Featured Research

from universities, journals, and other organizations

'Yellow biotechnology': Using plants to silence insect genes in a high-throughput manner

Date:
February 2, 2012
Source:
Max Planck Institute for Chemical Ecology
Summary:
'Yellow biotechnology' refers to biotechnology with insects -- analogous to the green (plants) and red (animals) biotechnology. Active ingredients or genes in insects are characterized and used for research or application in agriculture and medicine. Scientists in Germany are now using a procedure which brings forward ecological research on insects: They study gene functions in moth larvae by manipulating genes using the RNA interference technology (RNAi). RNAi is induced by feeding larvae with plants that have been treated with viral vectors. This method -- called "plant virus based dsRNA producing system" (VDPS) -- increases sample throughput compared to the use of genetically transformed plants.

Nicotine-resistant larvae of the Tobacco hornworm Manduca sexta have become a new tool for investigating unknown gene functions in Lepidoptera – thanks to a novel RNAi-based procedure.
Credit: Copyright: Courtesy of Jan-Peter Kasper

'Yellow biotechnology' refers to biotechnology with insects -- analogous to the green (plants) and red (animals) biotechnology. Active ingredients or genes in insects are characterized and used for research or application in agriculture and medicine. Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, are now using a procedure which brings forward ecological research on insects: They study gene functions in moth larvae by manipulating genes using the RNA interference technology (RNAi). RNAi is induced by feeding larvae with plants that have been treated with viral vectors. This method -- called "plant virus based dsRNA producing system" (VDPS) -- increases sample throughput compared to the use of genetically transformed plants.

Natural toxins against herbivores

More than 200,000 insects species are herbivores. They depend on plants for food and have adapted their metabolism accordingly in the course of evolution to render plant defenses, such as the toxins plants produce to fend off herbivores, ineffective. The operating instructions of these detoxification processes are coded in different genes. Insects have evolved an enormous diversity of adaptation mechanisms; they colonize most habitats on this planet -- which makes them interesting research objects in ecological studies. Which insect species attack which plants species? Which toxins or signaling substances are involved? Has the insect species adapted to one specific plant species or is it a food generalist? Interesting for agriculture: Which genes allow particular pest insects, such as the pollen beetle Meligethes aeneus or the Western corn rootworm Diabrotica virgifera virgifera, to be so destructive to crop plants? Knowing these detoxification genes and switching them off with the consequence that plant toxins are no longer effective, is currently a research subject in plant breeding. First success stories have already been reported -- thanks to the use of RNAi technology.

Scientists at the Max Planck Institute for Chemical Ecology examined a well-known plant toxin: nicotine. Plants of the species Nicotiana attenuata (coyote tobacco) produce nicotine as a defensive substance against herbivores. However, it does not have any toxic effects on their worst enemy: larvae of the tobacco hornworm Manduca sexta. The insect is resistant against this alkaloid; genes that encode nicotine-catabolizing enzymes may be responsible for its resistance. These so called CYP genes are involved in the formation of cytochrome P450 enzymes; the expression of some of these genes is increased as soon as the insect larvae are exposed to nicotine in their food. Ian Baldwin and his team identified the DNA sequences of CYP genes in Manduca sexta and were able to switch off these genes using RNAi technology, but expressed in the plant.

Using plants to silence insect genes

RNA interference (RNAi) is triggered by the production of double-stranded RNA (dsRNA) comprising about 300 base pairs in the cells of tobacco plants. If larvae feed on these plant, the RNA is released in the insect gut. In the experiments, the dsRNA harbored the sequence of the insect gene,CYP6B46, a special cytochrome P450 oxidoreductase specific for Manduca sexta larvae. In a next step, the dsRNA was enzymatically broken down into smaller RNA segments; a special enzyme complex called RISC (RNA-induced silencing complex), which carries several of these RNA segments, specifically binds to the messenger RNA (mRNA) of the CYP6B46 gene and disassembles the mRNA in such a way that the cytochrome P450 enzyme cannot be produced anymore. "We were impressed by the high specificity of these RNAi experiments. The analysis of mRNA transcripts of closely related CYP6 genes revealed that only the CYP6B46 gene was silenced. This means that there was no collateral damage from the procedure: the gene silencing worked on only one targeted gene," says Ian Baldwin.

