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Tao Q, Jupa R, Luo J, Lux A, Kováč J, Wen Y, Zhou Y, Jan J, Liang Y, Li T. The apoplasmic pathway via the root apex and lateral roots contributes to Cd hyperaccumulation in the hyperaccumulator Sedum alfredii. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:739-751. [PMID: 28204505 PMCID: PMC5441904 DOI: 10.1093/jxb/erw453] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Although the significance of apoplasmic barriers in roots with regards to the uptake of toxic elements is generally known, the contribution of apoplasmic bypasses (ABs) to cadmium (Cd) hyperaccumulation is little understood. Here, we employed a combination of stable isotopic tracer techniques, an ABs tracer, hydraulic measurements, suberin lamellae staining, metabolic inhibitors, and antitranspirants to investigate and quantify the impact of the ABs on translocation of Cd to the xylem in roots of a hyperaccumulating (H) ecotype and a non-hyperaccumulating (NH) ecotype of Sedum alfredii. In the H ecotype, the Cd content in the xylem sap was proportional to hydrostatic pressure, which was attributed to pressure-driven flow via the ABs. The contribution of the ABs to Cd transportation to the xylem was dependent on the Cd concentration applied to the H ecotype (up to 37% at the highest concentration used). Cd-treated H ecotype roots showed significantly higher hydraulic conductance compared with the NH ecotype (76 vs 52 × 10–8 m s–1MPa–1), which is in accordance with less extensive suberization due to reduced expression of suberin-related genes. The main entry sites of apoplasmically transported Cd were localized in the root apexes and lateral roots of the H ecotype, where suberin lamellae were not well developed. These findings highlight the significance of the apoplasmic bypass in Cd hyperaccumulation in hyperaccumulating ecotypes of S. alfredii.
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Affiliation(s)
- Qi Tao
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
- Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynska dolina, Bratislava, Slovakia
| | - Radek Jupa
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska, Brno, Czech Republic
| | - Jipeng Luo
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Alexander Lux
- Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynska dolina, Bratislava, Slovakia
| | - Ján Kováč
- Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynska dolina, Bratislava, Slovakia
| | - Yue Wen
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Yimei Zhou
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Japenga Jan
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Yongchao Liang
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Tingqiang Li
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
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Sahebi M, Hanafi MM, Siti Nor Akmar A, Rafii MY, Azizi P, Tengoua FF, Nurul Mayzaitul Azwa J, Shabanimofrad M. Importance of silicon and mechanisms of biosilica formation in plants. BIOMED RESEARCH INTERNATIONAL 2015; 2015:396010. [PMID: 25685787 PMCID: PMC4317640 DOI: 10.1155/2015/396010] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 12/18/2014] [Accepted: 12/23/2014] [Indexed: 11/17/2022]
Abstract
Silicon (Si) is one of the most prevalent macroelements, performing an essential function in healing plants in response to environmental stresses. The purpose of using Si is to induce resistance to distinct stresses, diseases, and pathogens. Additionally, Si can improve the condition of soils, which contain toxic levels of heavy metals along with other chemical elements. Silicon minimizes toxicity of Fe, Al, and Mn, increases the availability of P, and enhances drought along with salt tolerance in plants through the formation of silicified tissues in plants. However, the concentration of Si depends on the plants genotype and organisms. Hence, the physiological mechanisms and metabolic activities of plants may be affected by Si application. Peptides as well as amino acids can effectively create polysilicic species through interactions with different species of silicate inside solution. The carboxylic acid and the alcohol groups of serine and asparagine tend not to engage in any significant role in polysilicates formation, but the hydroxyl group side chain can be involved in the formation of hydrogen bond with Si(OH)4. The mechanisms and trend of Si absorption are different between plant species. Furthermore, the transportation of Si requires an energy mechanism; thus, low temperatures and metabolic repressors inhibit Si transportation.
