| 38 matches found in 14 documents. Search time: 0.002 seconds. |
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Score: 10.00 |
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| Title: Identification and characterization of maize and barley Lsi2-like silicon efflux transporters reveals a distinct silicon uptake system from that in rice .
| | Author: Mitani N Chiba Y Yamaji N Ma JF | | Journal: Plant Cell Citation: V : 21 P : 2133-42 Year: 2009 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub19574435 Accession (PMID): 19574435 | | Abstract: Silicon ( Si ) uptake has been extensively examined in rice ( Oryza sativa ) , but it is poorly understood in other gramineous crops .
We identified Low Silicon Rice 2 ( Lsi2 ) -like Si efflux transporters from two important gramineous crops : maize ( Zea mays ) and barley ( Hordeum vulgare ) .
Both maize and barley Lsi2 expressed in Xenopus laevis oocytes showed Si efflux transport activity .
Furthermore , barley Lsi2 was able to recover Si uptake in a rice mutant defective in Si efflux .
Maize and barley Lsi2 were only expressed in the roots .
Expression of maize and barley Lsi2 was downregulated in response to exogenously applied Si .
Moreover , there was a significant positive correlation between the ability of roots to absorb Si and the expression levels of Lsi2 in eight barley cultivars , suggesting that Lsi2 is a key Si transporter in barley .
Immunostaining showed that maize and barley Lsi2 localized only at the endodermis , with no polarity .
Protein gel blot analysis indicated that maize and barley Lsi2 localized on the plasma membrane .
The unique features of maize and barley Si influx and efflux transporters , including their cell-type specificity and the lack of polarity of their localization in Lsi2 , indicate that these crops have a different Si uptake system from that in rice .
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[ Sen. 7, subscore: 2.00 ]: Moreover , there was a significant positive correlation between the ability of roots to absorb Si and the expression levels of Lsi2 in eight barley cultivars , suggesting that Lsi2 is a key Si transporter in barley .
[ Sen. 2, subscore: 1.00 ]: We identified Low Silicon Rice 2 ( Lsi2 ) -like Si efflux transporters from two important gramineous crops : maize ( Zea mays ) and barley ( Hordeum vulgare ) .
[ Sen. 3, subscore: 1.00 ]: Both maize and barley Lsi2 expressed in Xenopus laevis oocytes showed Si efflux transport activity .
[ Sen. 4, subscore: 1.00 ]: Furthermore , barley Lsi2 was able to recover Si uptake in a rice mutant defective in Si efflux .
[ Sen. 5, subscore: 1.00 ]: Maize and barley Lsi2 were only expressed in the roots .
[ Sen. 6, subscore: 1.00 ]: Expression of maize and barley Lsi2 was downregulated in response to exogenously applied Si .
[ Sen. 8, subscore: 1.00 ]: Immunostaining showed that maize and barley Lsi2 localized only at the endodermis , with no polarity .
[ Sen. 9, subscore: 1.00 ]: Protein gel blot analysis indicated that maize and barley Lsi2 localized on the plasma membrane .
[ Sen. 10, subscore: 1.00 ]: The unique features of maize and barley Si influx and efflux transporters , including their cell-type specificity and the lack of polarity of their localization in Lsi2 , indicate that these crops have a different Si uptake system from that in rice .
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Score: 6.00 |
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| Title: Functions and transport of silicon in plants .
| | Author: Ma JF Yamaji N | | Journal: Cell Mol Life Sci Citation: V : P : Year: 2008 Type: Publisher | | Literature: oryza Field: abstract Doc ID: pub18560761 Accession (PMID): 18560761 | | Abstract: Silicon exerts beneficial effects on plant growth and production by alleviating both biotic and abiotic stresses including diseases , pests , lodging , drought , and nutrient imbalance .
Recently , two genes ( Lsi1 and Lsi2 ) encoding Si transporters have been identified from rice .
