Soil may harbor answer to reducing arsenic in rice

May 1, 2013 under CANR News

Drs. Harsh Bias & Janine Sherrier work together with bacteria resistant rice plants at the Greenhouse.Harsh Bais and Janine Sherrier of the University of Delaware’s Department of Plant and Soil Sciences are studying whether a naturally occurring soil bacterium, referred to as UD1023 because it was first characterized at the University, can create an iron barrier in rice roots that reduces arsenic uptake.

Rice, grown as a staple food for a large portion of the world’s population, absorbs arsenic from the environment and transfers it to the grain. Arsenic is classified as a poison by the National Institutes of Health and is considered a carcinogen by the National Toxicology Program.

Long-term exposure to arsenic has been associated with skin, lung, bladder, liver, kidney and prostate cancers, and low levels can cause skin lesions, diarrhea and other symptoms.

The risks of arsenic in rice were recently highlighted in the national press, when arsenic was detected in baby foods made from rice. In regions of the world where rice is the major component of the human diet, the health of entire communities of people can be negatively impacted by arsenic contamination of rice.

Arsenic may occur naturally in the soil, as it does in many parts of Southeast Asia, or it may be a result of environmental contamination. Despite the health risks arsenic in rice poses to millions of people around the world, there are currently no effective agricultural methods in use to reduce arsenic levels.

Sherrier, professor, and Bais, associate professor, are investigating whether UD1023 — which is naturally found in the rhizosphere, the layer of soil and microbes adjacent to rice roots — can be used to block the arsenic uptake. Bais first identified the bacterial species in soil samples taken from rice fields in California.

The pair’s preliminary research has shown that UD1023 can mobilize iron from the soil and slow arsenic uptake in rice roots, but the researchers have not yet determined exactly how this process works and whether it will lead to reduced levels of arsenic in rice grains.

“We have a bacterium that moves iron, and we want to see if creating an iron shield around the rice roots will slow arsenic movement into other parts of the plant,” Bais said.

Sherrier and Bais, who received a 2012 seed grant for the project from Delaware’s National Science Foundation Experimental Program to Stimulate Competitive Research (EPSCoR), ultimately want to determine how UD1023 slows arsenic movement into rice roots and whether it will lead to reduced levels of arsenic in the rice grains, the edible portion of the plant.

“That is the most important part,” Bais said. “We don’t know yet whether we can reduce arsenic in the grains or reduce the upward movement of arsenic towards the grain, but we’re optimistic.”

Bais says that, if successful, the project could lead to practical applications in agriculture.

“The implications could be tremendous,” he said. “Coating seeds with bacteria is very easy. With this bacteria, you could implement easy, low-cost strategies that farmers could use that would reduce arsenic in the human food chain.”

Article by Juan C. Guerrero

Photo by Kathy F. Atkinson

This article can also be viewed on UDaily.

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Sherrier named acting deputy dean of College of Agriculture and Natural Resources

February 14, 2013 under CANR News

Dr. Janine Sherrier, Plant and Soil Science.Janine Sherrier has been named the acting deputy dean of the University of Delaware’s College of Agriculture and Natural Resources (CANR).

Sherrier, a professor in the Department of Plant and Soil Sciences with a secondary appointment in biological sciences, also directs a robust research program at the Delaware Biotechnology Institute (DBI).

Sherrier was one of the earliest hires for the DBI initiative and worked as part of the team to grow DBI into the center of research excellence that it is recognized to be today.

Sherrier earned her bachelor of science degree in biology at Baylor University and her doctorate in biology at Texas A&M University. Subsequently, Sherrier pursued postdoctoral research in genetics at the John Innes Centre, U.K., and postdoctoral research in biochemistry at the University of Cambridge, U.K.

She is a member of the American Society of Plant Biology, the American Association for the Advancement of Science and the International Society for Molecular Plant-Microbe Interactions. She is also currently serving as the leader of a federal program that supports outstanding early-career scientists engaged in agricultural research.

