silicon transporter in rice Ma, J.F; Tamai, K; Yamaji, N ...
Nature,
03/2006, Letnik:
440, Številka:
7084
Journal Article
Recenzirano
Silicon is beneficial to plant growth and helps plants to overcome abiotic and biotic stresses by preventing lodging (falling over) and increasing resistance to pests and diseases, as well as other ...stresses. Silicon is essential for high and sustainable production of rice, but the molecular mechanism responsible for the uptake of silicon is unknown. Here we describe the Low silicon rice 1 (Lsi1) gene, which controls silicon accumulation in rice, a typical silicon-accumulating plant. This gene belongs to the aquaporin family and is constitutively expressed in the roots. Lsi1 is localized on the plasma membrane of the distal side of both exodermis and endodermis cells, where casparian strips are located. Suppression of Lsi1 expression resulted in reduced silicon uptake. Furthermore, expression of Lsi1 in Xenopus oocytes showed transport activity for silicon only. The identification of a silicon transporter provides both an insight into the silicon uptake system in plants, and a new strategy for producing crops with high resistance to multiple stresses by genetic modification of the root's silicon uptake capacity.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Rice (Oryza sativa) accumulates very high concentrations of silicon (Si) in the shoots, and the deposition of Si as amorphous silica helps plants to overcome biotic and abiotic stresses. Here, we ...describe a transporter, Lsi6, which is involved in the distribution of Si in the shoots. Lsi6 belongs to the nodulin-26 intrinsic protein III subgroup of aquaporins and is permeable to silicic acid. Lsi6 is expressed in the leaf sheath and leaf blades as well as in the root tips. Cellular localization studies revealed that Lsi6 is found in the xylem parenchyma cells of the leaf sheath and leaf blades. Moreover, Lsi6 showed polar localization at the side facing toward the vessel. Knockdown of Lsi6 did not affect the uptake of Si by the roots but resulted in disordered deposition of silica in the shoots and increased excretion of Si in the guttation fluid. These results indicate that Lsi6 is a transporter responsible for the transport of Si out of the xylem and subsequently affects the distribution of Si in the leaf.
Significance Contamination of water and foods with arsenic (As) poses a threat to millions of people worldwide. Because the rice grain is the major source of As intake, reducing the transfer of As ...from soil to the grain is a pressing public health issue. We found that a member of the Oryza sativa C-type ATP-binding cassette transporter (OsABCC) family, OsABCC1, detoxifies As and reduces the amount of As in the rice grain. OsABCC1 in the upper nodes of rice plants restricts the distribution of As to the grain by sequestering it in the vacuoles of the phloem companion cells of diffuse vascular bundles directly connected to the grain. Our work suggests a strategy for limiting As accumulation in rice grains and thereby reducing human As exposure.
Arsenic (As) is a chronic poison that causes severe skin lesions and cancer. Rice ( Oryza sativa L.) is a major dietary source of As; therefore, reducing As accumulation in the rice grain and thereby diminishing the amount of As that enters the food chain is of critical importance. Here, we report that a member of the Oryza sativa C-type ATP-binding cassette (ABC) transporter (OsABCC) family, OsABCC1, is involved in the detoxification and reduction of As in rice grains. We found that OsABCC1 was expressed in many organs, including the roots, leaves, nodes, peduncle, and rachis. Expression was not affected when plants were exposed to low levels of As but was up-regulated in response to high levels of As. In both the basal nodes and upper nodes, which are connected to the panicle, OsABCC1 was localized to the phloem region of vascular bundles. Furthermore, OsABCC1 was localized to the tonoplast and conferred phytochelatin-dependent As resistance in yeast. Knockout of OsABCC1 in rice resulted in decreased tolerance to As, but did not affect cadmium toxicity. At the reproductive growth stage, the As content was higher in the nodes and in other tissues of wild-type rice than in those of OsABCC1 knockout mutants, but was significantly lower in the grain. Taken together, our results indicate that OsABCC1 limits As transport to the grains by sequestering As in the vacuoles of the phloem companion cells of the nodes in rice.
