| 36 matches found in 10 documents. Search time: 0.444 seconds. |
|---|
|
Score: 8.00 |
|---|
| Title: Mutation of the Plastidial { alpha } -Glucan Phosphorylase Gene in Rice Affects the Synthesis and Structure of Starch in the Endosperm .
| | Author: Satoh H Shibahara K Tokunaga T Nishi A Tasaki M Hwang SK Okita TW Kaneko N Fujita N Yoshida M Hosaka Y Sato A Utsumi Y Ohdan T Nakamura Y | | Journal: Plant Cell Citation: V : P : Year: 2008 Type: Publisher | | Literature: oryza Field: abstract Doc ID: pub18621947 Accession (PMID): 18621947 | | Abstract: Plastidial phosphorylase ( Pho1 ) accounts for approximately 96% of the total phosphorylase activity in developing rice ( Oryza sativa ) seeds .
From mutant stocks induced by N-methyl-N-nitrosourea treatment , we identified plants with mutations in the Pho1 gene that are deficient in Pho1 .
Strikingly , the size of mature seeds and the starch content in these mutants showed considerable variation , ranging from shrunken to pseudonormal The loss of Pho1 caused smaller starch granules to accumulate and modified the amylopectin structure .
Variation in the morphological and biochemical phenotype of individual seeds was common to all 15 pho1-independent homozygous mutant lines studied , indicating that this phenotype was caused solely by the genetic defect .
The phenotype of the pho1 mutation was temperature dependent .
While the mutant plants grown at 30 degrees C produced mainly plump seeds at maturity , most of the seeds from plants grown at 20 degrees C were shrunken , with a significant proportion showing severe reduction in starch accumulation .
These results strongly suggest that Pho1 plays a crucial role in starch biosynthesis in rice endosperm at low temperatures and that one or more other factors can complement the function of Pho1 at high temperatures .
| Matching Sentences:
[ Sen. 2, subscore: 2.00 ]: From mutant stocks induced by N-methyl-N-nitrosourea treatment , we identified plants with mutations in the Pho1 gene that are deficient in Pho1 .
[ Sen. 7, subscore: 2.00 ]: These results strongly suggest that Pho1 plays a crucial role in starch biosynthesis in rice endosperm at low temperatures and that one or more other factors can complement the function of Pho1 at high temperatures .
[ Sen. 1, subscore: 1.00 ]: Plastidial phosphorylase ( Pho1 ) accounts for approximately 96% of the total phosphorylase activity in developing rice ( Oryza sativa ) seeds .
[ Sen. 3, subscore: 1.00 ]: Strikingly , the size of mature seeds and the starch content in these mutants showed considerable variation , ranging from shrunken to pseudonormal The loss of Pho1 caused smaller starch granules to accumulate and modified the amylopectin structure .
[ Sen. 4, subscore: 1.00 ]: Variation in the morphological and biochemical phenotype of individual seeds was common to all 15 pho1-independent homozygous mutant lines studied , indicating that this phenotype was caused solely by the genetic defect .
[ Sen. 5, subscore: 1.00 ]: The phenotype of the pho1 mutation was temperature dependent .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
Score: 8.00 |
|---|
| Title: Rice endosperm-specific plastidial alpha-glucan phosphorylase is important for synthesis of short-chain malto-oligosaccharides .
| | Author: Hwang SK Nishi A Satoh H Okita TW | | Journal: Arch Biochem Biophys Citation: V : 495 P : 82-92 Year: 2010 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub20045390 Accession (PMID): 20045390 | | Abstract: Previous genetic studies have indicated that the type L alpha-glucan phosphorylase ( Pho1 ) has an essential role during the initiation process of starch biosynthesis during rice seed development .
To gain insight into its role in starch metabolism , we characterized the enzymatic properties of the Pho1 recombinant form .
Pho1 has significantly higher catalytic efficiency toward both linear and branched alpha-glucans in the synthesis direction than in the degradation direction with equilibrium constants for the various substrates ranging from 13 to 45 .
