"The enzyme is found in insect-resistant strains of corn, and it breaks down proteins and peptides in the insects’ gut. It is a unique active defense against herbivory," says Dawn Luthe, professor of plant stress biology at Penn State.
Luthe and researchers at Mississippi State University have since developed several lines of corn resistant to multiple pests, using conventional plant breeding and insect-resistant strains of corn from Antigua.
Researchers have found that when caterpillars fed on the insect-resistant plants, one enzyme -- Mir1-CP or maize insect resistance cysteine protease, in particular --accumulated at the feeding site within an hour of the caterpillar’s feeding and continued to accumulate at the site for several days.
"Upon isolation and purification of the enzyme, we found that Mir1-CP binds to chitin, a major component of insects and fungi," says Luthe. "Physiological tests show that caterpillars have impaired nutrient utilization when they eat the enzyme. They just can’t convert what they eat into body mass."
Luthe presented the findings at the annual meeting of the American Chemical Society today (March 30) in Atlanta.
With the help of antibodies specific to the enzyme, the researchers were able to determine that Mir1-CP is made in the vascular bundles, or strands of conducting vessels in the stem and leaves of a plant. Luthe thinks that when an insect starts feeding, the enzyme is probably transported to vascular tissue that conducts sugars and other metabolic products upward from the leaves, as well as to the soft tissue found in leaves and stem.
Though it is still unclear whether the transport of Mir1-CP is a specific response to the insect feeding, studies show that maize tissue that naturally expresses Mir1-CP causes a 50 percent inhibition in caterpillar growth. Transgenic black Mexican sweet corn cells that express Mir1-CP inhibit caterpillar growth by 70 percent, Luthe says.
Mir1-CP is harmful to caterpillars mainly because of its damaging effect on their peritrophic matrix. This is a membrane that lines the gut of most insects and aids digestion. It also protects the insects from being invaded by microorganisms and parasites through the food they eat.
At the heart of the matrix is a protein called the insect intestinal mucin, or IIM. It is very similar to the mucus layer in animals and is vital for nutrient utilization because it helps the flow of nutrients into the food gut.
The researchers tested the permeability of the matrix using blue dextran, a fermented sugar solution commonly used as a molecular size marker. Results showed that Mir1-CP created holes in the matrix.
To replicate the test in vivo, the researchers fed caterpillars with plants susceptible to the insects and those resistant to them. Results indicate that after seven days, the level of both IIM and IIM messenger RNA in insects that were feeding on the resistant plants had fallen significantly.
"If the IIM is being degraded by the enzyme, pieces of it should not appear in the fecal pellets of the insect," notes the Penn State researcher.
When used in conjunction with the Bt-toxin, a low dose of Mir1-CP was able to achieve a very high mortality rate in the insects, as well as an extremely low growth rate.
"In the long run, the enzyme degrades the insect’s peritrophic matrix and retards the caterpillar’s ability to generate a new one," says Luthe.
The research has potential global implications in generating a cheap and highly effective way of controlling crop pests.
Other authors of the paper include Tibor Pechan, Srinidi Mohan, Renuka Shivaji, Lorena Lopez, Alberto Camas, Erin Bassford, Seval Ozkan, Peter Ma, all at Mississippi State University; and W. Paul Williams, U.S.D.A.
Amitabh Avasthi | EurekAlert!
Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society
127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences