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Wei YM, Ren ZJ, Wang BH, Zhang L, Zhao YJ, Wu JW, Li LG, Zhang XS, Zhao XY. A nitrate transporter encoded by ZmNPF7.9 is essential for maize seed development. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2021; 308:110901. [PMID: 34034862 DOI: 10.1016/j.plantsci.2021.110901] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 03/23/2021] [Accepted: 03/26/2021] [Indexed: 06/12/2023]
Abstract
Nitrogen is an essential macronutrient for plants and regulates many aspects of plant growth and development. Nitrate is one of the major forms of nitrogen in plants. However, the role of nitrate uptake and allocation in seed development is not fully understood. Here, we identified the maize (Zea mays) small-kernel mutant zmnpf7.9 and characterized the candidate gene, ZmNPF7.9, which was the same gene as nitrate transport 1.5 (NRT1.5) in maize. This gene is specifically expressed in the basal endosperm transfer layer cells of maize endosperm. Dysfunction of ZmNPF7.9 resulted in delayed endosperm development, abnormal starch deposition and decreased hundred-grain weight. Functional analysis of cRNA-injected Xenopus oocytes showed that ZmNPF7.9 is a low-affinity, pH-dependent bidirectional nitrate transporter. Moreover, the amount of nitrate in mature seeds of the zmnpf7.9 mutant was reduced. These suggest that ZmNPF7.9 is involved in delivering nitrate from maternal tissues to the developing endosperm. Moreover, most of the key genes associated with glycolysis/gluconeogenesis, carbon fixation, carbon metabolism and biosynthesis of amino acids pathways in the zmnpf7.9 mutant were significantly down-regulated. Thus, our results demonstrate that ZmNPF7.9 plays a specific role in seed development and grain weight by regulating nutrition transport and metabolism, which might provide useful information for maize genetic improvement.
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Affiliation(s)
- Yi Ming Wei
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China
| | - Zhi Jie Ren
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Bo Hui Wang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China
| | - Lin Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China
| | - Ya Jie Zhao
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China
| | - Jia Wen Wu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China
| | - Le Gong Li
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Xian Sheng Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China; College of Life Sciences, Capital Normal University, Beijing, 100048, China.
| | - Xiang Yu Zhao
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China; College of Life Sciences, Capital Normal University, Beijing, 100048, China.
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Ma Z, Bykova NV, Igamberdiev AU. Cell signaling mechanisms and metabolic regulation of germination and dormancy in barley seeds. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.cj.2017.08.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Szewińska J, Simińska J, Bielawski W. The roles of cysteine proteases and phytocystatins in development and germination of cereal seeds. JOURNAL OF PLANT PHYSIOLOGY 2016; 207:10-21. [PMID: 27771502 DOI: 10.1016/j.jplph.2016.09.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Proteolysis is an important process for development and germination of cereal seeds. Among the many types of proteases identified in plants are the cysteine proteases (CPs) of the papain and legumain families, which play a crucial role in hydrolysing storage proteins during seed germination as well as in processing the precursors of these proteins and the inactive forms of other proteases. Moreover, all of the tissues of cereal seeds undergo progressive degradation via programed cell death, which is integral to their growth. In view of the important roles played by proteases, their uncontrolled activity could be harmful to the development of seeds and young seedlings. Thus, the activities of these enzymes are regulated by intracellular inhibitors called phytocystatins (PhyCys). The phytocystatins inhibit the activity of proteases of the papain family, and the presence of an additional motif in their C-termini allows them to also regulate the activity of members of the legumain family. A balance between the levels of cysteine proteases and phytocystatins is necessary for proper cereal seed development, and this is maintained through the antagonistic activities of gibberellins (GAs) and abscisic acid (ABA), which regulate the expression of the corresponding genes. Transcriptional regulation of cysteine proteases and phytocystatins is determined by cis-acting elements located in the promoters of these genes and by the expression of their corresponding transcription factors (TFs) and the interactions between different TFs.
