Sodium transport and HKT transporters: the rice model

Garciadeblás, Blanca; Senn, María Eugenia; Bañuelos, María Antonia; Rodríguez‐Navarro, Alonso

doi:10.1046/j.1365-313x.2003.01764.x

Cited by 344 publications

(386 citation statements)

References 58 publications

(107 reference statements)

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“…Moreover, the tail currents of AtHKT1;1 also showed a time-independent leak profile (Fig.1B). To sum up, the results indicated that OsHKT2;4 produces a unique current profile that is absent in oocytes expressing other HKT members, including several previously described for rice (5,6,(12)(13)(14). Channel.…”

Section: Resultssupporting

confidence: 51%

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A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel

Wang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

105

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Plant high-affinity K + transport (HKT) proteins are so named because of their relation to bacterial and fungal transporters that mediate high-affinity K + uptake. The view that HKT family members are sodium-selective uniporters or sodium-potassium symporters is widely held. We have found that one of the rice HKT proteins also functions as a Ca 2+ -permeable cation channel that conducts current carried by a wide range of monovalent and divalent cations. The HKT rice gene, named OsHKT2;4, is expressed in several cell types, including root hairs and vascular parenchyma cells. The protein is localized to the plasma membrane, thereby providing a mechanism for cation uptake and extrusion. This finding goes against firmly entrenched dogma in showing that HKT proteins can function as both ion carriers and channels. The study further extends the function of HKT proteins to Ca 2+ -linked processes and, in so doing, defines a previously undescribed type of Ca 2+ -permeable cation channels in plants. The work also raises questions about the evolutionary changes in this protein family following the divergence of monocots and dicots.calcium transport | moncot-dicot divergence | nonselective cation channel

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Section: Resultssupporting

confidence: 51%

“…Compared with a single AtHKT1;1 gene in the dicot model, Arabidopsis, rice, a monocot model, contains nine HKT-like genes (12), a striking departure from Arabidopsis. Available data suggest that various members within the rice HKT family may belong to either group 1 or to group 2 HKTs (13,14).…”

mentioning

confidence: 99%

A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel

Wang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

105

View full text Add to dashboard Cite

show abstract

“…Cereals possess a much larger number of HKT genes, e.g. five to 11 genes in the different wheat genomes (Huang et al, 2008) and nine genes in rice (Oryza sativa; Garciadeblás et al, 2003), leading to functional diversity within this family (Jabnoune et al, 2009;Corratgé-Faillie et al, 2010). Based on functional studies in heterologous systems (Xenopus oocytes or yeast cells) and phylogenetic analyses, higher plant HKT transporters have been sorted out into two subfamilies .…”

mentioning

confidence: 99%

The Rice Monovalent Cation Transporter OsHKT2;4: Revisited Ionic Selectivity

et al. 2012

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The family of plant membrane transporters named HKT (for high-affinity K+ transporters) can be subdivided into subfamilies 1 and 2, which, respectively, comprise Na+-selective transporters and transporters able to function as Na+-K+ symporters, at least when expressed in yeast (Saccharomyces cerevisiae) or Xenopus oocytes. Surprisingly, a subfamily 2 member from rice (Oryza sativa), OsHKT2;4, has been proposed to form cation/K+ channels or transporters permeable to Ca2+ when expressed in Xenopus oocytes. Here, OsHKT2;4 functional properties were reassessed in Xenopus oocytes. A Ca2+ permeability through OsHKT2;4 was not detected, even at very low external K+ concentration, as shown by highly negative OsHKT2;4 zero-current potential in high Ca2+ conditions and lack of sensitivity of OsHKT2;4 zero-current potential and conductance to external Ca2+. The Ca2+ permeability previously attributed to OsHKT2;4 probably resulted from activation of an endogenous oocyte conductance. OsHKT2;4 displayed a high permeability to K+ compared with that to Na+ (permeability sequence: K+ > Rb+ ≈ Cs+ > Na+ ≈ Li+ ≈ NH4 +). Examination of OsHKT2;4 current sensitivity to external pH suggested that H+ is not significantly permeant through OsHKT2;4 in most physiological ionic conditions. Further analyses in media containing both Na+ and K+ indicated that OsHKT2;4 functions as K+-selective transporter at low external Na+, but transports also Na+ at high (>10 mm) Na+ concentrations. These data identify OsHKT2;4 as a new functional type in the K+ and Na+-permeable HKT transporter subfamily. Furthermore, the high permeability to K+ in OsHKT2;4 supports the hypothesis that this system is dedicated to K+ transport in the plant.