Pho1 activity is strongly inhibited by its own reaction product ( Pi ) in the synthesis reaction ( K ( i ) =0 . 69 mM ) when amylopectin is the primer substrate , but this inhibition is less pronounced ( K ( i ) =14 . 2 mM ) when short alpha-glucan chains are used as primers .
Interestingly , even in the presence of Pi alone , Pho1 not only degrades maltohexaose but also extends them to synthesize longer MOSs .
Production of a broad spectrum of MOSs ( G4-G19 ) was stimulated by both Pi and Glc1P in an additive fashion .
Thus , even under physiological conditions of high Pi/Glc1P , Pho1 extends the chain length of short MOSs which can then be used as subsequent primer by starch synthase activities .
As ADP-glucose strongly inhibits Pho1 activity , Pho1 likely operates only during the initial stage and not during maturation phase of starch synthesis .
| Matching Sentences:
[ Sen. 8, subscore: 2.00 ]: As ADP-glucose strongly inhibits Pho1 activity , Pho1 likely operates only during the initial stage and not during maturation phase of starch synthesis .
[ Sen. 1, subscore: 1.00 ]: Previous genetic studies have indicated that the type L alpha-glucan phosphorylase ( Pho1 ) has an essential role during the initiation process of starch biosynthesis during rice seed development .
[ Sen. 2, subscore: 1.00 ]: To gain insight into its role in starch metabolism , we characterized the enzymatic properties of the Pho1 recombinant form .
[ Sen. 3, subscore: 1.00 ]: Pho1 has significantly higher catalytic efficiency toward both linear and branched alpha-glucans in the synthesis direction than in the degradation direction with equilibrium constants for the various substrates ranging from 13 to 45 .
[ Sen. 4, subscore: 1.00 ]: Pho1 activity is strongly inhibited by its own reaction product ( Pi ) in the synthesis reaction ( K ( i ) =0 . 69 mM ) when amylopectin is the primer substrate , but this inhibition is less pronounced ( K ( i ) =14 . 2 mM ) when short alpha-glucan chains are used as primers .
[ Sen. 5, subscore: 1.00 ]: Interestingly , even in the presence of Pi alone , Pho1 not only degrades maltohexaose but also extends them to synthesize longer MOSs .
[ Sen. 7, subscore: 1.00 ]: Thus , even under physiological conditions of high Pi/Glc1P , Pho1 extends the chain length of short MOSs which can then be used as subsequent primer by starch synthase activities .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
Score: 8.00 |
|---|
| Title: Uncoupling phosphate deficiency from its major effects on growth and transcriptome via PHO1 expression in Arabidopsis .
| | Author: Rouached H Stefanovic A Secco D Bulak Arpat A Gout E Bligny R Poirier Y | | Journal: Plant J Citation: V : 65 P : 557-70 Year: 2011 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub21288266 Accession (PMID): 21288266 | | Abstract: Inorganic phosphate ( Pi ) is one of the most limiting nutrients for plant growth in both natural and agricultural contexts .
Pi-deficiency leads to a strong decrease in shoot growth , and triggers extensive changes at the developmental , biochemical and gene expression levels that are presumably aimed at improving the acquisition of this nutrient and sustaining growth .
The Arabidopsis thaliana PHO1 gene has previously been shown to participate in the transport of Pi from roots to shoots , and the null pho1 mutant has all the hallmarks associated with shoot Pi deficiency .
We show here that A thaliana plants with a reduced expression of PHO1 in roots have shoot growth similar to Pi-sufficient plants , despite leaves being strongly Pi deficient .
Furthermore , the gene expression profile normally triggered by Pi deficiency is suppressed in plants with low PHO1 expression .
At comparable levels of shoot Pi supply , the wild type reduces shoot growth but maintains adequate shoot vacuolar Pi content , whereas the PHO1 underexpressor maintains maximal growth with strongly depleted Pi reserves .
Expression of the Oryza sativa ( rice ) PHO1 ortholog in the pho1 null mutant also leads to plants that maintain normal growth and suppression of the Pi-deficiency response , despite the low shoot Pi .
