Plant genetic engineering and genetically modified crop breeding: history and current status

Abstract

This review charts the major developments in the genetic manipulation of plant cells that have taken place since the first gene transfer experiments using Ti plasmids in 1983. Tremendous progress has been made in both our scientific understanding and technological capabilities since the first genetically modified (GM) crops were developed with single gene resistances to herbicides, insects, viruses, and the silencing of unde-sirable genes. Despite opposition in some parts of the world, the area planted with first generation GM crops has grown from 1.7 Mhm² in 1996 to 179.7 Mhm² hectares in 2015. The toolkit available for genetic modification has expanded greatly since 1996 and recently Nobel Laureates have called on Greenpeace to end their blanket opposition, and plant scientists have urged that consideration be given to the benefits of GM crops based on actual evidence. It is now possible to use GM to breed new crop cultivars resistant to a much wider range of pests and diseases, and to produce crops better able to adapt to climate change. The advent of new CRISPR-based technologies makes it possible to contemplate a much wider range of improvements based on transfer of new metabolic pathways and traits to improve nutritional quality, with a much greater degree of precision. Use of GM, sometimes in conjunction with other approaches, offers great opportunities for improving food quality, safety, and security in a changing world.

Keywords

plant transformation / transgene / genetic modification

References

[1] Griffith F. The significance of pneumococcal types. Journal of Hygiene, 1928, 27(2): 113–159

[2] Avery O T, Macleod C M, McCarty M. Studies on the chemical nature of the substance inducing transformation of pneumococcal types: induction of transformation by a desoxyribonucleic acid fraction isolated from pneumococcus type III. Journal of Experimental Medicine, 1944, 79(2): 137–158

[3] Jackson D A, Symons R H, Berg P. Biochemical method for inserting new genetic information into dna of simian virus 40: circular SV40 DNA molecules containing lambda phage genes and the galactose operon of Escherichia coli. Proceedings of the National Academy of Sciences of the United States of America, 1972, 69(10): 2904–2909

[4] Cohen S N, Chang A C, Boyer H W, Helling R B. Construction of biologically functional bacterial plasmids in vitro. Proceedings of the National Academy of Sciences of the United States of America, 1973, 70(11): 3240–3244

[5] Gilbert W, Maxam A. The nucleotide sequence of the lac operator. Proceedings of the National Academy of Sciences of the United States of America, 1973, 70(12): 3581–3584

[6] Sanger F, Nicklen S, Coulson A R. DNA sequencing with chain-terminating inhibitors. Proceedings of the National Academy of Sciences of the United States of America, 1977, 74(12): 5463–5467

[7] ISAAA. Biotech/GM crops planted on two billion hectares from 1996 to 2015. http://www.isaaa.org/kc/cropbiotechupdate/specialedition/2016/2016-04-13-cbu.html, 2016–10–12

[8] Sussex I M. The scientific roots of modern plant biotechnology. Plant Cell, 2008, 20(5): 1189–1198

[9] Miki B, McHugh S. Selectable marker genes in transgenic plants: applications, alternatives and biosafety. Journal of Biotechnology, 2004, 107(3): 193–232

[10] Gilissen L J, Metz P L, Stiekema W J, Nap J P. Biosafety of E. coli β-glucuronidase (GUS) in plants. Transgenic Research, 1998, 7(3): 157–163

[11] Shimomura O, Johnson F H, Saiga Y. Extraction, purification and properties of aequorin, a bioluminescent protein from the luminous hydromedusan, Aequorea. Journal of Cellular and Comparative Physiology, 1962, 59(3): 223–239

[12] Cubitt A B, Heim R, Adams S R, Boyd A E, Gross L A, Tsien R Y. Understanding, improving and using green fluorescent proteins. Trends in Biochemical Sciences, 1995, 20(11): 448–455

[13] Siemering K R, Golbik R, Sever R, Haseloff J. Mutations that suppress the thermosensitivity of green fluorescent protein. Current Biology, 1996, 6(12): 1653–1663

[14] Stewart C N Jr. The utility of green fluorescent protein in transgenic plants. Plant Cell Reports, 2001, 20(5): 376–382

[15] Tsien R Y. The green fluorescent protein. Annual Review of Biochemistry, 1998, 67(1): 509–544

[16] Chalfie M, Tu Y, Euskirchen G, Ward W W, Prasher D C. Green fluorescent protein as a marker for gene expression. Science, 1994, 263(5148): 802–805

[17] Wang X, Xue L, Sun J, Zuo J. The Arabidopsis BE1 gene, encoding a putative glycoside hydrolase localized in plastids, plays crucial roles during embryogenesis and carbohydrate metabolism. Journal of Integrative Plant Biology, 2010, 52(3): 273–288

[18] Chiu W, Niwa Y, Zeng W, Hirano T, Kobayashi H, Sheen J. Engineered GFP as a vital reporter in plants. Current Biology, 1996, 6(3): 325–330

[19] Aflalo C. Biologically localized firefly luciferase: a tool to study cellular processes. International Review of Cytology, 1991, 130: 269–323

[20] Ow D W, De Wet J R, Helinski D R, Howell S H, Wood K V, Deluca M. Transient and stable expression of the firefly luciferase gene in plant cells and transgenic plants. Science, 1986, 234(4778): 856–859

[21] Millar A, Short S, Hiratsuka K, Chua N H, Kay S. Firefly luciferase as a reporter of regulated gene expression in higher plants. Plant Molecular Biology Reporter, 1992, 10(4): 324–337

[22] McNabb D S, Reed R, Marciniak R A. Dual luciferase assay system for rapid assessment of gene expression in Saccharomyces cerevisiae. Eukaryotic Cell, 2005, 4(9): 1539–1549

[23] Bevan M W, Flavell R B, Chilton M D. A chimaeric antibiotic resistance gene as a selectable marker for plant cell transformation. Nature, 1983, 304(5922): 184–187

[24] Waldron C, Murphy E B, Roberts J L, Gustafson G D, Armour S L, Malcolm S K. Resistance to hygromycin B: a new marker for plant transformation studies. Plant Molecular Biology, 1985, 5(2): 103–108

[25] Block M D, Botterman J, Vandewiele M, Dockx J, Thoen C, Gossele V, Movva N R, Thompson C, Montagu M V, Leemans J. Engineering herbicide resistance in plants by expression of a detoxifying enzyme. EMBO Journal, 1987, 6(9): 2513–2518