Lsi1 ( low silicon 1 ) belongs to a Nod26-like major intrinsic protein subfamily in aquaporin , while Lsi2 encodes a putative anion transporter .
Lsi1 is localized on the distal side of both exodermis and endodermis in rice roots , while Lsi2 is localized on the proximal side of the same cells .
Lsi1 shows influx transport activity for Si , while Lsi2 shows efflux transport activity .
Therefore , Lsi1 is responsible for transport of Si from the external solution to the root cells , whereas Lsi2 is an efflux transporter responsible for the transport of Si from the root cells to the apoplast Coupling of Lsi1 with Lsi2 is required for efficient uptake of Si in rice .
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[ Sen. 6, subscore: 2.00 ]: Therefore , Lsi1 is responsible for transport of Si from the external solution to the root cells , whereas Lsi2 is an efflux transporter responsible for the transport of Si from the root cells to the apoplast Coupling of Lsi1 with Lsi2 is required for efficient uptake of Si in rice .
[ Sen. 2, subscore: 1.00 ]: Recently , two genes ( Lsi1 and Lsi2 ) encoding Si transporters have been identified from rice .
[ Sen. 3, subscore: 1.00 ]: Lsi1 ( low silicon 1 ) belongs to a Nod26-like major intrinsic protein subfamily in aquaporin , while Lsi2 encodes a putative anion transporter .
[ Sen. 4, subscore: 1.00 ]: Lsi1 is localized on the distal side of both exodermis and endodermis in rice roots , while Lsi2 is localized on the proximal side of the same cells .
[ Sen. 5, subscore: 1.00 ]: Lsi1 shows influx transport activity for Si , while Lsi2 shows efflux transport activity .
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Score: 5.00 |
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| Title: High-resolution secondary ion mass spectrometry reveals the contrasting subcellular distribution of arsenic and silicon in rice roots .
| | Author: Moore KL Schroder M Wu Z Martin BG Hawes CR McGrath SP Hawkesford MJ Feng Ma J Zhao FJ Grovenor CR | | Journal: Plant Physiol Citation: V : 156 P : 913-24 Year: 2011 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub21490163 Accession (PMID): 21490163 | | Abstract: Rice ( Oryza sativa ) takes up arsenite mainly through the silicic acid transport pathway .
Understanding the uptake and sequestration of arsenic ( As ) into the rice plant is important for developing strategies to reduce As concentration in rice grain .
In this study , the cellular and subcellular distributions of As and silicon ( Si ) in rice roots were investigated using high-pressure freezing , high-resolution secondary ion mass spectrometry , and transmission electron microscopy .
Rice plants , both the lsi2 mutant lacking the Si/arsenite efflux transporter Lsi2 and its wild-type cultivar , with or without an iron plaque , were treated with arsenate or arsenite .
The formation of iron plaque on the root surface resulted in strong accumulation of As and phosphorous on the epidermis .
The lsi2 mutant showed stronger As accumulation in the endodermal vacuoles , where the Lsi2 transporter is located in the plasma membranes , than the wild-type line .
As also accumulated in the vacuoles of some xylem parenchyma cells and in some pericycle cells , particularly in the wild-type mature root zone .
Vacuolar accumulation of As is associated with sulfur , suggesting that As may be stored as arsenite-phytochelatin complexes .
Si was localized in the cell walls of the endodermal cells with little apparent effect of the Lsi2 mutation on its distribution .
This study reveals the vacuolar sequestration of As in rice roots and contrasting patterns of As and Si subcellular localization , despite both being transported across the plasma membranes by the same transporters .
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[ Sen. 4, subscore: 2.00 ]: Rice plants , both the lsi2 mutant lacking the Si/arsenite efflux transporter Lsi2 and its wild-type cultivar , with or without an iron plaque , were treated with arsenate or arsenite .
[ Sen. 6, subscore: 2.00 ]: The lsi2 mutant showed stronger As accumulation in the endodermal vacuoles , where the Lsi2 transporter is located in the plasma membranes , than the wild-type line .
