California Ag Network

Tag: UC Riverside

  • Artificial Photosynthesis Can Produce Food Without Sunshine

    Photosynthesis has evolved in plants for millions of years to turn water, carbon dioxide, and the energy from sunlight into plant biomass and the foods we eat. This process, however, is very inefficient, with only about 1% of the energy found in sunlight ending up in the plant. Scientists at UC Riverside and the University of Delaware have found a way to bypass the need for biological photosynthesis altogether and create food independent of sunlight by using artificial photosynthesis.

    Plants are growing in complete darkness in an acetate medium that replaces biological photosynthesis. (Marcus Harland-Dunaway/UCR)

    The research, published in Nature Food, uses a two-step electrocatalytic process to convert carbon dioxide, electricity, and water into acetate, the form of the main component of vinegar. Food-producing organisms then consume acetate in the dark to grow. Combined with solar panels to generate the electricity to power the electrocatalysis, this hybrid organic-inorganic system could increase the conversion efficiency of sunlight into food, up to 18 times more efficient for some foods.

    “With our approach we sought to identify a new way of producing food that could break through the limits normally imposed by biological photosynthesis,” said corresponding author Robert Jinkerson, a UC Riverside assistant professor of chemical and environmental engineering.

    In order to integrate all the components of the system together, the output of the electrolyzer was optimized to support the growth of food-producing organisms. Electrolyzers are devices that use electricity to convert raw materials like carbon dioxide into useful molecules and products. The amount of acetate produced was increased while the amount of salt used was decreased, resulting in the highest levels of acetate ever produced in an electrolyzer to date.

    Experiments showed that a wide range of food-producing organisms can be grown in the dark directly on the acetate-rich electrolyzer output, including green algae, yeast, and fungal mycelium that produce mushrooms. Producing algae with this technology is approximately fourfold more energy efficient than growing it photosynthetically. Yeast production is about 18-fold more energy efficient than how it is typically cultivated using sugar extracted from corn.

    “We were able to grow food-producing organisms without any contributions from biological photosynthesis. Typically, these organisms are cultivated on sugars derived from plants or inputs derived from petroleum—which is a product of biological photosynthesis that took place millions of years ago. This technology is a more efficient method of turning solar energy into food, as compared to food production that relies on biological photosynthesis,” said Elizabeth Hann, a doctoral candidate in the Jinkerson Lab and co-lead author of the study.

    The potential for employing this technology to grow crop plants was also investigated. Cowpea, tomato, tobacco, rice, canola, and green pea were all able to utilize carbon from acetate when cultivated in the dark.

    By liberating agriculture from complete dependence on the sun, artificial photosynthesis opens the door to countless possibilities for growing food under the increasingly difficult conditions imposed by anthropogenic climate change. Drought, floods, and reduced land availability would be less of a threat to global food security if crops for humans and animals grew in less resource-intensive, controlled environments. Crops could also be grown in cities and other areas currently unsuitable for agriculture, and even provide food for future space explorers.

    “Using artificial photosynthesis approaches to produce food could be a paradigm shift for how we feed people. By increasing the efficiency of food production, less land is needed, lessening the impact agriculture has on the environment. And for agriculture in non-traditional environments, like outer space, the increased energy efficiency could help feed more crew members with less inputs,” said Jinkerson. This approach to food production was submitted to NASA’s Deep Space Food Challenge where it was a Phase I winner. — By Holly Ober, UC Riverside

    About UC Riverside

    The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California’s diverse culture, UCR’s enrollment is more than 26,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual impact of more than $2.7 billion on the U.S. economy. To learn more, visit www.ucr.edu.

  • How Stressed-out Plants Produce Their Own Aspirin

    Plants protect themselves from environmental hazards like insects, drought and heat by producing salicylic acid, also known as aspirin. A new understanding of this process may help plants survive increasing stress caused by climate change.

    UC Riverside scientists recently published a seminal paper in the journal Science Advances reporting how plants regulate the production of salicylic acid.

    Plants in a UCR laboratory changing color in response to high light stress. (Jin-Zheng Wang/UCR)

    The researchers studied a model plant called Arabidopsis, but they hope to apply their understanding of stress responses in the cells of this plant to many other kinds of plants, including those grown for food.

    Human skin produces reactive oxygen species in response to sun, which causes freckles. (Maria Casinos/iStock/Getty)

    “We’d like to be able to use the gained knowledge to improve crop resistance,” said Jin-Zheng Wang, UCR plant geneticist and co-first author on the new study. “That will be crucial for the food supply in our increasingly hot, bright world.”

