A novel methyl transferase induced by osmotic stress in the facultative halophyte Mesembryanthemum crystallinum

EMBO J. 1992 Jun;11(6):2077-85.

Abstract

Molecular mechanisms of osmotic stress tolerance were studied in Mesembryanthemum crystallinum (ice plant), a facultative halophyte capable of adjusting to and surviving in highly saline conditions. We screened a subtracted cDNA library enriched for salt stress-induced mRNAs to identify transcripts involved in this plant's adaptation to salinity. One mRNA, Imt1, was found to be up-regulated in leaves and, transiently, in roots. Nuclear run-on assays indicated that this mRNA is transcriptionally regulated. Imt1 encoded a predicted polypeptide of M(r) 40,250 which exhibited sequence similarity to several hydroxymethyl transferases. Expression of the protein in Escherichia coli and subsequent activity assays identified the protein as a novel myoinositol O-methyl transferase which catalyzes the first step in the biosynthesis of the cyclic sugar alcohol pinitol. Pinitol accumulates in salt-stressed M.crystallinum and is abundant in a number of salt- and drought-tolerant plants. The presence of high levels of sugar alcohols correlates with osmotolerance in a diverse range of organisms, including bacteria, fungi and algae, as well as higher plants. The stress-initiated transcriptional induction of IMT1 expression in a facultative halophyte provides strong support for the importance of sugar alcohols in establishing tolerance to osmotic stress in higher plants.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Blotting, Southern
  • Cloning, Molecular
  • DNA / genetics
  • DNA / isolation & purification
  • Enzyme Induction
  • Escherichia coli / genetics
  • Gene Library
  • Genes, Plant
  • Ice
  • Methyltransferases / biosynthesis*
  • Methyltransferases / genetics*
  • Methyltransferases / isolation & purification
  • Molecular Sequence Data
  • Molecular Weight
  • Osmolar Concentration
  • Plants / enzymology*
  • Plants / genetics
  • RNA, Messenger / genetics*
  • RNA, Messenger / metabolism
  • Recombinant Fusion Proteins / isolation & purification
  • Recombinant Fusion Proteins / metabolism
  • Transcription, Genetic

Substances

  • Ice
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • DNA
  • Methyltransferases

Associated data

  • GENBANK/M87340
  • GENBANK/X64335
  • GENBANK/X64555
  • GENBANK/X64556
  • GENBANK/X64629
  • GENBANK/X64700
  • GENBANK/X67723
  • GENBANK/X67724
  • GENBANK/X67725
  • GENBANK/X67726