[ Sen. 9, subscore: 1.00 ]: Si was localized in the cell walls of the endodermal cells with little apparent effect of the Lsi2 mutation on its distribution .
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Score: 4.00 |
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| Title: An efflux transporter of silicon in rice .
| | Author: Ma JF Yamaji N Mitani N Tamai K Konishi S Fujiwara T Katsuhara M Yano M | | Journal: Nature Citation: V : 448 P : 209-12 Year: 2007 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub17625566 Accession (PMID): 17625566 | | Abstract: Silicon is an important nutrient for the optimal growth and sustainable production of rice .
Rice accumulates up to 10% silicon in the shoot , and this high accumulation is required to protect the plant from multiple abiotic and biotic stresses .
A gene , Lsi1 , that encodes a silicon influx transporter has been identified in rice .
Here we describe a previously uncharacterized gene , low silicon rice 2 ( Lsi2 ) , which has no similarity to Lsi1 .
This gene is constitutively expressed in the roots .
The protein encoded by this gene is localized , like Lsi1 , on the plasma membrane of cells in both the exodermis and the endodermis , but in contrast to Lsi1 , which is localized on the distal side , Lsi2 is localized on the proximal side of the same cells .
Expression of Lsi2 in Xenopus oocytes did not result in influx transport activity for silicon , but preloading of the oocytes with silicon resulted in a release of silicon , indicating that Lsi2 is a silicon efflux transporter .
The identification of this silicon transporter revealed a unique mechanism of nutrient transport in plants : having an influx transporter on one side and an efflux transporter on the other side of the cell to permit the effective transcellular transport of the nutrients .
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[ Sen. 7, subscore: 2.00 ]: Expression of Lsi2 in Xenopus oocytes did not result in influx transport activity for silicon , but preloading of the oocytes with silicon resulted in a release of silicon , indicating that Lsi2 is a silicon efflux transporter .
[ Sen. 4, subscore: 1.00 ]: Here we describe a previously uncharacterized gene , low silicon rice 2 ( Lsi2 ) , which has no similarity to Lsi1 .
[ Sen. 6, subscore: 1.00 ]: The protein encoded by this gene is localized , like Lsi1 , on the plasma membrane of cells in both the exodermis and the endodermis , but in contrast to Lsi1 , which is localized on the distal side , Lsi2 is localized on the proximal side of the same cells .
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Score: 3.00 |
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| Title: Genotypic difference in silicon uptake and expression of silicon transporter genes in rice .
| | Author: Ma JF Yamaji N Tamai K Mitani N | | Journal: Plant Physiol Citation: V : 145 P : 919-24 Year: 2007 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub17905867 Accession (PMID): 17905867 | | Abstract: Rice ( Oryza sativa ) is a highly silicon ( Si ) -accumulating species that shows genotypic differences in Si accumulation .
We investigated the physiological and molecular mechanisms involved in the genotypic difference in Si uptake between the japonica var .
Nipponbare and the indica var .
Kasalath .
Both the Si concentration in the shoot and the Si uptake per root dry weight were higher in Nipponbare than in Kasalath grown in either soil or nutrient solution .
The Si uptake by a single root was also higher in Nipponbare than in Kasalath .
A kinetics study showed that Nipponbare and Kasalath had a similar K ( m ) value , whereas the V ( max ) was higher in Nipponbare .
The expression of two Si transporter genes ( Low silicon rice 1 [ Lsi1 ] and Lsi2 ) investigated using real-time reverse transcription polymerase chain reaction revealed higher expression of both genes in Nipponbare than in Kasalath .
Immunostaining with Lsi1 and Lsi2 antibodies revealed a similar pattern of subcellular localization of these two Si transporters in both varieties ; Lsi1 and Lsi2 were localized at the distal and proximal sides , respectively , of both exodermis and endodermis of the roots .