    Environmental stresses result in the formation of reactive oxygen species or ROS in all living organisms. Without sunscreen on a sunny day, human skin produces ROS, which causes freckles and burns. High levels of ROS in plants are lethal.

    As with many substances, the poison is in the amount. At low levels, ROS have an important function in plant cells.

    “At non-lethal levels, ROS are like an emergency call to action, enabling the production of protective hormones such as salicylic acid,” Wang said. “ROS are a double-edged sword.”

    The research team discovered that heat, unabated sunshine, or drought cause the sugar-making apparatus in plant cells to generate an initial alarm molecule known as MEcPP.

    UCR scientists Wilhelmina van de Ven, Katayoon Dehesh, Jin-Zheng Wang, who led the plant stress research. (UCR/Stan Lim)

    Going forward, the researchers want to learn more about MEcPP, which is also produced in organisms such as bacteria and malaria parasites. Accumulation of MEcPP in plants triggers the production of salicylic acid, which in turn begins a chain of protective actions in the cells.

    “It’s like plants use a painkiller for aches and pains, just like we do,” said Wilhelmina van de Ven, UCR plant biologist and co-first study author.

    The acid protects plants’ chloroplasts, which are the site of photosynthesis, a process of using light to convert water and carbon dioxide into sugars for energy.

    “Because salicylic acid helps plants withstand stresses becoming more prevalent with climate change, being able to increase plants’ ability to produce it represents a step forward in challenging the impacts of climate change on everyday life,” said Katayoon Dehesh, senior paper author and UCR distinguished professor of molecular biochemistry.

    “Those impacts go beyond our food. Plants clean our air by sequestering carbon dioxide, offer us shade, and provide habitat for numerous animals. The benefits of boosting their survival are exponential,” she said. — By Jules Bernstein, UC Riverside

  • PD/GWSS Board Ups Assessment Rate for 2022 California Grape Harvest

    The Pierce’s Disease/Glassy Winged Sharpshooter Board (PD/GWSS Board) recently voted to set the grower assessment rate in support of the Pierce’s Disease Control Program (Program) at $1.25 per $1,000 of crop value for the 2022 harvest. This assessment provides vital funding for research on GWSS and other designated vineyard pests and for research on developing crop resistance to PD.

    “CAWG fully supports this important program and we thank growers for their funding of the program,” said Tom Slater, Chair of the California Association of Winegrape Growers. “Inflation has increased costs of every aspect of our industry which includes research and costs of the Pierce’s Disease Control Program. CAWG appreciates the volunteer work of the PD/GWSS Board members, who represent the industry. Their due diligence, including choosing to invest in a science audit, helps contain costs and assure our assessment dollars are spent wisely.”

    “Wine Institute commends the Pierce’s Disease and Glassy-winged Sharpshooter Board and staff for their decades of work to protect California’s vineyards from invasive pests and diseases,” said Robert P. Koch, President & CEO of Wine Institute. “This commitment to research will continue to provide significant benefits to our wine communities.”

    In considering the 2022 rate adjustment, the PD/GWSS Board sought sufficient funds to support testing of clean plant material at UC Davis and an audit by the National Academy of Sciences (NAS). NAS will create an interdisciplinary committee to assess the current struggles facing the California wine grape industry in controlling grapevine viruses, with a specific focus on Grapevine red blotch virus and Grapevine leafroll associated virus type 3.

    “As the PD/GWSS Board discussed the assessment rate, we were mindful of the cost pressures our industry is facing and carefully constructed the upcoming budget to best balance our assessment dollars for maximum impact,” said Will Drayton, PD/GWSS Board chair. “We also know California winegrape growers continue to face pressure from grapevine viruses. As we set the Board’s budget for the coming year, we want to ensure growers have clean plant material and that the Board continues to wisely invest grower dollars in the best research for solutions to pests and diseases.”

    The committee will review the current and recent research activities of the PD/GWSS Board, and help direct a future funding approach to address the knowledge and management gaps required to minimize the spread of, and economic losses due to these viruses. The committee will also identify ways in which the PD/GWSS Board can draw from a wider breadth of researchers and utilize cutting edge genetic tools and platforms to combat these virus problems.

    Over the 21-year history of the program, the assessment has ranged from a high of $3.00 in 2001 to a low of $0.75 in 2015. The average annual harvest assessment is $1.40. The assessment was $1.00 for the 2019, 2020 and 2021 harvests. The 2022 harvest assessment will provide an estimated $3.5 million in funding.