[26] Sawasaki T, Seki M, Anzai H, Irifune K, Morikawa H. Stable transformation of Arabidopsis with the bar gene using particle bombardment. Transgenic Research, 1994, 3(5): 279–286

[27] Cao J, Duan X, McEiroy D, Wu R. Regeneration of herbicide resistant transgenic rice plants following microprojectile-mediated transformation of suspension culture cells. Plant Cell Reports, 1992, 11(11): 586–591

[28] Zuo J, Niu Q W, Ikeda Y, Chua N H. Marker-free transformation: increasing transformation frequency by the use of regeneration-promoting genes. Current Opinion in Biotechnology, 2002, 13(2): 173–180

[29] Kunkel T, Niu Q W, Chan Y S, Chua N H. Inducible isopentenyl transferase as a high-efficiency marker for plant transformation. Nature Biotechnology, 1999, 17(9): 916–919

[30] Covey S N, Lomonossoff G P, Hull R. Characterisation of cauliflower mosaic virus DNA sequences which encode major polyadenylated transcripts. Nucleic Acids Research, 1981, 9(24): 6735–6748

[31] Odell J T, Nagy F, Chua N H. Identification of DNA sequences required for activity of the cauliflower mosaic virus 35S promoter. Nature, 1985, 313(6005): 810–812

[32] Guilley H, Dudley R K, Jonard G, Balazs E, Richards K E. Transcription of cauliflower mosaic virus DNA: detection of promoter sequences, and characterization of transcripts. Cell, 1982, 30(3): 763–773

[33] Fang R X, Nagy F, Sivasubramaniam S, Chua N H. Multiple cis regulatory elements for maximal expression of the cauliflower mosaic virus 35S promoter in transgenic plants. Plant Cell, 1989, 1(1): 141–150

[34] Kay R, Chan A, Daly M, McPherson J. Duplication of CaMV 35S promoter sequences creates a strong enhancer for plant genes. Science, 1987, 236(4806): 1299–1302

[35] Yan L, Wei S, Wu Y, Hu R, Li H, Yang W, Xie Q. High-efficiency genome editing in Arabidopsis using YAO promoter-driven CRISPR/Cas9 system. Molecular Plant, 2015, 8(12): 1820–1823

[36] Wilkinson J E, Twell D, Lindsey K. Activities of CaMV 35S and nos promoters in pollen: implications for field release of transgenic plants. Journal of Experimental Botany, 1997, 48(2): 265–275

[37] McElroy D, Zhang W, Cao J, Wu R. Isolation of an efficient actin promoter for use in rice transformation. Plant Cell, 1990, 2(2): 163–171

[38] He C, Lin Z, McElroy D, Wu R. Identification of a rice actin2 gene regulatory region for high-level expression of transgenes in monocots. Plant Biotechnology Journal, 2009, 7(3): 227–239

[39] Jang I C, Choi W B, Lee K H, Song S I, Nahm B H, Kim J K. High-level and ubiquitous expression of the rice cytochrome c gene OsCc1 and its promoter activity in transgenic plants provides a useful promoter for transgenesis of monocots. Plant Physiology, 2002, 129(4): 1473–1481

[40] Jeon J S, Lee S, Jung K H, Jun S H, Kim C, An G. Tissue-preferential expression of a rice α-tubulin gene, OsTubA1, mediated by the first intron. Plant Physiology, 2000, 123(3): 1005–1014

[41] Lu J, Sivamani E, Li X, Qu R. Activity of the 5′ regulatory regions of the rice polyubiquitin rubi3 gene in transgenic rice plants as analyzed by both GUS and GFP reporter genes. Plant Cell Reports, 2008, 27(10): 1587–1600

[42] Wang J, Oard J H. Rice ubiquitin promoters: deletion analysis and potential usefulness in plant transformation systems. Plant Cell Reports, 2003, 22(2): 129–134

[43] Christensen A H, Sharrock R A, Quail P H. Maize polyubiquitin genes: structure, thermal perturbation of expression and transcript splicing, and promoter activity following transfer to protoplasts by electroporation. Plant Molecular Biology, 1992, 18(4): 675–689

[44] Schledzewski K, Mendel R. Quantitative transient gene expression: comparison of the promoters for maize polyubiquitin1, rice actin1, maize-derived Emu and CaMV 35S in cells of barley, maize and tobacco. Transgenic Research, 1994, 3(4): 249–255

[45] An G. Development of plant promoter expression vectors and their use for analysis of differential activity of nopaline synthase promoter in transformed tobacco cells. Plant Physiology, 1986, 81(1): 86–91

[46] Ebert P R, Ha S B, An G. Identification of an essential upstream element in the nopaline synthase promoter by stable and transient assays. Proceedings of the National Academy of Sciences of the United States of America, 1987, 84(16): 5745–5749

[47] Jeong H J, Jung K H. Rice tissue-specific promoters and condition-dependent promoters for effective translational application. Journal of Integrative Plant Biology, 2015, 57(11): 913–924

[48] Potenza C, Aleman L, Sengupta-Gopalan C. Targeting transgene expression in research, agricultural, and environmental applications: promoters used in plant transformation. In Vitro Cellular & Developmental Biology-Plant, 2004, 40(1): 1–22

[49] Saijo T, Nagasawa A. Development of a tightly regulated and highly responsive copper-inducible gene expression system and its application to control of flowering time. Plant Cell Reports, 2014, 33(1): 47–59

[50] Aoyama T, Chua N H. A glucocorticoid-mediated transcriptional induction system in transgenic plants. Plant Journal, 1997, 11(3): 605–612

[51] Zuo J, Niu Q W, Chua N H. An estrogen receptor-based transactivator XVE mediates highly inducible gene expression in transgenic plants. Plant Journal, 2000, 24(2): 265–273

[52] Deveaux Y, Peaucelle A, Roberts G R, Coen E, Simon R, Mizukami Y, Traas J, Murray J A, Doonan J H, Laufs P. The ethanol switch: a tool for tissue-specific gene induction during plant development. Plant Journal, 2003, 36(6): 918–930

[53] Wang X, Niu Q W, Teng C, Li C, Mu J, Chua N H, Zuo J. Overexpression of PGA37/MYB118 and MYB115 promotes vegetative-to-embryonic transition in Arabidopsis. Cell Research, 2009, 19(2): 224–235

[54] Okuzaki A, Konagaya K, Nanasato Y, Tsuda M, Tabei Y. Estrogen-inducible GFP expression patterns in rice (Oryza sativa L.). Plant Cell Reports, 2011, 30(4): 529–538