The concentration of essential mineral nutrients in the edible portion of plants such as grains may affect the nutritional value of these foods, while concentrations of toxic minerals in the plant ...are matter of food safety. Minerals taken up by the roots from soils are normally redirected at plant nodes before they are finally transported into developing seeds. However, the molecular mechanisms involved in this process have not been identified so far. Herein, we report on a transporter (Lsi6) responsible for the redirection of a plant nutrient at the node. Lsi6 is a silicon transporter in rice (Oryza sativa), and its expression in node I below the panicles is greatly enhanced when the panicle is completely emerged. Lsi6 is mainly localized at the xylem transfer cells located at the outer boundary region of the enlarged large vascular bundles in node I. Knockout of Lsi6 decreased Si accumulation in the panicles but increased Si accumulation in the flag leaf. These results suggest that Lsi6 is a transporter involved in intervascular transfer (i.e., transfer of silicon from the large vascular bundles coming from the roots to the diffuse vascular bundles connected to the panicles). These findings will be useful for selectively enhancing the accumulation of essential nutrients and reducing toxic minerals in the edible portion of cereals.
Here, we present a platelet‐facilitated photothermal tumor therapy (PLT‐PTT) strategy, in which PLTs act as carriers for targeted delivery of photothermal agents to tumor tissues and enhance the PTT ...effect. Gold nanorods (AuNRs) were first loaded into PLTs by electroporation and the resulting AuNR‐loaded PLTs (PLT‐AuNRs) inherited long blood circulation and cancer targeting characteristics from PLTs and good photothermal property from AuNRs. Using a gene‐knockout mouse model, we demonstrate that the administration of PLT‐AuNRs and localizing laser irradiation could effectively inhibit the growth of head and neck squamous cell carcinoma (HNSCC). In addition, we found that the PTT treatment augmented PLT‐AuNRs targeting to the tumor sites and in turn, improved the PTT effects in a feedback manner, demonstrating the unique self‐reinforcing characteristic of PLT‐PTT in cancer therapy.
Platelets (PLTs) are circulating sentinels that can accumulate in injured tissues to trigger the repair processes. Photothermal therapy (PTT) uses heat generated from light to ablate tumor tissues. Inspired by both observations, gold nanorods were loaded into PLTs for enhanced PTT of head and neck squamous cell carcinoma.
We perform decoy-state quantum key distribution between a low-Earth-orbit satellite and multiple ground stations located in Xinglong, Nanshan, and Graz, which establish satellite-to-ground secure ...keys with ∼kHz rate per passage of the satellite Micius over a ground station. The satellite thus establishes a secure key between itself and, say, Xinglong, and another key between itself and, say, Graz. Then, upon request from the ground command, Micius acts as a trusted relay. It performs bitwise exclusive or operations between the two keys and relays the result to one of the ground stations. That way, a secret key is created between China and Europe at locations separated by 7600 km on Earth. These keys are then used for intercontinental quantum-secured communication. This was, on the one hand, the transmission of images in a one-time pad configuration from China to Austria as well as from Austria to China. Also, a video conference was performed between the Austrian Academy of Sciences and the Chinese Academy of Sciences, which also included a 280 km optical ground connection between Xinglong and Beijing. Our work clearly confirms the Micius satellite as a robust platform for quantum key distribution with different ground stations on Earth, and points towards an efficient solution for an ultralong-distance global quantum network.
Previous studies found that cancer survivors had a reduced risk of dementia compared with the general population. However, these findings were uncertain because of survivor bias and a lack of ...stratification by cancer types. This current cohort study used data from the UK Biobank to explore these associations.
Multivariable Cox regression analyses were used to examine the association of cancer status and the risk of dementia with its subtypes after adjusting for age and sex. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated as a measure of relative risk by comparing observed dementia incidence among cancer patients.