These data show that it is possible to unlink low shoot Pi content with the responses normally associated with Pi deficiency through the modulation of PHO1 expression or activity .
These data also show that reduced shoot growth is not a direct consequence of Pi deficiency , but is more likely to be a result of extensive gene expression reprogramming triggered by Pi deficiency .
| Matching Sentences:
[ Sen. 3, subscore: 2.00 ]: The Arabidopsis thaliana PHO1 gene has previously been shown to participate in the transport of Pi from roots to shoots , and the null pho1 mutant has all the hallmarks associated with shoot Pi deficiency .
[ Sen. 7, subscore: 2.00 ]: Expression of the Oryza sativa ( rice ) PHO1 ortholog in the pho1 null mutant also leads to plants that maintain normal growth and suppression of the Pi-deficiency response , despite the low shoot Pi .
[ Sen. 4, subscore: 1.00 ]: We show here that A thaliana plants with a reduced expression of PHO1 in roots have shoot growth similar to Pi-sufficient plants , despite leaves being strongly Pi deficient .
[ Sen. 5, subscore: 1.00 ]: Furthermore , the gene expression profile normally triggered by Pi deficiency is suppressed in plants with low PHO1 expression .
[ Sen. 6, subscore: 1.00 ]: At comparable levels of shoot Pi supply , the wild type reduces shoot growth but maintains adequate shoot vacuolar Pi content , whereas the PHO1 underexpressor maintains maximal growth with strongly depleted Pi reserves .
[ Sen. 8, subscore: 1.00 ]: These data show that it is possible to unlink low shoot Pi content with the responses normally associated with Pi deficiency through the modulation of PHO1 expression or activity .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
Score: 7.00 |
|---|
| Title: Functional interaction between plastidial starch phosphorylase and starch branching enzymes from rice during the synthesis of branched maltodextrins .
| | Author: Nakamura Y Ono M Utsumi C Steup M | | Journal: Plant Cell Physiol Citation: V : 53 P : 869-78 Year: 2012 Type: In-Process | | Literature: oryza Field: abstract Doc ID: pub22414443 Accession (PMID): 22414443 | | Abstract: The present study established the way in which plastidial alpha-glucan phosphorylase ( Pho1 ) synthesizes maltodextrin ( MD ) which can be the primer for starch biosynthesis in rice endosperm .
The synthesis of MD by Pho1 was markedly accelerated by branching enzyme ( BE ) isozymes , although the greatest effect was exhibited by the presence of branching isozyme I ( BEI ) rather than by isozyme IIa ( BEIIa ) or isozyme IIb ( BEIIb ) .
The enhancement of the activity of Pho1 by BE was not merely due to the supply of a non-reducing ends .
At the same time , Pho1 greatly enhanced the BE activity , possibly by generating a branched carbohydrate substrate which is used by BE with a higher affinity .
The addition of isoamylase to the reaction mixture did not prevent the concerted action of Pho1 and BEI .
Furthermore , in the product , the branched structure was , at least to some extent , maintained .
Based on these results we propose that the interaction between Pho1 and BE is not merely due to chain-elongating and chain-branching reactions , but occurs in a physically and catalytically synergistic manner by each activating the mutual capacity of the other , presumably forming a physical association of Pho1 , BEI and branched MDs .
This close interaction might play a crucial role in the synthesis of branched MDs and the branched MDs can act as a primer for the biosynthesis of amylopectin molecules .
| Matching Sentences:
[ Sen. 7, subscore: 2.00 ]: Based on these results we propose that the interaction between Pho1 and BE is not merely due to chain-elongating and chain-branching reactions , but occurs in a physically and catalytically synergistic manner by each activating the mutual capacity of the other , presumably forming a physical association of Pho1 , BEI and branched MDs .
[ Sen. 1, subscore: 1.00 ]: The present study established the way in which plastidial alpha-glucan phosphorylase ( Pho1 ) synthesizes maltodextrin ( MD ) which can be the primer for starch biosynthesis in rice endosperm .