    Since 2019, the PD/GWSS Board has committed more than $11 million to research that benefits vineyard health. Below are a few examples of the outcomes of that research:

    • Discovery of potential biological control of PD using Paraburkholderia phytofirmans by Steven Lindow at UC Berkeley. The Board funded a new project this year at UC Davis to assess efficacy and compare with other biological control PD control tools, with the goal to produce data that would help directly lead to commercialization.

    • The recent successful laboratory use and publication of CRISPR/Cas9 genetic technology in GWSS through work at UC Riverside, which has the potential to revolutionize PD vector control by making GWSS unable to vector PD.

    • Improved understanding of the effects of grapevine red blotch on vine physiology and wine composition through recent work at UC Davis.

    • Improved understanding and communication of research-based control measures for Pierce’s disease as well as Board-designated viral diseases (red blotch, leafroll and fan leaf) through work at UC Cooperative Extension, Cornell University, and UC Berkeley.

      The Program has also had great success in treatment of GWSS in rural, suburban and urban settings. This includes nursey treatments, area wide management and the ongoing treatment for GWSS in residential Vacaville.

      A recent study led at UC Cooperative Extension, Kern County, found that Program-led efforts in area wide management of GWSS in the southern San Joaquin Valley have been a success and a good model for disease control. 

  • Genetic Insights Help Rice Survive Drought and Flood

    Plants — they’re just like us, with unique techniques for handling stress. To save one of the most important crops on Earth from extreme climate swings, scientists are mapping out plants’ own stress-busting strategies.

    Rice plant with roots visible. (Julia Bailey-Serres/UCR)

    A UC Riverside-led team has learned what happens to the roots of rice plants when they’re confronted with two types of stressful scenarios: too much water, or too little. These observations form the basis of new protective strategies.

    “This one crop is the major source of calories for upwards of 45 percent of humanity, but its harvests are in danger,” said Julia Bailey-Serres, UCR geneticist and study lead. “In the U.S., floods rival droughts in terms of damage to farmers’ crops each year.”

    While it is possible for rice to flourish in flooded soils, the plants yield less food or even die if the water is too deep for too long. This work simulated prolonged floods of five days or longer, in which plants were completely submerged. It also simulated drought conditions.

    In particular, the researchers examined the roots’ response to both types of conditions, because roots are the unseen first responders to flood and drought-related stress.

    Their work is described in a new paper published in the journal Developmental Cell.

    One key finding is about a cork-like substance, suberin, that’s produced by rice roots in response to stress. It helps protect from floods as well as from drought.

    “Suberin is a lipid molecule that helps any water drawn up by the roots make it to the shoots, and helps oxygen from shoots to reach roots,” Bailey-Serres said. “If we reinforce the plant’s ability to create suberin, rice has better chances for survival in all kinds of weather.”

    Rice experiments being conducted in a field. (Julia Bailey-Serres/UCR)

    The researchers were able to identify a network of genes that control suberin production and can use this information for gene editing or selective breeding.

    “Understanding suberin is particularly exciting because it is not susceptible to breakdown by soil microbes, so carbon that the plant puts into suberin molecules in the roots is trapped in the ground,” said Alex Borowsky, UCR computational biologist and study co-author. “This means that increasing suberin could help combat climate change by removing and storing carbon from the atmosphere.”

    The researchers also identified the genes controlling some of rice’s other stress behaviors.

    “One of our interesting findings is that when rice plants are submerged in water, the root cell growth cycle goes on pause, then switches back on shortly after the shoots have access to air,” Bailey-Serres said.

    In the future, the research team plans to test how modifying these stress responses can make the plant more resilient to both wet and dry conditions.

    “Now that we understand these responses, we have a roadmap to make targeted changes to the rice genome that will result in a more stress-tolerant plant,” Bailey-Serres said.

    Though heavy rains and droughts are both increasing as threats, Bailey-Serres has hope that new genetic technology can increase its resilience before it’s too late.

    “With genome editing, the fact that we can make a tiny but targeted change and protect a plant from disease is amazing. Though our crops are threatened, new technologies give us reasons to hope,” Bailey-Serres said. — By Jules Bernstein, UC Riverside

    About UC Riverside

    The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California’s diverse culture, UCR’s enrollment is more than 26,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual impact of more than $2.7 billion on the U.S. economy. To learn more, visit www.ucr.edu.

