title: Synthesis of inositol phosphate ligands of plant hormone-receptor complexes: pathways of inositol hexakisphosphate turnover.
abstract: Reduction of phytate is a major goal of plant breeding programs to improve the nutritional quality of crops. Remarkably, except for the storage organs of crops such as barley, maize and soybean, we know little of the stereoisomeric composition of inositol phosphates in plant tissues. To investigate the metabolic origins of higher inositol phosphates in photosynthetic tissues, we have radiolabelled leaf tissue of Solanum tuberosum with myo-[2-3H]inositol, undertaken a detailed analysis of inositol phosphate stereoisomerism and permeabilized mesophyll protoplasts in media containing inositol phosphates. We describe the inositol phosphate composition of leaf tissue and identify pathways of inositol phosphate metabolism that we reveal to be common to other kingdoms. Our results identify the metabolic origins of a number of higher inositol phosphates including ones that are precursors of cofactors, or cofactors of plant hormone-receptor complexes. The present study affords alternative explanations of the effects of disruption of inositol phosphate metabolism reported in other species, and identifies different inositol phosphates from that described in photosynthetic tissue of the monocot Spirodela polyrhiza. We define the pathways of inositol hexakisphosphate turnover and shed light on the occurrence of a number of inositol phosphates identified in animals, for which metabolic origins have not been defined.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, U.K.
authors.forename: David E
authors.initials: DE
authors.lastname: Hanke
authors.forename: Paroo N
authors.initials: PN
authors.lastname: Parmar
authors.forename: Samuel E K
authors.initials: SE
authors.lastname: Caddick
authors.forename: Porntip
authors.initials: P
authors.lastname: Green
authors.forename: Charles A
authors.initials: CA
authors.lastname: Brearley
mesh_terms: D007295:Inositol Phosphates / Q000096:biosynthesis / Q000302:isolation & purification; D008024:Ligands; D010833:Phytic Acid / Q000096:biosynthesis* / Q000302:isolation & purification; D010936:Plant Extracts / Q000096:biosynthesis* / Q000302:isolation & purification; D010937:Plant Growth Regulators / Q000096:biosynthesis* / Q000302:isolation & purification; D018515:Plant Leaves; D015398:Signal Transduction / Q000502:physiology*; D011198:Solanum tuberosum
chemical_list: D007295:Inositol Phosphates; D008024:Ligands; D010936:Plant Extracts; D010937:Plant Growth Regulators; D010833:Phytic Acid