| 21 matches found in 11 documents. Search time: 0.196 seconds. |
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Score: 7.00 |
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| Title: Functional diversity of isoamylase oligomers : the ISA1 homo-oligomer is essential for amylopectin biosynthesis in rice endosperm .
| | Author: Utsumi Y Utsumi C Sawada T Fujita N Nakamura Y | | Journal: Plant Physiol Citation: V : 156 P : 61-77 Year: 2011 Type: In-Process | | Literature: oryza Field: abstract Doc ID: pub21436381 Accession (PMID): 21436381 | | Abstract: Rice ( Oryza sativa ) endosperm has two isoamylase ( ISA ) oligomers , ISA1 homo-oligomer and ISA1-ISA2 hetero-oligomer .
To examine their contribution to starch synthesis , expression of the ISA1 or ISA2 gene was differently regulated in various transgenic plants .
Although suppression of ISA2 gene expression caused the endosperm to have only the homo-oligomer , no significant effects were detected on the starch phenotypes .
In contrast , ISA2 overexpression led to endosperm having only the hetero-oligomer , and starch synthesis in the endosperm was drastically impaired , both quantitatively and qualitatively , because the starch was devoid of typical starch features , such as thermal and x-ray diffraction properties , and water-soluble highly branched maltodextrins were accumulated .
In the ISA2 overexpressed line , about 60% to 70% of the ISA1-ISA2 hetero-oligomer was bound to starch , while the ISA homo and hetero-oligomers from the wild type were mostly present in the soluble form at the early milking stage of the endosperm .
Detailed analysis of the relative amounts of homo and hetero-oligomers in various lines also led us to the conclusion that the ISA1 homo-oligomer is essential , but not the ISA1-ISA2 oligomer , for starch production in rice endosperm .
The relative amounts of ISA1 and ISA2 proteins were shown to determine the ratio of both oligomers and the stoichiometry of both ISAs in the hetero-oligomer .
It was noted when compared with the homo-oligomer that all the hetero-oligomers from rice endosperm and leaf and potato ( Solanum tuberosum ) tuber were much more stable at 40 degrees C This study provides substantial data on the structural and functional diversity of ISA oligomers between plant it issues and species .
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[ Sen. 1, subscore: 2.00 ]: Rice ( Oryza sativa ) endosperm has two isoamylase ( ISA ) oligomers , ISA1 homo-oligomer and ISA1-ISA2 hetero-oligomer .
[ Sen. 6, subscore: 2.00 ]: Detailed analysis of the relative amounts of homo and hetero-oligomers in various lines also led us to the conclusion that the ISA1 homo-oligomer is essential , but not the ISA1-ISA2 oligomer , for starch production in rice endosperm .
[ Sen. 2, subscore: 1.00 ]: To examine their contribution to starch synthesis , expression of the ISA1 or ISA2 gene was differently regulated in various transgenic plants .
[ Sen. 5, subscore: 1.00 ]: In the ISA2 overexpressed line , about 60% to 70% of the ISA1-ISA2 hetero-oligomer was bound to starch , while the ISA homo and hetero-oligomers from the wild type were mostly present in the soluble form at the early milking stage of the endosperm .
[ Sen. 7, subscore: 1.00 ]: The relative amounts of ISA1 and ISA2 proteins were shown to determine the ratio of both oligomers and the stoichiometry of both ISAs in the hetero-oligomer .
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Score: 6.00 |
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| Title: Structural and enzymatic characterization of the isoamylase1 homo-oligomer and the isoamylase1-isoamylase2 hetero-oligomer from rice endosperm .
| | Author: Utsumi Y Nakamura Y | | Journal: Planta Citation: V : 225 ( 1 ) P : 75-87 Year: 2006 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub16953433 Accession (PMID): 16953433 | | Abstract: The present study established that there are two distinct polymeric forms of isoamylase1 ( ISA1 ) in rice endosperm : presumably a homo-pentamer of ISA1 and a hetero-hexamer composed of five ISA1 and one ISA2 .
The molecular sizes of the homo and hetero-oligomers , which could be fractionated by hydrophobic chromatography , were approximately 420-480 and 510-550 kDa , respectively .
The hetero-oligomer exhibited higher affinities for various branched polyglucans , especially for phytoglycogen , which had a K ( m ) value that was approximately 12 times lower relative to that with the homo-oligomer , although no marked differences were found in chain preferences for debranching of amylopectin and phytoglycogen between these forms .
The hetero-oligomer was active even when incubated at 50 degrees C for 10 min , while the homo-multimer was completely inactivated at 40 degrees C in 10 min .
