X α gal

The full‐length cDNA sequences of ZmDA1 and ZmSWEET4c were recombination into the pGBKT7 and pGADT7 separately. The yeast transformation followed the instructions of the yeast transformation kit (Clontech Matchmaler™ Mountain View, USA). The positive clones were screened by the ‐Leu–Trp and ‐Ade‐His‐Leu–Trp dropout supplements (Clontech Mountain View, USA), and the positive clones were coloured by X‐α‐Gal (Solarbio Beijing, China).

The full-length ORF of PtrARF2.1 was amplified with specific primers (Table S5), the amplification product was inserted into pGBKT7 (Clontech) using ClonExpress II (Vazyme Biotech, Nanjing, China) and the recombinant plasmid was introduced into the yeast strain Saccharomyces cerevisiae Gold2 by the method described previously (Zaragoza et al. 2004). Transformants were grown on SD medium lacking Trp (tryptophan) for selection of positive clones and then on SD medium lacking Trp, His (histidine) and Ade (adenine) for the transactivation assay. The X-α-gal (Solarbio, Beijing, China) was used to identify the transcription activation activity of PtrARF2.1.