regulating root structures. However, how drought and auxin jointly regulate root development is still less studied. In this study, it was found that APETALA2/ethylene-responsive element binding factors (AP2/ERF) transcription factor MdDREB2A could affect root development by regulating the transcription of AUXIN RESPONSE FACTOR 6 (MdARF6). Overexpression of MdDREB2A promoted root development both in apple and Arabidopsis. Further assays showed that MdDREB2A could regulate the expression of auxin related genes ARFs/IAAs. In addition, MdDREB2A could directly bind to the DRE cis-element in the promoter of MdARF6 to activate its transcription. Meanwhile, MdDREB2A could also promote the expression of auxin-responsive Gretchen Hagen3s (MdGH3s), which act the downstream of ARF6, thereby further regulating auxin-mediated root development. This work provides a novel perspective for drought and auxin crosstalk to regulate root development.