Plant Nucleases

Wilson, Curtis M.

doi:10.1104/pp.66.1.119

Cited by 12 publications

(2 citation statements)

References 22 publications

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“…As a group, the polypeptides synthesized in vitro are larger (33,300-39,000 daltons) than those synthesized in vivo (32, this is a general property of wheat endosperm, or whether there exists in wheat a wide range of ribonuclease activity, as reported in maize (46). In the absence of such information, it is prudent to use ribonuclease inhibitors or denaturing methods (10,19) in the isolation of mRNA from wheat endosperm.…”

Section: Resultsmentioning

confidence: 99%

In Vitro Synthesis of Wheat (Triticum aestivum L.) Storage Proteins

Greene

1981

Plant Physiol.

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Free and membrane-associated polysomes were isolated in approximately equal amounts from endosperm of wheat kernels harvested 20 days after anthesis. The presence of heparin in the homogenizing buffer minimized polysome degradation. Ribonucleic acid from the isolated polysomes, when translated in vitro in a wheat germ system, yielded products ranging in size from about 12,000 to about 80,000 daltons, including at least two polypeptides that co-migrated with seed extract proteins in sodium dodecyl sulfate polyacrylamide gel electrophoresis. The nature of the translation products of free and membrane-associated RNA are distinctly different, with membrane-associated RNA yielding a higher proportion of polypeptides in the size range of 30,000 to 37,000 daltons. Analysis of membraneassociated 3'-terminal polyadenylyl-containing RNA in vitro translation products, by solubility in 70% ethanol and by immunoprecipitation, indicates that the 33,000-to 37,000-dalton polypeptides contain gliadins, and the analysis provides evidence that these proteins are synthesized in association with membranous cell organelles. Gliadin polypeptides synthesized in vitro are larger than authentic gliadins and probably are precursors which, in vivo, undergo modification to yield the smaller final products.

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Section: Resultsmentioning

confidence: 99%

In Vitro Synthesis of Wheat (Triticum aestivum L.) Storage Proteins

Greene

1981

Plant Physiol.

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“…In general, this difference between inbred lines was also observed for zein accumulation and it may reflect differences in the genetic background of the inbred lines. Great differences in endosperm RNase activity have been observed in different maize inbred lines and hybrids (29). The LKR activity of opaque-2 endosperms was two to three times lower than that of normal endosperms.…”

Section: Kinetic Analysismentioning

confidence: 93%

Partial Purification and Characterization of Lysine-Ketoglutarate Reductase in Normal and Opaque-2 Maize Endosperms

Brochetto-Braga¹,

Leite²,

Arruda³

1992

Plant Physiol.

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Lysine-ketoglutarate reductase catalyzes the first step of lysine catabolism in maize (Zea mays L.) endosperm. The enzyme condenses L-lysine and a-ketoglutarate into saccharopine using NADPH as cofactor. It is endosperm-specific and has a temporal pattern of activity, increasing with the onset of kernel development, reaching a peak 20 to 25 days after pollination, and thereafter decreasing as the kernel approaches maturity. The enzyme was extracted from the developing maize endosperm and partially purified by ammonium-sulfate precipitation, anion-exchange chromatography on DEAE-cellulose, and affinity chromatography on Blue-Sepharose CL-6B. The preparation obtained from affinity chromatography was enriched 275-fold and had a specific activity of 411 by the opaque-2 mutation may explain, at least in part, the elevated concentration of lysine found in the opaque-2 endosperm.There is little information on lysine catabolism in higher plants. Most of the available data were obtained in studies on the incorporation and metabolism of radiolabeled precursors by plant tissues. Feeding experiments with ["4C]lysine demonstrated the incorporation of radioactivity into a-amino adipic acid and glutamic acid in wheat (18) and into saccharopine and diaminopimelic acid in maize and barley (16,26). In developing endosperm of maize and barley, radiolabeled lysine is incorporated primarily into glutamic acid and proline (4, 26). These findings indicate that lysine is catabolized in plants via the saccharopine pathway.The first enzymatic evidence for the operation of the saccharopine pathway for lysine catabolism in plants was obtained with the demonstration of LKR3 activity in immature endosperm of maize (3). LKR (EC 1.5.1.8) condenses lysine and a-ketoglutarate into saccharopine using NADPH as cofactor.An understanding of the pathways for lysine biosynthesis and degradation in plants has enormous importance because of the limiting concentration of this essential amino acid in major food sources such as cereals. Valuable information can be obtained by the elucidation of the properties of enzymes involved in the biosynthesis and catabolism of lysine and by the use of mutants in which the activities of the enzymes are altered.Since the discovery of the superior nutritive value of the high lysine maize mutant opaque-2 (15), there have been many studies on the effects of this mutant gene on protein and amino acid metabolism in maize endosperm. The opaque-2 gene is located on the short arm of chromosome 7 and its major effect is the reduction of the maize storage protein zein. This is a complex of polypeptides coded by a multigenic family located on chromosomes 4 and 7 (23). The opaque-2 gene in the homozygous form reduces the zein content of the endosperm by up to 70% (6). The reduction is

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