Tim Wallace
Genetic modification of food crops is, depending on your point of view, a wondrous technological solution to feed a growing global population or a hubris-soaked scientific monstrosity sowing the seeds of environmental apocalypse.
Yet the war over GM crops, though intense, has so far been restricted to a small number of battlefields – corn, soybean, tomatoes and canola, for instance – due to the limited list of plant species scientists have been able to successfully modify.
Now the stage may be set for a massive expansion in the theatres of conflict. A team of mostly Chinese scientists has announced a new technique, called pollen magnetofection, which they say overcomes the obstacles of traditional plant-transformation methods and clears the way to genetically modify “almost all crops”.
“At the moment, we are very limited as to which plants, and even types of plants – called cultivars – we are able to transform,” explains Rachel Burton, of the ARC Centre of Excellence in Plant Cell Walls at the University of Adelaide, who was not involved in the research.
“For example, we work with barley a lot, and are only able to make transgenic barley from about 10 cultivars. There are even more we can’t transform at all. This technology would change that.”
Almost all current GM methods involve regenerating a new plant from a single transformed cell using complicated in vitro culture processes. The alternative approach taken by Xiang Zhao, of the Chinese Academy of Agricultural Sciences in Beijing, and colleagues is to first manipulate the DNA of pollen, then use this pollen to fertilise a plant’s ovary and directly generate transgenic seeds.
The team details its methods in the journal Nature Plants.
Their key tool for overcoming the lack of success of previous efforts to genetically transform pollen is pairing magnetofection – the use of magnetic fields to direct foreign DNA to target cells – with nanobio technology, using magnetic nanoparticles to “smuggle” DNA into the heart of the pollen.
Magnetofection has mainly been used in animal science and medical research, as the researchers note in their paper, because the thicker cell walls of plants have proved more resistant to DNA incursions. Zhao and colleagues overcame this resistance by concentrating on pollen’s weakest points – the apertures that are exit points for the release of sperm cells during germination.
The scientists measured the size of these apertures, then chose nanoparticle delivery vehicles small enough to fit through them, transporting DNA cargo into the pollen.
The process is “a ground-breaking step towards eliminating the time-consuming steps of in vitro culture techniques”, says Chris Cazzonelli, of the Environmental Epigenetics Laboratory at Western Sydney University in Australia.
“It opens opportunities to transform new plant species not previously easily amenable to tissue culture or conventional transformation techniques.”
Monika Doblin, an expert on plant cell walls at the University of Melbourne, also in Australia, agrees a genetic transformation technique that can be easily applied to any pollen-producing plant species is a “significant advance”, though she notes the small species sample size and experiment numbers presented in the new paper. “Further investigation as to the effectiveness of this technique across a broad range of current crop species is warranted but, that said, it does sound promising,” she says.
The rewards and any risks, however, are likely to be limited to special cases, says Justin Borevitz, who specialises in food and environmental security at Australian National University in Canberra. “It may not be substantially different to existing agriculture technologies,” he adds. “Another tool for the genomic breeding toolbox.”
Anti-GM activists are nonetheless likely to greet the news with dread, while Burton reckons most plant scientists will see the prospect of more plant experimentation as a good thing.
“We have been doing this for thousands of years, since agriculture got going,” she says. “Usually we do it by conventional breeding.” Not only is this very slow but it brings “all the DNA, both the good and the bad, from both parents, and then you have to spend time getting rid of the bad stuff”. With genetic modification “you can add just the good bit that you want”.
Yet while generally in favour of GM technology and what it can do, Burton acknowledges there are potential issues, too. “We have to be careful we don’t make plants that are weedy, that can take over, wreck ecosystems and push native species out, for example,” she says. “We also have to be sure that we are not making toxic versions of plants – although we can do this by conventional breeding just as easily and with no regulations to stop it.”
