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Jeynes-Cupper K, Catoni M. Long distance signalling and epigenetic changes in crop grafting. FRONTIERS IN PLANT SCIENCE 2023; 14:1121704. [PMID: 37021313 PMCID: PMC10067726 DOI: 10.3389/fpls.2023.1121704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 03/10/2023] [Indexed: 06/19/2023]
Abstract
Humans have used grafting for more than 4000 years to improve plant production, through physically joining two different plants, which can continue to grow as a single organism. Today, grafting is becoming increasingly more popular as a technique to increase the production of herbaceous horticultural crops, where rootstocks can introduce traits such as resistance to several pathogens and/or improving the plant vigour. Research in model plants have documented how long-distance signalling mechanisms across the graft junction, together with epigenetic regulation, can produce molecular and phenotypic changes in grafted plants. Yet, most of the studied examples rely on proof-of-concept experiments or on limited specific cases. This review explores the link between research findings in model plants and crop species. We analyse studies investigating the movement of signalling molecules across the graft junction and their implications on epigenetic regulation. The improvement of genomics analyses and the increased availability of genetic resources has allowed to collect more information on potential benefits of grafting in horticultural crop models. Ultimately, further research into this topic will enhance our ability to use the grafting technique to exploit genetic and epigenetic variation in crops, as an alternative to traditional breeding.
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Affiliation(s)
| | - Marco Catoni
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- Institute for Sustainable Plant Protection, National Research Council of Italy, Torino, Italy
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2
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Kondhare KR, Patil NS, Banerjee AK. A historical overview of long-distance signalling in plants. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:4218-4236. [PMID: 33682884 DOI: 10.1093/jxb/erab048] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 02/01/2021] [Indexed: 06/12/2023]
Abstract
Be it a small herb or a large tree, intra- and intercellular communication and long-distance signalling between distant organs are crucial for every aspect of plant development. The vascular system, comprising xylem and phloem, acts as a major conduit for the transmission of long-distance signals in plants. In addition to expanding our knowledge of vascular development, numerous reports in the past two decades revealed that selective populations of RNAs, proteins, and phytohormones function as mobile signals. Many of these signals were shown to regulate diverse physiological processes, such as flowering, leaf and root development, nutrient acquisition, crop yield, and biotic/abiotic stress responses. In this review, we summarize the significant discoveries made in the past 25 years, with emphasis on key mobile signalling molecules (mRNAs, proteins including RNA-binding proteins, and small RNAs) that have revolutionized our understanding of how plants integrate various intrinsic and external cues in orchestrating growth and development. Additionally, we provide detailed insights on the emerging molecular mechanisms that might control the selective trafficking and delivery of phloem-mobile RNAs to target tissues. We also highlight the cross-kingdom movement of mobile signals during plant-parasite relationships. Considering the dynamic functions of these signals, their implications in crop improvement are also discussed.
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Affiliation(s)
- Kirtikumar R Kondhare
- Plant Molecular Biology Unit, Biochemical Sciences Division, CSIR-National Chemical Laboratory (NCL) Pune, Maharashtra, India
| | - Nikita S Patil
- Biology Division, Indian Institute of Science Education and Research (IISER) Pune, Maharashtra, India
| | - Anjan K Banerjee
- Biology Division, Indian Institute of Science Education and Research (IISER) Pune, Maharashtra, India
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Chen JR, Ou SL, Nieh TI, Lu CY, Ku HM. Molecular Dissection of Cucumis metuliferus Resistance against Papaya Ringspot Virus by Grafting. PLANTS (BASEL, SWITZERLAND) 2020; 9:E1666. [PMID: 33261122 PMCID: PMC7759848 DOI: 10.3390/plants9121666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/25/2020] [Accepted: 11/25/2020] [Indexed: 12/30/2022]
Abstract
Vegetable crops of the genus Cucumis are very popular worldwide and have great market value. However, their fruit quality and yield are hindered by viral diseases. C. metuliferus is considered a wild species with resistance to viral diseases that is lacking in cultivated crops of the Cucumis genus, such as melon. The C. metuliferus line L37 shows extreme resistance against Papaya ringspot virus (PRSV-HA), whereas line L35 is a susceptible line. In this study, reciprocal grafting experiments between L35 and L37 were performed, and the PRSV-HA strain was pre-inoculated in the rootstock leaves. The results revealed that the resistance signal in the L37 rootstock could transmit and provide resistance to the L35 scion. Subsequently, double sandwich grafting was performed using the pre-inoculated L35 as the rootstock, which was then grafted onto the L37 intermediate and the L35 scion. The results showed that PRSV-HA RNA accumulated in the L35 rootstock leaf, petiole, and stem tissues, whereas PRSV-HA RNA accumulated in some intermediate and scion petiole and stem tissues. No HCPro RNA was detected in the L35 scion leaves. The results showed that the suppression of the virus occurred in the leaves, and the resistance effect spread from the rootstock in the scion direction. Hence, this study has demonstrated that RNA silencing of systemic signals is responsible for L37 resistance against PRSV. C. metuliferus L37 could provide a valuable resistance source for crops of the Cucumis species against viral diseases through grafting.
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Affiliation(s)
- Jen-Ren Chen
- Section of Biotechnology, Taiwan Seed Improvement and Propagation Station, Taichung City 426, Taiwan
- Department of Agronomy, National Chung Hsing University, Taichung City 402, Taiwan
| | - Shang-Ling Ou
- Department of Agronomy, National Chung Hsing University, Taichung City 402, Taiwan
| | - Ting-Iun Nieh
- Department of Agronomy, National Chung Hsing University, Taichung City 402, Taiwan
| | - Chih-Yu Lu
- Department of Agronomy, National Chung Hsing University, Taichung City 402, Taiwan
| | - Hsin-Mei Ku
- Department of Agronomy, National Chung Hsing University, Taichung City 402, Taiwan
- Advanced Plant Biotechnology Center, National Chung Hsing University, Taichung City 402, Taiwan
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Liang D. A Salutary Role of Reactive Oxygen Species in Intercellular Tunnel-Mediated Communication. Front Cell Dev Biol 2018; 6:2. [PMID: 29503816 PMCID: PMC5821100 DOI: 10.3389/fcell.2018.00002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/18/2018] [Indexed: 12/17/2022] Open
Abstract
The reactive oxygen species, generally labeled toxic due to high reactivity without target specificity, are gradually uncovered as signaling molecules involved in a myriad of biological processes. But one important feature of ROS roles in macromolecule movement has not caught attention until recent studies with technique advance and design elegance have shed lights on ROS signaling for intercellular and interorganelle communication. This review begins with the discussions of genetic and chemical studies on the regulation of symplastic dye movement through intercellular tunnels in plants (plasmodesmata), and focuses on the ROS regulatory mechanisms concerning macromolecule movement including small RNA-mediated gene silencing movement and protein shuttling between cells. Given the premise that intercellular tunnels (bridges) in mammalian cells are the key physical structures to sustain intercellular communication, movement of macromolecules and signals is efficiently facilitated by ROS-induced membrane protrusions formation, which is analogously applied to the interorganelle communication in plant cells. Although ROS regulatory differences between plant and mammalian cells exist, the basis for ROS-triggered conduit formation underlies a unifying conservative theme in multicellular organisms. These mechanisms may represent the evolutionary advances that have enabled multicellularity to gain the ability to generate and utilize ROS to govern material exchanges between individual cells in oxygenated environment.
