Fig. 2. (A) Expression of AtMYB4 in leaves of wild-type (WT) and atmyb4^– mutant plants. Expression was monitored by RT–PCR amplification of first strand cDNA. The transcript of another MYB gene expressed in leaves, AtMYB16, was amplified from the same cDNA as a control. (B) HPLC traces of soluble phenolics in methanolic extracts from leaves of wild-type and atmyb4^– mutant plants. A single major peak absorbing at A₃₃₀ was confirmed to be sinapoyl malate by liquid chromatography mass spectrometry (LCMS). In the mutant the levels of sinapoyl malate were 6- to 7-fold higher than in wild type.