These results revealed that the genotypic difference in the Si accumulation results from the difference in abundance of Si transporters in rice roots .
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[ Sen. 9, subscore: 2.00 ]: Immunostaining with Lsi1 and Lsi2 antibodies revealed a similar pattern of subcellular localization of these two Si transporters in both varieties ; Lsi1 and Lsi2 were localized at the distal and proximal sides , respectively , of both exodermis and endodermis of the roots .
[ Sen. 8, subscore: 1.00 ]: The expression of two Si transporter genes ( Low silicon rice 1 [ Lsi1 ] and Lsi2 ) investigated using real-time reverse transcription polymerase chain reaction revealed higher expression of both genes in Nipponbare than in Kasalath .
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Score: 3.00 |
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| Title: Effects of active silicon uptake by rice on 29Si fractionation in various plant parts .
| | Author: Koster JR Bol R Leng MJ Parker AG Sloane HJ Ma JF | | Journal: Rapid Commun Mass Spectrom Citation: V : 23 P : 2398-402 Year: 2009 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub19603477 Accession (PMID): 19603477 | | Abstract: Rice ( Oryza sativa L ) accumulates large amounts of silicon which improves its growth and health due to enhanced resistance to biotic and abiotic stresses .
Silicon uptake and loading to xylem in rice are predominantly active processes performed by transporters encoded by the recently identified genes Lsi1 ( Si influx transporter gene ) and Lsi2 ( Si efflux transporter gene ) .
Silicon deposition in rice during translocation to upper plant it issues is known to discriminate against the heavier isotopes ( 29 ) Si and ( 30 ) Si , resulting in isotope fractionation within the plant .
We analyzed straw and husk samples of rice mutants defective in Lsi1 , Lsi2 or both for silicon content and delta ( 29 ) Si using isotope ratio mass spectrometry ( IRMS ) and compared these results with those for the corresponding wild-type varieties ( WT ) .
The silicon content was higher in husk than in straw .
All the mutant rice lines showed clearly lower silicon content than the WT lines ( 4-23% Si of WT ) .
The delta ( 29 ) Si was lower in straw and husk for the uptake defective mutant ( lsi1 ) than for WT , albeit delta ( 29 ) Si was 0 . 3 per thousand higher in husk than in straw in both lines .
The effect of defective efflux ( lsi2 ) differed for straw and husk with higher delta ( 29 ) Si in straw , but lower delta ( 29 ) Si in husk while WT showed similar delta ( 29 ) Si in both fractions .
These initial results show the potential of Si isotopes to enlighten the influence of active uptake on translocation and deposition processes in the plant .
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[ Sen. 2, subscore: 1.00 ]: Silicon uptake and loading to xylem in rice are predominantly active processes performed by transporters encoded by the recently identified genes Lsi1 ( Si influx transporter gene ) and Lsi2 ( Si efflux transporter gene ) .
[ Sen. 4, subscore: 1.00 ]: We analyzed straw and husk samples of rice mutants defective in Lsi1 , Lsi2 or both for silicon content and delta ( 29 ) Si using isotope ratio mass spectrometry ( IRMS ) and compared these results with those for the corresponding wild-type varieties ( WT ) .
[ Sen. 8, subscore: 1.00 ]: The effect of defective efflux ( lsi2 ) differed for straw and husk with higher delta ( 29 ) Si in straw , but lower delta ( 29 ) Si in husk while WT showed similar delta ( 29 ) Si in both fractions .
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Score: 3.00 |
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| Title: Silicon transporters in higher plants .
| | Author: Ma JF | | Journal: Adv Exp Med Biol Citation: V : 679 P : 99-109 Year: 2010 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub20666227 Accession (PMID): 20666227 | | Abstract: Silicon ( Si ) is the second most abundant element in the Earths crust and exerts beneficial effects on plant growth and production by alleviating both biotic and abiotic stresses including diseases , pests , lodging , drought and nutrient imbalance .