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Affiliation(s)
- Dacheng Liang
- Hubei Collaborative Innovation Center for Grain Industry, School of Agriculture, Yangtze University, Jingzhou, China.,Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, Yangtze University, Jingzhou, China
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5
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Ali ME, Waliullah S, Kobayashi K, Yaeno T, Yamaoka N, Nishiguchi M. Transmission of RNA silencing signal through grafting confers virus resistance from transgenically silenced tobacco rootstocks to non-transgenic tomato and tobacco scions. JOURNAL OF PLANT BIOCHEMISTRY AND BIOTECHNOLOGY 2016; 25:245-252. [DOI: 10.1007/s13562-015-0334-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Mermigka G, Verret F, Kalantidis K. RNA silencing movement in plants. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2016; 58:328-42. [PMID: 26297506 DOI: 10.1111/jipb.12423] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 08/20/2015] [Indexed: 05/21/2023]
Abstract
Multicellular organisms, like higher plants, need to coordinate their growth and development and to cope with environmental cues. To achieve this, various signal molecules are transported between neighboring cells and distant organs to control the fate of the recipient cells and organs. RNA silencing produces cell non-autonomous signal molecules that can move over short or long distances leading to the sequence specific silencing of a target gene in a well defined area of cells or throughout the entire plant, respectively. The nature of these signal molecules, the route of silencing spread, and the genes involved in their production, movement and reception are discussed in this review. Additionally, a short section on features of silencing spread in animal models is presented at the end of this review.
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Affiliation(s)
- Glykeria Mermigka
- Department of Biology, University of Crete, Heraklion, Crete, Greece
| | - Frédéric Verret
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece
| | - Kriton Kalantidis
- Department of Biology, University of Crete, Heraklion, Crete, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece
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Liang D, White RG, Waterhouse PM. Mobile gene silencing in Arabidopsis is regulated by hydrogen peroxide. PeerJ 2014; 2:e701. [PMID: 25551023 PMCID: PMC4277490 DOI: 10.7717/peerj.701] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 11/26/2014] [Indexed: 01/02/2023] Open
Abstract
In plants and nematodes, RNAi can spread from cells from which it is initiated to other cells in the organism. The underlying mechanism controlling the mobility of RNAi signals is not known, especially in the case of plants. A genetic screen designed to recover plants impaired in the movement but not the production or effectiveness of the RNAi signal identified RCI3, which encodes a hydrogen peroxide (H2O2)-producing type III peroxidase, as a key regulator of silencing mobility in Arabidopsis thaliana. Silencing initiated in the roots of rci3 plants failed to spread into leaf tissue or floral tissue. Application of exogenous H2O2 reinstated the spread in rci3 plants and accelerated it in wild-type plants. The addition of catalase or MnO2, which breaks down H2O2, slowed the spread of silencing in wild-type plants. We propose that endogenous H2O2, under the control of peroxidases, regulates the spread of gene silencing by altering plasmodesmata permeability through remodelling of local cell wall structure, and may play a role in regulating systemic viral defence.
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Affiliation(s)
- Dacheng Liang
- CSIRO Plant Industry , Canberra, ACT , Australia ; School of Molecular Bioscience, University of Sydney , Sydney, NSW , Australia
| | | | - Peter M Waterhouse
- CSIRO Plant Industry , Canberra, ACT , Australia ; School of Molecular Bioscience, University of Sydney , Sydney, NSW , Australia ; Centre for Tropical Crops and Biocommodities, Queensland University of Technology , Brisbane, QLD , Australia
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Catoni M, Lucioli A, Doblas-Ibáñez P, Accotto GP, Vaira AM. From immunity to susceptibility: virus resistance induced in tomato by a silenced transgene is lost as TGS overcomes PTGS. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:941-953. [PMID: 23738576 DOI: 10.1111/tpj.12253] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 05/20/2013] [Accepted: 05/31/2013] [Indexed: 06/02/2023]
Abstract
Tomato line 30.4 was obtained engineering the nucleocapsid (N) gene of tomato spotted wilt virus into plant genome, and immunity to tomato spotted wilt virus infection of its self-pollinated homozygous progeny was observed. Despite the presence of a high amount of transgenic transcripts, transgenic proteins have not been detected, suggesting a mechanism of resistance mediated by RNA. In the present study, we identify post-transcriptional gene silencing as the main mechanism of resistance, which is able to spread systemically through grafting, and show that the line 30.4 resistant plants produce both 24 and 21-22 nt N-gene specific siRNA classes. The transgenic locus in chromosome 4 shows complex multiple insertions of four T-DNA copies in various orientations, all with 3' end deletions in the terminator and part of the N gene. However, for three of them, polyadenylated transcripts are produced, due to flanking tomato genome sequences acting as alternative terminators. Interestingly, starting at the fifth generation after the transformation event, some individual plants show a tomato spotted wilt virus-susceptible phenotype. The change is associated with the disappearance of transgene-specific transcripts and siRNAs, and with hyper-methylation of the transgene, which proceeds gradually through the generations. Once it reaches a critical threshold, the shift from post-transcriptional gene silencing to transcriptional silencing of the transgene eliminates the previously well established virus resistance.
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Affiliation(s)
- Marco Catoni
- Istituto di Virologia Vegetale, Consiglio Nazionale delle Ricerche, Strada delle Cacce 73, 10135, Turin, Italy.
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Md. Ali E, Kobayashi K, Yamaoka N, Ishikawa M, Nishiguchi M. Graft transmission of RNA silencing to non-transgenic scions for conferring virus resistance in tobacco. PLoS One 2013; 8:e63257. [PMID: 23717405 PMCID: PMC3661558 DOI: 10.1371/journal.pone.0063257] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 03/31/2013] [Indexed: 11/19/2022] Open
Abstract
RNA silencing is a mechanism of gene regulation by sequence specific RNA degradation and is involved in controlling endogenous gene expression and defense against invasive nucleic acids such as viruses. RNA silencing has been proven to be transmitted between scions and rootstocks through grafting, mostly using transgenic plants. It has been reported that RNA silencing of tobacco endogenous genes, NtTOM1 and NtTOM3, that are required for tobamovirus multiplication, resulted in high resistance against several tobamoviruses. In the present study, we examined the graft transmission of RNA silencing for conferring virus resistance to non-transgenic scions of the same and different Nicotiana species grafted onto rootstocks in which both NtTOM1 and NtTOM3 were silenced. Non-transgenic Nicotiana tabacum (cvs. Samsun and Xanthi nc) and N. benthamiana were used as scions for grafting onto the rootstocks silenced with both genes. Short interfering RNA (siRNA) of NtTOM1 and NtTOM3 was detected in both the scions and the rootstocks eight weeks after grafting. The leaves were detached from the scions and inoculated with several tobamoviruses. The virus accumulation was tested by ELISA and northern blot analysis. The viruses were detected in grafted scions at extremely low levels, showing that virus resistance was conferred. These results suggest that RNA silencing was induced in and virus resistance was conferred to the non-transgenic scions by grafting onto silenced rootstocks. The effect of low temperature on siRNA accumulation and virus resistance was not significantly observed in the scions.