  • “Cautiously Optimistic” about Leaffooted Bug Lure & Trap

    Almond Board of California — With the rise of leaffooted bug damage showing up in almond kernels at the handler, the bottom line of growers is at stake. Research funded by the Almond Board of California and conducted at UC Riverside, is expanding much needed tools for effective IPM monitoring protocol to combat the pest.

    Across the industry, handlers have seen higher rates of brown spot damage caused by leaffooted bug – and true bugs, such as stink bug – which has led to increased rejection rates.

    Growers are limited to the best monitoring protocols available today, but they can be time and labor intensive, often pointing out damage after it’s too late to act.

    leaffooted bug on Almond (Photo Courtesy of the Almond Board of California)

    A multiyear effort led be UC Riverside Entomology Professor Jocelyn Millar – and funded by the Almond Board of California – has worked to improve the monitoring options for the pest.  

    “You can take beat samples of the crop canopy to look for adults or nymphs, but we’ve never established any kind of treatment threshold for that practice,” said Houston Wilson, assistant cooperative extension specialist in the Department of Entomology at UC Riverside and collaborator on the project. “You can look for signs of feeding damage, which manifests in gummosis, which can also be caused by a number of things.”

    Wilson said growers can cut gummy nuts open to look for evidence of leaffooted bug penetration of the kernel.

    “Identifying gummosis is easier because you can look for the signs, but it’s an artifact – by the time you see it, the leaffooted bug has already damaged the nuts,” Wilson said. “We don’t have a passive sampling system for leaffooted bug, like for navel orangeworm, where a pheromone attracts the insect to a trap,” Wilson said. “What we’re trying to develop is a lure – a pheromone – and a better trap.”

    leaffooted bug damaged nuts (Photo Courtesy of the Almond Board of California)
    First, the pheromone

    Over the past five years, Millar and his team have been isolating and identifying compounds that make up the leafooted bug pheromone. Nine compounds were identified, and the team began work to synthesize each one. Wilson said that some of the compounds were relatively easy to identify, but others were not, “the last pheromone compound we identified was entirely new to science.”

    In the latest project update, Millar noted that this new compound was a relatively small part of the overall pheromone composition but it packed the biggest punch, triggering the strongest responses from the bugs. Over the last two years, Millar’s team has been able to collect enough material to identify the compound and effectively synthesize it.

    Second, the trap

    At the same time as the pheromone work, the team at UC Riverside – and other collaborators such as Cooperative Extension Specialist Kent Daane – began looking at the best trap for the application. They tested multiple styles of traps and colors, ultimately identifying that a hanging cross-vane panel trap coated with a sticky substance – yellow or blue in color – performed the best for trapping leaffooted bug.

    With a fully recreated pheromone and an effective trap, the team ran trap trials in commercial almond, pistachio and pomegranate orchards in the Central Valley. Based on in-field trials, the team concluded that the trap and pheromone were both very effective and will look to the private sector to commercialize the new monitoring system.

    What’s next?

    “We demonstrated in field trials last summer and this spring that the synthetic pheromone blend is highly attractive to females,” Wilson said. “Now we’re looking at what minimal blend of compounds are needed to attract the pest. If we want this to be a commercially viable lure, we have to find the most cost-effective composition. In many cases, it’s not necessarily required to have the full bouquet of compounds in a pheromone blend to have a functional lure.”

    Once the right balance is determined for a synthetic blend that lures leaffooted bugs to a trap the next step is understanding what trap catch means on population density in an orchard. This will define treatment thresholds, giving growers guidance on timing to combat leaffooted bug before damage occurs on kernels. Private industry will likely takeover at this point to develop the traps for the industry. For Wilson, this prospect has him cautiously optimistic.

    “We’re very fired up with this pheromone blend, but I’m also trying not to get ahead of myself before we know what the cost will be for a commercial and scalable lure.”

    More information about best management practices of leaffooted bug is available at the UC Statewide IPM website.

  • Mating Disruption Research to Combat Spotted Lanternfly Included in CDPR’s $3.75 Million Investment

    The California Department of Pesticide Regulation (DPR) today awarded $3.75 million to fund 10 research projects that explore Integrated Pest Management (IPM) tools for urban, non-agricultural and agricultural pest management. The 2021-2022 DPR Grants Programs funded by the state budget represent a 617% increase from the previous year’s funding to accelerate the transition to safer, more sustainable pest management.

    “The grant projects we are funding today are critical to developing and expanding innovative practices and biological, non-chemical and physical tools to manage pests in agriculture, urban and other non-agricultural communities,” said DPR Director Julie Henderson. “The research will support the state’s work to accelerate a systemwide transition to safer, more sustainable pest management and better protect human health and the environment.”

