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Dinkeloo K, Pelly Z, McDowell JM, Pilot G. A split green fluorescent protein system to enhance spatial and temporal sensitivity of translating ribosome affinity purification. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 111:304-315. [PMID: 35436375 PMCID: PMC9544980 DOI: 10.1111/tpj.15779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/29/2022] [Accepted: 04/07/2022] [Indexed: 06/14/2023]
Abstract
Translating ribosome affinity purification (TRAP) utilizes transgenic plants expressing a ribosomal protein fused to a tag for affinity co-purification of ribosomes and the mRNAs that they are translating. This population of actively translated mRNAs (translatome) can be interrogated by quantitative PCR or RNA sequencing. Condition- or cell-specific promoters can be utilized to isolate the translatome of specific cell types, at different growth stages and/or in response to environmental variables. While advantageous for revealing differential expression, this approach may not provide sufficient sensitivity when activity of the condition/cell-specific promoter is weak, when ribosome turnover is low in the cells of interest, or when the targeted cells are ephemeral. In these situations, expressing tagged ribosomes under the control of these specific promoters may not yield sufficient polysomes for downstream analysis. Here, we describe a new TRAP system that employs two transgenes: One is constitutively expressed and encodes a ribosomal protein fused to one fragment of a split green fluorescent protein (GFP); the second is controlled by a stimulus-specific promoter and encodes the second GFP fragment fused to an affinity purification tag. In cells where both transgenes are active, the purification tag is attached to ribosomes by bi-molecular folding and assembly of the split GFP fragments. This approach provides increased sensitivity and better temporal resolution because it labels pre-existing ribosomes and does not depend on rapid ribosome turnover. We describe the optimization and key parameters of this system, and then apply it to a plant-pathogen interaction in which spatial and temporal resolution are difficult to achieve with current technologies.
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Affiliation(s)
- Kasia Dinkeloo
- School of Plant and Environmental Sciences, Virginia TechBlacksburgVirginia24061USA
| | - Zoe Pelly
- School of Plant and Environmental Sciences, Virginia TechBlacksburgVirginia24061USA
| | - John M. McDowell
- School of Plant and Environmental Sciences, Virginia TechBlacksburgVirginia24061USA
| | - Guillaume Pilot
- School of Plant and Environmental Sciences, Virginia TechBlacksburgVirginia24061USA
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Yu C, Yan M, Dong H, Luo J, Ke Y, Guo A, Chen Y, Zhang J, Huang X. Maize bHLH55 functions positively in salt tolerance through modulation of AsA biosynthesis by directly regulating GDP-mannose pathway genes. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2021; 302:110676. [PMID: 33288001 DOI: 10.1016/j.plantsci.2020.110676] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 08/31/2020] [Accepted: 09/03/2020] [Indexed: 05/21/2023]
Abstract
Ascorbic acid (AsA) is an antioxidant and enzyme co-factor that is vital to plant development and abiotic stress tolerance. However, the regulation mechanisms of AsA biosynthesis in plants remain poorly understood. Here, we report a basic helix-loop-helix 55 (ZmbHLH55) transcription factor that regulates AsA biosynthesis in maize. Analysis of publicly available transcriptomic data revealed that ZmbHLH55 is co-expressed with several genes of the GDP-mannose pathway. Experimental data showed that ZmbHLH55 forms homodimers localized to the cell nuclei, and it exhibits DNA binding and transactivation activity in yeast. Under salt stress conditions, knock down mutant (zmbhlh55) in maize accumulated lower levels of AsA compared with wild type, accompanied by lower antioxidant enzymes activity, shorter root length, and higher malondialdehyde (MDA) level. Gene expression data from the WT and zmbhlh55 mutant, showed that ZmbHLH55 positively regulates the expression of ZmPGI2, ZmGME1, and ZmGLDH, but negatively regulates ZmGMP1 and ZmGGP. Furthermore, ZmbHLH55-overexpressing Arabidopsis, under salt conditions, showed higher AsA levels, increased rates of germination, and elevated antioxidant enzyme activities. In conclusion, these results have identified previously unknown regulation mechanisms for AsA biosynthesis, indicating that ZmbHLH55 may be a potential candidate to enhance plant salt stress tolerance in the future.
