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Tran NT, Miles AK, Dietzgen RG, Shuey TA, Mudge SR, Papacek D, Chandra KA, Drenth A. Inoculum Dynamics and Infection of Citrus Fruit by Phyllosticta citricarpa. Phytopathology 2020; 110:1680-1692. [PMID: 32441591 DOI: 10.1094/phyto-02-20-0047-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Citrus black spot, caused by Phyllosticta citricarpa, is characterized by fruit blemishes and premature fruit drop, resulting in significant economic losses in summer rainfall areas. The pathogen forms both conidia and ascospores during its life cycle. However, the occurrence of these spores and their contributions to infection of fruit in field conditions are not well understood. Our research using direct leaf litter monitoring and volumetric spore trapping in Queensland orchards revealed that pseudothecia and ascospores in leaf litter as well as trapped ascospores had low abundance, while pycnidia and conidia were highly abundant. Both P. citricarpa and endophytic Phyllosticta spp. were identified, with P. citricarpa being dominant. In replicated field trials, we determined that infection of Imperial mandarin fruit by P. citricarpa occurred from fruit set until week 20 of fruit development, with the key infection events taking place between weeks 4 and 16 in Queensland subtropical conditions. These results demonstrate that protecting fruit during weeks 4 to 16 significantly reduced P. citricarpa infection. We found no significant correlation between the disease incidence in fruit and P. citricarpa conidial abundance in leaf litter or ascospore abundance measured by volumetric spore trapping. Therefore, it is suggested that inoculum sources in the tree canopy other than those detected by spore trapping and direct leaf litter monitoring may play a major role in the epidemiology of citrus black spot. Improved knowledge regarding epidemiology of P. citricarpa and an understanding of propagules causing infection may aid in development of more effective disease management strategies.
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Affiliation(s)
- Nga T Tran
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Andrew K Miles
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Ralf G Dietzgen
- Centre for Horticultural Science, QAAFI, The University of Queensland, Queensland Bioscience Precinct, St. Lucia 4072, Queensland, Australia
| | - Timothy A Shuey
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Stephen R Mudge
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - Dan Papacek
- Bugs for Bugs, Glenvale 4350, Queensland, Australia
| | - Kerri A Chandra
- Queensland Department of Agriculture and Fisheries, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
| | - André Drenth
- Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Ecosciences Precinct, Dutton Park 4102, Queensland, Australia
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Voss-Fels KP, Robinson H, Mudge SR, Richard C, Newman S, Wittkop B, Stahl A, Friedt W, Frisch M, Gabur I, Miller-Cooper A, Campbell BC, Kelly A, Fox G, Christopher J, Christopher M, Chenu K, Franckowiak J, Mace ES, Borrell AK, Eagles H, Jordan DR, Botella JR, Hammer G, Godwin ID, Trevaskis B, Snowdon RJ, Hickey LT. VERNALIZATION1 Modulates Root System Architecture in Wheat and Barley. Mol Plant 2018; 11:226-229. [PMID: 29056533 DOI: 10.1016/j.molp.2017.10.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/09/2017] [Accepted: 10/11/2017] [Indexed: 05/18/2023]
Affiliation(s)
- Kai P Voss-Fels
- Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Hannah Robinson
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Stephen R Mudge
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Cecile Richard
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Saul Newman
- CSIRO, Agriculture, Canberra, ACT 2601, Australia
| | - Benjamin Wittkop
- Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Andreas Stahl
- Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Wolfgang Friedt
- Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Matthias Frisch
- Department of Biometry and Population Genetics, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Iulian Gabur
- Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Anika Miller-Cooper
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Bradley C Campbell
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Alison Kelly
- Department of Agriculture and Fisheries, Leslie Research Facility, Toowoomba, QLD 4350, Australia
| | - Glen Fox
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Toowoomba, QLD 4350, Australia
| | - Jack Christopher
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Toowoomba, QLD 4350, Australia
| | - Mandy Christopher
- Department of Agriculture and Fisheries, Leslie Research Facility, Toowoomba, QLD 4350, Australia
| | - Karine Chenu
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Toowoomba, QLD 4350, Australia
| | - Jerome Franckowiak
- Department of Agronomy and Plant Genetics, University of Minnesota, St Paul, MN, USA
| | - Emma S Mace
- Department of Agriculture and Fisheries, Hermitage Research Facility, Warwick, QLD 4370, Australia
| | - Andrew K Borrell
- Queensland Alliance for Agriculture and Food Innovation, Hermitage Research Facility, The University of Queensland, Warwick, QLD 4370, Australia
| | | | - David R Jordan
- Queensland Alliance for Agriculture and Food Innovation, Hermitage Research Facility, The University of Queensland, Warwick, QLD 4370, Australia
| | - José R Botella
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Graeme Hammer
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Ian D Godwin
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Rod J Snowdon
- Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
| | - Lee T Hickey
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia.
