Tony Conner

1
Intragenics/cisgenics and other emerging
techniques for genetic modification

• Tony Conner

2
New techniques in crop breeding

• Plant breeders have always been rapid adopters of
  new technologies
• Haploid plants chromosome doubling
• Chromosome manipulation substitution addition
  lines between species
• Chemical- and radiation- induced mutations
• Cell tissue culture wide hybrids, in vitro
  fertilisation, protoplast fusion, spontaneous
  genetic changes

3
Molecular biology era

• Two key technologies
• - DNA diagnostics for marker-assisted selection
• - Genetic engineering, now allows the routine
  transfer of DNA from any source to crops
• Latter was a step too far for society
• Strict regulations throughout the world, usually
  embedded in legislation

4
Genetic modification refinements

• New breeding and genetic modification techniques
  have continued to rapidly evolve
• Unclear whether these new techniques result in
  GMOs as defined in legislation
• Growing interest in developing techniques that
  result in plants not containing any new DNA
  sequences
• In some cases the resulting changes are similar
  to, or identical to, those from breeding

5
Emerging issues

• Scientists are confused as to whether these
  techniques are, or should be, considered as
  producing GMOs
• Regulators are even more confused and are not
  prepared to make decisions
• In the modern era of public consultation, how can
  we expect society to debate the issues when
  products are ready to go, and the technology is
  still evolving?

6
Intragenics/cisgenics

• Genetic engineering of plants with their own DNA
• Assembly of vectors for gene transfer from the
  target species
• Transfer genes from the genepool to elite lines
  of the crop
• May or may not involve chimeric genes
• GM crops without foreign DNA
• Issues around the use of term cisgenics

7
Null segregants from transgenics

• Non-transgenic progeny segregating from plants
  heterozygous for transgenes
• These non-GM plants are still legally GM in many
  countries, including NZ and Europe
• Should these plants be considered transgenic?
• But what if the transgene has already been used
  to increase or decrease the frequency of natural
  recombination?
• Provides a valuable breeding tool to break-up or
  maintain linkages groups co-inherited genes

8
Grafting onto root stocks

• What if non-transgenic plants are grafted onto
  transgenic rootstocks?
• - resistance to root diseases in fruit trees or
  grapes on which non-GM scions are grown are the
  harvested fruit GM?
• - but what if rootstock transgenes are designed
  to translocate silencing micro-RNAs from the
  rootstock to the scion to induce changes in gene
  expression?

9
Targeted mutagenesis

• Allow the exact desired change to be induced in a
  genome
• Oligonucleotide-directed mutagenesis (ODGM) for
  site-specific alteration
• Oligonucleotide molecules are not incorporated
  into the genome
• Induce a DNA repair mechanism to make the desired
  change(s)
• Will become more important with whole genome
  sequence knowledge
• More precise and targeted than classical
  mutagens

10
Implications and issues arising

• No clear biological distinction between
  traditional plant breeding approaches and GMOs
• Complete continuum of technologies from
  traditional plant breeding to transgenics
• Matter of interpretation whether new techniques
  fall within the scope of GMO legislation
• Definitions of GMOs differ between countries
• Enforcement difficult when resulting organisms
  are indistinguishable from conventional breeding