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| Title: Isoform-specific effects of charged residues at borders of the M1-M2 loop of the Na , K-ATPase alpha subunit .
| | Author: Coppi MV Compton LA Guidotti G | | Journal: Biochemistry Citation: V : 38 ( 8 ) P : 2494-505 Year: 1999 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub10029544 Accession (PMID): 10029544 | | Abstract: The Na , K-ATPase is specifically inhibited by the cardiac glycoside , ouabain .
Via a largely undefined mechanism , the ouabain affinity of the Na , K-ATPase can be manipulated by mutating the residues at the borders of the first extracellular ( M1-M2 ) loop of the alpha subunit [ Price , E M , Rice , D A , and Lingrel , J B ( 1990 ) J Biol . Chem . 265 , 6638-6641 ] .
To address this issue , we compared the effects of two combinations of charged residues at the M1-M2 loop border , R113 , D124 and D113 , R124 ( numbered according to the rat alpha1 subunit ) , on the ouabain sensitivity of the alpha1 and alpha2 isoforms .
We report that ouabain sensitivity is dependent not only upon the identity of the residues at the M1-M2 loop border but also upon the context into which they are introduced .
Furthermore , at low concentrations of ATP , the identity of the residues at the M1-M2 loop border affects the regulation of ATP hydrolysis by potassium in an isoform-specific manner .
Analysis of chimeric alpha subunits reveals that the effects of potassium are determined primarily by the interaction of the N-terminus and M1-M2 loop with the C-terminal third of the alpha subunit .
M1-M2 loop border residues may , therefore , influence ouabain sensitivity indirectly by altering the stability or structure of the intermediate of the Na , K-ATPase catalytic cycle which is competent to bind ouabain .
| Matching Sentences:
[ Sen. 2, subscore: 1.00 ]: The Na , K-ATPase is specifically inhibited by the cardiac glycoside , ouabain . Via a largely undefined mechanism , the ouabain affinity of the Na , K-ATPase can be manipulated by mutating the residues at the borders of the first extracellular ( M1-M2 ) loop of the alpha subunit [ Price , E M , Rice , D A , and Lingrel , J B ( 1990 ) J Biol . Chem . 265 , 6638-6641 ] . To address this issue , we compared the effects of two combinations of charged residues at the M1-M2 loop border , R113 , D124 and D113 , R124 ( numbered according to the rat alpha1 subunit ) , on the ouabain sensitivity of the alpha1 and alpha2 isoforms . We report that ouabain sensitivity is dependent not only upon the identity of the residues at the M1-M2 loop border but also upon the context into which they are introduced . Furthermore , at low concentrations of ATP , the identity of the residues at the M1-M2 loop border affects the regulation of ATP hydrolysis by potassium in an isoform-specific manner . Analysis of chimeric alpha subunits reveals that the effects of potassium are determined primarily by the interaction of the N-terminus and M1-M2 loop with the C-terminal third of the alpha subunit .
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Score: 1.00 |
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| Title: A rice homolog of Cdk7/MO15 phosphorylates both cyclin-dependent protein kinases and the carboxy-terminal domain of RNA polymerase II .
| | Author: Yamaguchi M Umeda M Uchimiya H | | Journal: Plant J Citation: V : 16 ( 5 ) P : 613-9 Year: 1998 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub10036778 Accession (PMID): 10036778 | | Abstract: The activation of cyclin-dependent protein kinases ( CDKs ) requires phosphorylation of a threonine residue within the T-loop by a CDK-activating kinase ( CAK ) .
The R2 protein of rice is very similar to CAKs of animals and fission yeast at the amino acid level but phosphorylation by R2 has not yet been demonstrated .
When R2 was overexpressed in a CAK-deficient mutant of budding yeast , it suppressed the temperature sensitivity of the mutation .
Immunoprecipitates of rice proteins with the anti-R2 antibody phosphorylated human CDK2 , one of the rice CDKs ( Cdc2Os1 ) , and the carboxy-terminal domain ( CTD ) of the largest subunit of RNA polymerase II of Arabidopsis .
Mutational analysis indicated that R2 phosphorylated the threonine residue within the T-loop of CDK2 and Cdc2Os1 .
R2 was found mainly in two protein complexes which had molecular masses of 190 kDa and 70 kDa , respectively , whilst the CDK and CTD-kinase activities associated with R2 were identified in a complex of 105 kDa .