When the ISA1 homo-oligomer was incubated with the ISA2 protein expressed in Escherichia coli and applied onto a nondenature polyacrylamide gel , additional debranching activity bands which were specific for the purified ISA1-ISA2 preparation were also detected , indicating that ISA1 and ISA2 combine to form a hetero-oligomer .
These results suggest that the hetero-oligomer plays a predominant role in the amylopectin biosynthesis in rice endosperm although the homo-oligomer can complement the function of the hetero-oligomer at least to some extent .
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[ Sen. 1, subscore: 3.00 ]: The present study established that there are two distinct polymeric forms of isoamylase1 ( ISA1 ) in rice endosperm : presumably a homo-pentamer of ISA1 and a hetero-hexamer composed of five ISA1 and one ISA2 .
[ Sen. 5, subscore: 3.00 ]: When the ISA1 homo-oligomer was incubated with the ISA2 protein expressed in Escherichia coli and applied onto a nondenature polyacrylamide gel , additional debranching activity bands which were specific for the purified ISA1-ISA2 preparation were also detected , indicating that ISA1 and ISA2 combine to form a hetero-oligomer .
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Score: 5.00 |
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| Title: Complementation of sugary-1 phenotype in rice endosperm with the wheat isoamylase1 gene supports a direct role for isoamylase1 in amylopectin biosynthesis .
| | Author: Kubo A Rahman S Utsumi Y Li Z Mukai Y Yamamoto M Ugaki M Harada K Satoh H Konik-Rose C Morell M Nakamura Y | | Journal: Plant Physiol .
Citation: V : 137 ( 1 ) P : 43-56 Year: 2005 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub15618430 Accession (PMID): 15618430 | | Abstract: To examine the role of isoamylase1 ( ISA1 ) in amylopectin biosynthesis in plants , a genomic DNA fragment from Aegilops tauschii was introduced into the ISA1-deficient rice ( Oryza sativa ) sugary-1 mutant line EM914 , in which endosperm starch is completely replaced by phytoglycogen .
A tauschii is the D genome donor of wheat ( Triticum aestivum ) , and the introduced fragment effectively included the gene for ISA1 for wheat ( TaISA1 ) that was encoded on the D genome .
In TaISA1-expressing rice endosperm , phytoglycogen synthesis was substantially replaced by starch synthesis , leaving only residual levels of phytoglycogen .
The levels of residual phytoglycogen present were inversely proportional to the expression level of the TaISA1 protein , although the level of pullulanase that had been reduced in EM914 was restored to the same level as that in the wild type .
Small but significant differences were found in the amylopectin chain-length distribution , gelatinization temperatures , and A-type x-ray diffraction patterns of the starches from lines expressing TaISA1 when compared with wild-type rice starch , although in the first two parameters , the effect was proportional to the expression level of TaISA .
The impact of expression levels of ISA1 on starch structure and properties provides support for the view that ISA1 is directly involved in the synthesis of amylopectin . | Matching Sentences:
[ Sen. 1, subscore: 2.00 ]: To examine the role of isoamylase1 ( ISA1 ) in amylopectin biosynthesis in plants , a genomic DNA fragment from Aegilops tauschii was introduced into the ISA1-deficient rice ( Oryza sativa ) sugary-1 mutant line EM914 , in which endosperm starch is completely replaced by phytoglycogen .
[ Sen. 6, subscore: 2.00 ]: The impact of expression levels of ISA1 on starch structure and properties provides support for the view that ISA1 is directly involved in the synthesis of amylopectin .
[ Sen. 2, subscore: 1.00 ]: A tauschii is the D genome donor of wheat ( Triticum aestivum ) , and the introduced fragment effectively included the gene for ISA1 for wheat ( TaISA1 ) that was encoded on the D genome .
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Score: 3.00 |
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| Title: Roles of isoamylase and ADP-glucose pyrophosphorylase in starch granule synthesis in rice endosperm .
| | Author: Kawagoe Y Kubo A Satoh H Takaiwa F Nakamura Y | | Journal: Plant J Citation: V : 42 ( 2 ) P : 164-74 Year: 2005 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub15807780 Accession (PMID): 15807780 | | Abstract: Amyloplast-targeted green fluorescent protein ( GFP ) was used to monitor amyloplast division and starch granule synthesis in the developing endosperm of transgenic rice .
Two classical starch mutants , sugary and shrunken , contain reduced activities of isoamylase1 ( ISA1 ) and cytosolic ADP-glucose pyrophosphorylase , respectively .
Dividing amyloplasts in the wild-type and shrunken endosperms contained starch granules , whereas those in sugary endosperm did not contain detectable granules , suggesting that ISA1 plays a role in granule synthesis at the initiation step .
