Techniques that exploit pollen to genetically transform plants are a promising alternative to tissue culture techniques. This is because pollen releases active DNA to the ovaries of plants during fertilization. Indeed, researchers are now able to – more or less successfully – directly produce transgenic seeds by pollinating plants with pollen containing exogenous DNA using a variety of physical techniques.

The new field of nanobiotechnology – for example using nanoparticles to carry genes into a plant cell – could come into its own here, say researchers led by Haixin Cui of the Chinese Academy of Agricultural Sciences in Beijing. One particular technique that might be especially efficient is magnetofection, which relies on a magnetic force to help push nanoparticles loaded with DNA into target cells. Until now, this technique has mainly been tested on animal cells because plant cells, unlike their mammalian or bacteria counterparts, have thicker cell walls that are more difficult to get past.

This does not apply to most crop pollens, which have thin walls, and Cui’s team has now exploited this fact to deliver exogenous genes across the pollen wall membrane into the inside of pollen.

Transgenic varieties successfully generated from transformed seeds

In their experiments, the researchers used positively charged polyethyleneimine-coated Fe3O4 magnetic nanoparticles (MNPs) as the DNA carriers for binding with electrically negative DNA. After mixing the MNP/DNA complexes with cotton plant pollen, they then applied a magnetic field to direct the complexes into the pollen through their surface apertures (which have a diameter of around 5–10 microns). They then pollinated the plants with the magnetofected pollen to produce transgenic varieties that they successfully generated from transformed seeds.

“Our pollen magnetofection technique delivers exogenous DNA into pollen, directly generates transgenic seeds though pollination and fertilization, and creates genetically modified plants within a short period of time,” explains Cui. “What is more, the technique appears to protect DNA function against enzymatic degradation while bypassing the tedious procedure of in vitro tissue culture and regeneration.”

Although the researchers mainly looked at cotton as a model plant in this study, they say that their technique might be extended to other flowering plants since almost all of these can produce seeds by pollination.

New platform technology

“Pollen magnetofection is a new platform technology for genetically transforming crops for both basic and applied research such as plant science, genetic breeding and synthetic biology,” Cui tells nanotechweb.org. “We envisage that it will allow scientists to introduce new and beneficial traits into crops, especially in difficult-to-regenerate plants.”

The team, which also includes researchers from Cornell University and Rutgers University, is now looking to improve the efficiency of its technique by optimizing experimental conditions.

The research is detailed in Nature Plants doi:10.1038/s41477-017-0063-z.