These results indicate that R2 is closely related to CAKs of animals and fission yeast in terms of its phosphorylation activity and , moreover , that this CAK of rice is distinct from a CAK of the dicotyledonous plant Arabidopsis . | Matching Sentences:
[ Sen. 4, subscore: 1.00 ]: The activation of cyclin-dependent protein kinases ( CDKs ) requires phosphorylation of a threonine residue within the T-loop by a CDK-activating kinase ( CAK ) . The R2 protein of rice is very similar to CAKs of animals and fission yeast at the amino acid level but phosphorylation by R2 has not yet been demonstrated . When R2 was overexpressed in a CAK-deficient mutant of budding yeast , it suppressed the temperature sensitivity of the mutation . Immunoprecipitates of rice proteins with the anti-R2 antibody phosphorylated human CDK2 , one of the rice CDKs ( Cdc2Os1 ) , and the carboxy-terminal domain ( CTD ) of the largest subunit of RNA polymerase II of Arabidopsis . Mutational analysis indicated that R2 phosphorylated the threonine residue within the T-loop of CDK2 and Cdc2Os1 . R2 was found mainly in two protein complexes which had molecular masses of 190 kDa and 70 kDa , respectively , whilst the CDK and CTD-kinase activities associated with R2 were identified in a complex of 105 kDa . These results indicate that R2 is closely related to CAKs of animals and fission yeast in terms of its phosphorylation activity and , moreover , that this CAK of rice is distinct from a CAK of the dicotyledonous plant Arabidopsis .
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Score: 2.00 |
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| Title: Large-scale sequencing of plant genomes .
| | Author: Rounsley S Lin X Ketchum KA .
| | Journal: Curr . Opin . Plant Biol .
Citation: V : 1 ( 2 ) P : 136-41 Year: 1998 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub10066574 Accession (PMID): 10066574 | | Abstract: The large number of ESTs generated for Arabidopsis and rice in recent years now act as an important complement to whole genome sequencing projects .
The Arabidopsis Genome Initiative has begun a coordinated effort to sequence the entire genome and , as a result , increasing numbers of large sequence entries can be found in the public databases .
In addition , the mitochondrial genome of Arabidopsis has been completely sequenced .
Genome sequencing studies and the public sequence databases have begun to influence the direction of diverse areas of research from physiology to evolution .
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[ Sen. 1, subscore: 1.00 ]: The large number of ESTs generated for Arabidopsis and rice in recent years now act as an important complement to whole genome sequencing projects . The Arabidopsis Genome Initiative has begun a coordinated effort to sequence the entire genome and , as a result , increasing numbers of large sequence entries can be found in the public databases . In addition , the mitochondrial genome of Arabidopsis has been completely sequenced . Genome sequencing studies and the public sequence databases have begun to influence the direction of diverse areas of research from physiology to evolution .
[ Sen. 2, subscore: 1.00 ]: The large number of ESTs generated for Arabidopsis and rice in recent years now act as an important complement to whole genome sequencing projects . The Arabidopsis Genome Initiative has begun a coordinated effort to sequence the entire genome and , as a result , increasing numbers of large sequence entries can be found in the public databases . In addition , the mitochondrial genome of Arabidopsis has been completely sequenced . Genome sequencing studies and the public sequence databases have begun to influence the direction of diverse areas of research from physiology to evolution .
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Score: 1.00 |
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| Title: Nitrate-ammonium synergism in rice .
A subcellular flux analysis | | Author: Kronzucker HJ Siddiqi MY Glass AD Kirk GJ .
| | Journal: Citation: V : 119 ( 3 ) P : 1041-6 Year: 1999 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub10069842 Accession (PMID): 10069842 | | Abstract: Many reports have shown that plant growth and yield is superior on mixtures of NO3 and NH4+ compared with provision of either N source alone .
Despite its clear practical importance , the nature of this N-source synergism at the cellular level is poorly understood .
In the present study we have used the technique of compartmental analysis by efflux and the radiotracer 13N to measure cellular turnover kinetics , patterns of flux partitioning , and cytosolic pool sizes of both NO3 and NH4+ in seedling roots of rice ( Oryza sativa L cv IR72 ) , supplied simultaneously with the two N sources .
We show that plasma membrane fluxes for NH4+ , cytosolic NH4+ accumulation , and NH4+ metabolism are enhanced by the presence of NO3- , whereas NO3 fluxes , accumulation , and metabolism are strongly repressed by NH4+ .
However , net N acquisition and N translocation to the shoot with dual N-source provision are substantially larger than when NO3 or NH4+ is provided alone at identical N concentrations . | Matching Sentences:
[ Sen. 5, subscore: 1.00 ]: Many reports have shown that plant growth and yield is superior on mixtures of NO3 and NH4+ compared with provision of either N source alone . Despite its clear practical importance , the nature of this N-source synergism at the cellular level is poorly understood . In the present study we have used the technique of compartmental analysis by efflux and the radiotracer 13N to measure cellular turnover kinetics , patterns of flux partitioning , and cytosolic pool sizes of both NO3 and NH4+ in seedling roots of rice ( Oryza sativa L cv IR72 ) , supplied simultaneously with the two N sources . We show that plasma membrane fluxes for NH4+ , cytosolic NH4+ accumulation , and NH4+ metabolism are enhanced by the presence of NO3- , whereas NO3 fluxes , accumulation , and metabolism are strongly repressed by NH4+ . However , net N acquisition and N translocation to the shoot with dual N-source provision are substantially larger than when NO3 or NH4+ is provided alone at identical N concentrations .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
Score: 2.00 |
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| Title: A "defeated" rice resistance gene acts as a QTL against a virulent strain of Xanthomonas oryzae pv . oryzae .