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Lamont KC, Mudge SR, Liu G, Godwin ID. Expression patterns of the native Shrunken-2 promoter in Sorghum bicolor visualised through use of the GFP reporter gene. Plant Cell Rep 2017; 36:1689-1700. [PMID: 28721521 DOI: 10.1007/s00299-017-2182-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/09/2017] [Indexed: 06/07/2023]
Abstract
The AGPase large subunit (shrunken-2) promoter was demonstrated to be active in the placentochalaza and endosperm of developing grain as well as the root tips in transgenic sorghum. The temporal and spatial expression patterns of the Sorghum bicolor Shrunken-2 (Sh2) promoter were evaluated using the green fluorescence protein reporter gene (gfp) in transgenic sorghum, within the context of upregulating starch biosynthesis in the developing grain. GFP fluorescence was analysed throughout development in various tissue types using confocal laser scanning microscopy techniques. Sh2 promoter activity was first detected in the placentochalaza region of the developing caryopsis and apoplasm adjacent to the nucellar epidermis at 7 days post anthesis (dpa) where fluorescence remained relatively constant until 17 dpa. Fluorescence in this region weakened by 20 dpa and disappeared by 25 dpa. Expression was also detected in the developing endosperm, but not until 12 dpa, continuing until 25 dpa. Whilst the endosperm expression was expected, the fluorescence detected in the placentochalaza was completely unexpected. Although transcript presence does not mean the resulting biochemistry is also present, these preliminary findings may suggest alternate spatial activity of ADP-glucose pyrophosphorylase prior to uptake by the developing grain. Sh2 promoter activity was also unexpectedly detected in the root tips at all developmental time points. Sh2 promoter activity was not detected in any reproductive floral tissue (both pre and post anthesis) or in pollen. Similarly, no expression was detected in leaf tissue at any stage.
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Affiliation(s)
- Kyle C Lamont
- School of Agriculture and Food Sciences, The University of Queensland, Level 3, John Hines Building 62#, Brisbane, QLD, 4072, Australia.
| | - Stephen R Mudge
- School of Agriculture and Food Sciences, The University of Queensland, Level 3, John Hines Building 62#, Brisbane, QLD, 4072, Australia
| | - Guoquan Liu
- School of Agriculture and Food Sciences, The University of Queensland, Level 3, John Hines Building 62#, Brisbane, QLD, 4072, Australia
| | - Ian D Godwin
- School of Agriculture and Food Sciences, The University of Queensland, Level 3, John Hines Building 62#, Brisbane, QLD, 4072, Australia
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Jackson MA, Sternes PR, Mudge SR, Graham MW, Birch RG. Design rules for efficient transgene expression in plants. Plant Biotechnol J 2014; 12:925-33. [PMID: 24854834 DOI: 10.1111/pbi.12197] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 03/24/2014] [Accepted: 04/08/2014] [Indexed: 05/11/2023]
Abstract
Sustained expression of transgenes in specified developmental patterns is commonly needed in plant biotechnology, but obstructed by transgene silencing. Here, we present a set of gene design rules, tested on the silencing-susceptible beetle luc and bacterial ims genes, expressed in sugarcane. Designs tested independently or in combination included removal of rare codons, removal of RNA instability sequences, blocking of likely endogenous sRNA binding sites and randomization of non-rare codons. Stable transgene expression analyses, on multiple independent lines per construct, showed greatest improvement from the removal of RNA instability sequences, accompanied by greatly reduced transcript degradation evident in northern blot analysis. We provide a set of motifs that readily can be eliminated concurrently with rare codons and undesired structural features such as repeat sequences, using Gene Designer 2.0 software. These design rules yielded 935- and 5-fold increased expression in transgenic callus, relative to the native luc and ims sequences; and gave sustained expression under the control of sugarcane and heterologous promoters over several years in greenhouse and field trials. The rules can be applied easily with codon usage tables from any plant species, providing a simple and effective means to achieve sustained expression of otherwise silencing-prone transgenes in plants.