    DPR’s Research Grants Program funds projects that advance IPM, an approach that uses the least-toxic, effective method to solve pest problems. In the last decade, DPR has awarded $9,702,819 in research grants.

    Research projects funded for agricultural pest management:

    • Investigating a pesticide-free mating disruption approach using vibrational signals to control the spotted lanternfly, which presents particular risk to grapes, hops, apples and stone fruit, along with maple, poplar, walnut and willow trees. Spotted lanternfly is one of the most damaging invasive insects nationwide and has already caused significant harm to crops and landscapes across 11 states. This research will be led by Dr. Rodrigo Krugner at the United States Department of Agriculture – Agricultural Research Service (USDA ARS).

    • Evaluating an IPM approach that will disrupt insect behavior by targeting and interfering with a pest’s biological processes and minimizing possible unintended effects to other organisms. The project will evaluate the use of this tool for controlling diamondback moth and western flower thrips that impact California vegetable crops such as lettuce. This research will be led by Dr. Daniel Hasegawa at USDA ARS.

    • Assessing a biocontrol system for the management of tadpole shrimp in rice. Tadpole shrimp usefully eat some early season weeds but can cause damage to rice later in their lifecycle. To preserve their role in controlling weeds but diminish the shrimp’s later impact on the rice harvest, predator mosquito fish will be introduced mid-season to control the shrimp’s population when necessary. This research will be led by Dr. Ian Grettenberger at UC Davis.

    • Testing two emerging IPM technologies for agricultural use, the automatic release of biocontrol organisms using flying drones, and precision spray application technology, which uses much less pesticide than applying pesticide sprays using current techniques. This research will be led by Dr. Ian Grettenberger at UC Davis.

    • Developing an IPM software decision-making tool for pistachio growers that helps reduce pesticide use by guiding more precise pesticide applications when chemical use is necessary. This IPM tool leverages smart technology to help growers transition from routine preventative spraying to more limited threshold-based chemical use. This research will be led by Dr. Themis Michailides at UC Davis.

    Research projects funded for urban and agriculture pest management:

      • Studying the use of a reduced-risk ”attract-and-kill” approach as an effective alternative to urban and agricultural pesticide spray programs for managing South American palm weevils, a pest that damages date palms in urban and agricultural environments. “Attract-and-kill” strategies use pheromones that attract the target pest to a small amount of pesticide that kills the insect, as opposed to spraying a large quantity of pesticide over an area to control pest populations. This research will be led by Dr. Mark Hoddle at UC Riverside.

      • Studying the impact and potential of using insect growth regulators that target Argentine ants for pest control in urban and agricultural environments. Insect growth regulators are new, safer pest management tools that pose a much lower risk of causing unintended damage to beneficial insects when compared to many traditional insecticides. This research will be led by Dr. Dong-Hwan Choe at UC Riverside.

    Research projects funded for urban and nonagricultural pest management:

    • Testing non-chemical entrapment methods for trapping, monitoring and eliminating bedbugs, a significant public health pest that disproportionately affects low-income Californians. This research will be led by Dr.Catherine Loudon at UC Irvine.

    • Creating a new set of guidelines for effectively identifying and managing biting mites, a common, but poorly understood indoor pest that is often misidentified and incorrectly managed. This research will be led Dr. Andrew Sutherland at UC Agriculture and Natural Resources (UCANR).

    • Assessing a baiting system for detecting western drywood termites to reduce the number of unnecessary fumigation treatments in California homes, especially in Southern California where termites represent a significant pest problem. This system would indicate when active termite infestations have returned and if preventative treatment is needed, greatly decreasing the amount of high-risk pesticide use in homes. This research will be led by Dr. Dong-Hwan Choe at UC Riverside.

      For more information on past recipients of DPR’s Grants Program, please visit DPR’s Grants Program webpage.

      ABOUT THE DEPARTMENT OF PESTICIDE REGULATION

      The California Department of Pesticide Regulation protects human health and the environment by fostering safer and sustainable pest management practices and operating a robust regulatory system to evaluate and register pesticides and monitor and regulate their sale and use across the state.

      DPR’s work includes conducting scientific evaluations of pesticides to assess and mitigate potential harm to human health or the environment prior to and following registration, registering all pesticides prior to sale or use in California, monitoring for pesticides in the air and water, and enforcing pesticide laws and regulations in coordination with 55 County Agricultural Commissioners and their combined 400 field inspectors across the state’s 58 counties. DPR invests in innovative research, outreach, and education to encourage the development and adoption of integrated pest management tools and practices and conducts outreach to ensure pesticide workers, farmworkers and local communities have access to pesticide safety information. More information about DPR.

