Arabidopsis mutants in the C-S lyase of glucosinolate biosynthesis establish a critical role for indole-3-acetaldoxime in auxin homeostasis

Plant J. 2004 Mar;37(5):770-7. doi: 10.1111/j.1365-313x.2004.02002.x.

Abstract

We report characterization of SUPERROOT1 (SUR1) as the C-S lyase in glucosinolate biosynthesis. This is evidenced by selective metabolite profiling of sur1, which is completely devoid of aliphatic and indole glucosinolates. Furthermore, following in vivo feeding with radiolabeled p-hydroxyphenylacetaldoxime to the sur1 mutant, the corresponding C-S lyase substrate accumulated. C-S lyase activity of recombinant SUR1 heterologously expressed in Escherichia coli was demonstrated using the C-S lyase substrate djenkolic acid. The abolishment of glucosinolates in sur1 indicates that the SUR1 function is not redundant and thus SUR1 constitutes a single gene family. This suggests that the "high-auxin" phenotype of sur1 is caused by accumulation of endogenous C-S lyase substrates as well as aldoximes, including indole-3-acetaldoxime (IAOx) that is channeled into the main auxin indole-3-acetic acid (IAA). Thereby, the cause of the "high-auxin" phenotype of sur1 mutant resembles that of two other "high-auxin" mutants, superroot2 (sur2) and yucca1. Our findings provide important insight to the critical role IAOx plays in auxin homeostasis as a key branching point between primary and secondary metabolism, and define a framework for further dissection of auxin biosynthesis.

MeSH terms

  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Plant
  • Glucosinolates / biosynthesis*
  • Indoleacetic Acids / biosynthesis
  • Indoleacetic Acids / physiology*
  • Indoles / metabolism*
  • Lyases / genetics
  • Lyases / metabolism*
  • Multigene Family
  • Mutation
  • Oximes / metabolism*

Substances

  • Arabidopsis Proteins
  • Glucosinolates
  • Indoleacetic Acids
  • Indoles
  • Oximes
  • indole-3-acetaldoxime
  • Lyases
  • carbon-sulfur lyase