Silicon is taken up by the roots in the form ofsilicic acid , a noncharged molecule .
Recently both influx ( Lsil ) and efflux ( Lsi2 ) transporters for silicic acid have been identified in gramineous plants including rice , barley and maize .
Lsil and its homologs are influx Si transporters , which belong to a Nod26-like major intrinsic protein ( NIP ) subfamily in the aquaporin protein family .
They are responsible for the transport of Si from the external solution to the root cells .
On the other hand , Lsi2 and its homologs are efflux Si transporters , belonging to putative anion transporters and are responsible for the transport of Si out of the cells toward the xylem .
All influx transporters show polar localization at the distal side .
Among efflux transporters , Lsi2 in rice shows polar localization at the proximal side , but that in barley and maize does not show polar localization .
The cell-specificity of localization of Si transporters and expression patterns are different between species .
Rice Si transporters are also permeable to arsenite .
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[ Sen. 3, subscore: 1.00 ]: Recently both influx ( Lsil ) and efflux ( Lsi2 ) transporters for silicic acid have been identified in gramineous plants including rice , barley and maize .
[ Sen. 6, subscore: 1.00 ]: On the other hand , Lsi2 and its homologs are efflux Si transporters , belonging to putative anion transporters and are responsible for the transport of Si out of the cells toward the xylem .
[ Sen. 8, subscore: 1.00 ]: Among efflux transporters , Lsi2 in rice shows polar localization at the proximal side , but that in barley and maize does not show polar localization .
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Score: 2.00 |
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| Title: Transporters of arsenite in rice and their role in arsenic accumulation in rice grain .
| | Author: Ma JF Yamaji N Mitani N Xu XY Su YH McGrath SP Zhao FJ | | Journal: Proc Natl Acad Sci U S A Citation: V : 105 P : 5-31 Year: 2008 Type: In-Process | | Literature: oryza Field: abstract Doc ID: pub18626020 Accession (PMID): 18626020 | | Abstract: Arsenic poisoning affects millions of people worldwide .
Human arsenic intake from rice consumption can be substantial because rice is particularly efficient in assimilating arsenic from paddy soils , although the mechanism has not been elucidated .
Here we report that two different types of transporters mediate transport of arsenite , the predominant form of arsenic in paddy soil , from the external medium to the xylem .
Transporters belonging to the NIP subfamily of aquaporins in rice are permeable to arsenite but not to arsenate .
Mutation in OsNIP2 ; 1 ( Lsi1 , a silicon influx transporter ) significantly decreases arsenite uptake .
Furthermore , in the rice mutants defective in the silicon efflux transporter Lsi2 , arsenite transport to the xylem and accumulation in shoots and grain decreased greatly .
Mutation in Lsi2 had a much greater impact on arsenic accumulation in shoots and grain in field-grown rice than Lsi1 .
Arsenite transport in rice roots therefore shares the same highly efficient pathway as silicon , which explains why rice is efficient in arsenic accumulation .
Our results provide insight into the uptake mechanism of arsenite in rice and strategies for reducing arsenic accumulation in grain for enhanced food safety .
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[ Sen. 6, subscore: 1.00 ]: Furthermore , in the rice mutants defective in the silicon efflux transporter Lsi2 , arsenite transport to the xylem and accumulation in shoots and grain decreased greatly .
[ Sen. 7, subscore: 1.00 ]: Mutation in Lsi2 had a much greater impact on arsenic accumulation in shoots and grain in field-grown rice than Lsi1 .
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Score: 2.00 |
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| Title: The rice aquaporin Lsi1 mediates uptake of methylated arsenic species .
| | Author: Li RY Ago Y Liu WJ Mitani N Feldmann J McGrath SP Ma JF Zhao FJ | | Journal: Plant Physiol Citation: V : 150 P : 2071-80 Year: 2009 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub19542298 Accession (PMID): 19542298 | | Abstract: Pentavalent methylated arsenic ( As ) species such as monomethylarsonic acid [ MMA ( V ) ] and dimethylarsinic acid [ DMA ( V ) ] are used as herbicides or pesticides , and can also be synthesized by soil microorganisms or algae through As methylation .