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Affiliation(s)
- Chunmei Yu
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Ming Yan
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Huizhen Dong
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Jie Luo
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Yongchao Ke
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Anfang Guo
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Yanhong Chen
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Jian Zhang
- Ministry of Agriculture Scientific Observing and Experimental Station of Maize in Plain Area of Southern Region, School of Life Sciences, Nantong University, 226019, China
| | - Xiaosan Huang
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
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3
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Narjala A, Nair A, Tirumalai V, Hari Sundar GV, Shivaprasad PV. A conserved sequence signature is essential for robust plant miRNA biogenesis. Nucleic Acids Res 2020; 48:3103-3118. [PMID: 32025695 PMCID: PMC7102948 DOI: 10.1093/nar/gkaa077] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 01/23/2020] [Accepted: 01/29/2020] [Indexed: 12/19/2022] Open
Abstract
Micro (mi)RNAs are 20–22nt long non-coding RNA molecules involved in post-transcriptional silencing of targets having high base-pair complementarity. Plant miRNAs are processed from long Pol II-transcripts with specific stem-loop structures by Dicer-like (DCL) 1 protein. Although there were reports indicating how a specific region is selected for miRNA biogenesis, molecular details were unclear. Here, we show that the presence of specific GC-rich sequence signature within miRNA/miRNA* region is required for the precise miRNA biogenesis. The involvement of GC-rich signatures in precise processing and abundance of miRNAs was confirmed through detailed molecular and functional analysis. Consistent with the presence of the miRNA-specific GC signature, target RNAs of miRNAs also possess conserved complementary sequence signatures in their miRNA binding motifs. The selection of these GC signatures was dependent on an RNA binding protein partner of DCL1 named HYL1. Finally, we demonstrate a direct application of this discovery for enhancing the abundance and efficiency of artificial miRNAs that are popular in plant functional genomic studies.
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Affiliation(s)
- Anushree Narjala
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India.,SASTRA University, Thirumalaisamudram, Thanjavur 613401, India
| | - Ashwin Nair
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India.,SASTRA University, Thirumalaisamudram, Thanjavur 613401, India
| | - Varsha Tirumalai
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India.,SASTRA University, Thirumalaisamudram, Thanjavur 613401, India
| | - G Vivek Hari Sundar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India
| | - Padubidri V Shivaprasad
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India
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Sánchez-Simarro J, Bernat-Silvestre C, Gimeno-Ferrer F, Selvi-Martínez P, Montero-Pau J, Aniento F, Marcote MJ. Loss of Arabidopsis β-COP Function Affects Golgi Structure, Plant Growth and Tolerance to Salt Stress. FRONTIERS IN PLANT SCIENCE 2020; 11:430. [PMID: 32351533 PMCID: PMC7175232 DOI: 10.3389/fpls.2020.00430] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 03/24/2020] [Indexed: 05/20/2023]
Abstract
The early secretory pathway involves bidirectional transport between the endoplasmic reticulum (ER) and the Golgi apparatus and is mediated by coat protein complex I (COPI)-coated and coat protein complex II (COPII)-coated vesicles. COPII vesicles are involved in ER to Golgi transport meanwhile COPI vesicles mediate intra-Golgi transport and retrograde transport from the Golgi apparatus to the ER. The key component of COPI vesicles is the coatomer complex, that is composed of seven subunits (α/β/β'/γ/δ/ε/ζ). In Arabidopsis two genes coding for the β-COP subunit have been identified, which are the result of recent tandem duplication. Here we have used a loss-of-function approach to study the function of β-COP. The results we have obtained suggest that β-COP is required for plant growth and salt tolerance. In addition, β-COP function seems to be required for maintaining the structure of the Golgi apparatus.
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Carbonell A, López C, Daròs JA. Fast-Forward Identification of Highly Effective Artificial Small RNAs Against Different Tomato spotted wilt virus Isolates. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2019; 32:142-156. [PMID: 30070616 DOI: 10.1094/mpmi-05-18-0117-ta] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Artificial small RNAs (sRNAs), including artificial microRNAs (amiRNAs) and synthetic trans-acting small interfering RNAs (syn-tasiRNAs), are used to silence viral RNAs and confer antiviral resistance in plants. Here, the combined use of recent high-throughput methods for generating artificial sRNA constructs and the Tomato spotted wilt virus (TSWV)-Nicotiana benthamiana pathosystem allowed for the simple and rapid identification of amiRNAs with high anti-TSWV activity. A comparative analysis between the most effective amiRNA construct and a syn-tasiRNA construct including the four most effective amiRNA sequences showed that both were highly effective against two different TSWV isolates. These results highlight the usefulness of this high-throughput methodology for the fast-forward identification of artificial sRNAs with high antiviral activity prior to time-consuming generation of stably transformed plants.