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Affiliation(s)
- Joanna Szewińska
- Warsaw University of Life Sciences-SGGW, Faculty of Agriculture and Biology, Department of Biochemistry, Nowoursynowska 159 street, Warsaw 02-776, Poland.
| | - Joanna Simińska
- Warsaw University of Life Sciences-SGGW, Faculty of Agriculture and Biology, Department of Biochemistry, Nowoursynowska 159 street, Warsaw 02-776, Poland
| | - Wiesław Bielawski
- Warsaw University of Life Sciences-SGGW, Faculty of Agriculture and Biology, Department of Biochemistry, Nowoursynowska 159 street, Warsaw 02-776, Poland
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Aryal UK, Ross ARS, Krochko JE. Enrichment and Analysis of Intact Phosphoproteins in Arabidopsis Seedlings. PLoS One 2015; 10:e0130763. [PMID: 26158488 PMCID: PMC4497735 DOI: 10.1371/journal.pone.0130763] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 05/23/2015] [Indexed: 12/19/2022] Open
Abstract
Protein phosphorylation regulates diverse cellular functions and plays a key role in the early development of plants. To complement and expand upon previous investigations of protein phosphorylation in Arabidopsis seedlings we used an alternative approach that combines protein extraction under non-denaturing conditions with immobilized metal-ion affinity chromatography (IMAC) enrichment of intact phosphoproteins in Rubisco-depleted extracts, followed by identification using two-dimensional gel electrophoresis (2-DE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In-gel trypsin digestion and analysis of selected gel spots identified 144 phosphorylated peptides and residues, of which only18 phosphopeptides and 8 phosphosites were found in the PhosPhAt 4.0 and P3DB Arabidopsis thaliana phosphorylation site databases. More than half of the 82 identified phosphoproteins were involved in carbohydrate metabolism, photosynthesis/respiration or oxidative stress response mechanisms. Enrichment of intact phosphoproteins prior to 2-DE and LC-MS/MS appears to enhance detection of phosphorylated threonine and tyrosine residues compared with methods that utilize peptide-level enrichment, suggesting that the two approaches are somewhat complementary in terms of phosphorylation site coverage. Comparing results for young seedlings with those obtained previously for mature Arabidopsis leaves identified five proteins that are differentially phosphorylated in these tissues, demonstrating the potential of this technique for investigating the dynamics of protein phosphorylation during plant development.
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Affiliation(s)
- Uma K. Aryal
- National Research Council of Canada, Saskatoon, SK, S7N 0W9, Canada
| | - Andrew R. S. Ross
- National Research Council of Canada, Saskatoon, SK, S7N 0W9, Canada
- * E-mail:
| | - Joan E. Krochko
- National Research Council of Canada, Saskatoon, SK, S7N 0W9, Canada
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Pratelli R, Pilot G. Regulation of amino acid metabolic enzymes and transporters in plants. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:5535-56. [PMID: 25114014 DOI: 10.1093/jxb/eru320] [Citation(s) in RCA: 196] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Amino acids play several critical roles in plants, from providing the building blocks of proteins to being essential metabolites interacting with many branches of metabolism. They are also important molecules that shuttle organic nitrogen through the plant. Because of this central role in nitrogen metabolism, amino acid biosynthesis, degradation, and transport are tightly regulated to meet demand in response to nitrogen and carbon availability. While much is known about the feedback regulation of the branched biosynthesis pathways by the amino acids themselves, the regulation mechanisms at the transcriptional, post-transcriptional, and protein levels remain to be identified. This review focuses mainly on the current state of our understanding of the regulation of the enzymes and transporters at the transcript level. Current results describing the effect of transcription factors and protein modifications lead to a fragmental picture that hints at multiple, complex levels of regulation that control and coordinate transport and enzyme activities. It also appears that amino acid metabolism, amino acid transport, and stress signal integration can influence each other in a so-far unpredictable fashion.