Of the appointment, Sherrier said, “I consider it an honor and privilege to serve my college for a year as acting deputy dean. My highest priority is to provide members of my college with the resources required for high-quality student education, community outreach, and internationally-competitive research programs.”

Sherrier continued, adding that CANR Dean Mark Rieger “brings great ideas and an energizing enthusiasm, and I am pleased to be working as part of his team.”

Rieger said that he is “delighted that Dr. Sherrier has joined the college’s administrative team. As a world-class molecular biologist, she brings a strong background in research, which will be the focus of her appointment. Most importantly, I have found her to be truly passionate about the advancement of the college and agriculture and natural resource issues in general.”

Sherrier currently teaches courses in plant development biology, current topics of plant biology, and mentors undergraduate and graduate students in her research laboratory.

The research being conducted in her laboratory focuses on the beneficial symbiotic relationship between plants in the legume family and the soil microbe rhizobia, and the resulting development of a nitrogen-fixing root nodule. Her research program includes both a strong fundamental research component and the direct application of that knowledge into the development of new resources to address the immediate needs of growers.

Article by Adam Thomas

Photo by Kathy F. Atkinson

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Tunisian Fulbright Scholar studying beneficial bacteria for legumes

May 29, 2012 under CANR News

At first glance, it wouldn’t seem like Delaware and the Sahara Desert have a lot in common. However, on closer inspection, the mid-Atlantic state and the arid regions of southern Tunisia in Africa are more similar than they first appear.

That is one reason why Mokhtar Rejili, a professor from the University of Gabes in Tunisia, is excited to be at the University of Delaware on a Fulbright Scholarship working with UD’s Janine Sherrier on the study of legumes native to his home country.

Of the similarities between the two seemingly disparate locations, Sherrier, a professor in the Department of Plant and Soil Sciences in UD’s College of Agriculture and Natural Resources, explained that Delaware has sandy soil and shoreline salt stress. “Our sandy soils dry out very rapidly and our crop plants can be subject to salt stress. There are also common stresses experienced by plants grown in the two locations, albeit to different levels of severity,” she said.

The scientists are collaborating on research to identify beneficial bacteria to help the plants grow more successfully under conditions of drought and salt stress. Rejili specifically studies legumes that grow in conditions of extreme drought and severe salt stress, and his Tunisian team identifies bacteria that interact with the plant roots growing on the outskirts of the Sahara.

Sherrier is recognized internationally as a scientific expert on bacterial interactions with legumes, and together, the two scientists are working on a research project that will help farmers in Tunisia and Delaware.

The scientists are conducting research that focuses specifically on the type of beneficial bacteria that associate with legume roots and provide nitrogen to the plant. Nitrogen is an essential nutrient for plant growth, and it is often provided to the plant by the application of chemical fertilizers or manure. This is costly for growers and contributes to environmental pollution.

The beneficial bacteria studied by the team can convert a small amount of the nitrogen that is naturally abundant in the Earth’s atmosphere into a form that can meet the nutritional needs of the plant. This reduces the cost of crop production for the grower and also protects the environment from damage caused by fertilizer runoff from agricultural fields.

“The plants form close relationships with the beneficial microbes. They develop a new organ on their roots for the bacteria to reside and provide the right environment and all the energy required for the bacteria to convert atmospheric nitrogen into fertilizer,” Sherrier said. “At a practical level, that means plants growing in soils without sufficient nitrogen can still have productive growth.”

Benefits to health and the environment

Rejili explained that this is especially important for extremely hot and dry areas, like southern Tunisia, where a chemical fertilizer would be of little help to the plants. Such fertilizers are often too expensive to even consider using and, worse, can be detrimental to human health.

“The fertilization of crops is limited to only the well-developed countries,” said Rejili, noting the high costs involved in producing fertilizer, only a small fraction of which is used by the plant. The remainder goes deep into the soil, where “it will contaminate the soil and the water, or it will evaporate into the atmosphere, leading to pollution,” he said, adding this poses “a big question to our health.”

Sherrier said that fertilizer use doesn’t pose a health risk just in Tunisia, it does so in America as well.