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Mudge SR, Basnayake SWV, Moyle RL, Osabe K, Graham MW, Morgan TE, Birch RG. Mature-stem expression of a silencing-resistant sucrose isomerase gene drives isomaltulose accumulation to high levels in sugarcane. Plant Biotechnol J 2013; 11:502-9. [PMID: 23297683 DOI: 10.1111/pbi.12038] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/22/2012] [Accepted: 11/26/2012] [Indexed: 05/25/2023]
Abstract
Isomaltulose (IM) is a natural isomer of sucrose. It is widely approved as a food with properties including slower digestion, lower glycaemic index and low cariogenicity, which can benefit consumers. Availability is currently limited by the cost of fermentative conversion from sucrose. Transgenic sugarcane plants with developmentally-controlled expression of a silencing-resistant gene encoding a vacuole-targeted IM synthase were tested under field conditions typical of commercial sugarcane cultivation. High yields of IM were obtained, up to 483 mm or 81% of total sugars in whole-cane juice from plants aged 13 months. Using promoters from sugarcane to drive expression preferentially in the sugarcane stem, IM levels were consistent between stalks and stools within a transgenic line and across consecutive vegetative field generations of tested high-isomer lines. Germination and early growth of plants from setts were unaffected by IM accumulation, up to the tested level around 500 mm in flanking stem internodes. These are the highest yields ever achieved of value-added materials through plant metabolic engineering. The sugarcane stem promoters are promising for strategies to achieve even higher IM levels and for other applications in sugarcane molecular improvement. Silencing-resistant transgenes are critical to deliver the potential of these promoters in practical sugarcane improvement. At the IM levels now achieved in field-grown sugarcane, direct production of IM in plants is feasible at a cost approaching that of sucrose, which should make the benefits of IM affordable on a much wider scale.
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Affiliation(s)
- Stephen R Mudge
- Hines Plant Science Building, The University of Queensland, Brisbane, Qld, Australia
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Paungfoo-Lonhienne C, Lonhienne TGA, Mudge SR, Schenk PM, Christie M, Carroll BJ, Schmidt S. DNA is taken up by root hairs and pollen, and stimulates root and pollen tube growth. Plant Physiol 2010; 153:799-805. [PMID: 20388669 PMCID: PMC2879792 DOI: 10.1104/pp.110.154963] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 04/08/2010] [Indexed: 05/18/2023]
Abstract
Phosphorus (P) enters roots as inorganic phosphate (P(i)) derived from organic and inorganic P compounds in the soil. Nucleic acids can support plant growth as the sole source of P in axenic culture but are thought to be converted into P(i) by plant-derived nucleases and phosphatases prior to uptake. Here, we show that a nuclease-resistant analog of DNA is taken up by plant cells. Fluorescently labeled S-DNA of 25 bp, which is protected against enzymatic breakdown by its phosphorothioate backbone, was taken up and detected in root cells including root hairs and pollen tubes. These results indicate that current views of plant P acquisition may have to be revised to include uptake of DNA into cells. We further show that addition of DNA to P(i)-containing growth medium enhanced the growth of lateral roots and root hairs even though plants were P replete and had similar biomass as plants supplied with P(i) only. Exogenously supplied DNA increased length growth of pollen tubes, which were studied because they have similar elongated and polarized growth as root hairs. Our results indicate that DNA is not only taken up and used as a P source by plants, but ironically and independent of P(i) supply, DNA also induces morphological changes in roots similar to those observed with P limitation. This study provides, to our knowledge, first evidence that exogenous DNA could act nonspecifically as signaling molecules for root development.