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Affiliation(s)
- Alberto Carbonell
- 1 Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València), 46022 Valencia, Spain; and
| | - Carmelo López
- 2 Instituto de Conservación y Mejora de la Agrodiversidad Valenciana, Universitat Politècnica de València, 46022 Valencia, Spain
| | - José-Antonio Daròs
- 1 Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València), 46022 Valencia, Spain; and
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Abstract
Plants are attractive platforms for synthetic biology and metabolic engineering. Plants' modular and plastic body plans, capacity for photosynthesis, extensive secondary metabolism, and agronomic systems for large-scale production make them ideal targets for genetic reprogramming. However, efforts in this area have been constrained by slow growth, long life cycles, the requirement for specialized facilities, a paucity of efficient tools for genetic manipulation, and the complexity of multicellularity. There is a need for better experimental and theoretical frameworks to understand the way genetic networks, cellular populations, and tissue-wide physical processes interact at different scales. We highlight new approaches to the DNA-based manipulation of plants and the use of advanced quantitative imaging techniques in simple plant models such as Marchantia polymorpha. These offer the prospects of improved understanding of plant dynamics and new approaches to rational engineering of plant traits.
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Affiliation(s)
- Christian R Boehm
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Bernardo Pollak
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | | | | | - Jim Haseloff
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
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Moyle RL, Carvalhais LC, Pretorius LS, Nowak E, Subramaniam G, Dalton-Morgan J, Schenk PM. An Optimized Transient Dual Luciferase Assay for Quantifying MicroRNA Directed Repression of Targeted Sequences. FRONTIERS IN PLANT SCIENCE 2017; 8:1631. [PMID: 28979287 PMCID: PMC5611435 DOI: 10.3389/fpls.2017.01631] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 09/05/2017] [Indexed: 05/04/2023]
Abstract
Studies investigating the action of small RNAs on computationally predicted target genes require some form of experimental validation. Classical molecular methods of validating microRNA action on target genes are laborious, while approaches that tag predicted target sequences to qualitative reporter genes encounter technical limitations. The aim of this study was to address the challenge of experimentally validating large numbers of computationally predicted microRNA-target transcript interactions using an optimized, quantitative, cost-effective, and scalable approach. The presented method combines transient expression via agroinfiltration of Nicotiana benthamiana leaves with a quantitative dual luciferase reporter system, where firefly luciferase is used to report the microRNA-target sequence interaction and Renilla luciferase is used as an internal standard to normalize expression between replicates. We report the appropriate concentration of N. benthamiana leaf extracts and dilution factor to apply in order to avoid inhibition of firefly LUC activity. Furthermore, the optimal ratio of microRNA precursor expression construct to reporter construct and duration of the incubation period post-agroinfiltration were determined. The optimized dual luciferase assay provides an efficient, repeatable and scalable method to validate and quantify microRNA action on predicted target sequences. The optimized assay was used to validate five predicted targets of rice microRNA miR529b, with as few as six technical replicates. The assay can be extended to assess other small RNA-target sequence interactions, including assessing the functionality of an artificial miRNA or an RNAi construct on a targeted sequence.