[55] Ambavaram M M, Basu S, Krishnan A, Ramegowda V, Batlang U, Rahman L, Baisakh N, Pereira A. Coordinated regulation of photosynthesis in rice increases yield and tolerance to environmental stress. Nature Communications, 2014, 5: 5302

[56] Caddick M X, Greenland A J, Jepson, Krause K P, Qu N, Riddell K V, Salter M G, Schuch W, Sonnewald U, Tomsett A B. An ethanol inducible gene switch for plants used to manipulate carbon metabolism. Nature Biotechnology, 1998, 16(2): 177–180

[57] Gatz C, Frohberg C, Wendenburg R. Stringent repression and homogeneous de-repression by tetracycline of a modified CaMV 35S promoter in intact transgenic tobacco plants. Plant Journal, 1992, 2(3): 397–404

[58] Cocking E C. Turning point article plant protoplasts. In Vitro Cellular & Developmental Biology-Plant, 2000, 36(2): 77–82

[59] Johnson C M, Carswell G K, Shillito R D. Direct gene transfer via polyethylene glycol. Journal of Tissue Culture Methods, 1989, 12(4): 127–133

[60] Davey M R, Anthony P, Power J B, Lowe K C. Plant protoplasts: status and biotechnological perspectives. Biotechnology Advances, 2005, 23(2): 131–171

[61] Klein T M, Wolf E D, Wu R, Sanford J C. High-velocity microprojectiles for delivering nucleic acids into living cells. Nature, 1987, 327(6117): 70–73

[62] Wang K, Drayton P, Frame B, Dunwell J, Thompson J. Whisker-mediated plant transformation: an alternative technology. In Vitro Cellular & Developmental Biology-Plant, 1995, 31(2): 101–104

[63] Potrykus I. Gene transfer to plants: assessment and perspectives. Physiologia Plantarum, 1990, 79(1): 125–134

[64] Bock R. Engineering plastid genomes: methods, tools, and applications in basic research and biotechnology. Annual Review of Plant Biology, 2015, 66(1): 211–241

[65] Fraley R T, Rogers S G, Horsch R B, Sanders P R, Flick J S, Adams S P, Bittner M L, Brand L A, Fink C L, Fry J S, Galluppi G R, Goldberg S B, Hoffmann N L, Woo S C. Expression of bacterial genes in plant cells. Proceedings of the National Academy of Sciences of the United States of America, 1983, 80(15): 4803–4807

[66] Herrera-Estrella L, Depicker A, Van Montagu M, Schell J. Expression of chimaeric genes transferred into plant cells using a Ti-plasmid-derived vector. Nature, 1983, 303(5914): 209–213

[67] Hoekema A, Hirsch P R, Hooykaas P J J, Schilperoort R A. A binary plant vector strategy based on separation of vir- and T-region of the Agrobacterium tumefaciens Ti-plasmid. Nature, 1983, 303(5913): 179–180

[68] Bevan M. Binary Agrobacterium vectors for plant transformation. Nucleic Acids Research, 1984, 12(22): 8711–8721

[69] Lee L Y, Gelvin S B. T-DNA binary vectors and systems. Plant Physiology, 2008, 146(2): 325–332

[70] Clough S J, Bent A F. Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant Journal, 1998, 16(6): 735–743

[71] Saha P, Blumwald E. Spike-dip transformation of Setaria viridis. Plant Journal, 2016, 86(1): 89–101

[72] Nguyen T, Liu X, Derocher J. Floral dip method for transformation of camelina. United States of America, 2014, 8779238

[73] Ow D W. The long road to recombinase-mediated plant transformation. Plant Biotechnology Journal, 2016, 14(2): 441–447

[74] Zuo J, Niu Q W, Moller S G, Chua N H. Chemical-regulated, site-specific DNA excision in transgenic plants. Nature Biotechnology, 2001, 19(2): 157–161

[75] Terada R, Urawa H, Inagaki Y, Tsugane K, Iida S. Efficient gene targeting by homologous recombination in rice. Nature Biotechnology, 2002, 20(10): 1030–1034

[76] Steinert J, Schiml S, Puchta H. Homology-based double-strand break-induced genome engineering in plants. Plant Cell Reports, 2016, 35(7): 1429–1438

[77] Townsend J A, Wright D A, Winfrey R J, Fu F, Maeder M L, Joung J K, Voytas D F. High-frequency modification of plant genes using engineered zinc-finger nucleases. Nature, 2009, 459(7245): 442–445

[78] Funke T, Han H, Healy-Fried M L, Fischer M, Schonbrunn E. Molecular basis for the herbicide resistance of Roundup Ready crops. Proceedings of the National Academy of Sciences of the United States of America, 2006, 103(35): 13010–13015

[79] Temple W. Review of the evidence relating to glyphosate and carcinogenicity. http://www.epa.govt.nz/Publications/EPA_glyphosate_review.pdf, 2016–10–12

[80] Perlak F J, Fuchs R L, Dean D A, McPherson S L, Fischhoff D A. Modification of the coding sequence enhances plant expression of insect control protein genes. Proceedings of the National Academy of Sciences of the United States of America, 1991, 88(8): 3324–3328

[81] Höfte H, Whiteley H R. Insecticidal crystal proteins of Bacillus thuringiensis. Microbiological Reviews, 1989, 53(2): 242–255

[82] Cao J, Zhao J Z, Tang D, Shelton M, Earle D. Broccoli plants with pyramided cry1Ac and cry1C Bt genes control diamondback moths resistant to Cry1A and Cry1C proteins. Theoretical and Applied Genetics, 2002, 105(2–3): 258–264

[83] McGaughey W H, Whalon M E. Managing insect resistance to Bacillus thuringiensis toxins. Science, 1992, 258(5087): 1451–1455

[84] Ricroch A E, Hénard-Damave M C. Next biotech plants: new traits, crops, developers and technologies for addressing global challenges. Critical Reviews in Biotechnology, 2016, 36(4): 675–690

[85] Fitch M M M, Manshardt R M, Gonsalves D, Slightom J L, Sanford J C. Virus resistance papaya derived from tissue bombarded with the coat protein gene of papaya ringspot virus. Nature Biotechnology, 1992, 10(11): 1466–1472

[86] Geo Pie Project #8. Genetically engineered foods: plant virus resistance. https://scholarworks.iupui.edu/bitstream/handle/1805/813/GE%20plant%20virus%20resistance.pdf, 2016–10–12