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Mudge SR, Osabe K, Casu RE, Bonnett GD, Manners JM, Birch RG. Efficient silencing of reporter transgenes coupled to known functional promoters in sugarcane, a highly polyploid crop species. Planta 2009; 229:549-58. [PMID: 19011894 DOI: 10.1007/s00425-008-0852-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Accepted: 10/24/2008] [Indexed: 05/25/2023]
Abstract
Sugarcane is a crop of great interest for engineering of sustainable biomaterials and biofuel production. Isolated sugarcane promoters have generally not maintained the expected patterns of reporter transgene expression. This could arise from defective promoters on redundant alleles in the highly polyploid genome, or from efficient transgene silencing. To resolve this question we undertook detailed analysis of a sugarcane gene that combines a simple pattern in genomic Southern hybridization analysis with potentially useful, sink-specific, expression. Sequence analysis indicates that this gene encodes a member of the SHAQYF subfamily of MYB transcription factors. At least eight alleles were revealed by PCR analysis in sugarcane cultivar Q117 and a similar level of heterozygosity was seen in BAC clones from cultivar Q200. Eight distinct promoter sequences were isolated from Q117, of which at least three are associated with expressed alleles. All of the isolated promoter variants were tested for ability to drive reporter gene expression in sugarcane. Most were functional soon after transfer, but none drove reporter activity in mature stems of regenerated plants. These results show that the ineffectiveness of previously tested sugarcane promoters is not simply due to the isolation of non-functional promoter copies from the polyploid genome. If the unpredictable onset of silencing observed in most other plant species is associated with developmental polyploidy, approaches that avoid efficient transgene silencing in polyploid sugarcane are likely to have much wider utility in molecular improvement.
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Affiliation(s)
- Stephen R Mudge
- Botany Department, School of Integrative Biology, The University of Queensland, Brisbane, 4072, Australia.
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Rae AL, Jarmey JM, Mudge SR, Smith FW. Over-expression of a high-affinity phosphate transporter in transgenic barley plants does not enhance phosphate uptake rates. Funct Plant Biol 2004; 31:141-148. [PMID: 32688886 DOI: 10.1071/fp03159] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Transgenic barley plants that over-express the gene encoding a phosphate transporter were generated and used to test the hypothesis that manipulation of transporters may lead to improved phosphate uptake by plant roots. Replicate T2 seedlings from a homozygous line with a single locus insertion were grown in dilute flow culture. The phosphate contents and uptake rates of these plants were compared with control transgenic and wild-type plants. When external phosphate concentration was maintained at 10 μM, all plants including the transgenic over-expressing line displayed low rates of phosphate uptake and contained high levels of phosphate in the shoot tissue. When external phosphate concentration was maintained at 2 μM, the uptake rates increased to a similar level in all plant lines. Three transgenic over-expressing lines were then grown in soil at a range of phosphate concentrations and the dry weights and total phosphorus contents of the shoots were measured and compared to a transgenic control line. The results showed that over-expression of the gene encoding a phosphate transporter did not improve the uptake of phosphate under any of the conditions tested. Transporter activity is likely to be influenced by post-transcriptional mechanisms and will require further investigation before this strategy can be applied to improving plant nutrition.
