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Publication Type J
Authors Ishitani, M., A. L. Majumder, A. Bornhouser, C. B. Michalowski, R. G. Jensen and H. J. Bohnert
Title Coordinate transcriptional induction of myo-inositol metabolism during environmental stress
Source Plant Journal
Author Keywords halophyte mesembryanthemum-crystallinum; plant gene; myo-inositol-1-phosphate synthase; phosphoenolpyruvate carboxylase; saccharomyces-cerevisiae; facultative halophyte; arabidopsis-thaliana; structural gene; ice plant; salt
Abstract The pathway from glucose 6-phosphate (G 6-P) to myo-inositol 1-phosphate (Ins 1-P) and myo-inositol (Ins) is essential for the synthesis of various metabolites. In the halophyte Mesembryanthemum crystallinum (common ice plant), two enzymes, myo-inositol O-methyltransferase (IMT1) and ononitol epimerase (OEP1), extend this pathway and lead to the accumulation of methylated inositols, D-ononitol and D-pinitol, which serve as osmoprotectants. This paper describes transcripts for the enzyme, Inps1, encoding myo-inositol 1-phosphate synthase (INPS1), from the ice plant. Two Inps-like sequences are present in the genome. The deduced amino acid sequences of the cloned transcript are 49.5% and 87-90%, respectively, identical to those of yeast and other higher plant sequences. Inps1 RNA amounts are upregulated at least fivefold and amounts of free Ins accumulate approximately 10-fold during salinity stress. Inps1 induction is by transcription, similar to the induction of Imt1. In contrast, Arabidopsis thaliana does not show upregulation of Inps1 or increased amounts of Ins when salt-stressed. The lack of Inps1 induction in Arabidopsis exemplifies differences in glycophytic and halophytic regulation of gene expression at the point of entry into a pathway that leads to osmoprotection. The stress-induced coordinate upregulation of this pathway and its extension by novel enzymes in the ice plant also highlights biochemical differences.
Author Address UNIV ARIZONA,DEPT BIOCHEM,TUCSON,AZ 85721. UNIV ARIZONA,DEPT PLANT SCI,TUCSON,AZ 85721. UNIV ARIZONA,DEPT MOLEC & CELLULAR BIOL,TUCSON,AZ 85721.
29-Character Source Abbreviation Plant J.
Publication Date Apr
Year Published 1996
Volume 9
Issue 4
Beginning Page 537-548
Unique Article Identifier ISI:A1996UF34000010
Plants associated with this reference

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