The battle never ends. Growers, across regions and soil types and seasons, are constantly fighting against all the elements to produce healthy (and profitable) crops. They contend against the weather, insects, changing consumer tastes, diseases and more, always hopeful for a good harvest. Luckily, there is an army of scientists marching right alongside them, always striving to make the process easier.
Research at MIT have recently developed a new genetic tool that could help plants resist fungal infections and survive drought conditions. It sounds like something out of a sci-fi film – the technique uses nanoparticles to deliver genes into the chloroplasts of plant cells, including vegetables. Doing so could help overcome the difficulties involved in genetically modifying plants, currently a complex and time-consuming process customized for each species being worked with.
“This is a universal mechanism that works across plant species,” Michael Strano, a professor of chemical engineering at MIT, said about the new method. Strano collaborated with Nam-Hai Chua, the deputy chair of the Temasek Life Sciences Laboratory at the National University of Singapore and a professor emeritus at Rockefeller University, to see how this technology could work.
“This is an important first step toward chloroplast transformation,” Chua said. “This technique can be used for rapid screening of candidate genes for chloroplast expression in a wide variety of crop plants.”
This study is the first to come from the Singapore-MIT Alliance for Research and Technology (SMART) program in Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP), led by Strano and Chua – teaming up just like Tony Stark and Bruce Banner did in “The Avengers.”
Strano and his colleagues discovered a few years ago that by tuning the size and electrical charge of nanoparticles, they could design the nanoparticles to penetrate plant cell membranes. This mechanism, called lipid exchange envelope penetration (LEEP), allowed them to create plants that glow by embedding nanoparticles carrying luciferase (a light-emitting protein) into their leaves.
Once they achieved this, plant biologists began asking if the process could be used to genetically engineer plants – specifically, to get genes into chloroplasts. Plant cells have dozens of chloroplasts, so inducing them (instead of just the nucleus) to express genes could be a way to generate much greater quantities of a desired protein.
The chloroplast contains about 80 genes which code for proteins required to perform photosynthesis. The chloroplast also has its own ribosomes, allowing it to assemble proteins inside itself. Until recently, it has been very difficult for scientists to get genes into the chloroplast – the only existing technique used a high-pressure “gene gun” to force genes into the cells, which can damage the plant and is not very efficient.
MIT created nanoparticles consisting of carbon nanotubes wrapped in chitosan, a naturally occurring sugar. To get the nanoparticles into plant leaves, researchers applied a needleless syringe filled with the particle solution to the lower side of the leaf surface. Particles entered the leaf through tiny pores called stomata, which normally control water evaporation. Inside the leaf, the nanoparticles passed into the chloroplasts. After the particles get inside the chloroplast, the DNA is naturally released from the nanoparticles and can be translated into proteins.
In this study, researchers delivered a gene for a fluorescent yellow protein, which made it easy to spot when expressed in the leaves. They found that about 47 percent of the plant cells produced the protein – but they believe that number could be higher if they deliver more particles. It can be tested on a lot of different plants too. This study tested the process on spinach, watercress, arugula and more.
The goal of this new tool is to allow plant biologists more easily engineer a variety of desirable traits in vegetables and crops. Agricultural researchers in Singapore are interested in creating leafy vegetables and crops that can grow at higher densities, for urban farming. Other aims include creating drought-resistant crops, engineering crops to be resistant to fungal infections and modifying other plants so they don’t take up arsenic from groundwater.
And because the engineered genes are carried only in the chloroplasts, which are inherited maternally, they can be passed to offspring but can’t be transferred to other plant species.
And so the battle continues to find and grow the best produce. Our secret weapon against the randomness of the world is science.