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Combining Genome-Wide Association Mapping and Transcriptional Networks to Identify Novel Genes Controlling Glucosinolates in Arabidopsis thaliana

Figure 1

GSL Biosynthesis and Cloned QTL.

Arrows show the known and predicted steps for GSL biosynthesis with the gene name for each biochemical reaction within the arrow. For compounds that are undetected intermediates, chemical names only are provided. For detected compounds, both the structure and chemical name are provided. The position of known genetic loci controlling biosynthetic variation is shown in italics. (A) The pathway and genes responsible for the production of the core GSL structure from tryptophan (indolic GSL) and methionine (aliphatic GSL). (B) The chain elongation cycle for aliphatic GSL production. Each cycle of these reactions adds a single carbon to a 2-oxo-acid, which is then trans-aminated to generate homo-methionine for aliphatic GSL biosynthesis. The GSL.Elong QTL alters this cycle through variation at the MAM1, MAM2, and MAM3 genes that leads to differential GSL structure and content [71],[142]. (C) The enzymes and genetic loci controlling aliphatic GSL side chain modification within the Bay-0 × Sha RIL population. Side-chain modification is controlled by variation at the GSL.ALK QTL via cis-eQTL at the AOP2 and AOP3 genes. The Cvi and Sha accessions express AOP2 to produce alkenyl GSL. In contrast, the Ler and Bay-0 accessions express AOP3 to produce hydroxyl GSL. Col-0 is null for both AOP2 and AOP3, producing only the precursor methylsulfinyl GSL [61],[143]. The GSL.OX QTL appear to be controlled by cis-eQTL regulating flavin-monoxygenase enzymes (GS-OX1 to 5) that oxygenate a methylthio to methylsulfinyl GSL [55],[58]. The GSL.OH QTL is a cis-eQTL in the GS-OH gene which encodes the enzyme for the oxygenation reaction [56].

Figure 1