The use of additional CYP RNAi probes revealed further interesting results: Young caterpillars which had ingested dsRNA of the CYP4M3 gene gained significantly less weight within 14 days in comparison to larvae reared on control plants -- very likely a consequence of the nicotine and its toxic effect which had been restored by switching off the CYP gene. The RNAi experiments had been conducted using plant viral vectors. Unlike genetically transformed tobacco plants in which CYP dsRNA is produced constitutively, the virus vector-based technique provides dsRNA transiently produced in wildtype tobacco plants. Both methods worked well but the "plant virus-based dsRNA producing system" (VDPS) allows for a throughput of RNAi samples that is four times faster. Many unknown functions of different insect genes involved in the adaptation of insects to their environment can now be analyzed using the VDPS technique.

However, it is still unclear how the individual steps in the RNAi mechanism -- from producing dsRNA in the plant cell via their uptake in the insect gut to the silencing of the detoxification genes -- are accomplished to induce a maximum effect. One experiment provided some interesting information: If the enzymatic step which dices dsRNA into small fragments is inhibited in the experimental plants, the amount of transcripts of the detoxification gene was reduced even further. Therefore the plant mediated RNAi procedure may be more effective, if the caterpillars ingest complete dsRNA instead of smaller diced RNA segments.


Story Source:

The above story is based on materials provided by Max Planck Institute for Chemical Ecology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Pavan Kumar, Sagar Subhash Pandit, Ian T. Baldwin. Tobacco Rattle Virus Vector: A Rapid and Transient Means of Silencing Manduca sexta Genes by Plant Mediated RNA Interference. PLoS ONE, 2012; 7 (2): e31347 DOI: 10.1371/journal.pone.0031347

Cite This Page:

Max Planck Institute for Chemical Ecology. "'Yellow biotechnology': Using plants to silence insect genes in a high-throughput manner." ScienceDaily. ScienceDaily, 2 February 2012. <www.sciencedaily.com/releases/2012/02/120202151248.htm>.
Max Planck Institute for Chemical Ecology. (2012, February 2). 'Yellow biotechnology': Using plants to silence insect genes in a high-throughput manner. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2012/02/120202151248.htm
Max Planck Institute for Chemical Ecology. "'Yellow biotechnology': Using plants to silence insect genes in a high-throughput manner." ScienceDaily. www.sciencedaily.com/releases/2012/02/120202151248.htm (accessed April 23, 2014).

Share This



More Plants & Animals News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Leopard Bites Man in India

Raw: Leopard Bites Man in India

AP (Apr. 22, 2014) A leopard caused panic in the city of Chandrapur on Monday when it sprung from the roof of a house and charged at rescue workers. (April 22) Video provided by AP
Powered by NewsLook.com
Iowa College Finds Beauty in Bulldogs

Iowa College Finds Beauty in Bulldogs

AP (Apr. 22, 2014) Drake University hosts 35th annual Beautiful Bulldog Contest. (April 21) Video provided by AP
Powered by NewsLook.com
805-Pound Shark Caught Off The Coast Of Florida

805-Pound Shark Caught Off The Coast Of Florida

Newsy (Apr. 22, 2014) One Florida fisherman caught a 805-pound shark off the coast of Florida earlier this month. Video provided by Newsy
Powered by NewsLook.com
Breakfast Foods Are Getting Pricier

Breakfast Foods Are Getting Pricier

AP (Apr. 21, 2014) Breakfast is now being served with a side of sticker shock. The cost of morning staples like bacon, coffee and orange juice is on the rise because of global supply problems. (April 21) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins