Scientists demonstrate first use of nanotechnology to enter plant cells

A team of Iowa State University plant scientists and materials chemists have successfully used nanotechnology to penetrate plant cell walls and simultaneously deliver a gene and a chemical that triggers its expression with controlled precision. Their breakthrough brings nanotechnology to plant biology and agricultural biotechnology, creating a powerful new tool for targeted delivery into plant cells.

The research, "Mesoporous Silica Nanoparticles Deliver DNA and Chemicals into Plants," is a highlighted article in the May issue of Nature Nanotechnology. The scientists are Kan Wang, professor of agronomy and director of the Center for Plant Transformation, Plant Sciences Institute; Victor Lin, professor of chemistry and senior scientist, U.S. Department of Energy’s Ames Laboratory; Brian Trewyn, assistant scientist in chemistry; and Francois Torney, formerly a post-doctoral scientist in the Center for Plant Transformation and now a scientist with Biogemma, Clermond-Ferrand, France.

Currently, scientists can successfully introduce a gene into a plant cell. In a separate process, chemicals are used to activate the gene’s function. The process is imprecise and the chemicals could be toxic to the plant.

"With the mesoporous nanoparticles, we can deliver two biogenic species at the same time," Wang said. "We can bring in a gene and induce it in a controlled manner at the same time and at the same location. That’s never been done before."

The controlled release will improve the ability to study gene function in plants. And in the future, scientists could use the new technology to deliver imaging agents or chemicals inside cell walls. This would provide plant biologists with a window into intracellular events.

The Iowa State team, which has been working on the research in plants for less than three years, started with an Iowa State University proprietary technology developed previously by Lin’s research group. It is a porous, silica nanoparticle system. Spherical in shape, the particles have arrays of independent porous channels. The channels form a honeycomb-like structure that can be filled with chemicals or molecules.

"One gram of this kind of material can have a total surface area of a football field, making it possible to carry a large payload," Trewyn said.

Lin’s nanoparticle has a unique "capping" strategy that seals the chemical goods inside. In previous studies, his group successfully demonstrated that the caps can be chemically activated to pop open and release the cargo inside of animal cells. This unique feature provides total control for timing the delivery

The team’s first attempt to use the porous silica nanoparticle to deliver DNA through the rigid wall of the plant cell was unsuccessful. The technology had worked more readily in animals cells because they don’t have walls. The nanoparticles can enter animal cells through a process called endocytosis — the cell swallows or engulfs a molecule that is outside of it. The biologists attempted to mimic that process by removing the wall of the plant cell (called making protoplasts), forcing it to behave like an animal cell and swallow the nanoparticle. It didn’t work.

They decided instead to modify the surface of the particle with a chemical coating.

"The team found a chemical we could use that made the nanoparticle look yummy to the plant cells so they would swallow the particles," Torney said.

It worked. The nanoparticles were swallowed by the plant protoplasts, which are a type of spherical plant cells without cell walls.

Most plant transformation, however, occurs with the use of a gene gun, not through endocytosis. In order to use the gene gun to introduce the nanoparticles to walled plant cells, the chemists made another clever modification on the particle surface. They synthesized even smaller gold particles to cap the nanoparticles. These "golden gates" not only prevented chemical leakage, but also added weight to the nanoparticles, enabling their delivery into the plant cell with the standard gene gun.

The biologists successfully used the technology to introduce DNA and chemicals to Arabidopsis, tobacco and corn plants.

"The most tremendous advantage is that you can deliver several things into a plant cell at the same time and release them whenever you want," Torney said.

"Until now, you were at nature’s mercy when you delivered a gene into a cell," Lin said. "There’s been no precise control as to whether the cells will actually incorporate the gene and express the consequent protein. With this technology, we may be able to control the whole sequence in the future."

And once you get inside the plant cell wall, it opens up "whole new possibilities," Wang said.

"We really don’t know what’s going on inside the cell. We’re on the outside looking in. This gets us inside where we can study the biology per se," Wang said.

Source: Iowa State University

Related stories:

New gene that helps plants beat the heat
Michigan State University plant scientists have discovered another piece of the genetic puzzle that controls how plants respond to high temperatures. That may allow plant breeders to create new varieties of crops that flourish in warmer, drier climates.
Scientists identify gene that may contribute to improved rice yield
A team of scientists, including Penn State Distinguished Professor of Biology Hong Ma, has identified a gene in rice that controls the size and weight of rice grains. The gene may prove to be useful for breeding high-yield rice and, thus, may benefit the vast number of people who rely on this staple food for survival. "Our work shows that it is possible to increase rice's yield by enhancing the expression of a particular gene," said Ma. The team's results will be published on 28 September 2008 in an early online edition of the journal Nature Genetics, and in the November print issue of the journal.
Insight into the evolution of parasitism
Scientists at the Max Planck Institute for Developmental Biology, together with American colleagues, have decoded the genome of the Pristionchus pacificus nematode, thereby gaining insight into the evolution of parasitism. In their work, which has been published in the latest edition of Nature Genetics, the scientists from Professor Ralf J. Sommer's department in Tübingen have shown that the genome of the nematode consists of a surprisingly large number of genes, some of which have unexpected functions.
Using novel tool, researchers dig through cell 'trash' and find treasure
A person's trash can reveal valuable information, as detectives, historians and identity thieves well know. Likewise, a cell's "trash" may yield certain treasures, University of Delaware researchers have found.
Scientists discover cancer-causing role of gene proteins
Dr. Tak Mak and scientists at The Campbell Family Institute for Breast Cancer Research at Princess Margaret Hospital have discovered the role of two "cousins" in the genetic family tree of cancer development.
Photosynthesizing bacteria with a day-night cycle contain rare chromosome
Researchers sequencing the DNA of blue-green algae found a linear chromosome harboring genes important for producing biofuels. Simultaneously analyzing the complement of proteins revealed more genes on the linear and the typical circular chromosomes then they'd have found with DNA sequencing alone.
Researchers discover atomic bomb effect results in adult-onset thyroid cancer
Radiation from the atomic bomb blasts in Hiroshima and Nagasaki, Japan, in 1945, likely rearranged chromosomes in some survivors who later developed papillary thyroid cancer as adults, according to Japanese researchers.
Key to virulence protein entry into host cells discovered
Researchers from the Virginia Bioinformatics Institute (VBI) at Virginia Tech have identified the region of a large family of virulence proteins in oomycete plant pathogens that enables the proteins to enter the cells of their hosts. The protein region contains the amino acid sequence motifs RXLR and dEER and has the ability to carry the virulence proteins across the membrane surrounding plant cells without any additional machinery from the pathogen.

News discussion:

Nanotechnology news