  • Scientists can Switch on Plants’ Response to Light

    Scientists have figured out how plants respond to light and can flip this genetic switch to encourage food growth. The discovery could help increase food supply for an expanding population with shrinking opportunities for farming. The research on this genetic switch, led by UC Riverside, has now been published in the journal Nature Communications. 

    Almost every aspect of plant growth and development is influenced by light. Plants are able to sense light, as well as temperature, with a protein called phytochrome B. This protein conveys light information into the cell that changes the expression of genomes, altering plant growth. However, phytochrome B cannot interact directly with the plant’s DNA. For that, plant cells rely on a family of eight proteins called PIFs.

    “The activity of these PIFs is directly controlled by phytochrome,” said lead study author and UCR botany professor Meng Chen. In addition to controlling the amount of PIFs that accumulate in plant cells, the scientists have learned that when phytochrome B is activated by light, it inhibits the activity of the PIFs.

    “PIFS are like chefs in a restaurant. You can regulate the number of them. Get rid of half, for example and you reduce the restaurant’s productivity,” Chen explained. “Alternatively, you could keep all chefs — in our case, PIFs — but tie up their hands. That could also slow down their work the same as getting rid of half of them. That’s what we’re saying.”

    The scientists also found another key component of plants’ light response. PIFs have two parts; one part that binds to genes, and one that activates the genes, which tell the plant to perform different functions such as growing or flowering. This study found the precise location of these activator regions — the first time this has been done in plant cells.

    To find this activation region, Chen’s team chopped the protein into many small pieces. Then, they examined whether any of the pieces were able to activate genes and found that one of them was. For more detail, the scientists then changed the amino acids on a PIF, where they believed the activator region to reside, and observed how the plant responded. This allowed them to be sure where the gene activator region is located as well as how it is built.

    “This approach allowed us to surprisingly recognize the similarities between this part of the PIF in plants and a tumor-suppressing protein in humans,” Chen said. In fact, Chen said the basic gene activation mechanisms in plant, yeast, and animal cells bear remarkable similarities to one another.

    “Plants, animals, and fungi (like baker’s yeast) all evolved from a common ancestor,” Chen said. “Genetic information in DNA converts to RNA to protein, and that basic function is conserved through these gene activators across three kingdoms of life, before plants, animals and fungi diverged.”

    One of the biggest reasons to study these cellular functions is to manipulate them. In this case, the discovery could allow scientists to turn light and temperature-related genes on and off to benefit crop growers.

    Dark-grown (left) and light-grown (right) Arabidopsis seedlings. In the dark, PIF3 (and other PIFs) has full activity, so the seedling is very tall. In the light, phytochrome B inhibits the stability and activity of PIF3, slowing seedling growth. (Meng Chen/UCR)

    Part of the strategy to increase crop yields is to grow more plants per acre of land. Currently, if you place crops too close together, plants can “see” the competing neighbors through their shade. Then plants will use more energy for growing taller toward the light, but not necessarily for maximizing leaf growth and seed production.

    Alternatively, if plants can ignore their neighbors and concentrate on leaf and seed production instead of growing taller, growers can increase yield on the same acreage.

    “You don’t want only stems to grow, you want yield,” Chen said. “For that, plants need energy to make leaves so they can increase photosynthesis, the process of making food out of sunlight. You want the right part of the plant to grow.”

    Chen’s group demonstrated that by reducing the activity of PIF proteins, they could slow down stem growth.  This study thus uncovered a precise way to make the plants grow shorter, so that seeds, fruit and edible portions of the plant can grow, even in shade.

    “Now we know how plants turn genes on and off in response to changes in light and temperature,” Chen said. “It’s the first step toward controlling their responses to light and temperature, and making them more tolerant of different, sometimes challenging environments in a changing climate.” — By Jules Bernstein, UC Riverside

  • Yeast and Bacteria Together Biosynthesize Plant Hormones for Weed Control

    Plants regulate their growth and development using hormones, including a group called strigolactones that prevent excessive budding and branching. For the first time, scientists led by UC Riverside have synthesized strigolactones from microbes. The work is published in the open-access journal, Science Advances.

    Strigolactones also help plant roots form symbiotic relationships with microorganisms that allow the plant to absorb nutrients from the soil. These two factors have led to agricultural interest in using strigolactones to control the growth of weeds and root parasites, as well as improving nutrient uptake.

