The genome editing tool CRISPR has transformed many areas of biology, but
using it to enhance crops such as wheat and corn remains difficult because
of the plants' tough cell walls. Now, a team of researchers has creatively
solved that problem by using pollen from one genetically modified (GM) plant
to carry CRISPR's components into another plant's cells.
The researchers used haploid induction, an odd phenomenon which allows
pollen to fertilize plants without permanently transferring male genetic
material to offspring. The new plants only have a female set of chromosomes,
which makes them haploid instead of the traditional diploid.
The research team used a corn line that can be transformed with CRISPR using
bacteria or gene gun technology, and that has a crippled version of a gene,
MATRILINEAL, making its pollen able to trigger haploid induction. They then
transformed this corn line with a gRNA/Cas9 combinations programmed to
target genes related to different desirable traits. The pollen of these
transformed plants could then spread the gRNA and Cas9 editing machinery to
other corn varieties that had been recalcitrant to CRISPR.
This haploid induction-edit (HI-edit), as the researchers call the CRISPR
pollen method, has only been done in laboratories. However, the researchers
say that if it were done in the field, the changes would not spread because
the male genome in the pollen disappears shortly after fertilization.