Subcellular localization of rice hexokinase (OsHXK) family members in the mesophyll protoplasts of tobacco

Cheng, Weiguo; Zhang, H.; Zhou, Xiaoyun; Liu, H.; Liu, Yu-xin; Li, J.; Han, Shengcheng; Wang, Y.

doi:10.1007/s10535-011-0025-7

Cited by 29 publications

(17 citation statements)

References 31 publications

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“…2c and Additional file 1: Table S3). Similar results were obtained for the cytosolic HXKs of rice, OsHXK7 and OsHXK8 [12, 37], suggesting that ZmHXK7 and ZmHXK8 could be in the cytosol. This is possible even if the TargetP 1.1 software [35] predicted that ZmHXK8 was located at the chloroplast.…”

Section: Resultssupporting

confidence: 81%

“…There are no chloroplast or Golgi HXKs as suggested before [9, 26], the localization analysis on protoplast corroborates the phylogenetic analysis, in which only dicot plants have plastid HXK (Additional file 1: Figure S1). The absence of a chloroplast HXK (type A HXKs) in maize suggests that Glc is phosphorylated by cytosolic isoenzymes and used in starch and fatty acid synthesis when night-time energy supply is limited in the chloroplast [24, 37, 48–51]. However, it was also suggested that type A HXKs are only expressed in plants that tend to accumulate starch, which is not the case in maize [25, 52].…”

Section: Discussionmentioning

confidence: 99%

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Biochemical properties and subcellular localization of six members of the HXK family in maize and its metabolic contribution to embryo germination

et al. 2019

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BackgroundSeed germination is a crucial process in the plant life cycle when a dramatic variation of type and sugar content occurs just as the seed is hydrated. The production of hexose 6 phosphate is a key node in different pathways that are required for a successful germination. Hexokinase (HXK) is the only plant enzyme that phosphorylates glucose (Glc), so it is key to fueling several metabolic pathways depending on their substrate specificity, metabolite regulatory responses and subcellular localization. In maize, the HXK family is composed of nine genes, but only six of them (ZmHXK4–9) putatively encode catalytically active enzymes. Here, we cloned and functionally characterized putative catalytic enzymes to analyze their metabolic contribution during germination process.ResultsFrom the six HXKs analyzed here, only ZmHXK9 has minimal hexose phosphorylating activity even though enzymatic function of all isoforms (ZmHXK4–9) was confirmed using a yeast complementation approach. The kinetic parameters of recombinant proteins showed that ZmHXK4–7 have high catalytic efficiency for Glc, fructose (Fru) and mannose (Man), ZmHXK7 has a lower Km for ATP, and together with ZmHXK8 they have lower sensitivity to inhibition by ADP, G6P and N-acetylglucosamine than ZmHXK4–6 and ZmHXK9. Additionally, we demonstrated that ZmHXK4–6 and ZmHXK9 are located in the mitochondria and their location relies on the first 30 amino acids of the N-terminal domain. Otherwise, ZmHXK7–8 are constitutively located in the cytosol. HXK activity was detected in cytosolic and mitochondrial fractions and high Glc and Fru phosphorylating activities were found in imbibed embryos.ConclusionsConsidering the biochemical characteristics, location and the expression of ZmHXK4 at onset of germination, we suggest that it is the main contributor to mitochondrial activity at early germination times, at 24 h other ZmHXKs also contribute to the total activity. While in the cytosol, ZmHXK7 could be responsible for the activity at the onset of germination, although later, ZmHXK8 also contributes to the total HXK activity. Our observations suggest that the HXKs may be redundant proteins with specific roles depending on carbon and ATP availability, metabolic needs, or sensor requirements. Further investigation is necessary to understand their specific or redundant physiological roles.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1605-x) contains supplementary material, which is available to authorized users.

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Section: Resultssupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Biochemical properties and subcellular localization of six members of the HXK family in maize and its metabolic contribution to embryo germination

et al. 2019

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“…Proteomic analysis of mitochondrial proteins has located Arabidopsis AtHXK1 and AtHXK2 enzymes on the outside of the mitochondrial membrane (Giege et al, 2003; Heazlewood et al, 2004). Studies based on the use of GFP fusion proteins have shown that Arabidopsis AtHXK1 and AtHXK2, tomato SlHXK1, 2, and 3, Nicotiana benthamiana NbHXK1, rice OsHXK 2, 3, 5, 6, and 9, Sorghum SbHXK3, Populus trichocarpa PtHXK1, and spinach ( Spinacia oleracea ) SoHXK1 are associated with mitochondria (Cho et al, 2006a; Damari-Weissler et al, 2006, 2007; Kandel-Kfir et al, 2006; Kim et al, 2006; Balasubramanian et al, 2007; Karve et al, 2008, 2010; Cheng et al, 2011). Deletion of the putative N-terminal membrane anchor domains of the Arabidopsis AtHXK1, tomato SlHXK 1, 2, and 3, and the N. benthamiana NbHXK1 proteins resulted in their localization to the cytosol, confirming that this domain is a membrane anchor domain (Damari-Weissler et al, 2006; Kim et al, 2006; Balasubramanian et al, 2007).…”

