Yi Li

Nanjing Agricultural University, Nan-ching, Jiangsu Sheng, China

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Publications (36)120.89 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Transgenic plant technology provides a powerful tool to improve abiotic stress tolerance of crop plants. However, introgression of stress tolerance genes into weedy relatives may lead to increased potential of their persistence and invasiveness, resulting in undesirable ecological consequences. A variety of gene confinement strategies have been developed to stop unwanted transgene movement. In this review, we discuss some of these strategies, such as male and female sterility, GeneSafe, parthenocarpy, chloroplast transformation and gene deletor technologies. In the case of the gene deletor technology, it may eliminate all transgenes from pollen, seeds, fruits or other organs when their functions are no longer needed or their presence may cause concerns. The gene deletor and other technologies can be useful to reduce unintended dispersal of stress tolerance genes and thus may facilitate commercialization of transgenic crops with enhanced tolerance to abiotic stresses.
    Critical Reviews in Plant Sciences 03/2014; 33(2-3). DOI:10.1080/07352689.2014.870414 · 5.29 Impact Factor
  • New and Future Developments in Catalysis, 1st edited by Steven Suib, 09/2013: chapter Hybrid Plant Systems for Breeding and Gene Confinement in Bioenergy Crops; Elsevier., ISBN: 9780444538789
  • Yi Li
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    ABSTRACT: Environmental and food safety concerns over transgenic plants have hampered commercial applications of transgenic plant technology worldwide. A recently developed transgene deletion technology, named gene deletor technology, may be used to eliminate all transgenes from pollen, seeds, fruits or other organs when functions of transgenes are no longer needed or their presence may cause concerns. In this review, I will briefly describe the principle of the gene deletor technology with major supporting experimental data. I will also explain main characteristics and requirements of the gene deletor technology. Finally, I will discuss the gene deletor technology in the context of how it may be used to alleviate environmental and food safety concerns over transgenic plants in vegetatively and sexually propagated plants, to prevent volunteer transgenic plants, to protect proprietary transgenic technologies, and to allow farmers to reuse their harvested seeds for future planting.
    12/2012; 7(6). DOI:10.1007/s11515-012-1195-1
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    ABSTRACT: Euonymus alatus (Thunb.) Sieb. is a popular landscape plant in the United States due to its brilliant red fall foliage. It is also an important ornamental plant in many other areas of the world such as China, Japan and Europe. However, E. alatus is considered as a highly invasive plant species in the US. Mutation breeding can be used to create sterile, non-invasive cultivars. Seeds are the most commonly used explants for mutagen treatments, but E. alatus mature seeds possess prolonged dormancy and only a low percentage of them germinate even after 18 months of cold stratification. Here we report an immature embryo culture method for E. alatus ‘Compactus’ to circumvent the seed dormancy problem. Also, we have found that activated charcoal, gibberellic acid (GA3) and 6-benzyladenine (BA) can reduce the dormancy of isolated embryos, which suggests that abscisic acid (ABA) might play a role in controlling seed dormancy. We have further demonstrated that exogenous ABA enhances dormancy of isolated E. alatus embryos while fluridone, an inhibitor for ABA biosynthesis, can effectively break their dormancy. These results, particularly the effect of fluridone, suggest that continuous ABA biosynthesis plays an important role in controlling the dormancy of E. alatus seeds.
    Plant Cell Tissue and Organ Culture 01/2012; 108(3). DOI:10.1007/s11240-011-0063-z · 2.61 Impact Factor
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    ABSTRACT: Euonymus alatus, well known as “burning bush”, is an extremely popular landscape plant in the United States because of its excellent fall color. As E. alatus is also highly invasive, development of sterile, non-invasive, seedless triploid E. alatus is in high demand. Here we report successful production of triploid E. alatus using endosperm tissues as explants. In our study, approximately 50% of immature endosperm explants and 14% of mature endosperm explants formed compact, green calli after culture in dark for 8 weeks and then under light for 4 weeks on a MS medium. Approximately 5.6% of the immature endosperm-derived calli and 13.4% of mature endosperm-derived calli initiated shoots. Eighty five percent of shoots rooted after culture on WPM media. Twelve independently regenerated triploid plants have been identified. Triploid plant regeneration rates observed were 0.42% from immature endosperm explants and 0.34% from mature endosperm explants, respectively, based on the number of endosperm explants cultured. Because triploid plants are normally seedless and sterile, non-invasive, triploid E. alatus plants that retain the desirable horticultural characteristics of the parent cultivar can be used to replace the currently used invasive counterparts.
