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New Plant Breeding Techniques - 2013 workshop report

(June 2014)

Executive Summary

Food Standards Australia New Zealand (FSANZ) hosted a technical workshop to discuss a number of new plant breeding techniques that have come to the attention of regulators. This was the second workshop to be hosted by FSANZ on this topic. A number of scientists with expertise in plant breeding and biotechnology were invited to participate in the workshop.

The objectives of the workshop were to: enhance FSANZ’s scientific knowledge and understanding of each of the techniques; and to discuss scientific, technical and regulatory issues, including whether derived food products should be regarded as genetically modified (GM) food. The scientific conclusions of the workshop may constitute a relevant consideration to which FSANZ may have regard when considering applications to amend Standard 1.5.2 – Food produced using Gene Technology in the Australia New Zealand Food Standards Code. 

The techniques discussed were:
  1. Accelerated breeding following induction of early flowering – a technique for shortening the flowering time in tree species, to accelerate the breeding process. It involves using a transgenic early flowering plant line as one of the breeding parents. In the final breeding steps, plant lines are selected that have not inherited the early flowering transgene.
  2. Targeted mutagenic techniques – a range of techniques that have been developed for introducing mutations at specific sites in genomes. This is in contrast to more traditional mutagenic techniques where mutations are random. Depending on how the various targeted techniques are deployed, mutations can either be restricted to one or a few nucleotides or involve the insertion of a new piece of DNA. The specific techniques discussed were:
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    a.transcription activator-like effector nucleases (TALENs) – artificial restriction endonuclease enzymes generated by fusing a transcription activator-like effector DNA binding domain to a non-specific DNA cleavage domain (nuclease).
    b.type II clustered, regularly interspaced, short palindromic repeats (CRISPR)/Cas systems – an engineered DNA targeting complex which relies on a small guide RNA in association with an endonuclease (Cas9) to target specific sites in the genome for cleavage.
    c.meganucleases - endonucleases with large cleavage sites that can target specific sites in the genome.
    d.triplex-forming oligonucleotides - short, single-stranded, synthetic oligonucleotides that are linked to a restriction endonuclease for targeting specific sites in the genome. 
     
  3. Agro-infiltration – a technique that is primarily used for the transient and localised expression of genes in a plant typically without any integration of the introduced DNA into the plant genome. It involves infiltrating tissues (usually intact leaves) with a liquid suspension of Agrobacterium containing the vector. The technique was primarily developed for use as a research tool however is now being used as a production platform for high value proteins, e.g. vaccines.
In relation to accelerated breeding following induction of early flowering it was concluded the final food producing lines would be comparable to those developed using a conventional plant breeding approach. Derived food products should therefore not be regarded as GM food. It would be important from a safety perspective however for the early flowering transgenic parent line to be fully characterised to make it easier to ensure any introduced transgenes have been excluded from the final food-producing lines. This technique is still in the research phase, therefore commercial products are not expected for some time.

For the targeted mutagenic techniques it was concluded they are all conceptually similar to zinc finger nuclease technology, which was discussed in the first FSANZ workshop. When used to introduce small changes only, such techniques do not present a significantly greater food safety concern than other forms of mutagenesis.  Providing any transgenes have been segregated away from the final food producing lines, derived foods would be similar to food produced using traditional mutagenic techniques. Such foods should therefore not be regarded as GM. When used to introduce a new gene however, the techniques would be equivalent to transgenesis and, as such, any food products should be regarded as GM.

For Agro-infiltration it was concluded the technique would have limited applicability to food. As any food products that are produced using this type of expression system will be purified proteins, and the plants in which they are produced will not themselves be used as food, there are no significant food safety concerns. Whether the purified protein products are regarded as GM foods would depend on their use and whether the plants from which they are derived are themselves GM.

Acknowledgement

FSANZ thanks all participants for generously donating their time and for enthusiastically contributing their knowledge and expertise to the discussions.


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