Phytic acid represents 10 to 15% of total phosphorus in alfalfa root and crown

Campbell, M. H.; Dunn, Robert L.; Ditterline, R. L.; Pickett, Suewiya G.; Raboy, Victor

doi:10.1080/01904169109364253

Cited by 30 publications

(16 citation statements)

References 11 publications

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“…Saxena (1963) suggested that root phytase could be operative in the utilization of soil-borne phytate, which usually represents the bulk of organic phosphate in agricultura1 soils (Anderson, 1980). Severa1 authors (Tarafdar and Claassen, 1988; Adams and Pate, 1992) whether in these cases phytate was hydrolyzed by an extracellular or an intracellular phytase (Islam et al, 1979;Kraus, 1989 (Campbell et al, 1991). These findings are in line with earlier results by Roberts and Loewus (1968) and Scheiner et al (1978), who demonstrated the accumulation of phytate in duckweed.…”

supporting

confidence: 82%

“…In addition, phytate was identified as a compound representing up to 14% of total P (290 pg 8-l dry weight) in root and crown tissue of alfalfa (Campbell et al, 1991). These findings are in line with earlier results by Roberts and Loewus (1968) and Scheiner et al (1978), who demonstrated the accumulation of phytate in duckweed.…”

supporting

confidence: 82%

“…Since as in seeds appreciable amounts of phytate (290 /xg g^1 dry matter) were detected in root and crown tissue of alfalfa (Campbell et al, 1991) and in Wolffiella floridana (Roberts and Loewus, 1968), root phytase might be responsible for the hydrolysis of an endogeneous substrate that appears to be deposited as P-rich globoids in the pericycle…”

Section: Discussionmentioning

confidence: 99%

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Maize Root Phytase (Purification, Characterization, and Localization of Enzyme Activity and Its Putative Substrate)

Hübel

Beck

1996

Plant Physiology

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Three phytase (EC 3.1.3.26) isoforms from the roots of 8-d-old maize (Zea mays 1. var Consul) seedlings were separated from phosphatases and purified to near homogeneity. The molecular mass of the native protein was 71 kD, and the isoelectric points of the three isoforms were pH 5.0, 4.9, and 4.8. Each of the three isoforms consisted of two subunits with a molecular mass of 38 kD.The temperature and pH optima (40"C, pH 5.0) of these three isoforms, as well as the apparent Michaelis constants for sodium inositol hexakisphosphate (phytate) (43, 25, and 24 p~) as determined by the release of inorganic phosphate, were only slightly different. Phytate concentrations higher than 300 p~ were inhibitory to all three isoforms. In contrast, the dephosphorylation of 4-nitrophenyl phosphate was not inhibited by any substrate concentration, but the Michaelis constants for this substrate were considerably higher (137-157 PM). Hydrolysis of phytate by the phytase isoforms is a nonrandom reaction. D/L-hOSitOl-l,2,3,4,5-pentakisphosphate was identified as the first and D/L-inOSitOl-1,2,5,6-tetrakisphosphate as the second intermediate in phytate hydrolysis. Phytase activity was localized in root slices. Although phosphatase activity was present in the stele and the cortex of the primary root, phytase activity was confined to the endodermis.Phytate was identified as the putative native substrate in maize roots (45 pg P g-' dry matter). It was readily labeled upon supplying [32Plphosphate to the roots.Phytate (inositolhexakisphosphate, InsP,) is the major storage form of phosphate in seeds and pollen. Although synthesis of phytate during seed filling and breakdown in the early phase of germination have been widely investigated, the role of phytate and phytase (EC 3.1.3.26) in nonreproducing plant tissues has not yet been elucidated. Saxena (1963) suggested that root phytase could be operative in the utilization of soil-borne phytate, which usually represents the bulk of organic phosphate in agricultura1 soils (Anderson, 1980). Severa1 authors (Tarafdar and Claassen, 1988; Adams and Pate, 1992) whether in these cases phytate was hydrolyzed by an extracellular or an intracellular phytase (Islam et al., 1979;Kraus, 1989 (Campbell et al., 1991). These findings are in line with earlier results by Roberts and Loewus (1968) and Scheiner et al. (1978), who demonstrated the accumulation of phytate in duckweed. Thus, in roots and shoots phytases might be involved in the breakdown of phytate, as in seeds.In addition to a possible role as a P-storage compound, phytate may also be effective as a chelator in the detoxification of heavy metal ions in plant tissue. Van Steveninck et al. (1993,1994 showed that roots of various plant species were able to immobilize excessively supplied zinc in globular, P-rich intracellular inclusions deposited in the root elongation zone. These deposits were similar to globoids that were found by Lott and Ockenden (1986) in seeds.The present work is a continuation of our investigations on phytases in maize root...