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Affiliation(s)
- Mahbod Sahebi
- Laboratory of Plantation Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Mohamed M. Hanafi
- Laboratory of Plantation Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
- Department of Land Management, Faculty of Agriculture, 43400 Serdang, Selangor, Malaysia
| | - Abdullah Siti Nor Akmar
- Laboratory of Plantation Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Mohd Y. Rafii
- Laboratory of Food Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Parisa Azizi
- Laboratory of Food Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - F. F. Tengoua
- Laboratory of Plantation Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Jamaludin Nurul Mayzaitul Azwa
- Laboratory of Plantation Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - M. Shabanimofrad
- Laboratory of Food Crops, Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
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Fulweiler RW, Maguire TJ, Carey JC, Finzi AC. Does elevated CO2 alter silica uptake in trees? FRONTIERS IN PLANT SCIENCE 2015; 5:793. [PMID: 25628636 PMCID: PMC4292721 DOI: 10.3389/fpls.2014.00793] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Accepted: 12/19/2014] [Indexed: 05/11/2023]
Abstract
Human activities have greatly altered global carbon (C) and Nitrogen (N) cycling. In fact, atmospheric concentrations of carbon dioxide (CO2) have increased 40% over the last century and the amount of N cycling in the biosphere has more than doubled. In an effort to understand how plants will respond to continued global CO2 fertilization, long-term free-air CO2 enrichment experiments have been conducted at sites around the globe. Here we examine how atmospheric CO2 enrichment and N fertilization affects the uptake of silicon (Si) in the Duke Forest, North Carolina, a stand dominated by Pinus taeda (loblolly pine), and five hardwood species. Specifically, we measured foliar biogenic silica concentrations in five deciduous and one coniferous species across three treatments: CO2 enrichment, N enrichment, and N and CO2 enrichment. We found no consistent trends in foliar Si concentration under elevated CO2, N fertilization, or combined elevated CO2 and N fertilization. However, two-thirds of the tree species studied here have Si foliar concentrations greater than well-known Si accumulators, such as grasses. Based on net primary production values and aboveground Si concentrations in these trees, we calculated forest Si uptake rates under control and elevated CO2 concentrations. Due largely to increased primary production, elevated CO2 enhanced the magnitude of Si uptake between 20 and 26%, likely intensifying the terrestrial silica pump. This uptake of Si by forests has important implications for Si export from terrestrial systems, with the potential to impact C sequestration and higher trophic levels in downstream ecosystems.
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Affiliation(s)
- Robinson W. Fulweiler
- Department of Earth and the Environment, Boston UniversityBoston, MA, USA
- Department of Biology, Boston UniversityBoston, MA, USA
| | | | - Joanna C. Carey
- The Ecosystems Center, Marine Biological LaboratoryWoods Hole, MA, USA
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Krishnamurthy P, Ranathunge K, Nayak S, Schreiber L, Mathew MK. Root apoplastic barriers block Na+ transport to shoots in rice (Oryza sativa L.). JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4215-28. [PMID: 21558150 PMCID: PMC3153681 DOI: 10.1093/jxb/err135] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 03/26/2011] [Accepted: 04/04/2011] [Indexed: 05/18/2023]
Abstract
Rice is an important crop that is very sensitive to salinity. However, some varieties differ greatly in this feature, making investigations of salinity tolerance mechanisms possible. The cultivar Pokkali is salinity tolerant and is known to have more extensive hydrophobic barriers in its roots than does IR20, a more sensitive cultivar. These barriers located in the root endodermis and exodermis prevent the direct entry of external fluid into the stele. However, it is known that in the case of rice, these barriers are bypassed by most of the Na(+) that enters the shoot. Exposing plants to a moderate stress of 100 mM NaCl resulted in deposition of additional hydrophobic aliphatic suberin in both cultivars. The present study demonstrated that Pokkali roots have a lower permeability to water (measured using a pressure chamber) than those of IR20. Conditioning plants with 100 mM NaCl effectively reduced Na(+) accumulation in the shoot and improved survival of the plants when they were subsequently subjected to a lethal stress of 200 mM NaCl. The Na(+) accumulated during the conditioning period was rapidly released when the plants were returned to the control medium. It has been suggested that the location of the bypass flow is around young lateral roots, the early development of which disrupts the continuity of the endodermal and exodermal Casparian bands. However, in the present study, the observed increase in lateral root densities during stress in both cultivars did not correlate with bypass flow. Overall the data suggest that in rice roots Na(+) bypass flow is reduced by the deposition of apoplastic barriers, leading to improved plant survival under salt stress.