Section: Intracellular Localization Of Hxks and Frksmentioning

confidence: 99%

“…However, cytosolic HXK were also identified in monocots. Four of the 10 rice HXKs, OsHXK1, OsHXK7, OsHXK8, and OsHXK10 lack or have a truncated N-terminal membrane anchor domain and are located in the cytosol (Cho et al, 2006a; Cheng et al, 2011). Cheng et al (2011) suggested that OsHXK1, OsHXK7, and OsHXK8 are also located within nuclei.…”

Section: Intracellular Localization Of Hxks and Frksmentioning

confidence: 99%

Hexose Kinases and Their Role in Sugar-Sensing and Plant Development

Granot¹,

David‐Schwartz²,

Kelly³

2013

Front. Plant Sci.

189

150

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Hexose sugars, such as glucose and fructose produced in plants, are ubiquitous in most organisms and are the origin of most of the organic matter found in nature. To be utilized, hexose sugars must first be phosphorylated. The central role of hexose-phosphorylating enzymes has attracted the attention of many researchers, leading to novel discoveries. Only two families of enzymes capable of phosphorylating glucose and fructose have been identified in plants; hexokinases (HXKs), and fructokinases (FRKs). Intensive investigations of these two families in numerous plant species have yielded a wealth of knowledge regarding the genes number, enzymatic characterization, intracellular localization, and developmental and physiological roles of several HXKs and FRKs. The emerging picture indicates that HXK and FRK enzymes found at specific intracellular locations play distinct roles in plant metabolism and development. Individual HXKs were shown for the first time to be dual-function enzymes – sensing sugar levels independent of their catalytic activity and controlling gene expression and major developmental pathways, as well as hormonal interactions. FRK, on the other hand, seems to play a central metabolic role in vascular tissues, controlling the amounts of sugars allocated for vascular development. While a clearer picture of the roles of these two types of enzymes is emerging, many questions remain unsolved, such as the specific tissues and types of cells in which these enzymes function, the roles of individual HXK and FRK genes, and how these enzymes interact with hormones in the regulation of developmental processes. It is anticipated that ongoing efforts will broaden our knowledge of these important plant enzymes and their potential uses in the modification of plant traits.

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“…Additionally, most pathogenicities are related to gene function in the cell membrane, cytosol, and nucleus, suggesting that the localization of the protein is also an important factor for gene function. Similarly, rice hexokinase 10 (OsHXK10), a key player in sugar signaling and metabolism, has been shown to be differentially localized in the cytoplasm and mitochondria in a tobacco expression system [53] , [54] . Other members of HXK, OsHXK5 and OsHXK6 have recently been reported to retain a dual targeting ability for the mitochondria and the nucleus and to function as part of a glucose sensor in the cell [55] .…”

Section: Discussionmentioning

confidence: 99%

A Pepper MSRB2 Gene Confers Drought Tolerance in Rice through the Protection of Chloroplast-Targeted Genes

Kim

Park²,

Chae³

et al. 2014

PLoS ONE

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BackgroundThe perturbation of the steady state of reactive oxygen species (ROS) due to biotic and abiotic stresses in a plant could lead to protein denaturation through the modification of amino acid residues, including the oxidation of methionine residues. Methionine sulfoxide reductases (MSRs) catalyze the reduction of methionine sulfoxide back to the methionine residue. To assess the role of this enzyme, we generated transgenic rice using a pepper CaMSRB2 gene under the control of the rice Rab21 (responsive to ABA protein 21) promoter with/without a selection marker, the bar gene.ResultsA drought resistance test on transgenic plants showed that CaMSRB2 confers drought tolerance to rice, as evidenced by less oxidative stress symptoms and a strengthened PSII quantum yield under stress conditions, and increased survival rate and chlorophyll index after the re-watering. The results from immunoblotting using a methionine sulfoxide antibody and nano-LC-MS/MS spectrometry suggest that porphobilinogen deaminase (PBGD), which is involved in chlorophyll synthesis, is a putative target of CaMSRB2. The oxidized methionine content of PBGD expressed in E. coli increased in the presence of H2O2, and the Met-95 and Met-227 residues of PBGD were reduced by CaMSRB2 in the presence of dithiothreitol (DTT). An expression profiling analysis of the overexpression lines also suggested that photosystems are less severely affected by drought stress.ConclusionsOur results indicate that CaMSRB2 might play an important functional role in chloroplasts for conferring drought stress tolerance in rice.

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Subcellular localization of rice hexokinase (OsHXK) family members in the mesophyll protoplasts of tobacco

Cited by 29 publications

References 31 publications

Biochemical properties and subcellular localization of six members of the HXK family in maize and its metabolic contribution to embryo germination

Biochemical properties and subcellular localization of six members of the HXK family in maize and its metabolic contribution to embryo germination

Hexose Kinases and Their Role in Sugar-Sensing and Plant Development

A Pepper MSRB2 Gene Confers Drought Tolerance in Rice through the Protection of Chloroplast-Targeted Genes

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