[87] Scorza R, Kriss A B, Callahan A M, Webb K, Demuth M, Gottwald T. Spatial and temporal assessment of pollen- and seed-mediated gene flow from genetically engineered plum Prunus domestica. PLoS One, 2013, 8(10): e75291

[88] Baulcombe D. Viruses and gene silencing in plants. in Calisher C H, Horzinek M C, eds. 100 years of virology: The birth and growth of a discipline. Vienna: Springer Vienna, 1999, 189–201

[89] Sudarshana M R, Roy G, Falk B W. Methods for engineering resistance to plant viruses. in Ronald P C, eds. Plant-pathogen interactions: methods and protocols. 1nd. Totowa NJ: Humana Press, 2007, 183–195

[90] Halpin C. Gene stacking in transgenic plants—the challenge for 21st century plant biotechnology. Plant Biotechnology Journal, 2005, 3(2): 141–155

[91] James C. Global status of commercialized biotech/GM crops. ISAAA Brief No. 49. New York: The International Service for the Acquisition of Agri-biotech Applications (ISAAA), 2014

[92] James C. Preview: global status of commercialized transgenic crops. ISAAA Briefs No. 30. New York: The International Service for the Acquisition of Agri-biotech Applications (ISAAA), 2003

[93] Casini A, Storch M, Baldwin G S, Ellis T. Bricks and blueprints: methods and standards for DNA assembly. Nature Reviews Molecular Cell Biology, 2015, 16(9): 568–576

[94] Ow D W. Recombinase-directed plant transformation for the post-genomic era. in Town C, eds. Functional genomics. Dordrecht: Springer Netherlands, 2002, 183–200

[95] Li Z, Xing A, Moon B P, McCardell R P, Mills K, Falco S C. Site-specific integration of transgenes in soybean via recombinase-mediated DNA cassette exchange. Plant Physiology, 2009, 151(3): 1087–1095

[96] Li Z, Moon B P, Xing A, Liu Z B, McCardell R P, Damude H G, Falco S C. Stacking multiple transgenes at a selected genomic site via repeated recombinase-mediated DNA cassette exchanges. Plant Physiology, 2010, 154(2): 622–631

[97] Depicker A, Herman L, Jacobs A, Schell J, Van Montagu M. Frequencies of simultaneous transformation with different T-DNAs and their relevance to the Agrobacterium/plant cell interaction. Molecular & General Genetics, 1985, 201(3): 477–484

[98] De Block M, Debrouwer D. Two T-DNA’s co-transformed into Brassica napus by a double Agrobacterium tumefaciens infection are mainly integrated at the same locus. Theoretical and Applied Genetics, 1991, 82(3): 257–263

[99] McCormac A C, Fowler M R, Chen D F, Elliott M C. Efficient co-transformation of Nicotiana tabacum by two independent T-DNAs, the effect of T-DNA size and implications for genetic separation. Transgenic Research, 2001, 10(2): 143–155

[100] Li L, Zhou Y, Cheng X, Sun J, Marita J M, Ralph J, Chiang V L. Combinatorial modification of multiple lignin traits in trees through multigene cotransformation. Proceedings of the National Academy of Sciences of the United States of America, 2003, 100(8): 4939–4944

[101] Hu W J, Harding S A, Lung J, Popko J L, Ralph J, Stokke D D, Tsai C J, Chiang V L. Repression of lignin biosynthesis promotes cellulose accumulation and growth in transgenic trees. Nature Biotechnology, 1999, 17(8): 808–812

[102] Ye X, Al-Babili S, Kloti A, Zhang J, Lucca P, Beyer P, Potrykus I. Engineering the provitamin A (β-carotene) biosynthetic pathway into (carotenoid-free) rice endosperm. Science, 2000, 287(5451): 303–305

[103] Datta K, Baisakh N, Oliva N, Torrizo L, Abrigo E, Tan J, Rai M, Rehana S, Al-Babili S, Beyer P, Potrykus I, Datta S K. Bioengineered ‘golden’ indica rice cultivars with β-carotene metabolism in the endosperm with hygromycin and mannose selection systems. Plant Biotechnology Journal, 2003, 1(2): 81–90

[104] Paine J A, Shipton C A, Chaggar S, Howells R M, Kennedy M J, Vernon G, Wright S Y, Hinchliffe E, Adams J L, Silverstone A L, Drake R. Improving the nutritional value of Golden Rice through increased pro-vitamin A content. Nature Biotechnology, 2005, 23(4): 482–487

[105] Zhu C, Naqvi S, Breitenbach J, Sandmann G, Christou P, Capell T. Combinatorial genetic transformation generates a library of metabolic phenotypes for the carotenoid pathway in maize. Proceedings of the National Academy of Sciences of the United States of America, 2008, 105(47): 18232–18237

[106] Joel A. 107 Nobel laureates sign letter blasting Greenpeace over GMOs. https://www.washingtonpost.com/news/speaking-of-science/wp/2016/06/29/more-than-100-nobel-laureates-take-on-greenpeace-over-gmo-stance/, 2016–06–30

[107] Westhoff P, Herrmann R G. Complex RNA maturation in chloroplasts. The psbB operon from spinach. European Journal of Biochemistry, 1988, 171(3): 551–564

[108] Zhou F, Karcher D, Bock R. Identification of a plastid intercistronic expression element (IEE) facilitating the expression of stable translatable monocistronic mRNAs from operons. Plant Journal, 2007, 52(5): 961–972

[109] Nakashita H, Arai Y, Shikanai T, Doi Y, Yamaguchi I. Introduction of bacterial metabolism into higher plants by polycistronic transgene expression. Bioscience, Biotechnology, and Biochemistry, 2001, 65(7): 1688–1691

[110] Magee A M, Horvath E M, Kavanagh T A. Pre-screening plastid transgene expression cassettes in Escherichia coli may be unreliable as a predictor of expression levels in chloroplast-transformed plants. Plant Science, 2004, 166(6): 1605–1611

[111] Lu Y, Rijzaani H, Karcher D, Ruf S, Bock R. Efficient metabolic pathway engineering in transgenic tobacco and tomato plastids with synthetic multigene operons. Proceedings of the National Academy of Sciences of the United States of America, 2013, 110(8): E623–E632

[112] de Felipe P. Skipping the co-expression problem: the new 2A “CHYSEL” technology. Genetic Vaccines and Therapy, 2004, 2(1): 13