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Affiliation(s)
- Emran Md. Ali
- Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Japan
| | - Kappei Kobayashi
- Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Japan
| | - Naoto Yamaoka
- Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Japan
| | - Masayuki Ishikawa
- Plant-Microbe Interactions Research Unit, National Institute of Agrobiological Sciences, 2-1-2 Kan-nondai, Tsukuba, Ibaraki, Japan
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10
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Kasai A, Sano T, Harada T. Scion on a stock producing siRNAs of potato spindle tuber viroid (PSTVd) attenuates accumulation of the viroid. PLoS One 2013; 8:e57736. [PMID: 23469061 PMCID: PMC3585205 DOI: 10.1371/journal.pone.0057736] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 01/24/2013] [Indexed: 02/02/2023] Open
Abstract
Plants can attenuate the replication of plant viruses and viroids by RNA silencing induced by virus and viroid infection. In higher plants, silencing signals such as small interfering RNAs (siRNAs) produced by RNA silencing can be transported systemically through phloem, so it is anticipated that antiviral siRNA signals produced in a stock would have the potential to attenuate propagation of viruses or viroids in the scion. To test whether this is indeed the case, we prepared transgenic tobacco (Nicotiana benthamiana) expressing a hairpin RNA (hpRNA) of Potato spindle tuber viroid (PSTVd) in companion cells by using a strong companion cell-specific promoter. A grafting experiment of the wild type tobacco scion on the top of the transgenic tobacco stock revealed that accumulation of PSTVd challenge-inoculated into the scion was apparently attenuated compared to the control grafted plants. These results indicate that genetically modified rootstock expressing viroid-specific siRNAs can attenuate viroid accumulation in a non-genetically modified scion grafted on the stock.
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Affiliation(s)
- Atsushi Kasai
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
| | - Teruo Sano
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
| | - Takeo Harada
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
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11
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Liang D, White RG, Waterhouse PM. Gene silencing in Arabidopsis spreads from the root to the shoot, through a gating barrier, by template-dependent, nonvascular, cell-to-cell movement. PLANT PHYSIOLOGY 2012; 159:984-1000. [PMID: 22582134 PMCID: PMC3387722 DOI: 10.1104/pp.112.197129] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 05/10/2012] [Indexed: 05/18/2023]
Abstract
Upward long-distance mobile silencing has been shown to be phloem mediated in several different solanaceous species. We show that the Arabidopsis (Arabidopsis thaliana) seedling grafting system and a counterpart inducible system generate upwardly spreading long-distance silencing that travels not in the phloem but by template-dependent reiterated short-distance cell-to-cell spread through the cells of the central stele. Examining the movement of the silencing front revealed a largely unrecognized zone of tissue, below the apical meristem, that is resistant to the silencing signal and that may provide a gating or protective barrier against small RNA signals. Using a range of auxin and actin transport inhibitors revealed that, in this zone, alteration of vesicular transport together with cytoskeleton dynamics prevented or retarded the spread of the silencing signal. This suggests that small RNAs are transported from cell to cell via plasmodesmata rather than diffusing from their source in the phloem.
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Affiliation(s)
- Dacheng Liang
- Commonwealth Scientific and Industrial Research Organization Plant Industry, Canberra, Australian Capital Territory 2601, Australia.
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12
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Haroldsen VM, Szczerba MW, Aktas H, Lopez-Baltazar J, Odias MJ, Chi-Ham CL, Labavitch JM, Bennett AB, Powell ALT. Mobility of Transgenic Nucleic Acids and Proteins within Grafted Rootstocks for Agricultural Improvement. FRONTIERS IN PLANT SCIENCE 2012; 3:39. [PMID: 22645583 PMCID: PMC3355758 DOI: 10.3389/fpls.2012.00039] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 02/17/2012] [Indexed: 05/03/2023]
Abstract
Grafting has been used in agriculture for over 2000 years. Disease resistance and environmental tolerance are highly beneficial traits that can be provided through use of grafting, although the mechanisms, in particular for resistance, have frequently been unknown. As information emerges that describes plant disease resistance mechanisms, the proteins, and nucleic acids that play a critical role in disease management can be expressed in genetically engineered (GE) plant lines. Utilizing transgrafting, the combination of a GE rootstock with a wild-type (WT) scion, or the reverse, has the potential to provide pest and pathogen resistance, impart biotic and abiotic stress tolerance, or increase plant vigor and productivity. Of central importance to these potential benefits is the question of to what extent nucleic acids and proteins are transmitted across a graft junction and whether the movement of these molecules will affect the efficacy of the transgrafting approach. Using a variety of specific examples, this review will report on the movement of organellar DNA, RNAs, and proteins across graft unions. Attention will be specifically drawn to the use of small RNAs and gene silencing within transgrafted plants, with a particular focus on pathogen resistance. The use of GE rootstocks or scions has the potential to extend the horticultural utility of grafting by combining this ancient technique with the molecular strategies of the modern era.
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Affiliation(s)
| | - Mark W. Szczerba
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Hakan Aktas
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
- Department of Horticulture, Faculty of Agriculture, University of Suleyman DemirelIsparta, Turkey
| | - Javier Lopez-Baltazar
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
- Instituto Tecnologico del Valle de OaxacaOaxaca, Mexico
| | - Mar Joseph Odias
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | | | - John M. Labavitch
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Alan B. Bennett
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Ann L. T. Powell
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
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Bai S, Kasai A, Yamada K, Li T, Harada T. A mobile signal transported over a long distance induces systemic transcriptional gene silencing in a grafted partner. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4561-70. [PMID: 21652532 PMCID: PMC3170550 DOI: 10.1093/jxb/err163] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 03/24/2011] [Accepted: 04/26/2011] [Indexed: 05/18/2023]
Abstract
Transcriptional gene silencing (TGS) can be induced by promoter-targeted small interfering RNA (siRNA). Long-distance transmission of TGS by viral infection in plants has been reported. However, systemic TGS has not been observed in the case of using an inverted repeat transgene as the silencing trigger. Here it is reported that a mobile signal, presumably the siRNA, produced from a hairpin structure transgene controlled by a companion cell-specific promoter can also induce transmissible TGS in both a modified agroinfiltration and a grafting system. Although the transmissible TGS occurred only in cells located in the vicinity of a leaf vein in the scion, very strong silencing was observed in the root system, especially the lateral roots, including the root apical meristem. The transmissible TGS was maintained through tissue culture and subsequently inherited by the progeny. The results suggest the potential application of mobile promoter-targeting siRNA in horticulture for improvement of plant cultivars by grafting.
