Expression pattern analysis of MdbHLH093. (a) Quantitative real-time PCR (qRT–PCR) analysis of MdbHLH093 in plants infected with powdery mildew. (b) Relative expression of MdbHLH093 in apple root, stem, leaf, flower and fruit. MdTubulin was used as an internal reference gene. Error bars are calculated from three biological experiments and show the standard deviation of the mean. Asterisks indicate statistical significance (*, p < 0.05; **, p < 0.01; Student’s t-test). (c) Subcellular localization of MdbHLH093 in tobacco leaves. Green fluorescent protein (GFP) signals were detected with a laser confocal microscope. Scale bar = 25 μm. (d) The MdbHLH093 Yeast autoactivation transformation experiment, co-transformation of AD/T with BD/P53 or BD/Lam into yeast cells was used as positive and negative controls, respectively.