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“…High-affinity Na + uptake has been reported in K + -starved seedlings of wheat [93], rice [44], and barley [53]. However, there is no direct evidence that a channel/ transporter functions in Na + -selective uptake in plant roots.…”

Section: Sodium Transportersmentioning

confidence: 99%

“…Unlike Arabidopsis containing one HKT gene, seven HKT genes have been identified in rice cv. Nipponbare [44]. Given this large number of genes, rice may be a better model for understanding the role of HKTs in regulating Na + transport [142].…”

Section: Sodium Transportersmentioning

confidence: 99%

Toward Understanding Molecular Mechanisms of Abiotic Stress Responses in Rice

Gao

Chao

Lin

2008

Rice

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Plants have evolved delicate mechanisms to cope with environmental stress. Following exposure to environmental stimuli, extracellular signals are perceived and transmitted through signal transduction cascades. Upon receipt and transmission of the signals, a number of stressrelated genes are induced, leading to stress adaptation in plant cells. Rice, which is a critical food grain for a large portion of the world's population, is frequently impacted by several abiotic stressors, the most important of which are drought, salinity, and cold. Exposure to environmental conditions outside of acceptable tolerance ranges can negatively affect rice growth and production. In this paper, a review of rice responses to abiotic stress is presented, with particular attention to the genes and pathways related to environmental stress tolerance. It is apparent that, while progress has been made in identifying genes involved in stress adaptation, many questions remain. Understanding the mechanisms of stress response in rice is important for all research designed to develop new rice varieties with improved tolerance.Keywords Abiotic stress . Rice . Signal perception and transduction . Transcription factor . Stress tolerance Plant growth and productivity can be adversely affected by abiotic stress. Plants are exposed to any number of potentially adverse environmental conditions such as water deficit, high salinity, extreme temperature, and submergence. In response, plants have evolved delicate mechanisms, from the molecular to the physiological level, to adapt to stressful environments.Rice is the staple food for more than half of the world's population. Evolved in a semi-aquatic, low-radiation habitat, rice exhibits distinct tolerance and susceptibilities to abiotic stresses among domesticated cereal crops [92]. Rice thrives in waterlogged soil and can tolerate submergence at levels that would kill other crops, and is moderately tolerant of salinity and soil acidity but is highly sensitive to drought and cold [92]. Cultivated over a broad region between 45°north and south latitudes, rice plants are faced with low temperature in temperate regions, submergence in tropical regions, water deficit in humid tropics, and other stressors [109].Arabidopsis is a good model in plant molecular biology and genetics research, and the majority of studies examining the impacts of abiotic stress have employed this plant [37,85,165,183,193]. The signaling pathways and regulatory network in Arabidopsis have been well characterized and well reviewed. Although progresses were also made on rice, reviews were less focused on this most important crop because of little functional genes characterized. Recent years, multiple genes contributing to abiotic stress responses in rice were identified by using genetics, reverse genetics, and molecular biology method. Here, we Rice

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Sodium transport and HKT transporters: the rice model

Cited by 344 publications

References 58 publications

A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel

A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel

The Rice Monovalent Cation Transporter OsHKT2;4: Revisited Ionic Selectivity

Toward Understanding Molecular Mechanisms of Abiotic Stress Responses in Rice

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