Topsoil, the rich upper layer of soil full of microorganisms and nutrients, is essential for modern agriculture. Some say we are running out.

Many cash crops such as corn are only grown for a few months of the year, so for the remaining months, fields often lay barren. This results in erosion as passing winds lift the topsoil and carry it away, which is not so easily replenished. Each inch of topsoil can take 500-1000 years to regenerate, but according to Our World in Data, 16% of topsoils aren’t expected to last the next hundred years. 

A solution to this pressing concern is the implementation of cover crops, which are grown to protect the topsoil during the off-season of the primary crop. Legumes like clover are popular cover crops for their ability to fix nitrogen into the soil, a natural fertilizer for the cash crop in the next season. However, cover crop implementation has not been widespread, with less than 5% of total US cropland using them in 2022. Although nitrogen fixation has its perks, the value it offers to farmers isn’t always enough for them to justify the time and resources required to manage a whole new crop.

Introducing pennycress, which can be grown during corn’s off-season, but also produces seeds rich in lipids, sparking interest in its use in biofuels. Pennycress seeds can reach an oil content of 36%, and its chemical composition makes it a prime contender for sustainable aviation fuel (SAF). The crop is already optimized for biofuels, found to be 93% efficient at oil production, but without much domestication, it does have some area for growth. Its inconsistency in response to stressful stimuli makes it less reliable, warranting genetic improvements.

To increase pennycress’ resilience to abiotic stress (drought, heat, cold tolerance, waterlogging), the US Department of Energy is funding labs across the country to target several issues. An oversensitive plant can change its flowering time, reducing yield by making seeds prematurely or not making them at all by waiting too long, overlapping with the season of higher priority crops. Farmers won’t prioritize a cover crop over corn, so if seeds aren’t harvested by May, they never will be. 

Ideally, a plant will accumulate sugars and fats throughout its growing season before producing seeds to create the next generation. However, when plants detect stimuli that indicate poor environmental conditions, such as drought or competition, they will create seeds early. This enables them to pass on their genes when they might not otherwise survive, but the reduced photosynthesizing time comes at a cost to yield.

This is a problem for pennycress, because when it’s planted at the end of the corn season, the corn will cast shade on the seedlings. Detecting the foliar shade, the pennycress plants know they have competition and bolt to seed early, reducing yield. However, the mechanism pennycress plants use to tell the difference between normal shade and foliar shade can be manipulated, which is the target of the Nusinow lab.

Dr. Dmitri Nusinow at the Donald Danforth Plant Science Center is one of many scientists involved in the DoE grant, offering unique experience in plants’ light detection from his work in circadian clocks. Plants absorb specific wavelengths of light during photosynthesis, spanning the visible light spectrum until about 680 nanometers, a wavelength that represents red light. Wavelengths beyond the 680 nm mark are considered far-red light, and since they aren’t absorbed during photosynthesis, pass right through the leaf. Plants under foliar shade can detect a higher ratio of far-red light to red light, which they use to determine how much competition they have. To address this problem, the Nusinow lab is targeting a gene called PHYTOCHROME-INTERACTING FACTOR 7 (PIF7), known in model plant Arabidopsis thaliana. In addition to detecting foliar shade, PIF7 is also involved in heat stress, allowing researchers to address two stimuli at once.

To observe the functions of PIF7 in response to heat and foliar shade, researchers used CRISPR-Cas9 to knock out the gene. After viewing the results, they had to identify the best form of the gene to use. Using a mutant population of pennycress sequenced from the DoE project, the Nusinow lab is able to plant a variety of genotypes and observe their performance in various conditions. Through the use of elevated temperatures and far-red light to represent foliar shade, they can choose the best form of PIF7 to improve pennycress’ performance. 

In addition to ignoring corn, eliminating foliar shade responses in pennycress will prevent it from decreasing seed production by viewing itself as competition. Pennycress yields do not increase when a higher density of seeds are planted due to their aversion to competition, so research of the Nusinow lab could also increase yields in that respect.

However, academic labs are not the only ones interested in pennycress. The DoE grant includes the company CoverCress, a St. Louis startup owned by Bayer with a business model centering around pennycress. Instead of having farmers make the investment to buy seeds of a new crop, they supply the seeds themselves and pay farmers for their harvest. This allows hesitant farmers to benefit and contribute to sustainable practices when they might not have risked buying and selling seeds on their own. Having CoverCress on the grant also makes it more appealing for governmental investors: because companies have to turn a profit, they have a strong incentive to see that the project makes it to customers.

Since CoverCress gives out their own seed, they are able to use their own improved seed, known as golden pennycress. By mutating a gene involved in tannin production, a cell layer is removed in the seeds, turning them from their normal black color to a golden yellow and improving the rate and uniformity of their germination. Crucially, this also prevents them from contributing to the seed bank: seeds will not come back to germinate in future seasons to compete with other crops.

Even more than protecting topsoil and producing SAF, pennycress has potential in other areas. Growing after the corn season, it uses some leftover fertilizer, preventing nitrogen runoff in the winter. The other labs working on pennycress are working to improve its yield in other ways, but also increasing its range of applications. One project involves changing the chemical properties of the grain, as when its seeds are pressed for oil, a seed cake is left behind that could be used for animal feed. As the seed cake currently contains undesired antinutritional compounds, research is ongoing to find a solution. Already, pennycress has been edited for the food industry: by mutating two genes to completely eliminate uric acid content, its oil becomes something that resembles canola oil.

“Pennycress is easily converted from an oil that’s used for jet planes for one that’s used for feed.” -Dmitri Nusinow

“Pennycress is easily converted from an oil that’s used for jet planes for one that’s used for feed.” -Dmitri Nusinow

Pennycress has a lot of potential to improve modern agriculture in a sustainable way. There are new projects lined up to contribute to pennycress research, but the DoE grant hasn’t been renewed yet. However, despite the detriment done to science funding this year, researchers are optimistic toward biofuel projects, as the Trump administration seems to support an increase in biofuel production. Hopefully, the grant will be renewed and improvements will be continue to be made on pennycress, creating a lucrative crop that protects agriculture and replaces fossil aviation fuel.

The views, opinions, and/or findings expressed are those of the author and should not be interpreted as representing the official views or policies of the Department of Energy of the U.S. Government.

This week marks the three-year anniversary of my website, and while that is very exciting, it comes with a bit of an adjustment. 

Starting this website is one of the best decisions I’ve ever made, not only for teaching me about my field, but for keeping me engaged and active when it comes to learning about things I would never otherwise hear about. However, as the quality of my work and the caliber of research I’m conducting has improved, writing an article every week has become increasingly strenuous. 

As I start at UC Berkeley this fall, I want to focus more of that time into actual laboratory research, an opportunity I never had before. I will be switching to a monthly format, but because I’ll have more time, I will be making better content. Starting with this article, I intend to hold more interviews, allowing me to ask the questions I normally have to ignore when articles are my only source of information. Of course, interviews won’t replace my current format, just add to it.

Check out the Nusinow Lab! 

Other sources are embedded.