[ Sen. 2, subscore: 1.00 ]: The synthesis of MD by Pho1 was markedly accelerated by branching enzyme ( BE ) isozymes , although the greatest effect was exhibited by the presence of branching isozyme I ( BEI ) rather than by isozyme IIa ( BEIIa ) or isozyme IIb ( BEIIb ) .
[ Sen. 3, subscore: 1.00 ]: The enhancement of the activity of Pho1 by BE was not merely due to the supply of a non-reducing ends .
[ Sen. 4, subscore: 1.00 ]: At the same time , Pho1 greatly enhanced the BE activity , possibly by generating a branched carbohydrate substrate which is used by BE with a higher affinity .
[ Sen. 5, subscore: 1.00 ]: The addition of isoamylase to the reaction mixture did not prevent the concerted action of Pho1 and BEI .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
Score: 6.00 |
|---|
| Title: Characterization of the rice PHO1 gene family reveals a key role for OsPHO1 ; 2 in phosphate homeostasis and the evolution of a distinct clade in dicotyledons .
| | Author: Secco D Baumann A Poirier Y | | Journal: Plant Physiol Citation: V : 152 P : 1693-704 Year: 2010 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub20081045 Accession (PMID): 20081045 | | Abstract: Phosphate homeostasis was studied in a monocotyledonous model plant through the characterization of the PHO1 gene family in rice ( Oryza sativa ) .
Bioinformatics and phylogenetic analysis showed that the rice genome has three PHO1 homologs , which cluster with the Arabidopsis ( Arabidopsis thaliana ) AtPHO1 and AtPHO1 ; H1 , the only two genes known to be involved in root-to-shoot transfer of phosphate .
In contrast to the Arabidopsis PHO1 gene family , all three rice PHO1 genes have a cis-natural antisense transcript located at the 5 end of the genes .
Strand-specific quantitative reverse transcription-PCR analyses revealed distinct patterns of expression for sense and antisense transcripts for all three genes , both at the level of it issue expression and in response to nutrient stress .
The most abundantly expressed gene was OsPHO1 ; 2 in the roots , for both sense and antisense transcripts .
However , while the OsPHO1 ; 2 sense transcript was relatively stable under various nutrient deficiencies , the antisense transcript was highly induced by inorganic phosphate ( Pi ) deficiency .
Characterization of Ospho1 ; 1 and Ospho1 ; 2 insertion mutants revealed that only Ospho1 ; 2 mutants had defects in Pi homeostasis , namely strong reduction in Pi transfer from root to shoot , which was accompanied by low-shoot and high-root Pi .
Our data identify OsPHO1 ; 2 as playing a key role in the transfer of Pi from roots to shoots in rice , and indicate that this gene could be regulated by its cis-natural antisense transcripts .
Furthermore , phylogenetic analysis of PHO1 homologs in monocotyledons and dicotyledons revealed the emergence of a distinct clade of PHO1 genes in dicotyledons , which include members having roles other than long-distance Pi transport .
| Matching Sentences:
[ Sen. 3, subscore: 2.00 ]: In contrast to the Arabidopsis PHO1 gene family , all three rice PHO1 genes have a cis-natural antisense transcript located at the 5 end of the genes .
[ Sen. 9, subscore: 2.00 ]: Furthermore , phylogenetic analysis of PHO1 homologs in monocotyledons and dicotyledons revealed the emergence of a distinct clade of PHO1 genes in dicotyledons , which include members having roles other than long-distance Pi transport .
[ Sen. 1, subscore: 1.00 ]: Phosphate homeostasis was studied in a monocotyledonous model plant through the characterization of the PHO1 gene family in rice ( Oryza sativa ) .
[ Sen. 2, subscore: 1.00 ]: Bioinformatics and phylogenetic analysis showed that the rice genome has three PHO1 homologs , which cluster with the Arabidopsis ( Arabidopsis thaliana ) AtPHO1 and AtPHO1 ; H1 , the only two genes known to be involved in root-to-shoot transfer of phosphate .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
