Fig. 6: Stereochemical diversity of wild tomato steroidal glycoalkaloids.
From: Enzymatic twists evolved stereo-divergent alkaloids in the Solanaceae family
a Extracted ion chromatograms (EICs) showing accumulation of α-tomatine C25 isomers in domesticated and wild tomato species. Arrows indicate 25S and 25R isomer. b LC-MS analysis of SGA aglycones (tomatidine and soladulcidine) in S. lycopersicum, S. pennellii, and S. cheesmaniae leaves. c Production of SGA aglycone isomers (tomatidenol and solasodine) by S. pennellii GAME8-1 or GAME8-2, or S. cheesmaniae GAME8 in N. benthamiana leaves analyzed by LC-MS. As controls we used GAME8 genes from tomato and eggplant. d Multiple sequence alignment of active sites’ amino acid sequences from GAME8 enzymes with 25S (red) or 25R (purple) or mixed stereospecificity. SgalGAME8 corresponds to GAME8 enzyme from Solanum galapagense (see Fig. 7 for more details). Differential amino acids are highlighted in yellow and pale blue. e qPCR expression analysis of SpGAME8 genes in S. pennellii leaf (n = 8 of independent measurements for each gene, P = 4.70744E-15). f Analysis of relative concentration of 25S and 25R α-tomatine isomers in S. pennellii leaf (n = 7, independent measurement, P = 2.02513E-08). Comparing (e, f), we can see that levels of gene expression correlate with metabolite content in the same tissue. g Map of northwestern part of South America showing origins of wilds tomato accessions used in this study (Fig. 6a); the blue star on the map represents Lima, the capital of Peru. h EICs showing accumulation of α-tomatine C25 isomers in selected S. pennellii introgression lines (ILs) and in parental species. Arrows indicate 25S and 25R isomer. Asterisks indicate statistically significant differences determined by two-sided Student’s t-test (*** −P < 0.001). Box plots show all data points, center line represents median value, bounds correspond to upper and lower quartile, and whiskers represent min and max values.