“The overuse of fertilizer impacts human health,” said Sherrier, explaining that a recent Environmental Protection Agency (EPA) survey of well water quality in Delaware’s southern counties showed that more than 50 percent of the wells had nitrogen contamination above the levels recommended for drinking water and required remediation.

Sherrier said that while Rejili is interested in helping out his home country, he is also concerned about improving crop production and health for Delawareans.

“People from Delaware love their lima beans, but the beneficial bacteria are not present at very high levels in our soils. Our growers add fertilizer to ensure a good yield. That’s expensive for them, and it’s not good for our environment,” said Sherrier, adding that Rejili has taken on a leadership role on one of her projects to identify beneficial bacteria from Delaware soils that could be added to the soil early in the growth season instead of chemical fertilizer.

Sherrier also explained that the damage to the environment is not just in the fertilizer application, it’s also in the way fertilizer is made. “There’s a huge energy cost associated with making fertilizer,” said Sherrier, explaining that the process requires high pressure and high temperatures, and uses 4 percent of the world’s natural gas supply annually.

“When you burn that natural gas, it releases carbon dioxide into the atmosphere,” she said, adding that there are additional environmental costs in transporting the fertilizer.

Inexpensive option

Besides the environmental and health considerations of cutting down on fertilizer use, the beneficial bacteria could also be an inexpensive option for growers, something that is of particular importance in developing countries.

“We would like to provide whatever help we can to allow the people of Tunisia to support their own food production,” Sherrier said. “Food security is a huge concern for any country. This inexpensive approach to food production protects their environment and helps provide the people with a basic level of security that every human being deserves.”

Providing an inexpensive and reliable food source for developing countries is not the only benefit of this research, however. Being able to grow legumes in areas that have harsh landscapes, like southern Tunisia, will enable the growth of forage crops in areas prone to desertification. This will allow livestock to graze in the area, and will help stabilize a sandy landscape that is prone to degradation from unforgiving winds.

“If you have a few plants that can survive in that area, they can protect soils and prevent the region from converting into desert. This will help preserve the land for food or forage production,” explained Sherrier.

Beneficial bacteria

Sherrier worked closely with the U.S. Department of Agriculture (USDA) and the Delaware Department of Natural Resources and Environmental Control (DNREC) to arrange for the team to study Tunisian plants in her Delaware laboratory. For some of the species, it is the first time that these legumes will be studied outside of Tunisia.

Rejili is evaluating the diversity of bacteria associated with these plants and performing experiments to determine which ones provide the most benefits. In a laboratory setting, the team is inoculating plants with individual strains of beneficial bacteria and evaluating the plant’s performance.

“The bacteria infect the plant root,” Sherrier said, “and when you talk about an infection, most people think, ‘Oh, no! You need to spray something to get rid of that.’ However, in undisturbed natural environments, the bacteria normally infect the plants, boosting their immune systems and helping the plants acquire essential nutrients. This is very similar to the benefits people gain from the bacteria which naturally reside in our digestive tract.”

Said Rejili of the plant interacting with the bacteria, “We can say they are beneficial interactions. So the plants give carbohydrates to bacteria and bacteria gives nitrogen to the plants. So there is an exchange.”

The two hope that when Rejili’s 10-month stay concludes, they can continue their collaboration. “This is a great starting point, and it’s really what the Fulbright progam is all about,” said Sherrier. “It’s helping to build bridges scientifically and culturally.”

Article by Adam Thomas

Photo by Danielle Quigley

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Reducing fertilizer use through beneficial microbe reactions

May 8, 2012 under CANR News

Janine Sherrier, professor in the Department of Plant and Soil Sciences at the University of Delaware, is part of a team that has been awarded $6.8 million from the National Science Foundation (NSF) to study the legume Medicago truncatula.

Sherrier leads one of four research groups participating in this project, which represents a collaborative effort between researchers at the Noble Foundation, the Boyce Thompson Institute at Cornell University, the University of Delaware, and the University of North Texas.