    2011 ASHS Annual Conference; 09/2011
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    ABSTRACT: Additional index words. invasive ornamental plants, winged euonymus, sterility, flow cytometry, ploidy Abstract. Euonymus alatus (Thunb.) Sieb., commonly known as ''burning bush,'' is an extremely popular landscape plant in the United States as a result of its brilliant showy red leaves in fall. However, E. alatus is also seriously invasive because of its prolific seed production and effective seed dispersal by birds. Thus, development of sterile, non-invasive, seedless triploid E. alatus is in high demand. In this article, we report successful production of triploid E. alatus using endosperm tissues as explants. In our study, ' '50% of immature endosperm explants and 14% of mature endosperm explants formed compact, green calli after culture in the dark for 8 weeks and then under light for 4 weeks on Murashige and Skoog (MS) medium supplemented with 2.2 mM BA and 2.7 mM a-naphthaleneacetic acid (NAA). Approximately 5.6% of the immature endosperm-derived calli and 13.4% of mature endosperm-derived calli initiated shoots within 8 weeks after they were cultured on MS medium with 4.4 mM benzyladenine (BA) and 0.5 mM indole-3-butyric acid (IBA). Eighty-five percent of shoots rooted after culture on woody plant medium (WPM) containing 4.9 mM IBA for 2 weeks and then on hormone-free WPM medium containing 2.0 gÁL –1 activated charcoal for 4 weeks. Eight indepen-dently regenerated triploid plants have been identified. Triploid plant regeneration rates observed were 0.42% from immature endosperm explants and 0.34% from mature endosperm explants, respectively, based on the number of endosperm explants cultured. Because triploid plants cannot produce viable seeds, and thus are sterile and non-invasive, some triploid E. alatus plant lines reported here can be used to replace the currently used invasive counterparts. Chemical names used: benzyladenine (BA), indole-3-butyric acid (IBA), and a-naphthaleneacetic acid (NAA). Euonymus alatus (Thunb.) Sieb. is a de-ciduous shrub belonging to the family of Celastraceae. It was introduced into the United States from northeastern/central China in 1860 (Chen et al., 2006; Dirr, 1998) for horticultural purposes. E. alatus is considered one of the great aesthetic and highly adaptable shrubs for the American gardeners (Dirr, 1998). Because of its brilliant red fall leaf color, it is commonly referred as ''burning bush.'' As a result of its huge economical value and pop-ularity, E. alatus has been extensively sold by nurseries, contributing significantly to the $16 billion U.S. ornamental horticulture industry (U.S. Department of Agriculture, 2005a). There are various cultivars of E. alatus
    HortScience: a publication of the American Society for Horticultural Science 08/2011; 46(8):1141-1147. · 0.86 Impact Factor
  • 01/2010; 1(1):163-176. DOI:10.4155/bfs.09.11
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    ABSTRACT: Genetic modification of dedicated bioenergy crops is in its infancy; however, there are numerous advantages to the use of these tools to improve crops used for biofuels. Potential improved traits through genetic engineering (GE) include herbicide resistance, pest-, drought-, cold- and salt-tolerance, lower inputs, compositional alterations, addition of cellulases and other biofuels-specific traits such as increased biomass yields and increased photosynthetic efficiencies. To achieve these goals on an agricultural scale, these improvements must meet regulatory standards for release into the environment. In most cases, these criteria will probably require gene confinement strategies to prevent gene flow into wild and non-transgenic populations. Here, we consider the options for prevention or mitigation of gene flow in genetically modified (GM) biofuels crops.
    12/2009: pages 299-315;
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    ABSTRACT: Gene flow from transgenic plants is an environmental and regulatory concern. While biocontainment might be achieved using male sterility or transgenic mitigation tools, we believe that perhaps the optimal solution might be simply to remove transgenes from pollen. Male sterility might not be ideal for many pollinators, and might not be implementable using standardized genes. Transgenic mitigation might not be useful to control conspecific gene flow (e.g. crop to crop), and relies on competition and not biocontainment per se. Site-specific recombination systems could allow highly efficient excision of transgenes in pollen to eliminate, or at least minimize, unwanted transgene movement via pollen dispersal. There are other potential biotechnologies, such as zinc finger nucleases, that could be also used for transgene excision.