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Affiliation(s)
- Réjane Pratelli
- Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA 24060, USA
| | - Guillaume Pilot
- Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA 24060, USA
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Fan X, Xie D, Chen J, Lu H, Xu Y, Ma C, Xu G. Over-expression of OsPTR6 in rice increased plant growth at different nitrogen supplies but decreased nitrogen use efficiency at high ammonium supply. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 227:1-11. [PMID: 25219300 DOI: 10.1016/j.plantsci.2014.05.013] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Revised: 05/19/2014] [Accepted: 05/21/2014] [Indexed: 05/20/2023]
Abstract
Nitrogen (N) plays a critical role in plant growth and productivity and PTR/NRT1 transporters are critical for rice growth. In this study, OsPTR6, a PTR/NRT1 transporter, was over-expressed in the Nipponbare rice cultivar by Agrobacterium tumefaciens transformation using the ubiquitin (Ubi) promoter. Three single-copy T2 generation transgenic lines, named OE1, OE5 and OE6, were produced and subjected to hydroponic growth experiments in different nitrogen treatments. The results showed the plant height and biomass of the over-expression lines were increased, and plant N accumulation and glutamine synthetase (GS) activities were enhanced at 5.0mmol/L NH4(+) and 2.5mmol/L NH4NO3. The expression of OsATM1 genes in over-expression lines showed that the OsPTR6 over expression increased OsAMT1.1, OsATM1.2 and OsAMT1.3 expression at 0.2 and 5.0mmol/L NH4(+) and 2.5mmol/L NH4NO3. However, nitrogen utilisation efficiency (NUE) was decreased at 5.0mmol/LNH4(+). These data suggest that over-expression of the OsPTR6 gene could increase rice growth through increasing ammonium transporter expression and glutamine synthetase activity (GSA), but decreases nitrogen use efficiency under conditions of high ammonium supply.
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Affiliation(s)
- Xiaorong Fan
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
| | - Dan Xie
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Jingguang Chen
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Haiyan Lu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Yanling Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Cui Ma
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Guohua Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
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Tnani H, López-Ribera I, García-Muniz N, Vicient CM. ZmPTR1, a maize peptide transporter expressed in the epithelial cells of the scutellum during germination. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2013; 207:140-147. [PMID: 23602109 DOI: 10.1016/j.plantsci.2013.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 03/08/2013] [Accepted: 03/09/2013] [Indexed: 06/02/2023]
Abstract
In plants, peptide transporter/nitrate transporter 1 (PTR/NRT1) family proteins transport a variety of substrates such as nitrate, di- and tripepetides, auxin and carboxylates across membranes. We isolated and characterized ZmPTR1, a maize member of this family. ZmPTR1 protein sequence is highly homologous to the previously characterized di- and tripeptide Arabidopsis transporters AtPTR2, AtPTR4 and AtPTR6. ZmPTR1 gene is expressed in the cells of the scutellar epithelium during germination and, to a less extent, in the radicle and the hypocotyl. Arabidopsis thaliana lines overexpressing ZmPTR1 performed better than control plants when grown on a medium with Ala-Ala dipeptide as the unique N source. Our results suggest that ZmPTR1 plays a role in the transport into the embryo of the small peptides produced during enzymatic hydrolysis of the storage proteins in the endosperm.
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Affiliation(s)
- Hedia Tnani
- Department of Molecular Genetics, Centre for Research in Agrigenomics CSIC-IRTA-UAB-UB, Campus Universitat Autònoma de Barcelona, Bellaterra-Cerdanyola del Vallès, 08193 Barcelona, Spain
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Tnani H, García-Muniz N, Vicient CM, López-Ribera I. Expression profile of maize (Zea mays) scutellar epithelium during imbibition. JOURNAL OF PLANT PHYSIOLOGY 2012; 169:1430-1433. [PMID: 22784472 DOI: 10.1016/j.jplph.2012.05.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 05/10/2012] [Accepted: 05/11/2012] [Indexed: 06/01/2023]
Abstract
The scutellum is a shield-shaped structure surrounding the embryo axis in grass species. The scutellar epithelium (Sep) is a monolayer of cells in contact with the endosperm. The Sep plays an important role during seed germination in the secretion of gibberellins and hydrolytic enzymes and in the transport of the hydrolized products to the growing embryo. We identified 30 genes predominantly expressed after imbibition in the Sep as compared to other parts of the scutellum. A high proportion of these genes is involved in metabolic processes. Some other identified genes are involved in the synthesis or modification of cell walls, which may be reflected in the changes of cell shape and cell wall composition that can be observed during imbibition. One of the genes encodes a proteinase that belongs to a proteinase family typical of carnivorous plants. Almost nothing is known about their role in other plants or organs, but the scutellar presence may point to a "digestive" function during germination. Genes involved in the production of energy and the transport of peptides were also identified.