[113] Zhao Q, Liu M, Tan M, Gao J, Shen Z. Expression of Cry1Ab and Cry2Ab by a polycistronic transgene with a self-cleavage peptide in rice. PLoS One, 2014, 9(10): e110006

[114] Belhaj K, Chaparro Garcia A, Kamoun S, Patron N J, Nekrasov V. Editing plant genomes with CRISPR/Cas9. Current Opinion in Biotechnology, 2015, 32: 76–84

[115] Auer T O, Duroure K, De Cian A, Concordet J P, Del Bene F. Highly efficient CRISPR/Cas9-mediated knock-in in zebrafish by homology-independent DNA repair. Genome Research, 2014, 24(1): 142–153

[116] Wang Y, Cheng X, Shan Q, Zhang Y, Liu J, Gao C, Qiu J L. Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew. Nature Biotechnology, 2014, 32(9): 947–951

[117] Ecker J R, Davis R W. Inhibition of gene expression in plant cells by expression of antisense RNA. Proceedings of the National Academy of Sciences of the United States of America, 1986, 83(15): 5372–5376

[118] Smith C J S, Watson C F, Ray J, Bird C R, Morris P C, Schuch W, Grierson D. Antisense RNA inhibition of polygalacturonase gene expression in transgenic tomatoes. Nature, 1988, 334(6184): 724–726

[119] Sheehy R E, Pearson J, Brady C J, Hiatt W R. Molecular characterization of tomato fruit polygalacturonase. Molecular & General Genetics, 1987, 208(1): 30–36

[120] van der Krol A R, Lenting P E, Veenstra J, van der Meer I M, Koes R E, Gerats A G M, Mol J N M, Stuitje A R. An anti-sense chalcone synthase gene in transgenic plants inhibits flower pigmentation. Nature, 1988, 333(6176): 866–869

[121] Smith C J, Watson C F, Bird C R, Ray J, Schuch W, Grierson D. Expression of a truncated tomato polygalacturonase gene inhibits expression of the endogenous gene in transgenic plants. Molecular & General Genetics, 1990, 224(3): 477–481

[122] Smith C J S, Watson C F, Morris P C, Bird C R, Seymour G B, Gray J E, Arnold C, Tucker G A, Schuch W, Harding S, Grierson D. Inheritance and effect on ripening of antisense polygalacturonase genes in transgenic tomatoes. Plant Molecular Biology, 1990, 14(3): 369–379

[123] van der Krol A R, Mur L A, Beld M, Mol J N, Stuitje A R. Flavonoid genes in petunia: addition of a limited number of gene copies may lead to a suppression of gene expression. Plant Cell, 1990, 2(4): 291–299

[124] Jorgensen R. Altered gene expression in plants due totrans interactions between homologous genes. Trends in Biotechnology, 1990, 8: 340–344

[125] Grierson D, Fray R G, Hamilton A J, Smith C J S, Watson C F. Does co-suppression of sense genes in transgenic plants involve antisense RNA? Trends in Biotechnology, 1991, 9(1): 122–123

[126] Sijen T, Wellink J, Hiriart J B, Van Kammen A. RNA-mediated virus resistance: role of repeated transgenes and delineation of targeted regions. Plant Cell, 1996, 8(12): 2277–2294

[127] Gazzani S, Lawrenson T, Woodward C, Headon D, Sablowski R. A link between mRNA turnover and RNA interference in Arabidopsis. Science, 2004, 306(5698): 1046–1048

[128] Thran M, Link K, Sonnewald U. The Arabidopsis DCP2 gene is required for proper mRNA turnover and prevents transgene silencing in Arabidopsis. Plant Journal, 2012, 72(3): 368–377

[129] Herr A J, Molnar A, Jones A, Baulcombe D C. Defective RNA processing enhances RNA silencing and influences flowering of Arabidopsis. Proceedings of the National Academy of Sciences of the United States of America, 2006, 103(41): 14994–15001

[130] Cluster P D, O’Dell M, Metzlaff M, Flavell R B. Details of T-DNA structural organization from a transgenic Petunia population exhibiting co-suppression. Plant Molecular Biology, 1996, 32(6): 1197–1203

[131] Flavell R B. Inactivation of gene expression in plants as a consequence of specific sequence duplication. Proceedings of the National Academy of Sciences of the United States of America, 1994, 91(9): 3490–3496

[132] Que Q, Wang H Y, English J J, Jorgensen R A. The frequency and degree of cosuppression by sense chalcone synthase transgenes are dependent on transgene promoter strength and are reduced by premature nonsense codons in the transgene coding sequence. Plant Cell, 1997, 9(8): 1357–1368

[133] Han Y, Griffiths A, Li H, Grierson D. The effect of endogenous mRNA levels on co-suppression in tomato. FEBS Letters, 2004, 563(1–3): 123–128

[134] Baulcombe D C. RNA as a target and an initiator of post-transcriptional gene silencing in trangenic plants. Plant Molecular Biology, 1996, 32(1): 79–88

[135] Ratcliff F, Martin-Hernandez A M, Baulcombe D C. Tobacco rattle virus as a vector for analysis of gene function by silencing. Plant Journal, 2001, 25(2): 237–245

[136] Mei Y, Zhang C, Kernodle B M, Hill J H, Whitham S A. A foxtail mosaic virus vector for virus-induced gene silencing in maize. Plant Physiology, 2016, 171(2): 760–772

[137] Liu N, Xie K, Jia Q, Zhao J, Chen T, Li H, Wei X, Diao X, Hong Y, Liu Y. Foxtail mosaic virus-induced gene silencing in monocot plants. Plant Physiology, 2016, 171(3): 1801–1807

[138] Hamilton A J, Brown S, Yuanhai H, Ishizuka M, Lowe A, Solis A G A, Grierson D. A transgene with repeated DNA causes high frequency, post-transcriptional suppression of ACC-oxidase gene expression in tomato. Plant Journal, 1998, 15(6): 737–746

[139] Hamilton A J, Baulcombe D C. A species of small antisense RNA in posttranscriptional gene silencing in plants. Science, 1999, 286(5441): 950–952

[140] Fire A, Xu S, Montgomery M K, Kostas S A, Driver S E, Mello C C. Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature, 1998, 391(6669): 806–811

[141] Baulcombe D. RNA silencing. Trends in Biochemical Sciences, 2005, 30(6): 290–293

