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41.
Expression and Accumulation Patterns of Nitrogen-Responsive Lipoxygenase in Soybeans 总被引:3,自引:1,他引:2
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Gene expression and protein accumulation patterns of nitrogen-responsive lipoxygenase (LOX-NR), as a representative vegetative storage protein, were investigated in nonnodulated soybeans (Glycine max [L.] Merr. cv Wye). The form of available nitrogen (supplied as NH4NO3, NH4+, NO3-, or urea) influenced the mRNA level and the amount of LOX protein, indicating that preferential accumulation of LOX may occur. Soybeans were grown with 0, 2, 5, and 16 mM total nitrogen to determine the extent to which LOX accumulation responded to soil nitrogen levels. Analysis of both mRNA and protein levels was conducted in shoot tips, stems, pod walls, and leaves over the entire life cycle of the plant. A general correlation between increasing available nitrogen level and LOX level was seen in the shoot tip and other organs throughout the soybean life cycle. However, appreciable amounts of LOX-NR mRNA and protein accumulated even when plants were grown under conditions of nitrogen deficiency. The results indicate that LOX may play an important role as a temporary storage site for amino acids in the developing shoot tip. The expression patterns of LOX-NR in plants grown under nitrogen deficiency suggest that these proteins, although responsive to nitrogen status, may not function solely as temporary storage pools for amino acids. 相似文献
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Ouabain-insensitive salt and water movements in duck red cells. II. The role of chloride in the volume response
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This paper describes the effect of external chloride on the typical swelling response induced in duck red cells by hypertonicity or norepinephrine. Lowering chloride inhibits swelling and produces concomitant changes in net movements of sodium and potassium in ouabain-treated cells, which resemble the effect of lowering external sodium or potassium. Inhibition is the same whether chloride is replaced with gluconate or with an osmotic equivalent of sucrose. Since changes in external chloride also cause predictable changes in cell chloride, pH, and water, these variables were systematically investigated by varying external pH along with chloride. Lowering pH to 6.60 does not abolish the response if external chloride levels are normal, although the cells are initially swollen due to the increased acidity. Cells deliberately preswollen in hypotonic solutions with appropriate ionic composition can also respond to norepinephrine by further swelling. These results rule out initial values of cell water, chloride, and pH as significant variables affecting the response. Initial values of the chloride equilibrium potential do have marked effect on the direction and rate of net water movement. If chloride is lowered by replacement with the permeant anion, acetate, E(Cl) is unchanged and a normal response to norepinephrine, which is inhibited by furosemide, is observed. Increasing internal sodium by the nystatin technique also inhibits the response. A theory is developed which depicts that the cotransport carrier proposed in the previous paper (W.F. Schmidt and T.J. McManus. 1977b. J. Gen. Physiol. 70:81-97) moves in response to the net electrochemical potential difference driving sodium and potassium across the membrane. Predictions of this theory fit the data for both cations and anions. 相似文献
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Two novel gene orders and the role of light-strand replication in rearrangement of the vertebrate mitochondrial genome 总被引:22,自引:8,他引:14
Macey JR; Larson A; Ananjeva NB; Fang Z; Papenfuss TJ 《Molecular biology and evolution》1997,14(1):91-104
Two novel mitochondrial gene arrangements are identified in an agamid
lizard and a ranid frog. Statistical tests incorporating phylogeny indicate
a link between novel vertebrate mitochondrial gene orders and movement of
the origin of light-strand replication. A mechanism involving errors in
light-strand replication and tandem duplication of genes is proposed for
rearrangement of vertebrate mitochondrial genes. A second mechanism
involving small direct repeats also is identified. These mechanisms
implicate gene order as a reliable phylogenetic character. Shifts in gene
order define major lineages without evidence of parallelism or reversal.
The loss of the origin of light-strand replication from its typical
vertebrate position evolves in parallel and, therefore, is a less reliable
phylogenetic character. Gene junctions also evolve in parallel. Sequencing
across multigenic regions, in particular transfer RNA genes, should be a
major focus of future systematic studies to locate novel gene orders and to
provide a better understanding of the evolution of the vertebrate
mitochondrial genome.
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50.
The soybean 94-kilodalton vegetative storage protein is a lipoxygenase that is localized in paraveinal mesophyll cell vacuoles. 总被引:22,自引:3,他引:19
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Soybean leaves contain three proteins (the vegetative storage proteins or VSPs) that respond to nitrogen status and are believed to be involved in the temporary storage of nitrogen. One of these proteins, with a molecular mass of 94 kD and termed vsp94, was microsequenced. Partial amino acid sequence indicated that vsp94 was highly homologous to the lipoxygenase protein family. Further evidence that vsp94 is a lipoxygenase was obtained by demonstrating that vsp94 cross-reacted with a lipoxygenase antibody. Also, a lipoxygenase cDNA coding region was able to detect changes in an mRNA that closely parallel changes in vsp94 protein levels resulting from alteration of nitrogen sinks. Extensive immunocytochemical data indicate that this vsp94/lipoxygenase is primarily expressed in the paraveinal mesophyll cells and is subcellularly localized in the vacuole. These observations are significant in that they suggest that plant lipoxygenases may be bifunctional proteins able to function enzymatically in the hydroperoxidation of lipids and also to serve a role in the temporary storage of nitrogen during vegetative growth. 相似文献