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Affiliation(s)
| | - Kosala Ranathunge
- Institute of Cellular and Molecular Botany (IZMB), University of Bonn, Kirschallee 1, D-53115, Bonn, Germany
| | - Shraddha Nayak
- National Centre for Biological Sciences, TIFR, Bangalore 560065, India
| | - Lukas Schreiber
- Institute of Cellular and Molecular Botany (IZMB), University of Bonn, Kirschallee 1, D-53115, Bonn, Germany
| | - M. K. Mathew
- National Centre for Biological Sciences, TIFR, Bangalore 560065, India
- To whom correspondence should be addressed. E-mail:
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Lin SI, Santi C, Jobet E, Lacut E, El Kholti N, Karlowski WM, Verdeil JL, Breitler JC, Périn C, Ko SS, Guiderdoni E, Chiou TJ, Echeverria M. Complex regulation of two target genes encoding SPX-MFS proteins by rice miR827 in response to phosphate starvation. PLANT & CELL PHYSIOLOGY 2010; 51:2119-31. [PMID: 21062869 DOI: 10.1093/pcp/pcq170] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Here we report on the characterization of rice osa-miR827 and its two target genes, OsSPX-MFS1 and OsSPX-MFS2, which encode SPX-MFS proteins predicted to be implicated in phosphate (Pi) sensing or transport. We first show by Northern blot analysis that osa-miR827 is strongly induced by Pi starvation in both shoots and roots. Hybridization of osa-miR827 in situ confirms its strong induction by Pi starvation, with signals concentrated in mesophyll, epidermis and ground tissues of roots. In parallel, we analyzed the responses of the two OsSPX-MFS1 and OsSPX-MFS2 gene targets to Pi starvation. OsSPX-MFS1 mRNA is mainly expressed in shoots under sufficient Pi supply while its expression is reduced on Pi starvation, revealing a direct relationship between induction of osa-miR827 and down-regulation of OsSPX-MFS1. In contrast, OsSPX-MFS2 responds in a diametrically opposed manner to Pi starvation. The accumulation of OsSPX-MFS2 mRNA is dramatically enhanced under Pi starvation, suggesting the involvement of complex regulation of osa-miR827 and its two target genes. We further produced transgenic rice lines overexpressing osa-miR827 and T-DNA knockout mutant lines in which the expression of osa-miR827 is abolished. Compared with wild-type controls, both target mRNAs exhibit similar changes, their expression being reduced and increased in overexpressing and knockout lines, respectively. This suggests that OsSPX-MFS1 and OsSPX-MFS2 are both negatively regulated by osa-miR827 abundance although they respond differently to external Pi conditions. We propose that this is a complex mechanism comprising fine tuning of spatial or temporal regulation of both targets by osa-miR827.