    These root-extruding compounds don’t come without risks. They also stimulate germination of witchweeds and broomrapes, which can cause entire crops of grain to fail, making thorough research essential prior to commercial development. Scientists are still learning about the physiological roles played by this diverse group of hormones in plants. Until recently, manufacturing pure strigolactones for scientific study has been difficult and too costly for agricultural use.

    Yanran Li

    “Our work provides a unique platform to investigate strigolactone biosynthesis and evolution, and it lays the foundation for developing strigolactone microbial bioproduction processes as alternative sourcing,” said corresponding author Yanran Li, a UC Riverside assistant professor of chemical and environmental engineering.

    Together with co-corresponding author Kang Zhou at National University Singapore, Li directed a group that inserted plant genes associated with strigolactone production into ordinary baker’s yeast and nonpathogenic Escherichia colibacteria that together produced a range of strigolactones.

    Producing strigolactones from yeast turned out to be very challenging. Although engineered yeast is known to modify the strigolactone precursor, called carlactone, it could not synthesize carlactone with any of the specific genes used by the researchers.

    “This project started in early 2018, yet for over 20 months there was basically no progress. The gatekeeping enzyme DWRF27 is not functional no matter how we try in yeast,” Li said. “Kang developed a microbial consortium technique to produce a Taxol precursor in 2015 and that inspired this wonderful collaboration.”

    The team turned toward E. coli, which had already been shown capable of producing carlactone. The carlactone it produced, however, was unstable and could not be further modified by engineered E. coli into any strigolactones. Li’s group managed to optimize and stabilize the carlactone precursor.

    To their delight, when the yeast and bacteria were cultured together in the same medium, the E. coli and yeast worked as a team: E. coli made carlactone, and the yeast transformed it into various final strigolactone products. The method also produced enough strigolactones to extract and study. Using this platform, the group identified the function of multiple strigolactone biosynthetic enzymes, showing that sweet orange and grape have the potential to synthesize orobanchol-type strigolactones.

    The team also engineered microbe metabolism to boost strigolactone production threefold to 47 micrograms per liter, enough for scientific study. Though commercial production of strigolactones is still a long way off, the new method for biosynthesizing them from a yeast-bacterium consortium will help scientists learn more about this important group of plant hormones, especially the enzymes involved.

    Enzymes are protein catalysts and are responsible for modification of carlactone by yeast. Because carlactone is unstable, it cannot be purchased from commercial sources. As a result, many plant scientists have difficulty studying new enzymes that may work to transform carlactone into strigolactones.

    “The new yeast-bacterium co-culture provides a convenient way for scientists to complete such works because the bacterium makes carlactone in situ,” Zhou said. “With discovery of more enzymes and optimization of the microbial consortium, we can manufacture strigolactones in quantity in the future.”

    Li and Zhou were joined in the research by Sheng Wu, Anqi Zhou, and Alex Valenzuela of UC Riverside; and Xiaoqiang Ma at the Singapore-MIT Alliance for Research and Technology. The paper, “Establishment of strigolactone-producing bacterium-yeast consortium,” is available here. — By Holly Ober, UC Riverside

  • Critical Groundwater Supplies May Never Recover From Drought

    Illustration of groundwater location. (USGS)

    Along with hurricanes and wildfires, there’s another important, but seldom-discussed effect of climate change — toxic water and sinking land made worse by groundwater drought. Water from snow and rain seeps deep into the ground between layers of soil and accumulates in sponge-like underground bathtubs, called aquifers. Farmers rely heavily on this groundwater to irrigate their crops when they can’t get enough water from surface water sources.

    Roughly 85 percent of Californians also rely on groundwater for some portion of their water supply. Worldwide, an estimated two billion people depend on it. However, excessive groundwater use combined with droughts has caused land surface to sink, damaging critical infrastructure including roads, buildings, and sewage and water pipes.

    New UC Riverside research shows groundwater takes an average of three years to recover from drought — if it ever recovers at all. In the largest study of its kind, scientists found that this recovery time only applies to aquifers that aren’t touched by human activity, and the recovery time might be even longer in regions with excessive pumping.

    For groundwater levels to recover after a drought, new precipitation requires time to percolate through the soil and recharge the depleted aquifer. The researchers show that this process can take several years longer in areas with deeper groundwater levels.

    “If people pump groundwater without first letting it recharge, groundwater levels keep going down, the cost of pumping goes up, and the land sinks,” explained Hoori Ajami, UCR groundwater hydrologist and study co-author and principal investigator on this project.