    Trends in Biotechnology 10/2009; 28(1):3-8. DOI:10.1016/j.tibtech.2009.09.008 · 10.04 Impact Factor
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    ABSTRACT: The cytokinin biosynthesis gene, isopentenyl transferase (ipt), under the control of an 821 bp fragment of the LEACO1 gene promoter (from Lycopersicon esculentum) was introduced into Dendranthema x grandiflorium 'Iridon' (chrysanthemum). LEACO1(0.821kb)-ipt transgenic lines grown in the vegetative state, exhibited a range of phenotypic changes including increased branching and reduced internode lengths. LEACO1(0.821kb)-ipt transgenic lines grown in the generative state, exhibited increased flower bud count that ranged from 3.8- to 6.7-times the number produced by wild-type plants. Dramatic increases in flower number were associated with a delay of flower bud development and a decrease in flower bud diameter. RT-PCR analysis indicated differences in ipt gene expression between individual transgenic lines that exhibited a range of phenotypes. Within an individual transgenic line, RT-PCR analysis revealed changes in ipt gene expression at different stages of generative shoot development. Expression of ipt in transgenic lines correlated well with high concentrations of the sum total to bioactive cytokinins plus the glucosides and phosphate derivatives of these species, under both vegetative and generative growth conditions. In general, transgenic lines accumulated higher concentrations of both storage-form cytokinins (O-glucosides) and deactivated-form cytokinins (N-glucosides) in generative shoots of than in vegetative shoots. Based on the range of phenotypes observed in various transgenic chrysanthemum lines, we conclude that the LEACO1 (0.821kb) -ipt gene appears to have great potential for use in ornamental crop improvement.
    Plant Cell Reports 07/2009; 28(9):1351-62. DOI:10.1007/s00299-009-0735-x · 2.94 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 05/2009; 40(19). DOI:10.1002/chin.200919261
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    ABSTRACT: Dioscorea zingiberensis Wright has been cultivated as a pharmaceutical crop for production of diosgenin, a precursor for synthesis of various important steroid drugs. Because breeding of D.zingiberensis through sexual hybridization is difficult due to its unstable sexuality and differences in timing of flowering in male and female plants, gene transfer approaches may play a vital role in its genetic improvement. In this study, the Agrobacterium tumefaciens-mediated transformation of D.zingiberensis was investigated with leaves and calli as explants. The results showed that both leaf segments and callus pieces were sensitive to 30mg/l hygromycin and 50–60mg/l kanamycin, and using calli as explants and addition of acetosyringone (AS) in cocultivation medium were crucial for successful transformation. We first immersed callus explants in A.tumefaciens cells for 30min and then transferred the explants onto a co-cultivation medium supplemented with 200μM AS for 3days. Three days after, we cultured the infected explants on a selective medium containing 50mg/l kanamycin and 100mg/l timentin for formation of kanamycin-resistant calli. After the kanamycin-resistant calli were produced, we transferred them onto fresh selective medium for shoot induction. Finally, the kanamycin resistant shoots were rooted and the stable incorporation of the transgene into the genome of D.zingiberensis plants was confirmed by GUS histochemical assay, PCR and Southern blot analyses. The method reported here can be used to produce transgenic D.zingiberensis plants in 5months and the transformation frequency is 24.8% based on the numbers of independent transgenic plants regenerated from initial infected callus explants.
    Plant Cell Tissue and Organ Culture 02/2009; 96(3):317-324. DOI:10.1007/s11240-008-9489-3 · 2.61 Impact Factor
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    ABSTRACT: We investigated the possibility of producing chicken alpha interferon (ChIFN-alpha) in transgenic plants. The cDNA encoding ChIFN-alpha was introduced into lettuce (Lactuca sativa L.) plants by using an agro-infiltration transient expression system. The ChIFN-alpha gene was correctly transcribed and translated in the lettuce plants according to RT-PCR and ELISA assays. Recombinant protein exhibited antiviral activity in vitro by inhibition of vesicular stomatitis virus (VSV) replication on chicken embryonic fibroblast (CEF). The results demonstrate that biologically active avian cytokine with potential pharmaceutical applications could be expressed in transgenic lettuce plants and that it is possible to generate interferon protein in forage plants for preventing infectious diseases of poultry.
    Journal of Zhejiang University SCIENCE B 06/2008; 9(5):351-5. DOI:10.1631/jzus.B0710596 · 1.29 Impact Factor
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    ABSTRACT: Chemical synthesis of DNA sequences provides a powerful tool for modifying genes and for studying gene structure, expression and function. Modified genes and consequently protein/enzymes can bridge genomics and proteomics research or facilitate commercial applications of gene and protein technologies. In this review, we will summarize various strategies, designing softwares and error correction methods for chemical gene synthesis, particularly for the synthesis and assembly of long DNA molecules based on polymerase cycling assembly. Also, we will briefly discuss some of the major applications of chemical synthesis of DNA sequences in basic research and applied areas.
    FEMS Microbiology Reviews 06/2008; 32(3):522-40. DOI:10.1111/j.1574-6976.2008.00109.x · 13.81 Impact Factor
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    ABSTRACT: We have recently developed an in vitro plant regeneration method and an Agrobacterium tumefaciens-mediated genetic transformation method for Euonymus alatus. More than 60% cotyledon explants from 10-day old E. alatus seedlings produced 3 shoots on average with woody plant medium (WPM) in the presence of 5.0 mg/L 6-benzylaminopurine (BA) and 0.2 mg/L α-naphthalene acetic acid (NAA). Approximately 80% of shoots produced roots with 0.3 mg/L NAA and 0.5 mg/L IBA. We have constructed a “super sterile” gene cassette that should lead to a male and female sterility and production of normal sized fruits when expressed in plants. We have demonstrated that in tobacco and tomato plants the sterile gene cassette is effective to abolish pollen or seed formation but capable of producing normal sized fruit. The “super sterile” gene cassette was also used to generate transgenic E. alatus plants. Because an intron containing gusplus gene was incorporated into the “super sterile” gene cassette, the E. alatus plants that were transformed with the sterile gene cassette have been confirmed based on the expression of the gusplusgene and an additional molecular analysis.
    Acta horticulturae 01/2008; 769:21-29.
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    ABSTRACT: Here we report the effect of the 35S promoter sequence on activities of the tissue- and organ-specific gene promoters in tobacco plants. In the absence of the 35S promoter sequence the AAP2 promoter is active only in vascular tissues as indicated by expression of the AAP2:GUS gene. With the 35S promoter sequence in the same T-plasmid, transgenic plants exhibit twofold to fivefold increase in AAP2 promoter activity and the promoter becomes active in all tissue types. Transgenic plants hosting the ovary-specific AGL5:iaaM gene (iaaM coding an auxin biosynthetic gene) showed a wild-type phenotype except production of seedless fruits, whereas plants hosting the AGL5:iaaM gene along with the 35S promoter sequence showed drastic morphological alterations. RT-PCR analysis confirms that the phenotype was caused by activation of the AGL5:iaaM gene in non-ovary organs including roots, stems and flowers. When the pollen-, ovule- and early embryo-specific PAB5:barnase gene (barnase coding a RNase gene) was transformed, the presence of 35S promoter sequence drastically reduced transformation efficiencies. However, the transformation efficiencies were restored in the absence of 35S promoter, indicating that the 35S promoter might activate the expression of PAB5:barnase in non-reproductive organs such as calli and shoot primordia. Furthermore, if the 35S promoter sequence was replaced with the NOS promoter sequence, no alteration in AAP2, AGL5 or PAB5 promoter activities was observed. Our results demonstrate that the 35S promoter sequence can convert an adjacent tissue- and organ-specific gene promoter into a globally active promoter.
    Plant Cell Reports 09/2007; 26(8):1195-203. DOI:10.1007/s00299-007-0307-x · 2.94 Impact Factor
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    ABSTRACT: Cotton (Gossypium hirsutum L.) fibers, one of the most important natural raw materials for textile industry, are highly elongated trichomes from epidermal cells of cotton ovules. DET2, an Arabidopsis steroid 5d-reductase, is considered to catalyze a major rate-limiting in brassinosteroid (BR) biosynthesis. To understand the role of BRs in cotton fiber development, GhDET2, which putatively encodes a steroid 5alpha-reductase by sequence comparison, was cloned from developing fiber cells. In vitro assessment of GhDET2 protein activity confirmed that GhDET2 encodes a functional steroid 5alpha-redutase. High levels of GhDET2 transcript were detected during the fiber initiation stage and the fiber rapid elongation stage. Antisense-mediated suppression of GhDET2 inhibited both fiber initiation and fiber elongation. Similarly, treating cultured ovules with finasteride, a steroid 5alpha-reductase inhibitor, reduced fiber elongation. Inhibition of fiber cell elongation by expression of antisense GhDET2 or the finasteride treatment could be reversed by epibrassinolide, a biologically active BR. Furthermore, seed coat-specific expression of GhDET2 increased fiber number and length. Therefore, GhDET2 and BRs play a crucial role in the initiation and elongation of cotton fiber cells, suggesting that modulation of BR biosynthesis factors may improve fiber quality or yield.
