The scientific and technological literature is abuzz with nanotechnology
and its manufacturing and medical applications. But it is in an area with a
less glitzy aura—plant sciences—where nanotechnology advancements are
contributing dramatically to agriculture.
Researchers at Iowa
State University
have now demonstrated the ability to deliver proteins and DNA into plant cells,
simultaneously. This is important because it now opens up opportunities for
more sophisticated and targeted plant genome editing-techniques that require
the precise delivery of both protein and DNA to bring about specific gene
modifications in crop plants. Such modifications are becoming more and more
important in the face of our changing climates as new insect pests, plant
diseases, and soil stresses emerge where previously there were few.
While DNA delivery into cells has become routine, delivering proteins and
enzymes to both animal and plant cells has proved more challenging. The Iowa State
team’s protein delivery advancement is an important achievement toward this
end.
A research paper describing the advancement has been published online by Advanced Functional Materials. The work
was partially sponsored by Pioneer Hi-Bred with long-term support from Iowa State
University’s Plant
Sciences Institute.
The Iowa State research team includes Kan Wang,
professor of agronomy; Brian Trewyn, associate scientist in chemistry; Susana
Martin-Ortigosa, a post-doctoral research associate in agronomy; and Justin
Valenstein, a chemistry doctoral student.
Nanoparticles are tiny materials that are the size equivalent of several
molecules sitting side-by-side or the size of a big virus. A single nanometer
is one-billionth of a meter. The virus that causes AIDS is roughly 100 nm in
diameter.
Using new and improved custom-built honeycomb-like mesoporous silica
nanoparticles that the Iowa
State team designed five
years ago, the researchers have demonstrated co-delivery of functional protein
and DNA into plant cells.
The first generation of these customized particles were relatively small
(100 nm) and so the available packing spaces were unable to accommodate larger
functional molecules such as proteins or enzymes. This next generation is five
times the size (500 nm) and looks something like an ultrafine piece of
Honeycomb cereal.
The key to the researchers’ success is a newly devised method for making
larger uniform pouches in the custom nanoparticles. An additional modification—gold
plating the entire silica particle prior to packing—improved DNA and protein
binding for a more secure payload.
To test the new particle’s effectiveness, Wang and her colleagues loaded
the pores with a green florescent protein derived from jelly fish, which serves
as a photo marker inside the plant cell. Next, these particles were coated with
DNA encoding a red protein from coral. The complex was then shot into plant
cells using a gene gun, a traditional gene delivery method that gets foreign
material past the plant’s protective cell wall.
The gold plating innovation added some greatly needed ballistic heft to the
particles, ensuring their ability to cannonball through the plant cell wall once
released from the gene gun.
Cells that fluoresce both red and green at the same time confirm successful
delivery. The team has demonstrated success in onion, tobacco, and maize cells.
The work is a tangible realization of efforts the team had in the design
stage just two years ago when colleague Victor Lin of Iowa State University and the U.S. Department of
Energy’s Ames Laboratory unexpectedly died. “He was such a brilliant
scientist,” says Wang. “We all felt completely lost when we lost
him.”
But the team pulled together, capitalizing on the excellent training all
had received from working with Lin to make this next generation particle a
reality.
“We would have been unable
to work out anything without each other,” says Wang. “This success
proves his legacy continues.”
