Glucosinolates (GSL) of cruciferous plants comprise a major group of
structurally diverse secondary compounds which act as deterrents against
aphids and microbial pathogens and have large commercial and ecological
impacts. While the transcriptional regulation governing the
biosynthesis and modification of GSL is now relatively well understood,
post-translational regulatory components that specifically determine the
structural variation of indole glucosinolates have not been reported.
We show that the cytoplasmic protein phosphatase 2A regulatory subunit
B'γ (PP2A-B'γ) physically interacts with indole glucosinolate
methyltransferases and controls the methoxylation of indole
glucosinolates and the formation of 4-methoxy-indol-3-yl-methyl
glucosinolate in Arabidopsis leaves. By taking advantage of proteomic
approaches and metabolic analysis we further demonstrate that PP2A-B'γ
is required to control the abundance of oligomeric protein complexes
functionally linked with the activated methyl cycle and the
trans-methylation capacity of leaf cells. These findings highlight the
key regulatory role of PP2A-B'γ in methionine metabolism and provide a
previously unrecognized perspective for metabolic engineering of
glucosinolate metabolism in cruciferous plants.