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Excision of selection markers from transgenic plants
trends in plant science Headlines
Antifungal activity in transgenic wheat
Nutritive value of GM potato
By placing the cDNA encoding the antifungal protein KP4 from the Ustilago maydis-infecting virus behind the maize ubiquitin promoter, KP4 can be transferred to wheat varieties that are particularly susceptible to stinking smut (Tilletia tritici) disease. The transgene is integrated and inherited over several generations. Of seven transgenic lines tested, three showed antifungal activity against U. maydis, correlating with the presence of the KP4 transgene, and exhibited increased endogenous resistance against stinking smut. Nat. Biotechnol. (2000) 18, 446–449.
The tuber-specific and constitutive expression of the seed albumin gene of the AmA1 protein from Amaranthus hypochondriacus has been reported in potato – the protein is found in the cytoplasm and vacuoles of transgenic tuber cells. The AmA1 protein is nonallergenic, rich in all essential amino acids, and the composition corresponds well with the World Health Organization standards for optimal human nutrition. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 3724–3729.
Excision of selection markers from transgenic plants A novel strategy to remove undesirable parts of a transgene construct after integration into the plant genome has been reported. Candidates for removal are herbicide or antibiotic resistance genes that are used in the selection process to recover GM transformants. The method makes use of the bacteriophage l NPTII gene, flanked by two 352 bp attachment P (attP) regions that mediate intrachromosomal recombination. Positive selection of excision was recorded through inclusion of a gene called tms2, which inhibits growth in the presence of certain hormones. Nat. Biotechnol. (2000) 18, 442–445.
Ceres and Genset milestone Ceres, Inc., a plant genomics company, and Genset (Paris, France), a human genomics company, have completed a full-length cDNAsequencing program in Arabidopsis thaliana. http://www.genengnews.com/news1.htm
Tree research set back after vandalism ‘Ministry of Forest Defense’ activists opposed to genetic engineering destroyed ~1600 coniferous tree seedlings and several older trees at the British Columbia Ministry of Forests ‘Tree Improvement Branch’ facilities (Saanichton, Canada). The research project, investigating insect resistance in spruce (Picea) trees has been set back five years. Researchers commented that the trees were the products of natural seed growth and were not genetically altered.
Microbial mix increases crop yields Nancy Kokalis-Burelle (Agricultural Research Service, Fort Pierce, FL, USA) and Gustafson Inc. (Plano, TX, USA) have developed a microbial mix, BioYield 213, containing Paenobacillus macerans and Bacillus amyloliquefacien, to reduce yield losses caused by soilborne pathogens of tomato, pepper and strawberries. The mix triggers the plant’s resistance mechanisms and would replace methyl bromide.
Chloroplast produces somatotropin Chloroplasts can express a secretory protein, human somatotropin, in a soluble, biologically active, disulfide-bonded form. High concentrations of recombinant protein accumulation are observed (.7% total soluble protein), .300-fold higher than a similar gene expressed using a nuclear transgenic approach. The plastid-expressed somatotropin is nearly devoid of complex post-translational modifications, effectively increasing the amount of usable recombinant protein. Because plastids are rarely transmitted to pollen, expressing transgenes in chloroplast genomes (transplastomics) is viewed as a way of preventing the transgenes’ spread to weedy relatives. Nat. Biotechnol. (2000) 18, 333–338.
1360 - 1385/00/$ – see front matter © 2000 Elsevier Science Ltd. All rights reserved.
Testing Bt refuge strategies in the field Bt transgenic plants can greatly reduce the use of broader spectrum insecticides, but there is concern that this technology might be short-lived because of insect resistance. Field tests on managing resistance to Bt-engineered plants using Bt-transgenic broccoli plants and the diamondback moth as a model system have been reported recently. Insects with a known frequency of resistance alleles were released, and the manner in which the refuge influenced both resistance allele frequency and pest population density was examined. The study shows that a separate refuge will be more effective at conserving susceptible larvae than a mixed refuge. When spraying the refuge to prevent economic loss to the crop, insects from the 20% sprayed refuge treatment and the 20% unsprayed refuge treatment showed no difference in changes in allele frequency, indicating that insects do not evolve resistance more rapidly. However, great care must be taken to ensure that refuges produce adequate numbers of susceptible alleles. Nat. Biotechnol. (2000) 18, 339–342.
Protein kinase required for salt tolerance Mutations in the Arabidopsis salt gene OVERLY SENSITIVE 2 (SOS2) cause Na1 and K1 imbalance and render plants more sensitive towards growth inhibition by high Na1 and low K1 environments. The SOS2 gene has been isolated and identified as a serine/threonine type protein kinase. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 3730–3734.