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Affiliation(s)
- Songling Bai
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan
| | - Atsushi Kasai
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
| | - Kaori Yamada
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
| | - Tianzhong Li
- College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China
| | - Takeo Harada
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan
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14
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Kasai A, Bai S, Li T, Harada T. Graft-transmitted siRNA signal from the root induces visual manifestation of endogenous post-transcriptional gene silencing in the scion. PLoS One 2011; 6:e16895. [PMID: 21347381 PMCID: PMC3036722 DOI: 10.1371/journal.pone.0016895] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 01/05/2011] [Indexed: 01/23/2023] Open
Abstract
In plants, post-transcriptional gene silencing (PTGS) spreads systemically, being transmitted from the silenced stock to the scion expressing the corresponding transgene. It has been reported that a graft-transmitted siRNA signal can also induce PTGS of an endogenous gene, but this was done by top-grafting using silenced stock. In the present study involving grafting of Nicotiana benthamiana, we found that PTGS of an endogenous gene, glutamate-1-semialdehyde aminotransferase (GSA), which acts as a visible marker of RNAi via inhibition of chlorophyll synthesis, was manifested along the veins of newly developed leaves in the wild-type scion by the siRNA signal synthesized only in companion cells of the rootstock.
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Affiliation(s)
- Atsushi Kasai
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
| | - Songling Bai
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
| | - Tianzhong Li
- Laboratory of Fruit Cell and Molecular Breeding, China Agriculture University, Beijing, China
| | - Takeo Harada
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
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15
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Are small RNAs a big help to plants? ACTA ACUST UNITED AC 2009; 52:212-23. [DOI: 10.1007/s11427-009-0034-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Accepted: 11/24/2008] [Indexed: 01/19/2023]
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16
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Campbell BA, Hallengren J, Hannapel DJ. Accumulation of BEL1-like transcripts in solanaceous species. PLANTA 2008; 228:897-906. [PMID: 18751722 DOI: 10.1007/s00425-008-0780-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 06/25/2008] [Indexed: 05/26/2023]
Abstract
Although numerous RNAs have been detected in the phloem, only a few have been confirmed to move long distances. In potato, full-length mRNA of the BEL1-like transcription factor, StBEL5, moves from leaf veins through the phloem to stolon tips to activate tuber formation. BEL1-like transcription factors are ubiquitous in plants and interact with KNOTTED1-types to regulate numerous developmental processes. To explore the range of KNOTTED1- and BEL1-like mRNAs present in phloem, an analysis of the transcript profile of phloem sap was undertaken. Using a modified technique for the collection of phloem-enriched exudate from excised stems, numerous RNAs encoding these transcription factors were detected in the phloem sap from several solanceous species. All seven known BEL1-like RNAs of potato were detected in the phloem-enriched exudates of stem, whereas several stolon-abundant RNAs were not. After refining the technique to minimize the contamination from RNA arising from wounded cells, KNOTTED1-like RNAs were detected in phloem-enriched sap of potato and BEL5 RNA was detected in the sap collected from two closely related nontuber-bearing potato species and tomato. BEL5 RNA was also detected in RNA extracted from leaf veins of tobacco. The detection of these full-length mRNAs from the KNOTTED1- and BEL1-like families in phloem sap indicates that their potential role as long-distance signals seems to be much more extensive than previously known.
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Affiliation(s)
- Brian A Campbell
- Department of Horticulture, Iowa State University, Ames, IA 50011-1100, USA
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17
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Abstract
When eukaryotic cells encounter double-stranded RNA, genes of matching sequence are silenced through RNA interference. Surprisingly, in some animals and plants, the same gene is specifically silenced even in cells that did not encounter the double-stranded RNA, due to the transport of a gene-specific silencing signal between cells. This silencing signal likely has an RNA component that gives it sequence-specificity, however its precise identity remains unknown. Studies in the worm Caenorhabditis elegans and in plants have revealed parts of a complex protein machinery that transports this silencing signal. Some of these proteins are conserved in vertebrates, including mammals, raising the possibility that higher animals can communicate gene-specific silencing information between cells. Such communication provides antiviral immunity in plants and perhaps in C. elegans. Identifying the transported silencing signal and deciphering the evolutionarily selected role of the transport machinery are some of the key challenges for the future.
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Affiliation(s)
- Antony M Jose
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
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18
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Saeed M, Zafar Y, Randles JW, Rezaian MA. A monopartite begomovirus-associated DNA beta satellite substitutes for the DNA B of a bipartite begomovirus to permit systemic infection. J Gen Virol 2007; 88:2881-2889. [PMID: 17872543 DOI: 10.1099/vir.0.83049-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA beta is a circular single-stranded satellite DNA which co-infects with certain monopartite helper begomoviruses to cause economically important diseases, such as cotton leaf curl disease (CLCuD). DNA beta encodes a single protein, betaC1. Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus in which both DNA A and DNA B are required for systemic infection. Inoculation of tomato plants with ToLCNDV DNA A alone induced local but not systemic infection, whereas co-inoculation with DNA A and the DNA beta associated with CLCuD resulted in systemic infection. DNA beta containing a disrupted betaC1 open reading frame (ORF) did not mobilize DNA A systemically. Co-inoculation of plants with DNA A and a construct of the betaC1 ORF, under the control of the cauliflower mosaic virus 35S promoter, resulted in the systemic movement of DNA A. In inoculated tobacco and onion epidermal cells, betaC1 fused to GFP was localized at the cell periphery in association with punctate bodies, around and within the cell nucleus and with the endoplasmic reticulum. It is concluded that heterologous betaC1 protein can replace the movement function of the DNA B of a bipartite begomovirus. Evidence is also provided that tomato leaf curl virus-encoded C4 protein confers the same movement function to ToLCNDV DNA A. The intracellular distribution of betaC1 is consistent with the hypothesis that it has a role in transporting the DNA A from the nuclear site of replication to the plasmodesmatal exit sites of the infected cell.
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Affiliation(s)
- Muhammad Saeed
- National Institute for Biotechnology and Genetic Engineering, PO Box 577, Jhang Road, Faisalabad, Pakistan
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia
- CSIRO Plant Industry, PO Box 350, Glen Osmond, SA 5064, Australia
| | - Yusuf Zafar
- National Institute for Biotechnology and Genetic Engineering, PO Box 577, Jhang Road, Faisalabad, Pakistan
| | - John W Randles
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia
| | - M Ali Rezaian
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia
- CSIRO Plant Industry, PO Box 350, Glen Osmond, SA 5064, Australia
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19
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Haque AKMN, Yamaoka N, Nishiguchi M. Cytosine methylation is associated with RNA silencing in silenced plants but not with systemic and transitive RNA silencing through grafting. Gene 2007; 396:321-31. [PMID: 17521830 DOI: 10.1016/j.gene.2007.04.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2006] [Revised: 04/04/2007] [Accepted: 04/04/2007] [Indexed: 10/23/2022]
Abstract
RNA silencing is often associated with methylation of the target gene. The DNA methylation level of transgenes was investigated in post-transcriptionally silenced or non-silenced Nicotiana benthamiana carrying either the 5' region (200 or 400 bp) or the entire region of the coat protein gene (CP, including the 3' non-translated region) of Sweet potato feathery mottle virus. Higher levels of transgene cytosine methylation were observed in both symmetrical (CpG, CpNpG) and non-symmetrical (CpHpH) contexts (CpG>CpNpG>CpHpH) in silenced lines, but there was very lower levels or no transgene methylation in non-silenced lines. RNA silencing was induced in non-silenced scions from silenced rootstocks and spread to the 3' region of the transgene mRNA (Haque et al., Plant Mol. Biol. 2007; 63: 35-47). In this system, transgene methylation levels were analyzed in scions at different time intervals after being grafted onto silenced or non-silenced rootstocks to investigate if transgene methylation was associated with induction or transitivity of RNA silencing. We observed that, there was no change of transgene methylation level in the initial target or in extended regions in scions. These results showed that transgene methylation was associated with RNA silencing in individual transformants, but it was not associated with systemic RNA silencing and/or transitive RNA silencing through grafting.
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Affiliation(s)
- A K M Nazmul Haque
- The United Graduate School of Agricultural Sciences, Ehime University, 3-5-7 Tarumi, Matsuyama 790-8566, Japan
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20
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Shimamura K, Oka SI, Shimotori Y, Ohmori T, Kodama H. Generation of secondary small interfering RNA in cell-autonomous and non-cell autonomous RNA silencing in tobacco. PLANT MOLECULAR BIOLOGY 2007; 63:803-13. [PMID: 17225952 DOI: 10.1007/s11103-006-9124-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Accepted: 12/15/2006] [Indexed: 05/13/2023]
Abstract
Small interfering RNA (siRNA) species with 21-25 nucleotides in length guide mRNA cleavage, translational arrest, and heterochromatin formation in RNA interference (RNAi). To delineate the target region of RNAi, a construct harboring a transcriptional fusion between parts of the target mRNA and the beta-glucuronidase gene was biolistically delivered into tobacco leaves showing an RNAi phenotype and the assay sequence was transiently expressed. The RNAi effect was monitored by amplification of this chimeric transcript. By using this assay method, we addressed the transitive RNA silencing of a tobacco endoplasmic reticulum omega-3 fatty acid desaturase gene (NtFAD3). In the NtFAD3 RNAi plants, the target region of RNAi was restricted in the inducer region corresponding to a stem sequence of the hairpin double-stranded RNA, indicating that endogenous NtFAD3 mRNA was not a template for an RNA-dependent RNA polymerase. The secondary NtFAD3 siRNAs were produced in the crossbred plants between the NtFAD3 overexpressed plant and the NtFAD3 RNAi plant. Similarly, the secondary siRNAs were generated in the systemically silenced scion. Although these secondary siRNAs originated preferentially from the 3' region downstream of the inducer region, the secondary siRNAs produced in the silenced scion (non-cell autonomous secondary siRNAs) resulted in the strong degradation of the target mRNA, but the secondary siRNAs in the crossbred plants (cell-autonomous secondary siRNAs) showed limited RNA degradation activity. These results showed that this in vivo assay for determination of RNAi efficiency is a useful tool to delineate RNAi mechanisms.
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21
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Mourrain P, van Blokland R, Kooter JM, Vaucheret H. A single transgene locus triggers both transcriptional and post-transcriptional silencing through double-stranded RNA production. PLANTA 2007; 225:365-79. [PMID: 16924537 DOI: 10.1007/s00425-006-0366-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2006] [Accepted: 07/10/2006] [Indexed: 05/11/2023]
Abstract
Silencing of a target locus by an unlinked silencing locus can result from transcription inhibition (transcriptional gene silencing; TGS) or mRNA degradation (post-transcriptional gene silencing; PTGS), owing to the production of double-stranded RNA (dsRNA) corresponding to promoter or transcribed sequences, respectively. The involvement of distinct cellular components in each process suggests that dsRNA-induced TGS and PTGS likely result from the diversification of an ancient common mechanism. However, a strict comparison of TGS and PTGS has been difficult to achieve because it generally relies on the analysis of distinct silencing loci. We describe a single transgene locus that triggers both TGS and PTGS, owing to the production of dsRNA corresponding to promoter and transcribed sequences of different target genes. We describe mutants and epigenetic variants derived from this locus and propose a model for the production of dsRNA. Also, we show that PTGS, but not TGS, is graft-transmissible, which together with the sensitivity of PTGS, but not TGS, to RNA viruses that replicate in the cytoplasm, suggest that the nuclear compartmentalization of TGS is responsible for cell-autonomy. In contrast, we contribute local and systemic trafficking of silencing signals and sensitivity to viruses to the cytoplasmic steps of PTGS and to amplification steps that require high levels of target mRNAs.
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Affiliation(s)
- Philippe Mourrain
- Laboratoire de Biologie Cellulaire, Institut Jean-Pierre Bourgin, INRA, 78026, Versailles Cedex, France
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22
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Haque AKMN, Tanaka Y, Sonoda S, Nishiguchi M. Analysis of transitive RNA silencing after grafting in transgenic plants with the coat protein gene of Sweet potato feathery mottle virus. PLANT MOLECULAR BIOLOGY 2007; 63:35-47. [PMID: 17160454 DOI: 10.1007/s11103-006-9070-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Accepted: 08/02/2006] [Indexed: 05/09/2023]
Abstract
We have previously reported the graft transmission of target specificity for RNA silencing using transgenic Nicotiana benthamiana plants expressing the coat protein gene (CP, including the 3' non-translated region) of Sweet potato feathery mottle virus. Transgenic plants carrying the 5' 200 and 400 bp regions of CP were newly produced. From these plants, two silenced and two non-silenced lines were selected to investigate the manifestation of transitive RNA silencing by graft experiments. Non-silenced scions carrying the entire transgene were grafted onto either 5' or 3' silencing inducer rootstocks. When non-silenced scions were grafted onto 5' silencing inducer rootstocks, RNA silencing was induced in the non-silenced scions and spread toward the 3' region of the transgene mRNA. Similarly, when non-silenced scions were grafted onto 3' silencing inducer rootstocks, RNA silencing was induced in the non-silenced scions, but was restricted to the 3' region of the transgene and did not spread to the 5' region. In addition, results from crossing experiments, involving non-silenced and 3' silencing inducer plants, confirmed the above finding. This indicates that RNA silencing spreads in the 5'-3' direction, not in the 3'-5' direction, along the transgene mRNA.
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Affiliation(s)
- A K M Nazmul Haque
- Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, 790-8566, Japan.