The transition from phytoglycogen to sugary-amylopectin was gradual in the boundary region between the inner and outer endosperms of sugary .
These results suggest that the synthesis of sugary-amylopectin and phytoglycogen involved a stochastic process and that ISA1 activity plays a critical role in the stochastic process in starch synthesis in rice endosperm .
The reduction of cytosolic ADP-glucose pyrophosphorylase activity in shrunken endosperm did not inhibit granule initiation but severely restrained the subsequent enlargement of granules .
The shrunken endosperm often developed pleomorphic amyloplasts containing a large number of underdeveloped granules or a large cluster of small grains of amyloplasts , each containing a simple-type starch granule .
Although constriction-type divisions of amyloplasts were much more frequent , budding-type divisions were also found in the shrunken endosperm .
We show that monitoring GFP in developing amyloplasts was an effective means of evaluating the roles of enzymes involved in starch granule synthesis in the rice endosperm . | Matching Sentences:
[ Sen. 2, subscore: 1.00 ]: Two classical starch mutants , sugary and shrunken , contain reduced activities of isoamylase1 ( ISA1 ) and cytosolic ADP-glucose pyrophosphorylase , respectively .
[ Sen. 3, subscore: 1.00 ]: Dividing amyloplasts in the wild-type and shrunken endosperms contained starch granules , whereas those in sugary endosperm did not contain detectable granules , suggesting that ISA1 plays a role in granule synthesis at the initiation step .
[ Sen. 5, subscore: 1.00 ]: These results suggest that the synthesis of sugary-amylopectin and phytoglycogen involved a stochastic process and that ISA1 activity plays a critical role in the stochastic process in starch synthesis in rice endosperm .
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Score: 3.00 |
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| Title: Characterization of pullulanase ( PUL ) -deficient mutants of rice ( Oryza sativa L ) and the function of PUL on starch biosynthesis in the developing rice endosperm .
| | Author: Fujita N Toyosawa Y Utsumi Y Higuchi T Hanashiro I Ikegami A Akuzawa S Yoshida M Mori A Inomata K Itoh R Miyao A Hirochika H Satoh H Nakamura Y | | Journal: J Exp Bot Citation: V : 60 P : 1009-23 Year: 2009 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub19190097 Accession (PMID): 19190097 | | Abstract: Rice ( Oryza sativa ) allelic sugary1 ( sug1 ) mutants defective in isoamylase 1 ( ISA1 ) accumulate varying levels of starch and phytoglycogen in their endosperm , and the activity of a pullulanase-type of a debranching enzyme ( PUL ) was found to correlate closely with the severity of the sug1 phenotype .
Thus , three PUL-deficient mutants were generated to investigate the function of PUL in starch biosynthesis .
The reduction of PUL activity had no pleiotropic effects on the other enzymes involved in starch biosynthesis .
The short chains ( DP < or = 13 ) of amylopectin in PUL mutants were increased compared with that of the wild type , but the extent of the changes was much smaller than that of sug1 mutants .
The alpha-glucan composition [ amylose , amylopectin , water-soluble polysaccharide ( WSP ) ] and the structure of the starch components ( amylose and amylopectin ) of the PUL mutants were essentially the same , although the average chain length of the B ( 2-3 ) chains of amylopectin in the PUL mutant was approximately 3 residues longer than that of the wild type .
The double mutants between the PUL-null and mild sug1 mutants still retained starch in the outer layer of endosperm it issue , while the amounts of WSP and short chains ( DP < or = 7 ) of amylopectin were higher than those of the sug1 mutant ; this indicates that the PUL function partially overlaps with that of ISA1 and its deficiency has a much smaller effect on the synthesis of amylopectin than ISA1 deficiency and the variation of the sug1 phenotype is not significantly dependent on the PUL activities .
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[ Sen. 6, subscore: 2.00 ]: The double mutants between the PUL-null and mild sug1 mutants still retained starch in the outer layer of endosperm it issue , while the amounts of WSP and short chains ( DP < or = 7 ) of amylopectin were higher than those of the sug1 mutant ; this indicates that the PUL function partially overlaps with that of ISA1 and its deficiency has a much smaller effect on the synthesis of amylopectin than ISA1 deficiency and the variation of the sug1 phenotype is not significantly dependent on the PUL activities .
[ Sen. 1, subscore: 1.00 ]: Rice ( Oryza sativa ) allelic sugary1 ( sug1 ) mutants defective in isoamylase 1 ( ISA1 ) accumulate varying levels of starch and phytoglycogen in their endosperm , and the activity of a pullulanase-type of a debranching enzyme ( PUL ) was found to correlate closely with the severity of the sug1 phenotype .
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