“The aim of this large project is to generate resources for the U.S. and international research communities. We will generate resources to help accelerate the transfer of fundamental laboratory research results into useful applications for crop production,” said Sherrier.

In past years, the NSF has supported projects to sequence the complete genomes of organisms, including M. truncatula. The resources generated by this new NSF grant will help researchers define the roles of all of the individual genes within the genome and to elucidate how they are important for legume growth.

“Legumes, such as beans and lentils, provide one third of the protein consumed as part of the human diet globally. Legumes also contribute fiber and micronutrients to the human diet and are utilized widely as forage crops for livestock,” said Sherrier.

M. truncatula has been selected as a research model to study the symbiotic relationships that are characteristic of legumes. Unlike many species of plants, legumes rely on interactions with rhizobia (naturally-occurring beneficial microbes) to supply them with nitrogen. Many crop plants are supplemented with industrially produced nitrogen fertilizer, and the synthesis of the fertilizer is an energy-intensive process.

“As much as four percent of the world’s natural gas is consumed in the production of nitrogen fertilizers, releasing carbon dioxide by-products into the atmosphere,” said Sherrier.

When nitrogen is not present at sufficient levels in the soil to support plant growth, legumes create a home for beneficial bacteria in their roots. The plant develops a novel root organ where bacteria can grow, multiply and enter the plant cell, and within the plant cells the bacteria convert atmospheric nitrogen into a fertilizer for the plant. This greatly reduces the amount of fertilizer and energy necessary to produce a successful crop, lowers production costs for farmers and reduces runoff of fertilizers into the groundwater.

The focus of Sherrier’s research program is on the protein-to-protein interactions that are necessary for such beneficial plant-bacteria relationships to occur.

“If the plant lacks a specific protein, then this can allow bacteria to enter the plant and simply take the sugar without producing anything in return. This would be detrimental for a crop,” she explained.

As part of the NSF-funded project, Sherrier’s team will also be developing and teaching a 4-H summer camp across Delaware to teach children about how different microbes are important for agriculture. Campers will participate in science-based activities, such as using microscopes and making yogurt. The camps will contribute to the development of future growers in all three counties.

Article by Jacob Crum

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Delaware EPSCoR announces 2012 seed grant recipients

March 7, 2012 under CANR News

The Delaware EPSCoR program has awarded seven seed grants to University of Delaware faculty whose projects address current environmental issues within the state.

EPSCoR, the Experimental Program to Stimulate Competitive Research, is a federal grant program of the National Science Foundation (NSF) that helps states develop their research capabilities so that they may compete for further federal funding.

Seed grants are typically in the $50,000 range and help researchers set the stage for applications to larger federal funding programs. Seed grant proposals are solicited annually during the fall semester. The selections were made by a committee of five senior faculty affiliated with the Delaware EPSCoR program and two external reviewers representing the Delaware Department of Natural Resources and Environmental Control (DNREC). This year’s funded projects are as follows:

Microbes that remove arsenic from rice

Rice is a staple in diets across the globe, but it is commonly contaminated by arsenic (As) in many developing nations. To solve this problem, University of Delaware scientists Harsh Bais and Janine Sherrier of the Department of Plant and Soil Sciences have proposed that the inoculation of rice with the bacterium EA106 will reduce arsenic accumulation within the edible portion of the plant, simultaneously improving quality and yield. Arsenic-contaminated rice represents a significant health risk to millions of people worldwide; in their research Bais and Sherrier plan to “systematically dissect the overall mechanism in As absorption and translocation in rice.” Their efforts will further probe the field of plant-microbial processes and how they may be used to agricultural advantage.

