Intragenics/cisgenics and other emerging techniques for genetic modification

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