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23
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Banerjee AK, Chatterjee M, Yu Y, Suh SG, Miller WA, Hannapel DJ. Dynamics of a mobile RNA of potato involved in a long-distance signaling pathway. THE PLANT CELL 2006; 18:3443-57. [PMID: 17189340 PMCID: PMC1785412 DOI: 10.1105/tpc.106.042473] [Citation(s) in RCA: 222] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 09/17/2006] [Accepted: 11/10/2006] [Indexed: 05/13/2023]
Abstract
BEL1-like transcription factors interact with Knotted1 types to regulate numerous developmental processes. In potato (Solanum tuberosum), the BEL1 transcription factor St BEL5 and its protein partner POTH1 regulate tuber formation by mediating hormone levels in the stolon tip. The accumulation of St BEL5 RNA increases in response to short-day photoperiods, inductive for tuber formation. RNA detection methods and heterografting experiments demonstrate that BEL5 transcripts are present in phloem cells and move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA to stolon tips is correlated with enhanced tuber production. Overexpression of BEL5 transcripts that include the untranslated sequences of the BEL5 transcript endows transgenic lines with the capacity to overcome the inhibitory effects of long days on tuber formation. Addition of the untranslated regions leads to preferential accumulation of the BEL5 RNA in stolon tips under short-day conditions. Using a leaf-specific promoter, the movement of BEL5 RNA to stolon tips was facilitated by a short-day photoperiod, and this movement was correlated with enhanced tuber production. These results implicate the transcripts of St BEL5 in a long-distance signaling pathway that are delivered to the target organ via the phloem stream.
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Affiliation(s)
- Anjan K Banerjee
- Department of Horticulture, Iowa State University, Ames, Iowa 50011-1100, USA
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24
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Shaharuddin NA, Han Y, Li H, Grierson D. The mechanism of graft transmission of sense and antisense gene silencing in tomato plants. FEBS Lett 2006; 580:6579-86. [PMID: 17113082 DOI: 10.1016/j.febslet.2006.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Revised: 11/05/2006] [Accepted: 11/06/2006] [Indexed: 10/23/2022]
Abstract
We investigated the effect of target mRNA level on grafting-transmitted gene silencing in tomato plants by using a strong ACC oxidase 1 (ACO1) silencer as the stock and transgenic ACO1 overexpressers as scions. Manifestation of graft transmission of sense gene silencing required a high initial level of target mRNA in the scion. A relatively high level of siRNA, similar to that in the strong ACO1 silencer, was also detected in the silencing-susceptible strong ACO1 overexpressers prior to grafting. After grafting the silencing signal from the stock enhanced the level of the siRNAs in the scion and the ACO1 mRNA level was reduced dramatically. Using stock and scions producing different siRNAs we provided evidence that the transmissible silencing signal does not correspond to the bulk siRNAs in the stock. We also showed, contrary to a previous report, that antisense silencing was graft-transmissible but it took longer to manifest itself. The delay in graft transmission from antisense-silenced plants could be attributed to the difference in the nature or strength of the signal or the mechanism of its amplification, but is further evidence of mechanistic similarities between sense and antisense silencing.
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Affiliation(s)
- Noor A Shaharuddin
- Plant Sciences Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
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25
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Fusaro AF, Matthew L, Smith NA, Curtin SJ, Dedic-Hagan J, Ellacott GA, Watson JM, Wang MB, Brosnan C, Carroll BJ, Waterhouse PM. RNA interference-inducing hairpin RNAs in plants act through the viral defence pathway. EMBO Rep 2006; 7:1168-75. [PMID: 17039251 PMCID: PMC1679793 DOI: 10.1038/sj.embor.7400837] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 09/15/2006] [Accepted: 09/18/2006] [Indexed: 11/09/2022] Open
Abstract
RNA interference (RNAi) is widely used to silence genes in plants and animals. It operates through the degradation of target mRNA by endonuclease complexes guided by approximately 21 nucleotide (nt) short interfering RNAs (siRNAs). A similar process regulates the expression of some developmental genes through approximately 21 nt microRNAs. Plants have four types of Dicer-like (DCL) enzyme, each producing small RNAs with different functions. Here, we show that DCL2, DCL3 and DCL4 in Arabidopsis process both replicating viral RNAs and RNAi-inducing hairpin RNAs (hpRNAs) into 22-, 24- and 21 nt siRNAs, respectively, and that loss of both DCL2 and DCL4 activities is required to negate RNAi and to release the plant's repression of viral replication. We also show that hpRNAs, similar to viral infection, can engender long-distance silencing signals and that hpRNA-induced silencing is suppressed by the expression of a virus-derived suppressor protein. These findings indicate that hpRNA-mediated RNAi in plants operates through the viral defence pathway.
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Affiliation(s)
- Adriana F Fusaro
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
| | - Louisa Matthew
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
| | - Neil A Smith
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
| | - Shaun J Curtin
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
- School of Wine and Food Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, New South Wales, 2678, Australia
| | - Jasmina Dedic-Hagan
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
- School of Biochemistry and Molecular Biology, Australian National University Canberra, Australian Capital Territory 2601, Australia
| | - Geoff A Ellacott
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
| | - John M Watson
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
| | - Ming-Bo Wang
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
| | - Chris Brosnan
- Department of Biochemistry and Molecular Biology, The University of Queensland, Queensland 4071, Australia
| | - Bernard J Carroll
- Department of Biochemistry and Molecular Biology, The University of Queensland, Queensland 4071, Australia
| | - Peter M Waterhouse
- CSIRO Plant Industry, PO Box 1600, Canberra, Australian Capital Territory 2601, Australia
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Tournier B, Tabler M, Kalantidis K. Phloem flow strongly influences the systemic spread of silencing in GFP Nicotiana benthamiana plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 47:383-94. [PMID: 16771840 DOI: 10.1111/j.1365-313x.2006.02796.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The term 'RNA silencing' describes a process that results in the specific degradation of an RNA target. In plants, silenced tissues can initiate the spreading of the process into non-silenced regions by a mobile signal that can be transmitted over long distances. In the present work, we made use of a modified grafting approach to elucidate the driving force behind long-distance transport of the silencing signal. We made reciprocal grafts of two GFP-transgenic Nicotiana benthamiana lines, the non-silenced line 16c (sensor) and the silenced line 6.4 (inducer). We show that the direction of systemic spread of silencing from inducer to sensor can be manipulated by altering sink/source relations in the plant. Using radioactive phosphate as a phloem tracer, we demonstrated that plants that transmitted silencing from silenced scion to non-silenced rootstock had developed a persisting phloem flow from scion to rootstock. These data provide experimental proof of what has been hypothesized so far, that the silencing signal travels via phloem from source to sink. We present here evidence that the appearance of systemic silencing is not an accidental stochastic process, but can be predicted on the basis of the direction of phloem flow.
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Affiliation(s)
- Barthélémy Tournier
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, GR-71110 Heraklion/Crete, Greece.