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MESH Headings
- Adaptation, Physiological
- DNA, Bacterial
- Gene Expression Regulation, Plant
- Genes, Plant
- MicroRNAs/physiology
- Oryza/cytology
- Oryza/genetics
- Oryza/metabolism
- Phosphates/deficiency
- Phosphates/metabolism
- Plant Roots/genetics
- Plant Shoots/genetics
- Plants, Genetically Modified/cytology
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/metabolism
- RNA Transport
- RNA, Messenger/genetics
- RNA, Plant/genetics
- Sequence Deletion
- Stress, Physiological
- Transcription, Genetic
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Affiliation(s)
- Shu-I Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
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Huang CF, Yamaji N, Nishimura M, Tajima S, Ma JF. A rice mutant sensitive to Al toxicity is defective in the specification of root outer cell layers. PLANT & CELL PHYSIOLOGY 2009; 50:976-85. [PMID: 19339508 DOI: 10.1093/pcp/pcp050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Outer cell layers of rice roots, which comprise epidermis, exodermis and sclerenchyma, have been proposed to protect the roots from various stresses in soil. Here, we report a mutant which is defective in the specification of outer cell layers, and examined the role of these layers in Al and other metal resistance. Morphological and histochemical observations revealed that the mutant isolated based on Al sensitivity frequently showed a disordered pattern of periclinal cell division in the epidermal layers at a region close to the root apical meristem. The lateral root caps in the mutant became difficult to peel off from the epidermis, and epidermal cells became smaller and irregular with far fewer root hairs. Furthermore, some exodermal cells were transformed into additional sclerenchyma cells. However, there was no difference in the inner cell layers between the wild-type rice and the mutant. The mutant showed similar root growth to the wild-type rice in the absence of Al, but greater inhibition of root elongation by Al was found in the mutant. Morin staining showed that Al penetrated into the inner cortical cells in the mutant. Furthermore, the mutant was also sensitive to other metals including Cd and La. Taken together, our results indicate that root outer cell layers protect the roots against the toxicity of Al and other metals by preventing metal penetration into the inner cells. Genetic analysis showed that the mutant phenotypes were controlled by a single recessive gene, which was located on the short arm of rice chromosome 2.
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Affiliation(s)
- Chao-Feng Huang
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
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Mitani N, Yamaji N, Ma JF. Identification of maize silicon influx transporters. PLANT & CELL PHYSIOLOGY 2009; 50:5-12. [PMID: 18676379 PMCID: PMC2638714 DOI: 10.1093/pcp/pcn110] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Accepted: 07/28/2008] [Indexed: 05/18/2023]
Abstract
Maize (Zea mays L.) shows a high accumulation of silicon (Si), but transporters involved in the uptake and distribution have not been identified. In the present study, we isolated two genes (ZmLsi1 and ZmLsi6), which are homologous to rice influx Si transporter OsLsi1. Heterologous expression in Xenopus laevis oocytes showed that both ZmLsi1 and ZmLsi6 are permeable to silicic acid. ZmLsi1 was mainly expressed in the roots. By contrast, ZmLsi6 was expressed more in the leaf sheaths and blades. Different from OsLsi1, the expression level of both ZmLsi1 and ZmLsi6 was unaffected by Si supply. Immunostaining showed that ZmLsi1 was localized on the plasma membrane of the distal side of root epidermal and hypodermal cells in the seminal and crown roots, and also in cortex cells in lateral roots. In the shoots, ZmLsi6 was found in the xylem parenchyma cells that are adjacent to the vessels in both leaf sheaths and leaf blades. ZmLsi6 in the leaf sheaths and blades also exhibited polar localization on the side facing towards the vessel. Taken together, it can be concluded that ZmLsi1 is an influx transporter of Si, which is responsible for the transport of Si from the external solution to the root cells and that ZmLsi6 mainly functions as a Si transporter for xylem unloading.
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Affiliation(s)
| | | | - Jian Feng Ma
- Research Institute for Bioresources, Okayama University, Kurashiki, 710-0046 Japan
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Guo ZG, Liu HX, Tian FP, Zhang ZH, Wang SM. Effect of silicon on the morphology of shoots and roots of alfalfa (Medicago sativa). ACTA ACUST UNITED AC 2006. [DOI: 10.1071/ea05117] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A silicon (Si)-deficient top soil was used in a pot experiment to investigate the effect of Si application on the shoot and root morphology of alfalfa (Medicago sativa L.). Silicon was applied to the alfalfa plants at 6 different rates (0, 0.025, 0.05, 0.10, 0.20, 0.30 g/kg), and each treatment was replicated 6 times. This study indicated that the Si content of roots and shoots increased significantly (P<0.05) with increasing Si concentration in the soil, and that the Si content of roots was greater than that of shoots. Plants treated with Si had increased leaf area, height, forage yield and shoots per plant during the reproductive period in comparison with controls. The application of Si also increased root volume, the number of secondary roots and root biomass. The effects of Si application were greater on roots than on shoots. The ratio of shoot to root dry weight was below 1.62 when Si was applied to plants and 1.91 without Si application. Overall, overcoming available Si deficiency resulted in a significant increase in shoot and root growth.
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