    Published in the Journal of Hydrology, the new study is the first to examine groundwater response to droughts on a continental scale. Previous investigations of groundwater drought have mostly relied on model simulations and covered smaller areas. This study relied on 30 years of daily measurements from 600 wells across the country.

    On average, the researchers determined it takes about two years for rainwater drought to become groundwater drought, though in some cases it takes as long as 15 years. Because of the long lag time, the effects aren’t felt or seen immediately. However, they can be severe.

    Groundwater drought combined with pumping can cause a gradual, uneven lowering of the land surface called subsidence. “It is a known problem in California’s Central Vaalley, exacerbated by climate factors and excessive water pumping,” Ajami said. “Subsidence causes irreversible damage to infrastructure, buildings and roads.”

    As the ground shifts and water level declines, contaminants in the soil, like arsenic, can mobilize and poison the water. In coastal areas, aquifers depleted by drought and pumping can fill up with salty sea water, making groundwater unusable for drinking or farming.

    “You start with a problem of water quantity, and you end up with a problem of water quality,” Ajami said.

    “Excessive pumping lowers the groundwater level, creating a downward spiral in which restoring the aquifer becomes harder and harder,” added study co-author Adam Schreiner-McGraw.

    To reduce the damage from prolonged droughts that are an inevitability as the planet continues to warm, the researchers have several recommendations. Most climate models show rain becoming more intense. Storing rain waters could recharge aquifers, speeding up the recovery process.

    The researchers also suggest that farmers improve irrigation efficiency and switch perennials like almonds, pistachios, and walnuts to annual, less water-intensive crops in areas where groundwater depletion is severe.

    “We need to improve our climate projections to include groundwater, so that we can better assess what we have and how to protect it,” Ajami said. “There are ways to better manage what we have.” — By Jules Bernstein, UC Riverside

  • NASA Funds Tiny Tomatoes for Vertical Farming on Earth and Space

    Urban agriculture offers many benefits for food production but often has higher costs relative to traditional farming and is limited to only a few crops. By 2050, there will be nine billion people on the planet, but arable land is decreasing. Global food production will need to double to meet food needs, though climate change complicates the problem more.

    Robert Jinkerson, an assistant professor of chemical and environmental engineering at UC Riverside, is working to change this by engineering the size and nutritional value of tomato plants to increase both the diversity and value of crops that can be grown in urban controlled environment agriculture, or CEA.

    Jinkerson has received a $450,000 New Innovator grant from the Foundation for Food & Agriculture Research, or FFAR, to advance this research. FFAR’s New Innovator in Food & Agriculture Research Award provides early career scientists with funding to conduct audacious food and agriculture research.

    “Urban controlled environment agriculture can offer many benefits for the production of crops and is likely to supply more food in the future as worldwide food demand increases,” Jinkerson said.

    Often these urban CEA systems are designed to have plant growth areas stacked vertically to save space. However, this also decreases the height available for plant growth, limiting the size of crops that can be cultivated in vertical farms to small leafy greens.

    “In order to overcome these size limitations and to increase the variety of crops that can be grown in vertical farms, we are engineering tomato plants to have a small stature and are optimized for this unique growing environment,” said Jinkerson, who uses CRISPR/Cas9 gene editing to modulate key genes involved in plant development and architecture.

    In addition to reducing the size of plants, this project will also increase the nutritional value of these crops by increasing their vitamin content, making urban agriculture more profitable.

    The potential applications for these tiny tomatoes don’t end on Earth.

    Jinkerson, along with Martha Orozco-Cárdenas, director of the UCR Plant Transformation Research Center, have been awarded a NASA Space Biology grant to evaluate tomatoes from their prior work on the International Space Station. These plants, also engineered with gene editing technology and dubbed Small Plants for Agriculture in Controlled Environments, or SPACE tomatoes, will be grown in the Advanced Plant Habitat onboard the ISS to determine how these plants grow in microgravity. The SPACE tomatoes will be grown ‘seed-to-seed,’ meaning seeds will be harvested and the next generation grown in space, completing an entire lifecycle. These experiments, which will happen after several years of trials on Earth, will help establish methodologies to grow food on long duration space missions.

    “We are extremely excited to receive support for these projects and hope that the results will help transform the way we produce food here on Earth and beyond,” said Jinkerson.

    About UC Riverside

    The University of California, Riverside (www.ucr.edu) is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California’s diverse culture, UCR’s enrollment is more than 24,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of almost $2 billion. To learn more, email news@ucr.edu.