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排序方式: 共有135条查询结果,搜索用时 15 毫秒
1.
Effect of iron availability on expression of the Bradyrhizobium japonicum hemA gene. 总被引:3,自引:2,他引:1 下载免费PDF全文
Bradyrhizobium japonicum produces delta-aminolevulinic acid, the universal precursor of tetrapyrroles, in a reaction catalyzed by the product of the hemA gene. Expression of the B. japonicum hemA gene is affected by iron availability. Activity of a hemA-lacZ fusion is increased approximately threefold by iron, and RNA analysis indicates that iron regulation is at the level of mRNA accumulation. To our knowledge, this is the first example of an iron-regulated heme biosynthetic gene in prokaryotes. 相似文献
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Mining iron: iron uptake and transport in plants 总被引:7,自引:0,他引:7
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IRT1, an Arabidopsis transporter essential for iron uptake from the soil and for plant growth 总被引:30,自引:0,他引:30 下载免费PDF全文
Vert G Grotz N Dédaldéchamp F Gaymard F Guerinot ML Briat JF Curie C 《The Plant cell》2002,14(6):1223-1233
Plants are the principal source of iron in most diets, yet iron availability often limits plant growth. In response to iron deficiency, Arabidopsis roots induce the expression of the divalent cation transporter IRT1. Here, we present genetic evidence that IRT1 is essential for the uptake of iron from the soil. An Arabidopsis knockout mutant in IRT1 is chlorotic and has a severe growth defect in soil, leading to death. This defect is rescued by the exogenous application of iron. The mutant plants do not take up iron and fail to accumulate other divalent cations in low-iron conditions. IRT1-green fluorescent protein fusion, transiently expressed in culture cells, localized to the plasma membrane. We also show, through promoter::beta-glucuronidase analysis and in situ hybridization, that IRT1 is expressed in the external cell layers of the root, specifically in response to iron starvation. These results clearly demonstrate that IRT1 is the major transporter responsible for high-affinity metal uptake under iron deficiency. 相似文献
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VLJ Whitehall TD Dumenil DM McKeone CE Bond ML Bettington RL Buttenshaw L Bowdler GW Montgomery LF Wockner BA Leggett 《Epigenetics》2014,9(11):1454-1460
The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features. 相似文献
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The ability of two strains of Lactobacillus acidophilus, CRL 640 and CRL 800, to survive and retain their biological activities under frozen storage was determined. Freezing and thawing, as well as frozen storage, damaged the cell membrane, rendering the microorganisms sensitive to sodium chloride and bile salts. Both lactic acid production and proteolytic activity were depressed after 21 days at -20 degreesC, whereas beta-galactosidase activity per cell unit was increased. Cell injury was partially overcome after repair in a salt-rich medium. Copyright 1998 Academic Press. 相似文献
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To identify possible iron sources for bacteroids in planta, soybean (Glycine max L. Merr.) symbiosomes (consisting of the bacteroid-containing peribacteroid space enclosed by the peribacteroid membrane [PBM]) and bacteroids were assayed for the ability to transport iron supplied as various ferric [Fe(III)]-chelates. Iron presented as a number of Fe(III)-chelates was transported at much higher rates across the PBM than across the bacteroid membranes, suggesting the presence of an iron storage pool in the peribacteroid space. Pulse-chase experiments confirmed the presence of such an iron storage pool. Because the PBM is derived from the plant plasma membrane, we reasoned that it may possess a ferric-chelate reductase activity similar to that present in plant plasma membrane. We detected ferric-chelate reductase activity associated with the PBM and suggest that reduction of Fe(III) to ferrous [Fe(II)] plays a role in the movement of iron into soybean symbiosomes. 相似文献
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OsZIP5 is a plasma membrane zinc transporter in rice 总被引:1,自引:0,他引:1
Sichul Lee Hee Joong Jeong Sun A. Kim Joohyun Lee Mary Lou Guerinot Gynheung An 《Plant molecular biology》2010,73(4-5):507-517
Zinc is essential for normal plant growth and development. To understand its transport in rice, we characterized OsZIP5, which is inducible under Zn deficiency. OsZIP5 complemented the growth defect of a yeast Zn-uptake mutant, indicating that OsZIP5 is a Zn transporter. The OsZIP5-GFP fusion protein was localized to the plasma membrane. Transgenic plants overexpressing the gene grew less well. Overexpression of the gene decreased the Zn concentration in shoots, but caused it to rise in the roots. Knockout plants showed no visible phenotypic changes under either normal or deficient conditions. However, they were tolerant to excess Zn and contained less Zn. In contrast, overexpressing transgenics were sensitive to excess Zn. These results indicate that OsZIP5 plays a role in Zn distribution within rice. 相似文献