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Affiliation(s)
- Anne L Rae
- CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Qld 4067, Australia. Corresponding author;
| | - Janine M Jarmey
- CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Qld 4067, Australia
| | - Stephen R Mudge
- CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Qld 4067, Australia. Current address: School of Life Sciences, University of Queensland, St Lucia, Qld 4072, Australia
| | - Frank W Smith
- CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Qld 4067, Australia
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Mudge SR, Rae AL, Diatloff E, Smith FW. Expression analysis suggests novel roles for members of the Pht1 family of phosphate transporters in Arabidopsis. Plant J 2002; 31:341-53. [PMID: 12164813 DOI: 10.1046/j.1365-313x.2002.01356.x] [Citation(s) in RCA: 297] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The completion of the Arabidopsis thaliana genome has revealed that there are nine members of the Pht1 family of phosphate transporters in this species. As a step towards identifying the role of this gene family in phosphorus nutrition, we have isolated the promoter regions from each of these genes, and fused them to the reporter genes beta-glucuronidase and/or green fluorescent protein. These chimeric genes have been introduced into A. thaliana, and reporter gene expression has been assayed in plants grown in soil containing high and low concentrations of inorganic phosphate (Pi). Four of these promoters were found to direct reporter gene expression in the root epidermis, and were induced under conditions of phosphate deprivation in a manner similar to previously characterised Pht1 genes. Other members of this family, however, showed expression in a range of shoot tissues and in pollen grains, which was confirmed by RT-PCR. We also provide evidence that the root epidermally expressed genes are expressed most strongly in trichoblasts, the primary sites for uptake of Pi. These results suggest that this gene family plays a wider role in phosphate uptake and remobilisation throughout the plant than was previously believed.
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Affiliation(s)
- Stephen R Mudge
- CSIRO Division of Plant Industry, 120 Meiers Road, Indooroopilly, Queensland 4068, Australia.
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Gleave AP, Mitra DS, Mudge SR, Morris BA. Selectable marker-free transgenic plants without sexual crossing: transient expression of cre recombinase and use of a conditional lethal dominant gene. Plant Mol Biol 1999; 40:223-35. [PMID: 10412902 DOI: 10.1023/a:1006184221051] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Transgenic tobacco plants were produced that contained single-copy pART54 T-DNA, with a 35S-uidA gene linked to loxP-flanked kanamycin resistance (nptII) and cytosine deaminase (codA) genes. Retransformation of these plants with pCre1 (containing 35S transcribed cre recombinase and hygromycin (hpt) resistance genes) resulted in excision of the loxP-flanked genes from the genome. Phenotypes of progeny from selfed-retransformed plants confirmed nptII and codA excision and integration of the cre-linked hpt gene. To avoid integration of the hpt gene, and thereby generate plants totally free of marker genes, we attempted to transiently express the cre recombinase. Agrobacterium tumefaciens (pCre1) was cocultivated with leaf discs of two pART54-transformed lines and shoots were regenerated in the absence of hygromycin selection. Nineteen of 773 (0.25%) shoots showed tolerance to 5-fluorocytosine (5-fc) which is converted to the toxic 5-fluorouracil by cytosine deaminase. 5-fc tolerance in six shoots was found to be due to excision of the loxP-flanked region of the pART54 T-DNA. In four of these shoots excision could be attributed to cre expression from integrated pCre1 T-DNA, whereas in two shoots excision appeared to be a consequence of transient cre expression from pCre1 T-DNA molecules which had been transferred to the plant cells but not integrated into the genome. The absence of selectable marker genes was confirmed by the phenotype of the T1 progeny. Therefore, through transient cre expression, marker-free transgenic plants were produced without sexual crossing. This approach could be applicable to the elimination of marker genes from transgenic crops which must be vegetatively propagated to maintain their elite genotype.
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MESH Headings
- Agrobacterium tumefaciens/growth & development
- Antimetabolites/pharmacology
- Coculture Techniques
- Crosses, Genetic
- DNA, Plant/genetics
- Flucytosine/pharmacology
- Gene Expression Regulation, Enzymologic
- Gene Expression Regulation, Plant
- Genes, Dominant/genetics
- Genes, Lethal/genetics
- Genetic Markers
- Genetic Vectors
- Integrases/genetics
- Phenotype
- Plants, Genetically Modified/drug effects
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/growth & development
- Plants, Toxic
- Nicotiana/drug effects
- Nicotiana/genetics
- Nicotiana/growth & development
- Transformation, Genetic
- Viral Proteins
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Affiliation(s)
- A P Gleave
- Plant Development Group, HortResearch, Auckland, New Zealand
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