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supporting

confidence: 82%

supporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

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Maize Root Phytase (Purification, Characterization, and Localization of Enzyme Activity and Its Putative Substrate)

Hübel

Beck

1996

Plant Physiology

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“…These results are consistent with the observations of Brearley and Hanke (1996a,b) in S. polyrrhiza, Igaue et al (1980) in rice suspension cells, and Roberts and Loewus (1968) in Lemna gibba. Although high levels of InsP 6 are generally associated with phosphate storage tissue, our results add to a body of evidence indicating a role for this compound in plant tissues not normally associated with storage functions (Roberts and Loewus 1968;Van Steveninck et al 1987;Campbell et al 1991;HuÈ bel and Beck 1996). The function of this InsP 6 accumulation is still unknown, Fig.…”

Section: Increased¯ux To Inositol Phosphates Occurs During Aba-inducesupporting

confidence: 61%

Abscisic acid-induced changes in inositol metabolism in Spirodela polyrrhiza

Flores

Smart

2000

Planta

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In response to abscisic acid (ABA), the duckweed Spirodela polyrrhiza (L.) activates a developmental pathway that culminates in the formation of dormant structures known as turions. Levels of the mRNA encoding D-myo-inositol-3-phosphate synthase (EC.5.5.1.4) which converts glucose-6-phosphate to inositol-3-phosphate, increase early in response to ABA. In order to understand the role of this enzyme in turion formation, we have investigated changes in inositol metabolism in ABA-treated plants. Here, we show that ABA-treatment leads to a 3-fold increase in free inositol, which peaks 2 d after treatment. This increase is followed by sequential increases in inositol phosphates and in accumulation of inositol hexakis-phosphate (InsP6), in particular. In addition, we observed an early increase in a novel inositol bisphosphate which is not directly on the pathway to InsP6. In control plants, we observed synthesis and turnover of both inositol pentakisphosphate and InsP6. Two compounds more polar than InsP6 (diphosphoinositol polyphosphates) were present in both ABA-treated and control plants. Together, this suggests that the role of InsP6 in plants may be more complex than simply that of a storage compound during dormancy.

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“…An iron/phosphorus ratio of about 1 in the particles of older mutant leaves could be an indication that the accumulated iron is precipitated as insoluble iron phos- phate or as another iron phosphate compound, for instance phytate. Phytate is considered to function as a reserve of phosphorus and various cations mainly in seeds (Cosgrove, 1980), but it has also been detected in roots (Campbell et al, 1991). The principle minerals stored as phytate are potassium and magnesium (Lott et al, 1982), but also copper, zinc, iron, and calcium (Maga, 1982;MikuS et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

Subcellular Localization and Characterization of Excessive Iron in the Nicotianamine-less Tomato Mutant chloronerva

1995

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To understand the function of the Fe2+-complexing compound nicotianamine (NA) in the iron metabolism of plants we have localized iron and other elements in the NA-containing tomato wild type (Lycopersicon esculentum) and its NA-free mutant chloronerva by quantitative x-ray microanalysis. Comparison of element composition of the rhizodermal cell walls indicated that the wild type accumulated considerable amounts of iron and phosphorus in the cell wall, whereas in the mutant iron and phosphorus were detected in the cytoplasm and vacuoles of the rhizodermis. In mutant leaves containing high iron concentrations in the symplast, electron-dense inclusions were detected in chloroplasts and phloem. Such particles, consisting mainly of iron and phosphorus, were never found in the wild type and were very rarely detected in young chlorotic mutant leaves or after treatment of the mutant with NA. For further characterization the electron-dense inclusions in mutant leaves were isolated and compared by sodium dodecyl sulfate-gel electrophoresis and immunoblotting to ferritin from iron-loaded Phaseolus vulgaris leaves. Antibodies raised against purified Phaseolus leaf ferritin were used. Neither in mutant nor in wild type (iron loaded and control) was ferritin protein detected. These results suggest that the electron-dense inclusions in mutant leaves are not identical with ferritin. It is concluded that NA is necessary to complex ferrous iron in a soluble and available form within the cells. In the absence of NA the precipitation of excessive iron in the form of insoluble ferric phosphate compounds could protect the cells from iron overload.

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Phytic acid represents 10 to 15% of total phosphorus in alfalfa root and crown

Cited by 30 publications

References 11 publications

Maize Root Phytase (Purification, Characterization, and Localization of Enzyme Activity and Its Putative Substrate)

Maize Root Phytase (Purification, Characterization, and Localization of Enzyme Activity and Its Putative Substrate)

Abscisic acid-induced changes in inositol metabolism in Spirodela polyrrhiza

Subcellular Localization and Characterization of Excessive Iron in the Nicotianamine-less Tomato Mutant chloronerva

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