We included 263,151 participants in the observational analysis. During a median follow-up of 9.18 years, dementia was diagnosed in 472 individuals with cancer and 3685 individuals without cancer, respectively. Cancer patients had lower risks of dementia (hazard ratio: 0.89, confidence interval: 0.81-0.98) and its subtypes (Alzheimer's disease AD: 0.85 0.74-0.98; vascular dementia VD: 0.81 0.66-0.99) in the Cox regression adjusted for age and sex. Individuals with cancers in the male genital system had substantially reduced risks of dementia (0.66 0.46-0.93) and AD (0.53 0.29-0.97) than those with cancers in other systems. Moreover, non-melanoma skin cancer and prostate cancer were associated with a reduced risk of dementia (0.79 0.62-0.99; 0.69 0.49-0.97), but not with AD or VD (P>0.05).
The current study supported a negative association between cancer and dementia risk, and encourages further exploration of the mechanistic basis of this inverse relationship to improve understanding.
The accumulation of silicon (Si) in the shoots varies considerably among plant species, but the mechanism responsible for this variation is poorly understood. The uptake system of Si was investigated ...in terms of the radial transport from the external solution to the root cortical cells and the release of Si from the cortical cells to the xylem in rice, cucumber, and tomato, which differ greatly in shoot Si concentration. Symplasmic solutions of the root tips were extracted by centrifugation. The concentrations of Si in the root-cell symplast in all species were higher than that in the external solution, although the concentration in rice was 3- and 5-fold higher than that in cucumber and tomato, respectively. A kinetic study showed that the radial transport of Si was mediated by a transporter with a Km value of 0.15 mM in all species, but with different Vmax values in the order of rice>cucumber>tomato. In the presence of the metabolic inhibitor 2,4-dinitrophenol, and at low temperature, the Si concentration in the root-cell symplast decreased to a level similar to that of the apoplasmic solution. These results suggest that both transporter-mediated transport and passive diffusion of Si are involved in the radial transport of Si and that the transporter-mediated transport is an energy-dependent process. The Si concentration of xylem sap in rice was 20- and 100-fold higher than that in cucumber and tomato, respectively. In contrast to rice, the Si concentration in the xylem sap was lower than that in the external solution in cucumber and tomato. A kinetic study showed that xylem loading of Si was also mediated by a kind of transporter in rice, but by passive diffusion in cucumber and tomato. These results indicate that a higher density of transporter for radial transport and the presence of a transporter for xylem loading are responsible for the high Si accumulation in rice.
Trivalent aluminium (Al3+) is the major toxin encountered by plants on acid soils. These cations inhibit root growth by damaging cells at the root apex. The physiology and genetics of Al3+ tolerance ...mechanisms involving organic anion efflux from roots have now been investigated in a range of species. Over the past decade, genes encoding these and other newly discovered mechanisms of tolerance have been cloned. In this review, we describe the genes controlling the genotypic variation in Al3+ tolerance for several important crop species. We focus on recent insights into the transcriptional regulation of these and other genes involved in Al3+ tolerance and discuss the pathways coordinating their expression in Arabidopsis and rice.
Summary
A number of plant species, including rice, secretes citrate from roots in response to Al stress. Here we characterized the functions of a gene, OsFRDL4 (Os01g0919100) that belongs to the ...multidrug and toxic compound extrusion (MATE) family in rice (Oryza sativa). Heterologous expression in Xenopus oocyte showed that the OsFRDL4 protein was able to transport citrate and was activated by Al. The expression level of the OsFRDL4 gene in roots was very low in the absence of Al, but was greatly enhanced by Al after short exposure. Furthermore, the OsFRDL4 expression was regulated by ART1, a C2H2‐type zinc finger transcription factor for Al tolerance. Transient expression of OsFRDL4 in onion epidermal cells showed that it localized to the plasma membrane. Immunostaining showed that OsFRDL4 was localized in all cells in the root tip. These expression patterns and cell specificity of localization of OsFRDL4 are different from other MATE members identified previously. Knockout of OsFRDL4 resulted in decreased Al tolerance and decreased citrate secretion compared with the wild‐type rice, but did not affect citrate concentration in the xylem sap. Furthermore, there is a positive correlation between OsFRDL4 expression level and the amount of citrate secretion in rice cultivars that are differing in Al tolerance. Taken together, our results show that OsFRDL4 is an Al‐induced citrate transporter localized at the plasma membrane of rice root cells and is one of the components of high Al tolerance in rice.
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