[142] Wesley S V, Helliwell C A, Smith N A, Wang M B, Rouse D T, Liu Q, Gooding P S, Singh S P, Abbott D, Stoutjesdijk P A, Robinson S P, Gleave A P, Green A G, Waterhouse P M. Construct design for efficient, effective and high-throughput gene silencing in plants. Plant Journal, 2001, 27(6): 581–590

[143] Yin Y, Chory J, Baulcombe D. RNAi in transgenic plants. Current Protocols in Molecular Biology, 2005, Unit 26.6

[144] Grierson D. Identifying and silencing tomato ripening genes with antisense genes. Plant Biotechnology Journal, 2016, 14(3): 835–838

[145] Grierson D. Ethylene and the control of fruit ripening. in Seymour G, Poole M, Giovannoni J, Tucker G, eds. Molecular Biology and Biochemistry of Fruit Ripening. John Wiley & Sons, Inc, 2013, 43–73

[146] Grierson D, Hamilton A J, Lycett G W. The life and times of ACC oxidase, alias TOM13. Molecular Biology Reports, 2013, 40(4): 3021–3022

[147] Prins M, Laimer M, Noris E, Schubert J, Wassenegger M, Tepfer M. Strategies for antiviral resistance in transgenic plants. Molecular Plant Pathology, 2008, 9(1): 73–83

[148] Koch A, Kogel K H. New wind in the sails: improving the agronomic value of crop plants through RNAi-mediated gene silencing. Plant Biotechnology Journal, 2014, 12(7): 821–831

[149] Baum J A, Bogaert T, Clinton W, Heck G R, Feldmann P, Ilagan O, Johnson S, Plaetinck G, Munyikwa T, Pleau M, Vaughn T, Roberts J. Control of coleopteran insect pests through RNA interference. Nature Biotechnology, 2007, 25(11): 1322–1326

[150] Nawaz-ul-Rehman M S, Mansoor S, Khan A A, Zafar Y, Briddon R W. RNAi-mediated male sterility of tobacco by silencing TA29. Molecular Biotechnology, 2007, 36(2): 159–165

[151] Wang X, Singer S D, Liu Z. Silencing of meiosis-critical genes for engineering male sterility in plants. Plant Cell Reports, 2012, 31(4): 747–756

[152] Coleman H D, Park J Y, Nair R, Chapple C, Mansfield S D. RNAi-mediated suppression of p-coumaroyl-CoA 3′-hydroxylase in hybrid poplar impacts lignin deposition and soluble secondary metabolism. Proceedings of the National Academy of Sciences of the United States of America, 2008, 105(11): 4501–4506

[153] Xu B, Escamilla-Trevino L L, Sathitsuksanoh N, Shen Z, Shen H, Zhang Y H, Dixon R A, Zhao B. Silencing of 4-coumarate: coenzyme A ligase in switchgrass leads to reduced lignin content and improved fermentable sugar yields for biofuel production. New Phytologist, 2011, 192(3): 611–625

[154] Jung J H, Fouad W M, Vermerris W, Gallo M, Altpeter F. RNAi suppression of lignin biosynthesis in sugarcane reduces recalcitrance for biofuel production from lignocellulosic biomass. Plant Biotechnology Journal, 2012, 10(9): 1067–1076

[155] Fornalé S, Capellades M, Encina A, Wang K, Irar S, Lapierre C, Ruel K, Joseleau J P, Berenguer J, Puigdomenech P, Rigau J, Caparros-Ruiz D. Altered lignin biosynthesis improves cellulosic bioethanol production in transgenic maize plants down-regulated for cinnamyl alcohol dehydrogenase. Molecular Plant, 2012, 5(4): 817–830

[156] Lee C, Teng Q, Huang W, Zhong R, Ye Z H. Down-regulation of PoGT47C expression in poplar results in a reduced glucuronoxylan content and an increased wood digestibility by cellulase. Plant & Cell Physiology, 2009, 50(6): 1075–1089

[157] Biswal A K, Hao Z, Pattathil S, Yang X, Winkeler K, Collins C, Mohanty S S, Richardson E A, Gelineo-Albersheim I, Hunt K, Ryno D, Sykes R W, Turner G B, Ziebell A, Gjersing E, Lukowitz W, Davis M F, Decker S R, Hahn M G, Mohnen D. Downregulation of GAUT12 in Populus deltoides by RNA silencing results in reduced recalcitrance, increased growth and reduced xylan and pectin in a woody biofuel feedstock. Biotechnology for Biofuels, 2015, 8(1): 41

[158] Kim M J, Yang S W, Mao H Z, Veena S P, Yin J L, Chua N H. Gene silencing of Sugar-dependent 1 (JcSDP1), encoding a patatin-domain triacylglycerol lipase, enhances seed oil accumulation in Jatropha curcas. Biotechnology for Biofuels, 2014, 7(1): 36

[159] Trentacoste E M, Shrestha R P, Smith S R, Gle C, Hartmann A C, Hildebrand M, Gerwick W H. Metabolic engineering of lipid catabolism increases microalgal lipid accumulation without compromising growth. Proceedings of the National Academy of Sciences of the United States of America, 2013, 110(49): 19748–19753

[160] Price D R, Gatehouse J A. RNAi-mediated crop protection against insects. Trends in Biotechnology, 2008, 26(7): 393–400

[161] Whyard S, Singh A D, Wong S. Ingested double-stranded RNAs can act as species-specific insecticides. Insect Biochemistry and Molecular Biology, 2009, 39(11): 824–832

[162] Wang J, Wu M, Wang B, Han Z. Comparison of the RNA interference effects triggered by dsRNA and siRNA in Tribolium castaneum. Pest Management Science, 2013, 69(7): 781–786

[163] Zhang J, Khan S A, Hasse C, Ruf S, Heckel D G, Bock R. Full crop protection from an insect pest by expression of long double-stranded RNAs in plastids. Science, 2015, 347(6225): 991–994

[164] Yoder J I, Scholes J D. Host plant resistance to parasitic weeds; recent progress and bottlenecks. Current Opinion in Plant Biology, 2010, 13(4): 478–484

[165] Aly R, Cholakh H, Joel D M, Leibman D, Steinitz B, Zelcer A, Naglis A, Yarden O, Gal-On A. Gene silencing of mannose 6-phosphate reductase in the parasitic weed Orobanche aegyptiaca through the production of homologous dsRNA sequences in the host plant. Plant Biotechnology Journal, 2009, 7(6): 487–498

