MdSPL14 and MdWRKY24 act coordinately to regulate CK levels by repressing MdCKX5 expression. A, B) EMSA indicating that the addition of MdSPL14 and MdWRKY24 enhances binding to biotin-labeled oligonucleotides of MdCKX5, respectively. C) LUC assay indicating that the coexpression of MdSPL14 and MdWRKY24 enhances the transcriptional repression activity of MdSPL14 and MdWRKY24 on MdCKX5 in apple calli. D) Relative LUC/REN activity of apple calli coexpressing MdSPL14, MdWRKY24, and proMdCKX5. Data are means ± Sd (n = 3). E to G) The relative expression levels of MdCKX5, and tZ and iP content in response to MdSPL14-OE, MdWRKY24-OE, and MdSPL14-OE + MdWRKY24-OE via agroinfiltration to leaves, with empty vector as control. WT, wild type; OE, overexpressing; FW, fresh weight. Data are means ± Sd (n = 3). Values with different letters are significantly different according to 1-way ANOVA followed by Tukey's test (P < 0.05).