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ISAAA releases new Pocket K on marker-free GM plants

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Manila, The Philippines
July 3, 2009

Pocket K No. 36: Marker-Free GM Plants
International Service for the Acquisition fo Agri-biotech Applications (ISAAA)

Introduction

Selectable marker genes are vital to the research and development of genetically modified (GM) crops. The methods used to introduce foreign DNA in a plant cell, either by microinjection, particle gun, electroporation or Agrobacterium, are relatively inefficient. Pinpointing cells that successfully incorporated foreign DNA in an ocean of non-transformed cells is akin to finding a needle in a haystack. To find transgenic cells, a marker gene is co-introduced with the gene of interest. These dominant genes confer resistance to antibiotics, such as hygromycin (hpt) and kanamycin (nptII), and herbicides, such as phosphinothricin (bar) and chlorosulfuron (als), that kill non-transformed cells. However, antibiotic and herbicide resistance marker genes may not be required in mature plants, especially when they are cultivated in fields.

The presence of these marker genes in commercialized transgenic crops has caused considerable public concern about the medical implications of GM food consumption and GM crop cultivation. Herbicide resistance genes might be transferred by outcrossing to weeds and wild crop relatives. There also exists the possibility, albeit extremely rare, of horizontal gene transfer from transgenic plants to soil and intestinal microorganisms, resulting in pathogens against which antibiotics currently being used are rendered ineffective. However, to date, no experiment has provided any evidence that the antibiotic markers presently in use pose risks to human or animal health.

Not all scientists agree with these claims. The difficulty of proving that the marker genes are indeed harmless has significantly limited the public acceptance of agricultural biotechnology.

A lot of research effort has been directed towards the development of marker-free transformation methods and selectable marker elimination strategies. Besides minimizing public concerns, the absence of resistance genes in transgenic plants could also reduce the costs for developing GM products and lessen the need for time-consuming safety evaluations, thereby speeding up the commercial release of new products. Generation of marker free plants likewise supports single line re-transformation, an important approach towards introduction of multiple genes for complex traits such as resistance to several pathogens and tolerance to abiotic stress.

There are several ways to either avoid or get rid of selectable marker genes. Methods that will allow the removal of DNA in plants as efficiently as it is inserted have been developed, such as the use of site-specific recombination, transposition and homologous recombination. Researchers have also described several substitute marker genes that have no harmful biological activities. The presence of these non-bacterial genes allows the plants to metabolize non-toxic agents normally harmful to them.

Complete Pocket K No. 36:
http://www.isaaa.org/kc/inforesources/publications/pocketk/default.html#Pocket_K_No._36.htm

 

Previous Pocket K in the series
  1. Q and A About Genetically Modified Crops
  2. Plant Products of Biotechnology
  3. Are Food Derived from GM Crops Safe?
  4. GM Crops and the Environment
  5. Documented Benefits of GM Crops
  6. Bt Insect Resistant Technology
  7. Labeling GM Foods
  8. Cartagena Protocol on Biosafety
  9. Intellectual Property Rights and Agricultural Biotechnology
  10. Herbicide Tolerance Technology: Glyphosate and Glufosinate
  11. Contribution of GM Technology to the Livestock Sector
  12. Delayed Ripening Technology
  13. Conventional Plant Breeding
  14. Tissue Culture Technology
  15. 'Omics' Sciences: Genomics, Proteomics, and Metabolomics 
  16. Global Status of Commercialized Biotech/GM Crops in 2006
  17. Genetic Engineering and GM Crops
  18. Ethics and Agricultural Biotechnology
  19. Molecular Breeding and Marker-Assisted Selection
  20. Microbial Fermentation
  21. Gene Switching and GURTs: What, How and Why?
  22. Plant Disease Diagnostics
  23. Bioinformatics for Plant Biotechnology
  24. Biotechnology for Green Energy: Biofuels
  25. Biotech Plants for Bioremediation
  26. Molecular Pharming and Biopharmaceuticals
  27. Biotechnology and Biofortification
  28. Kenya Biotechnology Development Policy Highlights
  29. Functional Foods & Biotechnology
  30. Contributions of Agricultural Biotechnology in Alleviation of Poverty and Hunger
  31. Biotechnology with Salinity for Coping in Problem Soils
  32. Biotechnology for the Development of Drought Tolerant Crops
  33. Communicating Crop Biotechnology
  34. RNAi for Crop Improvement
  35. Bt Brinjal in India
 

 


 

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