[166] Bandaranayake P C, Yoder J I. Trans-specific gene silencing of acetyl-CoA carboxylase in a root-parasitic plant. Molecular Plant-Microbe Interactions, 2013, 26(5): 575–584

[167] de Framond A, Rich P, McMillan J, Ejeta G. Effects of Striga parasitism of transgenic maize armed with RNAi constructs targeting essential S. asiatica genes. in Ejeta G, Gressel J, eds. Integrating new technologies for Striga control. 1nd. Singapore: World Scientific Publishing Company, 2007, 185–196

[168] Kirigia D, Runo S, Alakonya A. A virus-induced gene silencing (VIGS) system for functional genomics in the parasitic plant Striga hermonthica. Plant Methods, 2014, 10(1): 16

[169] Huang G, Allen R, Davis E L, Baum T J, Hussey R S. Engineering broad root-knot resistance in transgenic plants by RNAi silencing of a conserved and essential root-knot nematode parasitism gene. Proceedings of the National Academy of Sciences of the United States of America, 2006, 103(39): 14302–14306

[170] Sindhu A S, Maier T R, Mitchum M G, Hussey R S, Davis E L, Baum T J. Effective and specific in planta RNAi in cyst nematodes: expression interference of four parasitism genes reduces parasitic success. Journal of Experimental Botany, 2009, 60(1): 315–324

[171] Xue B, Hamamouch N, Li C, Huang G, Hussey R S, Baum T J, Davis E L. The 8D05 parasitism gene of Meloidogyne incognita is required for successful infection of host roots. Phytopathology, 2013, 103(2): 175–181

[172] Niu J, Liu P, Liu Q, Chen C, Guo Q, Yin J, Yang G, Jian H. Msp40 effector of root-knot nematode manipulates plant immunity to facilitate parasitism. Scientific Reports, 2016, 6: 19443

[173] Yadav B C, Veluthambi K, Subramaniam K. Host-generated double stranded RNA induces RNAi in plant-parasitic nematodes and protects the host from infection. Molecular and Biochemical Parasitology, 2006, 148(2): 219–222

[174] Lourenco-Tessutti I T, Souza J D Junior, Martins-de-Sa D, Viana A A, Carneiro R M, Togawa R C, de Almeida-Engler J, Batista J A, Silva M C, Fragoso R R, Grossi-de-Sa M F. Knock-down of heat-shock protein 90 and isocitrate lyase gene expression reduced root-knot nematode reproduction. Phytopathology, 2015, 105(5): 628–637

[175] Dinh P T, Zhang L, Mojtahedi H, Brown C R, Elling A A. Broad meloidogyne resistance in potato based on RNA interference of effector gene 16D10. Journal of Nematology, 2015, 47(1): 71–78

[176] Dutta T K, Banakar P, Rao U. The status of RNAi-based transgenic research in plant nematology. Frontiers in Microbiology, 2014, 5: 760

[177] Waltz E. USDA approves next-generation GM potato. Nature Biotechnology, 2015, 33(1): 12–13

[178] Waltz E. Nonbrowning GM apple cleared for market. Nature Biotechnology, 2015, 33(4): 326–327

[179] Nathans D, Smith H O. Restriction endonucleases in the analysis and restructuring of DNA molecules. Annual Review of Biochemistry, 1975, 44(1): 273–293

[180] Davis D, Stokoe D. Zinc finger nucleases as tools to understand and treat human diseases. BMC Medicine, 2010, 8(1): 42

[181] Sander J D, Dahlborg E J, Goodwin M J, Cade L, Zhang F, Cifuentes D, Curtin S J, Blackburn J S, Thibodeau-Beganny S, Qi Y, Pierick C J, Hoffman E, Maeder M L, Khayter C, Reyon D, Dobbs D, Langenau D M, Stupar R M, Giraldez A J, Voytas D F, Peterson R T, Yeh J R, Joung J K. Selection-free zinc-finger-nuclease engineering by context-dependent assembly (CoDA). Nature Methods, 2011, 8(1): 67–69

[182] Li T, Liu B, Spalding M H, Weeks D P, Yang B. High-efficiency TALEN-based gene editing produces disease-resistant rice. Nature Biotechnology, 2012, 30(5): 390–392

[183] Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna J A, Charpentier E. A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science, 2012, 337(6096): 816–821

[184] Whitworth K M, Lee K, Benne J A, Beaton B P, Spate L D, Murphy S L, Samuel M S, Mao J, O’Gorman C, Walters E M, Murphy C N, Driver J, Mileham A, McLaren D, Wells K D, Prather R S. Use of the CRISPR/Cas9 system to produce genetically engineered pigs from in vitro-derived oocytes and embryos. Biology of Reproduction, 2014, 91(3): 78

[185] Pul U, Wurm R, Arslan Z, Geissen R, Hofmann N, Wagner R. Identification and characterization of E. coli CRISPR-cas promoters and their silencing by H-NS. Molecular Microbiology, 2010, 75(6): 1495–1512

[186] Silas S, Mohr G, Sidote D J, Markham L M, Sanchez-Amat A, Bhaya D, Lambowitz A M, Fire A Z. Direct CRISPR spacer acquisition from RNA by a natural reverse transcriptase-Cas1 fusion protein. Science, 2016, 351(6276): aad4234

[187] Bortesi L, Fischer R. The CRISPR/Cas9 system for plant genome editing and beyond. Biotechnology Advances, 2015, 33(1): 41–52

[188] Shalem O, Sanjana N E, Zhang F. High-throughput functional genomics using CRISPR-Cas9. Nature Reviews Genetics, 2015, 16(5): 299–311

[189] Sanchez-Rivera F J, Jacks T. Applications of the CRISPR-Cas9 system in cancer biology. Nature Reviews Cancer, 2015, 15(7): 387–395

[190] Nekrasov V, Staskawicz B, Weigel D, Jones J D, Kamoun S. Targeted mutagenesis in the model plant Nicotiana benthamiana using Cas9 RNA-guided endonuclease. Nature Biotechnology, 2013, 31(8): 691–693

[191] Li J F, Norville J E, Aach J, McCormack M, Zhang D, Bush J, Church G M, Sheen J. Multiplex and homologous recombination-mediated genome editing in Arabidopsis and Nicotiana benthamiana using guide RNA and Cas9. Nature Biotechnology, 2013, 31(8): 688–691

[192] Shan Q, Wang Y, Li J, Zhang Y, Chen K, Liang Z, Zhang K, Liu J, Xi J J, Qiu J L, Gao C. Targeted genome modification of crop plants using a CRISPR-Cas system. Nature Biotechnology, 2013, 31(8): 686–688