| | Author: Li ZK Luo LJ Mei HW Paterson AH Zhao XH Zhong DB Wang YP Yu XQ Zhu L Tabien R Stansel JW Ying CS .
| | Journal: Mol . Gen . Genet . Citation: V : 261 ( 1 ) P : 58-63 Year: 1999 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub10071210 Accession (PMID): 10071210 | | Abstract: The genetic components responsible for qualitative and quantitative resistance of rice plants to three strains ( CR4 , CXO8 , and CR6 ) of Xanthomonas oryzae pv . oryzae ( Xoo ) were investigated using a set of 315 recombinant inbred lines ( RILs ) from the cross Lemont ( japonica ) x Teqing ( indica ) and a complete linkage map with 182 well distributed RFLP markers .
We mapped a major gene ( Xa4 ) and ten quantitative trait loci ( QTLs ) which were largely responsible for segregation of the resistance phenotype in the RILs .
The Teqing allele at the Xa4 locus , Xa4T , acted as a dominant resistance gene against CR4 and CXO8 .
The breakdown of Xa4T-associated resistance mediated by the mutant allele at the avrXa4 locus in the virulent strain CR6 results from significant changes in both gene action ( lose of dominance ) and the magnitude of gene effect ( approximately 50% reduction ) .
Nevertheless , Xa4T still acted as a recessive QTL with a significant residual effect against CR6 .
The mutant alleles at the avrXa4 locus in CXO8 and CR6 that lead to a reduction in effect , or "breakdown" , of Xa4T were apparently accompanied by corresponding penalties for their fitness .
The quantitative component of resistance to Xoo in the RILs was largely due to a number of resistance QTLs .
Most resistance QTLs mapped to genomic locations where major resistance genes and/or QTLs for resistance to Xoo , blast and sheath blight were identified in the same cross .
Most QTLs showed consistent levels of resistance against all three Xoo strains .
Our results suggest that a high level of durable resistance to Xoo may be achieved by the cumulative effects of multiple QTLs , including the residual effects of "defeated" major resistance genes . | Matching Sentences:
[ Sen. 2, subscore: 1.00 ]: The genetic components responsible for qualitative and quantitative resistance of rice plants to three strains ( CR4 , CXO8 , and CR6 ) of Xanthomonas oryzae pv . oryzae ( Xoo ) were investigated using a set of 315 recombinant inbred lines ( RILs ) from the cross Lemont ( japonica ) x Teqing ( indica ) and a complete linkage map with 182 well distributed RFLP markers . We mapped a major gene ( Xa4 ) and ten quantitative trait loci ( QTLs ) which were largely responsible for segregation of the resistance phenotype in the RILs . The Teqing allele at the Xa4 locus , Xa4T , acted as a dominant resistance gene against CR4 and CXO8 . The breakdown of Xa4T-associated resistance mediated by the mutant allele at the avrXa4 locus in the virulent strain CR6 results from significant changes in both gene action ( lose of dominance ) and the magnitude of gene effect ( approximately 50% reduction ) . Nevertheless , Xa4T still acted as a recessive QTL with a significant residual effect against CR6 . The mutant alleles at the avrXa4 locus in CXO8 and CR6 that lead to a reduction in effect , or "breakdown" , of Xa4T were apparently accompanied by corresponding penalties for their fitness .
[ Sen. 7, subscore: 1.00 ]: The Teqing allele at the Xa4 locus , Xa4T , acted as a dominant resistance gene against CR4 and CXO8 . The breakdown of Xa4T-associated resistance mediated by the mutant allele at the avrXa4 locus in the virulent strain CR6 results from significant changes in both gene action ( lose of dominance ) and the magnitude of gene effect ( approximately 50% reduction ) . Nevertheless , Xa4T still acted as a recessive QTL with a significant residual effect against CR6 . The mutant alleles at the avrXa4 locus in CXO8 and CR6 that lead to a reduction in effect , or "breakdown" , of Xa4T were apparently accompanied by corresponding penalties for their fitness . The quantitative component of resistance to Xoo in the RILs was largely due to a number of resistance QTLs . Most resistance QTLs mapped to genomic locations where major resistance genes and/or QTLs for resistance to Xoo , blast and sheath blight were identified in the same cross . Most QTLs showed consistent levels of resistance against all three Xoo strains . Our results suggest that a high level of durable resistance to Xoo may be achieved by the cumulative effects of multiple QTLs , including the residual effects of "defeated" major resistance genes .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
