Yeast-two-hybrid (Y2H) assays
The Y2H studies were performed as reported by Wang et al (2018). Briefly, the cDNA library was constructed by the Oebiotech Company using the apple skin. The coding sequences of the targets, including the viral 2apol, MP, and CP, as well as truncated MdBT2 and ApNMV 1a, were amplified and inserted into pGAD424 and pGBT9 vectors. Different combinations of bait and prey constructs were co-transformed into yeast (Y2H Gold, Clontech), and then cultured on defective medium lacking lucine (Leu) and tryptophan (Trp) at 28 °C for 2-3 d. The yeast colonies were then transferred onto selection medium without Leu, Trp, histdine (His), and adenine (Ade) to determine the interactions between bait and prey proteins.