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Wang C, Chen X, Li H, Wang J, Hu Z. Artificial miRNA inhibition of phosphoenolpyruvate carboxylase increases fatty acid production in a green microalga Chlamydomonas reinhardtii. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:91. [PMID: 28413446 PMCID: PMC5390379 DOI: 10.1186/s13068-017-0779-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 04/06/2017] [Indexed: 05/06/2023]
Abstract
BACKGROUND Nutrient limitation, such as nitrogen depletion, is the most widely used method for improving microalgae fatty acid production; however, these harsh conditions also inhibit algal growth significantly and even kill cells at all. To avoid these problems, we used artificial microRNA (amiRNA) technology as a useful tool to manipulate metabolic pathways to increase fatty acid contents effectively in the green microalga Chlamydomonas reinhardtii. We down-regulated the expression of phosphoenolpyruvate carboxylase (PEPC), which catalyzes the formation of oxaloacetate from phosphoenolpyruvate and regulates carbon flux. RESULTS amiRNAs against two CrPEPC genes were designed and transformed into Chlamydomonas cells and amiRNAs were induced by heat shock treatment. The transcription levels of amiRNAs increased 16-28 times, resulting in the remarkable decreases of the expression of CrPEPCs. In the end, inhibiting the expression of the CrPEPC genes dramatically increased the total fatty acid content in the transgenic algae by 28.7-48.6%, which mostly increased the content of C16-C22 fatty acids. Furthermore, the highest content was that of C18:3n3 with an average increase of 35.75%, while C20-C22 fatty acid content significantly increased by 85-160%. CONCLUSIONS Overall our results suggest that heat shock treatment induced the expression of amiRNAs, which can effectively down-regulate the expression of CrPEPCs in C. reinhardtii, resulting in an increase of fatty acid synthesis with the most significant increase occurring for C16 to C22 fatty acids.
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Affiliation(s)
- Chaogang Wang
- Guangdong Technology Research Center for Marine Algal Bioengineering, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Guangdong Key Laboratory of Plant Epigenetics, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Xi Chen
- Guangdong Technology Research Center for Marine Algal Bioengineering, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Hui Li
- Guangdong Technology Research Center for Marine Algal Bioengineering, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Guangdong Key Laboratory of Plant Epigenetics, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Nanshan District Key Lab for Biopolymers and Safety Evaluation, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Jiangxin Wang
- Guangdong Technology Research Center for Marine Algal Bioengineering, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Guangdong Key Laboratory of Plant Epigenetics, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Nanshan District Key Lab for Biopolymers and Safety Evaluation, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Zhangli Hu
- Guangdong Technology Research Center for Marine Algal Bioengineering, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Guangdong Key Laboratory of Plant Epigenetics, College of Life Sciences, Shenzhen University, Shenzhen, 518060 People’s Republic of China
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Bredow M, Vanderbeld B, Walker VK. Knockdown of Ice-Binding Proteins in Brachypodium distachyon Demonstrates Their Role in Freeze Protection. PLoS One 2016; 11:e0167941. [PMID: 27959937 PMCID: PMC5154533 DOI: 10.1371/journal.pone.0167941] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 11/22/2016] [Indexed: 11/18/2022] Open
Abstract
Sub-zero temperatures pose a major threat to the survival of cold-climate perennials. Some of these freeze-tolerant plants produce ice-binding proteins (IBPs) that offer frost protection by restricting ice crystal growth and preventing expansion-induced lysis of the plasma membranes. Despite the extensive in vitro characterization of such proteins, the importance of IBPs in the freezing stress response has not been investigated. Using the freeze-tolerant grass and model crop, Brachypodium distachyon, we characterized putative IBPs (BdIRIs) and generated the first 'IBP-knockdowns'. Seven IBP sequences were identified and expressed in Escherichia coli, with all of the recombinant proteins demonstrating moderate to high levels of ice-recrystallization inhibition (IRI) activity, low levels of thermal hysteresis (TH) activity (0.03-0.09°C at 1 mg/mL) and apparent adsorption to ice primary prism planes. Following plant cold acclimation, IBPs purified from wild-type B. distachyon cell lysates similarly showed high levels of IRI activity, hexagonal ice-shaping, and low levels of TH activity (0.15°C at 0.5 mg/mL total protein). The transfer of a microRNA construct to wild-type plants resulted in the attenuation of IBP activity. The resulting knockdown mutant plants had reduced ability to restrict ice-crystal growth and a 63% reduction in TH activity. Additionally, all transgenic lines were significantly more vulnerable to electrolyte leakage after freezing to -10°C, showing a 13-22% increase in released ions compared to wild-type. IBP-knockdown lines also demonstrated a significant decrease in viability following freezing to -8°C, with some lines showing only two-thirds the survival seen in control lines. These results underscore the vital role IBPs play in the development of a freeze-tolerant phenotype and suggests that expression of these proteins in frost-susceptible plants could be valuable for the production of more winter-hardy crops.