    The Plant Journal 09/2007; 51(3):419-30. DOI:10.1111/j.1365-313X.2007.03144.x · 6.82 Impact Factor
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    ABSTRACT: To achieve a thermostable beta-glucuronidase (GUS) and identify key mutation sites, we applied in vitro directed evolution strategy through DNA shuffling and obtained a highly thermostable mutant GUS gene, gus-tr, after four rounds of DNA shuffling and screening. This variant had mutations in 15 nucleic acid sites, resulting in changes in 12 amino acids (AAs). Using gus-tr as the template, we further performed site-directed mutagenesis to reverse the individual mutation to the wild-type protein. We found that six sites (Q493R, T509A, M532T, N550S, G559S and N566S) present in GUS-TR3337, were the key AAs needed to confer its high thermostability. Of these, Q493R and T509A were not reported previously as important residues for thermostability of GUS. Furthermore, all of these six mutations must be present concurrently to confer the high thermostability. We expressed the gus-tr3337 gene and purified the GUS-TR3337 protein that contained the six AA mutations. Compared with the wild-type protein which lost its activity completely after 10 min at 70 degrees C, the mutant GUS-TR3337 protein retained 75% of its activity when heated at 80 degrees C for 10 min. The GUS-TR3337 exhibited high activity even heated at 100 degrees C for 30 min on nitrocellulose filter. The comparison of molecular models of the mutated and wild-type enzyme revealed the relation of protein function and these structural modifications.
    Protein Engineering Design and Selection 08/2007; 20(7):319-25. DOI:10.1093/protein/gzm023 · 2.32 Impact Factor
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    ABSTRACT: Pollen- and seed-mediated transgene flow is a concern in plant biotechnology. We report here a highly efficient 'genetically modified (GM)-gene-deletor' system to remove all functional transgenes from pollen, seed or both. With the three pollen- and/or seed-specific gene promoters tested, the phage CRE/loxP or yeast FLP/FRT system alone was inefficient in excising transgenes from tobacco pollen and/or seed, with no transgenic event having 100% efficiency. When loxP-FRT fusion sequences were used as recognition sites, simultaneous expression of both FLP and CRE reduced the average excision efficiency, but the expression of FLP or CRE alone increased the average excision efficiency, with many transgenic events being 100% efficient based on more than 25,000 T(1) progeny examined per event. The 'GM-gene-deletor' reported here may be used to produce 'non-transgenic' pollen and/or seed from transgenic plants and to provide a bioconfinement tool for transgenic crops and perennials, with special applicability towards vegetatively propagated plants and trees.
    Plant Biotechnology Journal 04/2007; 5(2):263-274. DOI:10.1111/j.1467-7652.2006.00237.x · 6.28 Impact Factor
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    ABSTRACT: Cytokinins play important roles in regulating plant growth and development. A new genetic construct for regulating cytokinin content in plant cells was cloned and tested. The gene coding for isopentenyl transferase (ipt) was placed under the control of a 0.821 kb fragment of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene promoter from Lycopersicon esculentum (LEACO1) and introduced into Nicotiana tabacum (cv. Havana). Some LEACO1(0.821) (kb)-ipt transgenic plant lines displayed normal shoot morphology but with a dramatic increase in the number of flower buds compared to nontransgenic plants. Other transgenic lines produced excessive lateral branch development but no change in flower bud number. Isolated leaves of transgenic tobacco plants showed a significantly prolonged retention of chlorophyll under dark incubation (25 degrees C for 20 days). Leaves of nontransformed plants senesced gradually under the same conditions. Experiments with LEACO1(0.821) (kb)-gus transgenic tobacco plants suggested auxin and ethylene involvement in induction of LEACO1(0.821) (kb) promoter activity. Multiple copies of nucleotide base sequences associated with either ethylene or auxin response elements were identified in the LEACO1(0.821) (kb) promoter fragment. The LEACO1(0.821) (kb)-ipt fusion gene appears to have potential utility for improving certain ornamental and agricultural crop species by increasing flower bud initiation and altering branching habit.
    Plant Cell Reports 12/2006; 25(11):1181-92. DOI:10.1007/s00299-006-0181-y · 2.94 Impact Factor

Publication Stats

853 Citations
120.89 Total Impact Points


  • 2014
    • Nanjing Agricultural University
      Nan-ching, Jiangsu Sheng, China
  • 2004–2012
    • University of Connecticut
      • Department of Plant Science and Landscape Architecture
      Storrs, Connecticut, United States
  • 2009
    • Shanghai Academy of Agricultural Sciences
      Shanghai, Shanghai Shi, China
  • 2007
    • Yangzhou University
      Chiang-tu, Jiangsu Sheng, China
  • 2006
    • Southwest University in Chongqing
      Pehpei, Chongqing Shi, China