Fig. 5

Selected reaction monitoring (SRM)-based quantitative strategies of targeted protein amount in tomato trichome gland cells (TGCs). a SRM determination of target protein abundance in the TGC sample using an AQUA peptide standard. A stable isotope-labeled AQUA peptide (GLAEEDPNEPHGLK) was used as an internal standard for the absolute quantification of the targeted K4ASM0 protein by SRM. b Biosynthesis workflow for the QconCAT peptide standards. Two QconCAT sequences covering 50 proteins involved in the synthesis of secondary metabolites (detailed information can be found in Additional file 8: Figure S4 and Additional file 9: Table S5) were designed in this study. Stable isotope-labeled QconCATs were synthesized using a wheat germ cell-free synthesis system. c SRM chromatogram of standard peptides (total 79 peptides) obtained by biosynthesis of stable isotope-labeled QconCATs. The synthesized QconCATs were purified with 6xHis-tag and digested with trypsin. The peptide mixtures derived from QconCATs were subjected to liquid chromatography (LC)-SRM. Fibrinopeptide released from the C terminus of QconCATs due to trypsin digestion was used for the absolute quantification of the synthesized QconCATs using SRM (Additional file 8: Figure S4C)