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Affiliation(s)
- Hedia Tnani
- Department of Molecular Genetics, Centre for Research in Agrigenomics CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès, Barcelona), Spain
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Tegeder M, Rentsch D. Uptake and partitioning of amino acids and peptides. MOLECULAR PLANT 2010; 3:997-1011. [PMID: 21081651 DOI: 10.1093/mp/ssq047] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Plant growth, productivity, and seed yield depend on the efficient uptake, metabolism, and allocation of nutrients. Nitrogen is an essential macronutrient needed in high amounts. Plants have evolved efficient and selective transport systems for nitrogen uptake and transport within the plant to sustain development, growth, and finally reproduction. This review summarizes current knowledge on membrane proteins involved in transport of amino acids and peptides. A special emphasis was put on their function in planta. We focus on uptake of the organic nitrogen by the root, source-sink partitioning, and import into floral tissues and seeds.
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Affiliation(s)
- Mechthild Tegeder
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA.
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Zhao X, Huang J, Yu H, Wang L, Xie W. Genomic survey, characterization and expression profile analysis of the peptide transporter family in rice (Oryza sativa L.). BMC PLANT BIOLOGY 2010; 10:92. [PMID: 20487558 PMCID: PMC3017762 DOI: 10.1186/1471-2229-10-92] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 05/20/2010] [Indexed: 05/21/2023]
Abstract
BACKGROUND Peptide transporter (PTR) family whose member can transport di-/tripeptides and nitrate is important for plant growth and development. Although the rice (Oryza sativa L.) genome has been sequenced for a few years, a genomic survey, characterization and expression profile analysis of the PTR family in this species has not been reported. RESULTS In this study, we report a comprehensive identification, characterization, phylogenetic and evolutionary analysis of 84 PTR family members in rice (OsPTR) as well as their whole-life expression patterns. Chromosomal distribution and sequence analysis indicate that nearly 70% of OsPTR members are involved in the tandem and segmental duplication events. It suggests that genome duplication might be a major mechanism for expansion of this family. Highly conserved motifs were identified in most of the OsPTR members. Meanwhile, expression profile of OsPTR genes has been analyzed by using Affymetrix rice microarray and real-time PCR in two elite hybrid rice parents, Minghui 63 and Zhenshan 97. Seven genes are found to exhibit either preferential or tissue-specific expression during different development stages of rice. Under phytohormone (NAA, GA3 and KT) and light/dark treatments, 14 and 17 OsPTR genes are differentially expressed respectively. Ka/Ks analysis of the paralogous OsPTR genes indicates that purifying selection plays an important role in function maintenance of this family. CONCLUSION These investigations add to our understanding of the importance of OsPTR family members and provide useful reference for selecting candidate genes for functional validation studies of this family in rice.