Impact of terrestrial phosphorus on eutrophication in the Chesapeake Bay

Principal investigator Deb Jaisi, assistant professor, and Donald Sparks, S. Hallock du Pont Chair of Soil and Environmental Chemistry, both of the Department of Plant and Soil Sciences, will investigate the concentrations of terrestrial and nonterrestrial phosphorus (P) input into the Chesapeake Bay over time. The prevailing notion is that the level of nonterrestrial P has remained constant since early civilization, and thus terrestrial P is the sole culprit in the eutrophication (increased concentrations of nutrients which result in algae blooms and fish kills) of the Chesapeake Bay. However, observed changes in the bottom water environment indicate that this is unlikely. Their study will influence future management strategies to limit nutrient pollution, with regulations possibly addressing both terrestrial and nonterrestrial P input. Sparks is director of the Delaware Environmental Institute.

Article by Jacob Crum

Photos by Ambre Alexander and Kathy F. Atkinson

For the complete article and list of seed grant recipients, view the full story on UDaily

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UD researchers identify novel regulatory network within legumes

January 26, 2012 under CANR News

Three collaborating laboratories in the Department of Plant and Soil Sciences at the University of Delaware — those of professors Blake Meyers, Janine Sherrier and Pamela J. Green — recently identified a novel regulatory network within legumes, including in alfalfa and soybean plants.

The work was performed predominantly by Jixian Zhai, a doctoral student in the department and was published in the December issue of the prestigious journal Genes & Development, one of the top journals in molecular biology and genetics. The genomics project was funded by a grant from the U.S. Department of Agriculture.

Conducting their research at the Delaware Biotechnology Institute (DBI), the investigators set out to get a comprehensive view of how small RNAs function in legumes and how they might be important to these plant species. They focused their work on the chromosomal sequences (genome) of Medicago, a legume genus that includes both the crop plant alfalfa and the species that was recently sequenced, Medicago truncatula.

The researchers sequenced libraries containing millions of small RNAs, important gene regulatory molecules, as well as the genes targeted by these small RNAs. Using advanced computational techniques to categorize the RNA sequences, they identified a novel function for a handful of “microRNAs” — special small RNAs that direct the targeted destruction of specific protein-coding messenger RNAs.

Among these plant microRNAs, the team determined that many target genes encode NBS-LRRs, or “guard proteins” that function in defense against pathogenic microbe infiltration. These NBS-LRRs function as an immune system to battle pathogens but presumably must be suppressed to allow the interactions with beneficial microbes for which legumes are particularly well known. The result of this microRNA targeting is a complex network of co-regulated small RNAs that Zhai characterized using a set of computational and statistical algorithms and analyses.

“The NBS-LRRs keep pathogens out, but these plant cells are still allowing beneficial microbes to enter,” says Sherrier. “The regulation of genes encoding NBS-LRR proteins has been largely unknown until now.”

Over time, these mechanisms have evolved into a more elaborate system in legumes to take advantage of this defense-suppressing system and facilitate the development of nodules, the specialized root structures of legumes in which the beneficial plant-microbe interactions take place.

“We may have found the ‘switch’ that recognizes good versus bad microbes,” adds Meyers, Edward F. and Elizabeth Goodman Rosenberg Professor and chair of the Department of Plant and Soil Sciences. “These guard proteins usually trigger cell death when a pathogen is recognized, but the plant cell is triggering cell death when it encounters a ‘good’ microbe. The circuit we identified may play a role in preventing cell death when the microbe is a friend.”

This discovery could ultimately prove important to the improvement of plant-microbe interactions in other crop plants by allowing plants to become healthier by letting in the good microbes, but keeping the pathogens out.

“We didn’t expect to find something as exciting as this,” says Sherrier. “It’s exciting because no one knows about this kind of gene control and also because it is showing us the diverse interaction between plants and bacterium as well as plants and fungi that could help us develop better mechanisms in other plants, like Arabidopsis.”

“Beyond the applied significance, the finding that NBS-LRR genes are key targets opens up a new frontier for basic research,” says Green, Crawford H. Greenewalt Professor of Plant and Soil Sciences.

If this diverse regulation of beneficial microbes could be added to other crop plants, it could mean scientists could program the plants to grow stronger and taller with less water, and even fertilize themselves.

Article by Blake Meyers and Laura Crozier

Photos by Evan Krape and Kathy F. Atkinson

This article was originally published on UDaily

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