The mechanism of MMA ( V ) and DMA ( V ) uptake remains unknown .
Recent studies have shown that arsenite is taken up by rice ( Oryza sativa ) roots through two silicon transporters , Lsi1 ( the aquaporin NIP2 ; 1 ) and Lsi2 ( an efflux carrier ) .
Here we investigated whether these two transporters also mediate the uptake of MMA ( V ) and DMA ( V ) .
MMA ( V ) was partly reduced to trivalent MMA ( III ) in rice roots , but only MMA ( V ) was translocated to shoots .
DMA ( V ) was stable in plants .
The rice lsi1 mutant lost about 80% and 50% of the uptake capacity for MMA ( V ) and DMA ( V ) , respectively , compared with the wild-type rice , whereas Lsi2 mutation had little effect .
The short-term uptake kinetics of MMA ( V ) can be described by a Michaelis-Menten plus linear model , with the wild type having 3 . 5-fold higher V ( max ) than the lsi1 mutant .
The uptake kinetics of DMA ( V ) were linear with the slope being 2 . 8-fold higher in the wild type than the lsi1 mutant .
Heterologous expression of Lsi1 in Xenopus laevis oocytes significantly increased the uptake of MMA ( V ) but not DMA ( V ) , possibly because of a very limited uptake of the latter .
Uptake of MMA ( V ) and DMA ( V ) by wild-type rice was increased as the pH of the medium decreased , consistent with an increasing proportion of the undissociated species .
The results demonstrate that Lsi1 mediates the uptake of undissociated methylated As in rice roots .
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[ Sen. 3, subscore: 1.00 ]: Recent studies have shown that arsenite is taken up by rice ( Oryza sativa ) roots through two silicon transporters , Lsi1 ( the aquaporin NIP2 ; 1 ) and Lsi2 ( an efflux carrier ) .
[ Sen. 7, subscore: 1.00 ]: The rice lsi1 mutant lost about 80% and 50% of the uptake capacity for MMA ( V ) and DMA ( V ) , respectively , compared with the wild-type rice , whereas Lsi2 mutation had little effect .
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Score: 2.00 |
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| Title: Transport of silicon from roots to panicles in plants .
| | Author: Ma JF Yamaji N Mitani-Ueno N | | Journal: Proc Jpn Acad Ser B Phys Biol Sci Citation: V : 87 P : 377-85 Year: 2011 Type: In-Process | | Literature: oryza Field: abstract Doc ID: pub21785256 Accession (PMID): 21785256 | | Abstract: Silicon ( Si ) is the most abundant minerals in soil and exerts beneficial effects on plant growth by alleviating various stresses .
The transport of Si from soil to the panicles is mediated by different transporters .
Lsi1 , belonging to a NIP group of the aquaporin family , is responsible for the uptake of Si from soil into the root cells in both dicots and monocots although its expression patterns and cellular localization differ with plant species .
The subsequent transport of Si out of the root cells towards the stele is medicated by an active efflux transporter , Lsi2 .
Lsi1 and Lsi2 are polarly localized at the distal and proximal sides , respectively , of both exodermis and endodermis in rice root .
Silicon in the xylem sap is presented in the form of monosilicic acid and is unloaded by Lsi6 , a homolog of Lsi1 in rice .
Lsi6 is also involved in the inter-vascular transfer of Si at the node , which is necessary for preferential Si distribution to the panicles .
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[ Sen. 4, subscore: 1.00 ]: The subsequent transport of Si out of the root cells towards the stele is medicated by an active efflux transporter , Lsi2 .
[ Sen. 5, subscore: 1.00 ]: Lsi1 and Lsi2 are polarly localized at the distal and proximal sides , respectively , of both exodermis and endodermis in rice root .
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