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Affiliation(s)
- Xiaobo Zhao
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China
| | - Jianyan Huang
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China
| | - Huihui Yu
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China
| | - Lei Wang
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China
| | - Weibo Xie
- National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China
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Paungfoo-Lonhienne C, Schenk PM, Lonhienne TGA, Brackin R, Meier S, Rentsch D, Schmidt S. Nitrogen affects cluster root formation and expression of putative peptide transporters. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:2665-76. [PMID: 19380419 PMCID: PMC2692012 DOI: 10.1093/jxb/erp111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 03/10/2009] [Accepted: 03/16/2009] [Indexed: 05/18/2023]
Abstract
Non-mycorrhizal Hakea actites (Proteaceae) grows in heathland where organic nitrogen (ON) dominates the soil nitrogen (N) pool. Hakea actites uses ON for growth, but the role of cluster roots in ON acquisition is unknown. The aim of the present study was to ascertain how N form and concentration affect cluster root formation and expression of peptide transporters. Hydroponically grown plants produced most biomass with low molecular weight ON>inorganic N>high molecular weight ON, while cluster roots were formed in the order no-N>ON>inorganic N. Intact dipeptide was transported into roots and metabolized, suggesting a role for the peptide transporter (PTR) for uptake and transport of peptides. HaPTR4, a member of subgroup II of the NRT1/PTR transporter family, which contains most characterized di- and tripeptide transporters in plants, facilitated transport of di- and tripeptides when expressed in yeast. No transport activity was demonstrated for HaPTR5 and HaPTR12, most similar to less well characterized transporters in subgroup III. The results provide further evidence that subgroup II of the NRT1/PTR family contains functional di- and tripeptide transporters. Green fluorescent protein fusion proteins of HaPTR4 and HaPTR12 localized to tonoplast, and plasma- and endomembranes, respectively, while HaPTR5 localized to vesicles of unknown identity. Grown in heathland or hydroponic culture with limiting N supply or starved of nutrients, HaPTR genes had the highest expression in cluster roots and non-cluster roots, and leaf expression increased upon re-supply of ON. It is concluded that formation of cluster roots and expression of PTR are regulated in response to N supply.
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Almagro A, Lin SH, Tsay YF. Characterization of the Arabidopsis nitrate transporter NRT1.6 reveals a role of nitrate in early embryo development. THE PLANT CELL 2008; 20:3289-99. [PMID: 19050168 PMCID: PMC2630450 DOI: 10.1105/tpc.107.056788] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 11/05/2008] [Accepted: 11/12/2008] [Indexed: 05/18/2023]
Abstract
This study of the Arabidopsis thaliana nitrate transporter NRT1.6 indicated that nitrate is important for early embryo development. Functional analysis of cDNA-injected Xenopus laevis oocytes showed that NRT1.6 is a low-affinity nitrate transporter and does not transport dipeptides. RT-PCR, in situ hybridization, and beta-glucuronidase reporter gene analysis showed that expression of NRT1.6 is only detectable in reproductive tissue (the vascular tissue of the silique and funiculus) and that expression increases immediately after pollination, suggesting that NRT1.6 is involved in delivering nitrate from maternal tissue to the developing embryo. In nrt1.6 mutants, the amount of nitrate accumulated in mature seeds was reduced and the seed abortion rate increased. In the mutants, abnormalities (i.e., excessive cell division and loss of turgidity), were found mainly in the suspensor cells at the one- or two-cell stages of embryo development. The phenotype of the nrt1.6 mutants revealed a novel role of nitrate in early embryo development. Interestingly, the seed abortion rate of the mutant was reduced when grown under N-deficient conditions, suggesting that nitrate requirements in early embryo development can be modulated in response to external nitrogen changes.
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Affiliation(s)
- Anabel Almagro
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
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Conde C, Silva P, Agasse A, Tavares RM, Delrot S, Gerós H. An Hg-sensitive channel mediates the diffusional component of glucose transport in olive cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2801-11. [PMID: 17706590 DOI: 10.1016/j.bbamem.2007.07.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Revised: 07/10/2007] [Accepted: 07/17/2007] [Indexed: 10/23/2022]
Abstract