Stress signaling H2O2, a central signaling molecule in stress and wounding responses, is a potent activator of cascades of mitogen-activated protein kinases (MAPKs) in Arabidopsis leaf cells, more specifically the protein kinase kinase kinase, ANP1. Manipulation of key regulators of an oxidative stress signaling pathway, such as ANP1, provides a strategy for engineering multiple stress tolerance that might greatly benefit agriculture. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 2940–2945. June 2000, Vol. 5, No. 6
237
Antifungal activity in transgenic wheat
Nutritive value of GM potato
By placing the cDNA encoding the antifungal protein KP4 from the Ustilago maydis-infecting virus behind the maize ubiquitin promoter, KP4 can be transferred to wheat varieties that are particularly susceptible to stinking smut (Tilletia tritici) disease. The transgene is integrated and inherited over several generations. Of seven transgenic lines tested, three showed antifungal activity against U. maydis, correlating with the presence of the KP4 transgene, and exhibited increased endogenous resistance against stinking smut. Nat. Biotechnol. (2000) 18, 446–449.
The tuber-specific and constitutive expression of the seed albumin gene of the AmA1 protein from Amaranthus hypochondriacus has been reported in potato – the protein is found in the cytoplasm and vacuoles of transgenic tuber cells. The AmA1 protein is nonallergenic, rich in all essential amino acids, and the composition corresponds well with the World Health Organization standards for optimal human nutrition. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 3724–3729.
Excision of selection markers from transgenic plants A novel strategy to remove undesirable parts of a transgene construct after integration into the plant genome has been reported. Candidates for removal are herbicide or antibiotic resistance genes that are used in the selection process to recover GM transformants. The method makes use of the bacteriophage l NPTII gene, flanked by two 352 bp attachment P (attP) regions that mediate intrachromosomal recombination. Positive selection of excision was recorded through inclusion of a gene called tms2, which inhibits growth in the presence of certain hormones. Nat. Biotechnol. (2000) 18, 442–445.
Ceres and Genset milestone Ceres, Inc., a plant genomics company, and Genset (Paris, France), a human genomics company, have completed a full-length cDNAsequencing program in Arabidopsis thaliana. http://www.genengnews.com/news1.htm
Tree research set back after vandalism ‘Ministry of Forest Defense’ activists opposed to genetic engineering destroyed ~1600 coniferous tree seedlings and several older trees at the British Columbia Ministry of Forests ‘Tree Improvement Branch’ facilities (Saanichton, Canada). The research project, investigating insect resistance in spruce (Picea) trees has been set back five years. Researchers commented that the trees were the products of natural seed growth and were not genetically altered.
Microbial mix increases crop yields Nancy Kokalis-Burelle (Agricultural Research Service, Fort Pierce, FL, USA) and Gustafson Inc. (Plano, TX, USA) have developed a microbial mix, BioYield 213, containing Paenobacillus macerans and Bacillus amyloliquefacien, to reduce yield losses caused by soilborne pathogens of tomato, pepper and strawberries. The mix triggers the plant’s resistance mechanisms and would replace methyl bromide.
Chloroplast produces somatotropin Chloroplasts can express a secretory protein, human somatotropin, in a soluble, biologically active, disulfide-bonded form. High concentrations of recombinant protein accumulation are observed (.7% total soluble protein), .300-fold higher than a similar gene expressed using a nuclear transgenic approach. The plastid-expressed somatotropin is nearly devoid of complex post-translational modifications, effectively increasing the amount of usable recombinant protein. Because plastids are rarely transmitted to pollen, expressing transgenes in chloroplast genomes (transplastomics) is viewed as a way of preventing the transgenes’ spread to weedy relatives. Nat. Biotechnol. (2000) 18, 333–338.
1360 - 1385/00/$ – see front matter © 2000 Elsevier Science Ltd. All rights reserved.
Testing Bt refuge strategies in the field Bt transgenic plants can greatly reduce the use of broader spectrum insecticides, but there is concern that this technology might be short-lived because of insect resistance. Field tests on managing resistance to Bt-engineered plants using Bt-transgenic broccoli plants and the diamondback moth as a model system have been reported recently. Insects with a known frequency of resistance alleles were released, and the manner in which the refuge influenced both resistance allele frequency and pest population density was examined. The study shows that a separate refuge will be more effective at conserving susceptible larvae than a mixed refuge. When spraying the refuge to prevent economic loss to the crop, insects from the 20% sprayed refuge treatment and the 20% unsprayed refuge treatment showed no difference in changes in allele frequency, indicating that insects do not evolve resistance more rapidly. However, great care must be taken to ensure that refuges produce adequate numbers of susceptible alleles. Nat. Biotechnol. (2000) 18, 339–342.
Protein kinase required for salt tolerance Mutations in the Arabidopsis salt gene OVERLY SENSITIVE 2 (SOS2) cause Na1 and K1 imbalance and render plants more sensitive towards growth inhibition by high Na1 and low K1 environments. The SOS2 gene has been isolated and identified as a serine/threonine type protein kinase. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 3730–3734.
Stress signaling H2O2, a central signaling molecule in stress and wounding responses, is a potent activator of cascades of mitogen-activated protein kinases (MAPKs) in Arabidopsis leaf cells, more specifically the protein kinase kinase kinase, ANP1. Manipulation of key regulators of an oxidative stress signaling pathway, such as ANP1, provides a strategy for engineering multiple stress tolerance that might greatly benefit agriculture. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 2940–2945. June 2000, Vol. 5, No. 6
237