[193] Brooks C, Nekrasov V, Lippman Z B, Van Eck J. Efficient gene editing in tomato in the first generation using the clustered regularly interspaced short palindromic repeats/CRISPR-associated9 system. Plant Physiology, 2014, 166(3): 1292–1297

[194] Zhou H, Liu B, Weeks D P, Spalding M H, Yang B. Large chromosomal deletions and heritable small genetic changes induced by CRISPR/Cas9 in rice. Nucleic Acids Research, 2014, 42(17): 10903–10914

[195] Fauser F, Schiml S, Puchta H. Both CRISPR/Cas-based nucleases and nickases can be used efficiently for genome engineering in Arabidopsis thaliana. Plant Journal, 2014, 79(2): 348–359

[196] Xing H L, Dong L, Wang Z P, Zhang H Y, Han C Y, Liu B, Wang X C, Chen Q J A. CRISPR/Cas9 toolkit for multiplex genome editing in plants. BMC Plant Biology, 2014, 14(1): 327

[197] O’Geen H, Yu A S, Segal D J. How specific is CRISPR/Cas9 really? Current Opinion in Chemical Biology, 2015, 29: 72–78

[198] Schiml S, Puchta H. Revolutionizing plant biology: multiple ways of genome engineering by CRISPR/Cas. Plant Methods, 2016, 12(1): 8

[199] Lowder L G, Zhang D, Baltes N J, Paul III J W, Tang X, Zheng X, Voytas D F, Hsieh T F, Zhang Y, Qi Y A. CRISPR/Cas9 toolbox for multiplexed plant genome editing and transcriptional regulation. Plant Physiology, 2015, 169(2): 971–985

[200] Ma X, Zhang Q, Zhu Q, Liu W, Chen Y, Qiu R, Wang B, Yang Z, Li H, Lin Y, Xie Y, Shen R, Chen S, Wang Z, Chen Y, Guo J, Chen L, Zhao X, Dong Z, Liu Y G. A Robust CRISPR/Cas9 system for convenient, high-efficiency multiplex genome editing in monocot and dicot plants. Molecular Plant, 2015, 8(8): 1274–1284

[201] Xie K, Minkenberg B, Yang Y. Boosting CRISPR/Cas9 multiplex editing capability with the endogenous tRNA-processing system. Proceedings of the National Academy of Sciences of the United States of America, 2015, 112(11): 3570–3575

[202] Zhang Z, Mao Y, Ha S, Liu W, Botella J R, Zhu J K. A multiplex CRISPR/Cas9 platform for fast and efficient editing of multiple genes in Arabidopsis. Plant Cell Reports, 2016, 35(7): 1519–1533

[203] Vazquez-Vilar M, Bernabe-Orts J M, Fernandez-Del-Carmen A, Ziarsolo P, Blanca J, Granell A, Orzaez D. A modular toolbox for gRNA-Cas9 genome engineering in plants based on the GoldenBraid standard. Plant Methods, 2016, 12(1): 10

[204] Cermák T, Baltes N J, Cegan R, Zhang Y, Voytas D F. High-frequency, precise modification of the tomato genome. Genome Biology, 2015, 16(1): 232

[205] Li Z, Liu Z B, Xing A, Moon B P, Koellhoffer J P, Huang L, Ward R T, Clifton E, Falco S C, Cigan A M. Cas9-guide RNA directed genome editing in soybean. Plant Physiology, 2015, 169(2): 960–970

[206] Sun Y, Zhang X, Wu C, He Y, Ma Y, Hou H, Guo X, Du W, Zhao Y, Xia L. Engineering herbicide-resistant rice plants through CRISPR/Cas9-mediated homologous recombination of acetolactate synthase. Molecular Plant, 2016, 9(4): 628–631

[207] Liu L, Fan X D. CRISPR-Cas system: a powerful tool for genome engineering. Plant Molecular Biology, 2014, 85(3): 209–218

[208] Baltes N J, Voytas D F. Enabling plant synthetic biology through genome engineering. Trends in Biotechnology, 2015, 33(2): 120–131

[209] Nejat N, Rookes J, Mantri N L, Cahill D M. Plant-pathogen interactions: toward development of next-generation disease-resistant plants. Critical Reviews in Biotechnology, 2016, 22: 1–9

[210] Xu R F, Li H, Qin R Y, Li J, Qiu C H, Yang Y C, Ma H, Li L, Wei P C, Yang J B. Generation of inheritable and “transgene clean” targeted genome-modified rice in later generations using the CRISPR/Cas9 system. Scientific Reports, 2015, 5: 11491

[211] Kanchiswamy C N, Malnoy M, Velasco R, Kim J S, Viola R. Non-GMO genetically edited crop plants. Trends in Biotechnology, 2015, 33(9): 489–491

[212] Abbott A. Europe’s genetically edited plants stuck in legal limbo. Nature, 2015, 528(7582): 319–320

[213] Huang S, Weigel D, Beachy R N, Li J. A proposed regulatory framework for genome-edited crops. Nature Genetics, 2016, 48(2): 109–111

[214] Streatfield S J, Kushnir N, Yusibov V. Plant-produced candidate countermeasures against emerging and reemerging infections and bioterror agents. Plant Biotechnology Journal, 2015, 13(8): 1136–1159

[215] Chan H T, Daniell H. Plant-made oral vaccines against human infectious diseases—Are we there yet? Plant Biotechnology Journal, 2015, 13(8): 1056–1070

[216] Shahid N, Daniell H. Plant-based oral vaccines against zoonotic and non-zoonotic diseases. Plant Biotechnology Journal, 2016, 14(11): 2079–2099

[217] Fahlgren N, Bart R, Herrera-Estrella L, Rellán-Álvarez R, Chitwood D H, Dinneny J R. Plant scientists: GM technology is safe. Science, 2016, 351(6275): 824

Acknowledgements

This work was supported by the National Natural Science Foundation of China (31371693, 31471556, 31600289 and 31471502).

Compliance with ethics guidelines

Xingchun Wang, Shujun Chang, Jie Lu, Rupert Fray, Don Grierson, and Yuanhuai Han declare that they have no conflict of interest or financial conflicts to disclose.

This article is a review and does not contain any studies with human or animal subjects performed by any of the authors.

RIGHTS & PERMISSIONS

The Author(s) 2017. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)