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27
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Kalantidis K, Tsagris M, Tabler M. Spontaneous short-range silencing of a GFP transgene in Nicotiana benthamiana is possibly mediated by small quantities of siRNA that do not trigger systemic silencing. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 45:1006-16. [PMID: 16507090 DOI: 10.1111/j.1365-313x.2006.02664.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A green fluorescent protein (GFP) transgene under the control of the 35S cauliflower mosaic virus (CaMV) promoter was introduced by Agrobacterium-mediated transformation into Nicotiana benthamiana to generate fourteen transgenic lines. Homozygous lines that contained one or two copies of the transgene showed great variation of GFP expression under ultraviolet (UV) light, which allowed classification into three types of transgenic plants. Plants from more than half of the transgenic lines underwent systemic RNA silencing and produced short interfering RNA (siRNA) as young seedlings, while plants of the remaining lines developed, in a spontaneous manner, defined GFP-silenced zones on their leaves, mostly in the form of circular spots that expanded to about 4-7 mm in size. In some of the latter lines, the GFP-silenced spots remained stable, but no systemic silencing occurred. Here we characterize this phenomenon, which we term spontaneous short-range silencing (SSRS). Biochemical analysis of silenced spot tissue did not reveal detectable levels of siRNA. However, agro-infiltration with the suppressor proteins P19 of cymbidium ring spot virus (CymRSV), HC-Pro of tobacco etch virus (TEV), and crosses to a P19 transgenic line, nevertheless suggests that low concentrations of siRNA may have a functional role in the locally silenced zone. We propose that small alterations in the steady-state concentration of siRNAs and their cognate mRNA are decisive with regard to whether silencing remains local or spreads in a systemic manner.
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Affiliation(s)
- Kriton Kalantidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Hellas, PO Box 1527, GR-71110 Heraklion, Crete, Greece.
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28
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Abstract
In plants and in some animals, the effects of post-transcriptional RNA silencing can extend beyond its sites of initiation, owing to the movement of signal molecules. Although the mechanisms and channels involved are different, plant and animal silencing signals must have RNA components that account for the nucleotide sequence-specificity of their effects. Studies carried out in plants and Caenorhabditis elegans have revealed that non-cell autonomous silencing is operated through specialized, remarkably sophisticated pathways and serves important biological functions, including antiviral immunity and, perhaps, developmental patterning. Recent intriguing observations suggest that systemic RNA silencing pathways may also exist in higher vertebrates.
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Affiliation(s)
- Olivier Voinnet
- Institut de Biologie Moléculaire des Plantes du CNRS UPR-2357, 12, rue du Général Zimmer, 67084 Strasbourg Cedex, France.
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29
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Hewezi T, Alibert G, Kallerhoff J. Local infiltration of high- and low-molecular-weight RNA from silenced sunflower (Helianthus annuus L.) plants triggers post-transcriptional gene silencing in non-silenced plants. PLANT BIOTECHNOLOGY JOURNAL 2005; 3:81-9. [PMID: 17168901 DOI: 10.1111/j.1467-7652.2004.00103.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Using grafting procedures, we have characterized post-transcriptional gene silencing (PTGS) in transgenic sunflower expressing beta-glucuronidase (GUS) activity. Silencing was observed as early as 2 weeks after grafting of non-silenced scions on to silenced rootstock. Transmission of the systemic signal occurs solely from stock to scion, is independent of the physiological age of the rootstock and is not heritable. Furthermore, we report, for the first time in plants, an easy and low-cost method of activating RNA silencing by infiltration of purified RNA from silenced plants. Local application of total RNA derived from silenced sunflower plants to leaves of non-silenced plants induces PTGS in newly developed leaves above the point of infiltration, as shown by reduced GUS activity and mRNA levels. Silenced plants contain 21-23-nucleotide RNAs hybridizing to transgene target sequences, in contrast with leaves of non-silenced plants. However, de novo production of GUS-specific short RNA in non-silenced plants can be activated by leaf infiltration of low-molecular-weight RNAs isolated from leaves of silenced plants. Significant levels were detected as early as 2 weeks after infiltration, peaked at 3 weeks and declined 5 weeks after infiltration. Our results provide evidence that RNA infiltration in sunflower induces transient silencing and is not transmitted to offspring. This approach could be of major use in dissecting the mechanisms involved in PTGS.
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Affiliation(s)
- Tarek Hewezi
- Laboratoire de Biotechnologies et Amélioration des Plantes, Ecole Nationale Supérieure Agronomique de Toulouse, Avenue de l'Agrobiopôle, BP 107, Auzeville Tolosane, 31326 Castanet Tolosan, France
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30
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Abstract
Grafting is a powerful but complex means to study the spread of RNA silencing
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Affiliation(s)
- Kriton Kalantidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Crete, Greece.
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31
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García-Pérez RD, Houdt HV, Depicker A. Spreading of post-transcriptional gene silencing along the target gene promotes systemic silencing. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 38:594-602. [PMID: 15125766 DOI: 10.1111/j.1365-313x.2004.02067.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Transitive silencing and grafting-induced gene silencing phenomena were combined to investigate whether a primary target beta-glucuronidase (gus) gene could promote the generation of systemic transitive silencing signals. Tobacco plants with hemizygous or homozygous silencer locus and in trans silenced primary target were used as a source of post-transcriptionally silenced rootstocks and tobacco plants with or without a secondary target locus as scion source. The silencer locus harbored two identical neomycin phosphotransferase II (nptII)-containing T-DNAs, integrated as an inverted repeat. The primary target locus carried a gus gene with homology to the transcribed region of the nptII gene only in the 3' untranslated region, whereas the secondary target locus had two or more copies of a gus gene without homology to transcribed sequences of the silencer locus. The upstream region of the initially targeted sequences of the in trans silenced gus gene could induce the production of a systemic signal. This signal was capable of triggering post-transcriptional gene silencing (PTGS) of the secondary target gus genes in the scion. In addition, the induction of systemic silencing was strikingly dosage dependent for the silencer as well as the primary target loci in the rootstock. Moreover, in the scions, the secondary target gus genes had to be present to generate detectable amounts of short interfering RNAs.
