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GrainGenes Reference Report: PYC-62-691

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Reference	PYC-62-691
Title	Seed phosphorus and inositol phosphate phenotype of barley low phytic acid genotypes
Journal	Phytochemistry
Year	2003
Volume	62
Pages	691-706
Author	Dorsch JA [ Show all 8 ]
Abstract	Summary: myo-Inositol-1,2,3,4,5,6-hexakisphosphate (Ins P6 or 'phytic acid') typically represents approximately 75% of the total phosphorus and > 80% of soluble myo-inositol (Ins) phosphates in seeds. The seed phosphorus and Ins phosphate phenotypes of four non-lethal barley (Hordeum vulgare L.) low phytic acid mutations are described. In seeds homozygous for M 635 and M 955 reductions in Ins P6, approximately 75 and >90% respectively, are accompanied by reductions in other Ins phosphates and molar-equivalent increases in Pi. This phenotype suggests a block in supply of substrate Ins. In seeds homozygous for barley low phytic acid 1-1 (lpa1-1), a 45% decrease in Ins P6 is mostly matched by an increase in Pi but also accompanied by small increases in Ins(1,2,3,4,6)P5. In seeds homozygous for barley lpa2-1, reductions in seed Ins P6 are accompanied by increases in both Pi and in several Ins phosphates, a phenotype that suggests a lesion in Ins phosphate metabolism, rather than Ins supply. The increased Ins phosphates in barley lpa2-1 seed are: Ins(1,2,3,4,6)P5; Ins(1,2,4,6)P4 and/or its enantiomer Ins(2,3,4,6)P4; Ins(1,2,3,4)P4 and/or its enantiomer Ins(1,2,3,6)P4; Ins(1,2,6)P3 and/or its enantiomer Ins(2,3,4)P3; Ins(1,5,6)P3 and/or its enantiomer Ins(3,4,5)P3 (the methods used here cannot distinguish between enantiomers). This primarily '5-OH' series of Ins phosphates differs from the '1-/3-OH' series observed at elevated levels in seed of the maize lpa2 genotype, but previous chromosomal mapping data indicated that the maize and barley lpa2 loci might be orthologs of a single ancestral gene. Therefore one hypothesis that might explain the differing lpa2 phenotypes is that their common ancestral gene encodes a multi-functional, Ins phosphate kinase with both '1-/-3-' and '5-kinase' activities. A putative pyrophosphate-containing Ins phosphate, possibly an Ins P7, was also observed in the mature seed of all barley genotypes except lpa2-1. Barley M 955 indicates that at least for this species, the ability to accumulate Ins P6 can be nearly abolished while retaining at least short-term (approximately 1.0 years) viability
External Databases	Pubmed: 12620321
Keyword	[ Hide all but 1 of 35 ] acid barley chromatography dictyostelium gene grain mutants hordeum hordeum vulgare immature soybean seeds increase inositol phosphates kinase locus low phytic acid maize mapping metabolism myoinositol myoinositol hexakisphosphate phenotype phosphate phosphorus phosphorylation phytic acid poaceae purification reduction seed seed phenotype series short term substrate synthase viability zea mays

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