In several organisms solute transport is mediated by the simultaneous operation of saturable and non-saturable (diffusion-like) uptake, but often the nature of the diffusive component remains elusive. The present work investigates the nature of the diffusive glucose transport in Olea europaea cell cultures. In this system, glucose uptake is mediated by a glucose-repressible, H(+) -dependent active saturable transport system that is superimposed on a diffusional component. The latter represents the major mode of uptake when high external glucose concentrations are provided. In glucose-sufficient cells, initial velocities of D- and L-[U-(14)C]glucose uptake were equal and obeyed linear concentration dependence up to 100 mM sugar. In sugar starved cells, where glucose transport is mediated by the saturable system, countertransport of the sugar pairs 3-O-methyl-D-glucose/D-[U-(14)C]glucose and 3-O-methyl-D-glucose/3-O-methyl-D-[U-(14)C]glucose was demonstrated. This countertransport was completely absent in glucose-sufficient cells, indicating that linear glucose uptake is not mediated by a typical sugar permease. The endocytic inhibitors wortmannin-A and NH(4)Cl inhibited neither the linear component of D- and L-glucose uptake nor the absorption of the nonmetabolizable glucose analog 3-O-methyl-D-[U-(14)C]glucose, thus excluding the involvement of endocytic mediated glucose uptake. Furthermore, the formation of endocytic vesicles assessed with the marker FM1-43 proceeded at a very slow rate. Activation energies for glucose transport in glucose sufficient cells and plasma membrane vesicles were 7 and 4 kcal mol(-1), respectively, lower than the value estimated for diffusion of glucose through the lipid bilayer of phosphatidylethanolamine liposomes (12 kcal mol(-1)). Mercury chloride inhibited both the linear component of sugar uptake in sugar sufficient cells and plasma membrane vesicles, and the incorporation of the fluorescent glucose analog 2-NBDG, suggesting protein-mediated transport. Diffusive uptake of glucose was inhibited by a drop in cytosolic pH and stimulated by the protein kinase inhibitor staurosporine. The data demonstrate that the low-affinity, high-capacity, diffusional component of glucose uptake occurs through a channel-like structure whose transport capacity may be regulated by intracellular protonation and phosphorylation/dephosphorylation.
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Affiliation(s)
- Carlos Conde
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
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Tsay YF, Chiu CC, Tsai CB, Ho CH, Hsu PK. Nitrate transporters and peptide transporters. FEBS Lett 2007; 581:2290-300. [PMID: 17481610 DOI: 10.1016/j.febslet.2007.04.047] [Citation(s) in RCA: 326] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2007] [Revised: 04/17/2007] [Accepted: 04/20/2007] [Indexed: 11/17/2022]
Abstract
In higher plants, two types of nitrate transporters, NRT1 and NRT2, have been identified. In Arabidopsis, there are 53 NRT1 genes and 7 NRT2 genes. NRT2 are high-affinity nitrate transporters, while most members of the NRT1 family are low-affinity nitrate transporters. The exception is CHL1 (AtNRT1.1), which is a dual-affinity nitrate transporter, its mode of action being switched by phosphorylation and dephosphorylation of threonine 101. Two of the NRT1 genes, CHL1 and AtNRT1.2, and two of the NRT2 genes, AtNRT2.1 and AtNRT2.2, are known to be involved in nitrate uptake. In addition, AtNRT1.4 is required for petiole nitrate storage. On the other hand, some members of the NRT1 family are dipeptide transporters, called PTRs, which transport a broad spectrum of di/tripeptides. In barley, HvPTR1, expressed in the plasma membrane of scutellar epithelial cells, is involved in mobilizing peptides, produced by hydrolysis of endosperm storage protein, to the developing embryo. In higher plants, there is another family of peptide transporters, called oligopeptide transporters (OPTs), which transport tetra/pentapeptides. In addition, some OPTs transport GSH, GSSH, GSH conjugates, phytochelatins, and metals.
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Affiliation(s)
- Yi-Fang Tsay
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
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WATERWORTH WANDAM, BRAY CLIFFORDM. Enigma variations for peptides and their transporters in higher plants. ANNALS OF BOTANY 2006; 98:1-8. [PMID: 16735405 PMCID: PMC2803549 DOI: 10.1093/aob/mcl099] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
BACKGROUND Two families of proteins that transport small peptides, the oligopeptide transporters (OPTs) and the peptide transporters (PTRs), have been recognized in eukaryotes. Higher plants contain a far greater number of genes for these transporters than do other eukaryotes. This may be indicative of the relative importance of (oligo)peptides and their transport to plant growth and metabolism. RECENT PROGRESS Recent studies are now allowing us to assign functions to these transporters and are starting to identify their in-planta substrates, revealing unexpected and important contributions of the transporters to plant growth and developmental processes. This Botanical Briefing appraises recent findings that PTRs and OPTs have key roles to play in the control of plant cell growth and development. Evidence is presented that some of these transporters have functions outside that of nitrogen nutrition and that these carriers can also surprise us with their totally unexpected choice of substrates.
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