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Affiliation(s)
- Melissa Bredow
- Department of Biology, Queen’s University, Kingston, ON, Canada
| | | | - Virginia K. Walker
- Department of Biology, Queen’s University, Kingston, ON, Canada
- Department of Biomedical and Molecular Sciences, and School of Environmental Studies, Queen’s University, Kingston, ON, Canada
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Tian B, Li J, Oakley TR, Todd TC, Trick HN. Host-Derived Artificial MicroRNA as an Alternative Method to Improve Soybean Resistance to Soybean Cyst Nematode. Genes (Basel) 2016; 7:E122. [PMID: 27941644 PMCID: PMC5192498 DOI: 10.3390/genes7120122] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/17/2016] [Accepted: 12/01/2016] [Indexed: 11/23/2022] Open
Abstract
The soybean cyst nematode (SCN), Heterodera glycines, is one of the most important pests limiting soybean production worldwide. Novel approaches to managing this pest have focused on gene silencing of target nematode sequences using RNA interference (RNAi). With the discovery of endogenous microRNAs as a mode of gene regulation in plants, artificial microRNA (amiRNA) methods have become an alternative method for gene silencing, with the advantage that they can lead to more specific silencing of target genes than traditional RNAi vectors. To explore the application of amiRNAs for improving soybean resistance to SCN, three nematode genes (designated as J15, J20, and J23) were targeted using amiRNA vectors. The transgenic soybean hairy roots, transformed independently with these three amiRNA vectors, showed significant reductions in SCN population densities in bioassays. Expression of the targeted genes within SCN eggs were downregulated in populations feeding on transgenic hairy roots. Our results provide evidence that host-derived amiRNA methods have great potential to improve soybean resistance to SCN. This approach should also limit undesirable phenotypes associated with off-target effects, which is an important consideration for commercialization of transgenic crops.
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Affiliation(s)
- Bin Tian
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, USA.
| | - Jiarui Li
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, USA.
- Bayer CropScience, 3500 Paramount Pkwy, Morrisville, NC 27560, USA.
| | - Thomas R Oakley
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, USA.
| | - Timothy C Todd
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, USA.
| | - Harold N Trick
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, USA.
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Yu S, Pratelli R, Denbow C, Pilot G. Suppressor mutations in the Glutamine Dumper1 protein dissociate disturbance in amino acid transport from other characteristics of the Gdu1D phenotype. FRONTIERS IN PLANT SCIENCE 2015; 6:593. [PMID: 26300894 PMCID: PMC4523740 DOI: 10.3389/fpls.2015.00593] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 07/17/2015] [Indexed: 05/05/2023]
Abstract
Intracellular amino acid transport across plant membranes is critical for metabolic pathways which are often split between different organelles. In addition, transport of amino acids across the plasma membrane enables the distribution of organic nitrogen through the saps between leaves and developing organs. Amino acid importers have been studied for more than two decades, and their role in this process is well-documented. While equally important, amino acid exporters are not well-characterized. The over-expression of GDU1, encoding a small membrane protein with one transmembrane domain, leads to enhancement of amino acid export by Arabidopsis cells, glutamine secretion at the leaf margin, early senescence and size reduction of the plant, possibly caused by the stimulation of amino acid exporter(s). Previous work reported the identification of suppressor mutations of the GDU1 over-expression phenotype, which affected the GDU1 and LOG2 genes, the latter encoding a membrane-bound ubiquitin ligase interacting with GDU1. The present study focuses on the characterization of three additional suppressor mutations affecting GDU1. Size, phenotype, glutamine transport and amino acid tolerance were recorded for recapitulation plants and over-expressors of mutagenized GDU1 proteins. Unexpectedly, the over-expression of most mutated GDU1 led to plants with enhanced amino acid export, but failing to display secretion of glutamine and size reduction. The results show that the various effects triggered by GDU1 over-expression can be dissociated from one another by mutagenizing specific residues. The fact that these residues are not necessarily conserved suggests that the diverse biochemical properties of the GDU1 protein are not only born by the characterized transmembrane and VIMAG domains. These data provide a better understanding of the structure/function relationships of GDU1 and may enable modifying amino acid export in plants without detrimental effects on plant fitness.
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Affiliation(s)
| | | | | | - Guillaume Pilot
- *Correspondence: Guillaume Pilot, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, 511 Latham Hall, 220 AG Quad Lane, Blacksburg, VA 24061, USA,
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