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PMID:19010999
| Citation |
Cho, JI, Ryoo, N, Eom, JS, Lee, DW, Kim, HB, Jeong, SW, Lee, YH, Kwon, YK, Cho, MH, Bhoo, SH, Hahn, TR, Park, YI, Hwang, I, Sheen, J and Jeon, JS (2009) Role of the rice hexokinases OsHXK5 and OsHXK6 as glucose sensors. Plant Physiol. 149:745-59 |
|---|---|
| Abstract |
The Arabidopsis (Arabidopsis thaliana) hexokinase 1 (AtHXK1) is recognized as an important glucose (Glc) sensor. However, the function of hexokinases as Glc sensors has not been clearly demonstrated in other plant species, including rice (Oryza sativa). To investigate the functions of rice hexokinase isoforms, we characterized OsHXK5 and OsHXK6, which are evolutionarily related to AtHXK1. Transient expression analyses using GFP fusion constructs revealed that OsHXK5 and OsHXK6 are associated with mitochondria. Interestingly, the OsHXK5DeltamTP-GFP and OsHXK6DeltamTP-GFP fusion proteins, which lack N-terminal mitochondrial targeting peptides, were present mainly in the nucleus with a small amount of the proteins seen in the cytosol. In addition, the OsHXK5NLS-GFP and OsHXK6NLS-GFP fusion proteins harboring nuclear localization signals were targeted predominantly in the nucleus, suggesting that these OsHXKs retain a dual-targeting ability to mitochondria and nuclei. In transient expression assays using promoterluciferase fusion constructs, these two OsHXKs and their catalytically inactive alleles dramatically enhanced the Glc-dependent repression of the maize (Zea mays) Rubisco small subunit (RbcS) and rice alpha-amylase genes in mesophyll protoplasts of maize and rice. Notably, the expression of OsHXK5, OsHXK6, or their mutant alleles complemented the Arabidopsis glucose insensitive2-1 mutant, thereby resulting in wild-type characteristics in seedling development, Glc-dependent gene expression, and plant growth. Furthermore, transgenic rice plants overexpressing OsHXK5 or OsHXK6 exhibited hypersensitive plant growth retardation and enhanced repression of the photosynthetic gene RbcS in response to Glc treatment. These results provide evidence that rice OsHXK5 and OsHXK6 can function as Glc sensors. |
| Links |
PubMed PMC2633841 Online version:10.1104/pp.108.131227 |
| Keywords |
Amino Acid Sequence; Arabidopsis/enzymology; Arabidopsis Proteins/metabolism; Biosensing Techniques; Caulimovirus/enzymology; Caulimovirus/genetics; Genes, Reporter; Glucose/metabolism; Green Fluorescent Proteins/genetics; Hexokinase/metabolism; Molecular Sequence Data; Oryza sativa/enzymology; Plant Proteins/metabolism; Repressor Proteins/genetics; Repressor Proteins/metabolism |
| edit table |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
|
enables |
GO:0004340: glucokinase activity |
ECO:0000315: mutant phenotype evidence used in manual assertion |
F |
Seeded From UniProt |
complete | |||
|
part_of |
GO:0005739: mitochondrion |
ECO:0000314: direct assay evidence used in manual assertion |
C |
Seeded From UniProt |
complete | |||
|
involved_in |
GO:0009749: response to glucose |
ECO:0000315: mutant phenotype evidence used in manual assertion |
P |
Seeded From UniProt |
complete | |||
| GO:0005739: mitochondrion |
ECO:0000314: |
C |
Figure 1A shows GFP tagged HXK5 colocalizes with mitochondria markers. |
complete | ||||
| GO:0004340: glucokinase activity |
ECO:0000315: |
F |
Figure 5D shows that overexpressing HXK5 increases glucose phosphorylation, and mutating HXK5 decreases phosphorylation. |
complete | ||||
| GO:0009749: response to glucose stimulus |
ECO:0000315: |
P |
Figure 8 shows that overexpressing HXK5 leads to an increase in the growth inhibition response to glucose. |
complete | ||||
| GO:0005739: mitochondrion |
ECO:0000314: |
C |
Figure 1B shows GFP tagged HXK6 colocalizes with mitochondria markers. |
complete | ||||
| GO:0004340: glucokinase activity |
ECO:0000315: |
F |
Figure 5D shows overexpressing HXK6 increased glucose phosphorylation, and mutating HXK6 decreases glucose phosphorylation. |
complete | ||||
| GO:0009749: response to glucose stimulus |
ECO:0000315: |
P |
Figure 8 shows that overexpressing HXK6 leads to an increase in the growth inhibition response to glucose. |
complete | ||||
|
involved_in |
GO:0009749: response to glucose |
ECO:0000315: mutant phenotype evidence used in manual assertion |
P |
Seeded From UniProt |
complete | |||
|
enables |
GO:0004340: glucokinase activity |
ECO:0000315: mutant phenotype evidence used in manual assertion |
F |
Seeded From UniProt |
complete | |||
|
part_of |
GO:0005739: mitochondrion |
ECO:0000314: direct assay evidence used in manual assertion |
C |
Seeded From UniProt |
complete | |||
See also
References
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