By Laura Tran, C2ST Intern, Rush University
Genetic engineering can be used to produce genetically modified organisms (GMOs) like weather-resistant crops, modified yeast or bacteria that produce insulin¹, and even animal organs suitable for human transplantation². GMO crops offer several advantages such as improved yields, enhanced nutritional value, and resistance to drought, frost, or pesky insects. However, making genetically modified food can be time-consuming and costly. Recent technology may be the solution to circumventing these issues.
Scientists in Japan have developed a way to modify crops without having to engage in genetic engineering³. The process involves spraying bioactive compounds into plant cells through their leaves. It seems so simple, we can hardly be-leaf it! However, designing and implementing this method came with its own set of challenges.
Three components must work in tandem: 1) a peptide nanocarrier (a vehicle), 2) bioactive molecules (the cargo), and 3) a spray atomizer (the delivery route).
First, for the “vehicle,” researchers used cell-penetrating peptides (CPPs) which penetrate plant cells (as the name suggests) by crossing the outer plant cell wall and inner plasma membrane. These peptides can target specific structures within the cells, such as chloroplasts. To determine which CPPs were the most effective at entering plant cells, researchers tagged natural and synthetic CPPs with fluorescent yellow dye and sprayed the leaves of different plant species (e.g., soybean, tomato, and thale cress) with the solution. Over time, they measured the amount of yellow color present to determine how well the CPPs could travel into the cells.
Second, for the “cargo,” a bioactive molecule (DNA or RNA) must be attached to the CPPs. These types of biomolecules can influence the plant’s gene expression. For example, researchers tested a transgenic plant that overexpresses yellow fluorescence and then designed a spray that contained RNA that interferes with the expression of the fluorescent protein. When they sprayed the leaves, the solution had silenced, or “turned off,” the expression of fluorescence.
Finally, for the “delivery route,” researchers developed a spray to apply the solution to plants because it has the most practical use under agricultural conditions. These sprays can be spread over large fields with ease. Although GMO crops⁴ grow in over 70 countries worldwide, this could greatly benefit farmers by providing a viable alternative to GMO crops. GMO crops offer more rapid crop improvement⁵ (several years) to the marketplace compared to the conventional method of selective breeding (which can take +10 years). However, GMO crops are developed by changing the genes of the plant. This newer “spray” technology may be able to circumvent the timely process of genetic modification and make functional changes to the current gene expression of plants in real-time.
This process is a promising way to “more naturally” alter traits in crops that would normally be developed as genetically modified organisms. As a targeted treatment, this foliar (leaf) spray does not have any major environmental downside effects. However, it will take some time to develop different combinations to improve this delivery system and ultimately improve quality traits in crops.