title: Expression of a Brassica isopropylmalate synthase gene in Arabidopsis perturbs both glucosinolate and amino acid metabolism.
abstract: Isopropylmalate synthase (IPMS) is a key enzyme in the biosynthesis of the essential amino acid leucine, and thus primary metabolism. In Arabidopsis, the functionally similar enzyme, methythiolalkylmalate synthase (MAM), is an important enzyme in the elongation of methionine prior to glucosinolate (GSL) biosynthesis, as part of secondary metabolism. We describe the cloning of an IPMS gene from Brassica, BatIMS, and its functional characterisation by heterologous expression in E. coli and Arabidopsis. Over expression of BatIMS in Arabidopsis resulted in plants with an aberrant phenotype, reminiscent of mutants in GSL biosynthesis. Metabolite analyses showed that these plants had both perturbed amino acid metabolism and enhanced levels of GSLs. Microarray profiling showed that BatIMS over expression caused up regulation of the genes for methionine-derived GSL biosynthesis, and down regulation of genes involved in leucine catabolism, in addition to perturbed expression of genes involved in auxin and ethylene metabolism. The results illustrate the cross talk that can occur between primary and secondary metabolism within transgenic plants.
authors.affiliation: John Innes Centre, Colney Lane, Norwich NR4 7UH, UK. ben.field@bbsrc.ac.uk
authors.forename: Ben
authors.initials: B
authors.lastname: Field
authors.forename: Caroline
authors.initials: C
authors.lastname: Furniss
authors.forename: Andrew
authors.initials: A
authors.lastname: Wilkinson
authors.forename: Richard
authors.initials: R
authors.lastname: Mithen
mesh_terms: D015079:2-Isopropylmalate Synthase / Q000235:genetics* / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D001937:Brassica / Q000201:enzymology*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D005961:Glucosinolates / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D030821:Plants, Genetically Modified; D051381:Rats
chemical_list: D000596:Amino Acids; D005961:Glucosinolates; D015079:2-Isopropylmalate Synthase