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Affiliation(s)
- Rubén Darío García-Pérez
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, Technologiepark 927, B-9052 Gent, Belgium
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Rutherford G, Tanurdzic M, Hasebe M, Banks JA. A systemic gene silencing method suitable for high throughput, reverse genetic analyses of gene function in fern gametophytes. BMC PLANT BIOLOGY 2004; 4:6. [PMID: 15090074 PMCID: PMC419348 DOI: 10.1186/1471-2229-4-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Accepted: 04/16/2004] [Indexed: 05/18/2023]
Abstract
BACKGROUND Ceratopteris richardii is a useful experimental system for studying gametophyte development and sexual reproduction in plants. However, few tools for cloning mutant genes or disrupting gene function exist for this species. The feasibility of systemic gene silencing as a reverse genetics tool was examined in this study. RESULTS Several DNA constructs targeting a Ceratopteris protoporphyrin IX magnesium chelatase (CrChlI) gene that is required for chlorophyll biosynthesis were each introduced into young gametophytes by biolistic delivery. Their transient expression in individual cells resulted in a colorless cell phenotype that affected most cells of the mature gametophyte, including the meristem and gametangia. The colorless phenotype was associated with a 7-fold decrease in the abundance of the endogenous transcript. While a construct designed to promote the transient expression of a CrChlI double stranded, potentially hairpin-forming RNA was found to be the most efficient in systemically silencing the endogenous gene, a plasmid containing the CrChlI cDNA insert alone was sufficient to induce silencing. Bombarded, colorless hermaphroditic gametophytes produced colorless embryos following self-fertilization, demonstrating that the silencing signal could be transmitted through gametogenesis and fertilization. Bombardment of young gametophytes with constructs targeting the Ceratopteris filamentous temperature sensitive (CrFtsZ) and uroporphyrin dehydrogenase (CrUrod) genes also produced the expected mutant phenotypes. CONCLUSION A method that induces the systemic silencing of target genes in the Ceratopteris gametophyte is described. It provides a simple, inexpensive and rapid means to test the functions of genes involved in gametophyte development, especially those involved in cellular processes common to all plants.
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Affiliation(s)
- George Rutherford
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
| | - Milos Tanurdzic
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
- Purdue Genetics Program, Purdue University, West Lafayette, IN 47907, USA
| | | | - Jo Ann Banks
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
- Purdue Genetics Program, Purdue University, West Lafayette, IN 47907, USA
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Mallory AC, Mlotshwa S, Bowman LH, Vance VB. The capacity of transgenic tobacco to send a systemic RNA silencing signal depends on the nature of the inducing transgene locus. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 35:82-92. [PMID: 12834404 DOI: 10.1046/j.1365-313x.2003.01785.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
RNA silencing is a conserved eukaryotic pathway in which double-stranded RNA (dsRNA) triggers destruction of homologous target RNA via production of short-interfering RNA (siRNA). In plants, at least some cases of RNA silencing can spread systemically. The signal responsible for systemic spread is expected to include an RNA component to account for the sequence specificity of the process, and transient silencing assays have shown that the capacity for systemic silencing correlates with the accumulation of a particular class of small RNA. Here, we report the results of grafting experiments to study transmission of silencing from stably transformed tobacco lines in the presence or absence of helper component-proteinase (HC-Pro), a viral suppressor of silencing. The studied lines carry either a tail-to-tail inverted repeat, the T4-IR transgene locus, or one of two different amplicon transgene loci encoding replication-competent viral RNA. We find that the T4-IR locus, like many sense-transgene-silenced loci, can send a systemic silencing signal, and this ability is not detectably altered by HC-Pro. Paradoxically, neither amplicon locus effectively triggers systemic silencing except when suppressed for silencing by HC-Pro. In contrast to results from transient assays, these grafting experiments reveal no consistent correlation between capacity for systemic silencing and accumulation of any particular class of small RNA. In addition, although all transgenic lines used to transmit systemic silencing signals were methylated at specific sites within the transgene locus, silencing in grafted scions occurred without detectable methylation at those sites in the target locus of the scion.
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Affiliation(s)
- Allison C Mallory
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
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Escobar MA, Civerolo EL, Polito VS, Pinney KA, Dandekar AM. Characterization of oncogene-silenced transgenic plants: implications for Agrobacterium biology and post-transcriptional gene silencing. MOLECULAR PLANT PATHOLOGY 2003; 4:57-65. [PMID: 20569363 DOI: 10.1046/j.1364-3703.2003.00148.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
SUMMARY Agrobacterium tumefaciens tumorigenesis is initiated by the horizontal transfer of a suite of oncogenes that alter hormone synthesis and sensitivity in infected plant cells. Transgenic plants silenced for the iaaM and ipt oncogenes are highly recalcitrant to tumorigenesis, and present a unique resource to elucidate fundamental questions related to Agrobacterium biology and post-transcriptional gene silencing (PTGS). The oncogene-silenced transgenic tomato line 01/6 was used to characterize A. tumefaciens growth in planta and to screen for iaaM and ipt sequence variants. Even in the absence of macroscopic and microscopic indications of tumorigenesis, A. tumefaciens is capable of long-term survival in the hypocotyl tissues of the 01/6 line. A. tumefaciens growth, however, is significantly reduced in the 01/6 line, with populations decreased by 96% relative to wild-type at 52 days post-inoculation. In addition, the 01/6 line displayed suppression of tumorigenesis against all 35 tested strains of A. tumefaciens. High target homology is an absolute requirement of PTGS, therefore this result suggests that regions of the iaaM and ipt oncogenes are very highly conserved across most A. tumefaciens strains. Finally, graft transmissibility of oncogene silencing was assessed by grafting various non-silenced tomato genotypes on to the 01/6 line. Phenotypic and molecular evidence (tumorigenesis and absence of small interfering RNAs, respectively) suggest that oncogene silencing is not graft-transmissible, at least to wild-type and antisense iaaM-over-expressing genotypes.
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Affiliation(s)
- M A Escobar
- Department of Pomology, University of California, 1 Shields Ave., Davis, CA 95616, USA
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Klahre U, Crété P, Leuenberger SA, Iglesias VA, Meins F. High molecular weight RNAs and small interfering RNAs induce systemic posttranscriptional gene silencing in plants. Proc Natl Acad Sci U S A 2002; 99:11981-6. [PMID: 12181491 PMCID: PMC129380 DOI: 10.1073/pnas.182204199] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2002] [Indexed: 11/18/2022] Open
Abstract
Posttranscriptional gene silencing (PTGS) in transgenic plants is an epigenetic form of RNA degradation related to PTGS and RNA interference (RNAi) in fungi and animals. Evidence suggests that transgene loci and RNA viruses can generate double-stranded RNAs similar in sequence to the transcribed region of target genes, which then undergo endonucleolytic cleavage to generate small interfering RNAs (siRNA) that promote degradation of cognate RNAs. The silent state in transgenic plants and in Caenorhabditis elegans can spread systemically, implying that mobile silencing signals exist. Neither the chemical nature of these signals nor their exact source in the PTGS pathway is known. Here, we use a positive marker system and real-time monitoring of green fluorescent protein expression to show that large sense, antisense, and double-stranded RNAs as well as double-stranded siRNAs delivered biolistically into plant cells trigger silencing capable of spreading locally and systemically. Systemically silenced leaves show greatly reduced levels of target RNA and accumulate siRNAs, confirming that RNA can induce systemic PTGS. The induced siRNAs represent parts of the target RNA that are outside of the region of homology with the triggering siRNA. Our results imply that siRNAs themselves or intermediates induced by siRNAs could comprise silencing signals and that these signals induce self-amplifying production of siRNAs.
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Affiliation(s)
- Ulrich Klahre
- Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
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