Fig. 4

Identifying metabolites and genes potentially involved in apple domestication. a The contents of tannins with significant differential accumulation in M. sieversii/ heirloom and heirloom/ cultivar comparisons. b Manhattan plots of procyanidin A2 by GWAS. c A phylogenetic tree for MD15G1051400 and other R2R3 MYB members. d,e qRT-PCR analysis of Myb9-like and LAR (leucoanthocyanidin reductase) in high- and low-procyanidin content apples. f,g Results of transient overexpression of Myb9-like and LAR in apple fruits than empty vector (pGreenII 62-SK) injections. h Nucleotide polymorphism identified in the promoter of LAR. i Box plot for procyanidins contents correlated with C and T in Chr16:3404850. j qRT-PCR analysis of LAR in Myb9-like overexpressing apple fruit. k GUS transactivation assay in apples. The GUS reporter vector contains the LAR promoter, while the effector vector contains Myb9-like. l A simplified metabolic biosynthetic pathway of procyanidins in fruit. ANR, anthocyanidin reductase; Cys-EC, 4β-(S-cysteinyl)-epicatechin. Data are expressed as mean ± sd. “*” indicate p ≤ 0.05 by t-test