Genome Editing in Flax in Response to Environmental Stress

The flax genome can be rapidly modified within a single generation in response to the growth environment. The variations do not appear to be due to either random mutations or movement of transposable elements, but rather that the genome appears to be able to switch between two well-defined, different sequences at many loci. The genomes of eight lines, (genotrophs) all derived from the same progenitor line (Pl), have been compared, by whole genome sequencing, to the reference genome of the flax variety Bethune. The differences fall into two main classes. One, where regions of the genome have insertions or deletions among the genotrophs compared to Pl, the second where Pl and the genotrophs have a large number of SNPs over a short region of the genome. Again, one of the sets of lines is the same as Bethune and the other is very different but each of the variants has a consistent sequence. One of the unanswered questions is the source of these variants since they are not present in an intact form in the progenitor genome. When the corresponding regions of the genomes of other flax accessions and even the wild progenitor of flax, Linum bienne, are characterized, the same two alternative structures are seen. The identification of the genes involved in producing these large reproducible modifications of the genome is ongoing.