An artist's rendering shows a needle-like
carbon nanotube delivering DNA through the wall of a plant cell. It also may be
possible to use this method inject a gene editing tool called CRISPR to alter a
plant's characteristics for breeding.
Courtesy
of Markita del Carpio Landry
Is
there an efficient way to tinker with the genes of plants? Being able to do
that would make breeding new varieties of crop plants faster and easier, but
figuring out exactly how to do it
has stumped plant scientists for decades.
Now researchers may have cracked it.
Modifying the genetics of a plant requires getting DNA into its
cells. That's fairly easy to do with animal cells, but with plants it's a
different matter.
"Plants
have not just a cell membrane, but also a cell wall," says Markita Landry,
assistant professor of chemical and biomolecular engineering at the University
of California, Berkeley.
Both methods have limitations. Gene guns aren't very efficient,
and some plants are hard, if not impossible, to infect with bacteria.
UC Berkeley researchers have found a way to do it using
something called carbon nanotubes, long stiff tubes of carbon that are really
small. Landry came up with the idea, and the curious thing is she's neither a nanotechnology
engineer nor a plant biologist.
"I'm a physicist," Landry says. "When I started
my lab at Berkeley two years ago, my lab was focused exclusively on imaging
between cells."
Markita Landry, assistant professor of chemical
and biomolecular engineering at the University of California, Berkeley, came up
with the idea of using carbon nanotubes to get DNA into plant cells.
Courtesy
of Marcelo Perez del Carpio
She was planning to use carbon nanotubes as kind of external
scaffolding around the cells to make it easier to see what was going on between
them. "This was a project that failed pretty hard and pretty quick,
because instead of staying outside of the plant cells as we had presumed, these
nanotubes were going straight into the cells," Landry says.
So in the spirit of corporate management gurus, she turned a
problem into an opportunity.
"We flipped it around and made it a DNA delivery platform
instead," she says.
A strand of DNA is small enough to slip through the plant cell
wall, but it's not rigid enough. "You can kind of think of it like a
floppy string," Landry says. "If you try to push a floppy string
through a sponge, it's not really going to work, but if you take a solid needle
and try to push it through a sponge, that will work much better."
Attaching the DNA to the carbon nanotube gives you that
nano-needle.
But that DNA only affects the single cell and lasts for just a
few days before it degrades. To make a permanent change, you need to affect the
plant's genome using a gene editing tool such as as CRISPR.
Landry says it also might be possible to use nanotubes to
deliver CRISPR. Once inside a cell, from let's say an apple tree, CRISPR could,
for example, turn off a gene that causes browning in apples.
"We would end up with an apple tree whose apples don't go
brown when you cut into them," Landry says.
The
idea of using carbon nanotubes to get DNA into plant cells is intriguing to
some scientists, but "I think they've got a little ways to go to make it
really interesting," says Laura Bartley,
associate professor of plant biology at the University of Oklahoma.
Bartley
says it will be important to show that the method works in different varieties
of plants besides the two Landry describes in a recent paper in Nature Nanotechnology:arugula and wheat. But she's
impressed that the new approach appears to be able to get DNA into grass plants
such as wheat.
"If it works the way they think it does, I can imagine a
lot of people wanting to use that," Bartley says.
In fact, she says she's thinking about trying the invention in
her work on grass plants.
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