Lincoln, Neb. —Each year, phytophagous pests are responsible for about 20% of crop losses worldwide.
Growers have relied on what were once considered silver bullets to manage the problem: insecticides and genetically modified plants. But while the two were successful to some extent, they failed to fully master the problem. In addition, these methods have raised various concerns: growing concern about the impact of pesticides on the environment and human health; consumer fatigue with eating chemically processed or genetically modified foods; and increasing insect resistance to many of the most commonly used pesticides.
That’s why a research team from the University of Nebraska-Lincoln is taking a closer look at an alternative method of pest control that could overcome or alleviate the problems associated with standard approaches. Entomologist Joe Louis and his collaborators recently received a grant of nearly $1.2 million from the WE Department of Agriculture to explore methods of enhancing the natural defense mechanisms of sorghum – a promising crop for food, feed and fuel – which would fortify it against sugarcane aphids, a pest that plagues the plant since 2013.
“Because pesticides stay in the environment and can affect food quality, we are thinking about how other approaches can be used,” said Louis, Eberhard Professor of Agricultural Entomology. “That’s why we started to develop the innate immunity of the plant. If we can strengthen many of these innate defenses, we can protect plants from the majority of these insect attacks in a way that may be more durable and long-lasting than current approaches.
The team also includes Tomas Helikar, Susan J. Rosowski Associate Professor of Biochemistry; Scott Sattler, assistant associate professor of agronomy and horticulture and molecular research biologist at the USDA‘s Agricultural Research Service; and Rupesh Kariyat of the University of Texas Rio Grande Valley.
The team is focusing on one of the most abundant components of plants: lignin. It plays a central role in the formation of rigid and stable cell walls and in facilitating water transport. Because the polymer is found throughout sorghum – including its outer surfaces – it is one of the first components that sugarcane aphids encounter when they insert their needle-like mouthpart into the plant.
But little is known about exactly how lignin can help sorghum repel sugarcane aphids. Louis and Sattler were intrigued by the potential defensive role of lignin when they noticed that in some sorghum plants, altered lignin levels impacted aphid behavior and the plant either became more resistant or more susceptible to the pest.
Preliminary data from these plants indicated that the monolignol pathway, which plays a key role in lignin synthesis, and a gene known as Brown midrib12, or Bmr12, located in the lignin biosynthetic pathway, could be particularly important in driving these changes.
To identify exactly how Bmr12 influences a plant’s natural immunity, Louis’ team will weave together a variety of approaches – transcriptomic, biochemical, electrophysiological, histological and computational biology. This broad and transdisciplinary approach is a major strength of the research.
“This is a holistic approach to understanding plant-aphid interactions, using multiple approaches to answer the question of how Bmr12 is involved in modulating sorghum defenses against aphids,” Louis said. “That’s how it stands out as a unique project.”
The IT component is particularly innovative. Helikar, an expert in computational systems biology, will develop a network analysis model showing how the behavior of Bmr12 has ripple effects throughout the plant. The system will allow the team to easily test hypotheses about how a change in Bmr12-associated pathways may impact a plant’s properties and defense mechanisms.
Louis and Helikar will introduce Husker students, undergraduate and graduate, to these computational approaches through new lab modules they are developing as part of the project. The new elements of the program aim to open students’ eyes to the power of interdisciplinary methods and computer modeling to solve problems in biology, entomology and ecology.
Kariyat, the University of Texas Rio Grande Valley collaborator, is leading an additional student outreach effort at a college in the Rio Grande Valley, where more than 90% of students are Hispanic. It will engage these students in inquiry-based experiments focused on plant-insect interactions.
Beyond its role in lignin production, Bmr12 can also influence a plant’s indirect defenses by producing volatile organic compounds that boost plant immunity. When certain pests attack, crops respond by producing these compounds. They strengthen plant tissues against pest damage and send airborne signals to neighboring plants, triggering their defense systems. Louis’ team will investigate how disruptive pathways associated with Bmr12 might enhance this protective mechanism.
In the long term, Louis sees work on Bmr12 as one piece of the larger puzzle of boosting natural plant immunity – there are many other genes and pathways that researchers can exploit to boost pest resistance. He does not expect natural immunity methods to completely supplant pesticides, but believes their use can be reduced to much lower levels.
“Ultimately, we hope to bring another tool to farmers that will help them reduce the use of toxic insecticides,” he said.
The research is funded by the Plant Biotic Interactions Programa joint initiative of the USDAfrom the National Institute of Food and Agriculture and the National Science Foundation.