The dandelion uses latex to protect its roots against insect feeding

January 05, 2016

Dandelions are troublesome weeds that are detested by most gardeners. Yet dandelions also have many insect enemies in nature. However, they are able to protect themselves with their latex, a milky, bitter-tasting sap. Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, and the University of Bern, Switzerland, have now demonstrated that a single compound in the latex protects dandelion roots against voracious cockchafer larvae. Thus, latex plays a crucial role in dandelion defense against root feeders. (PLOS Biology, January 2016, Open Access)

Dandelions are survival experts

Dandelions (Taraxacum officinale agg.) are well-known plants of European and Asian origin that have spread around most of the temperate world. Children love their yellow flowers and even more the fluffy seed heads with their parachute-like seeds that can travel long distances by wind. Young plants grow with such force that they can penetrate even asphalt. Therefore dandelions have become a symbol for survival in modern cities.

In fields and meadows, the plant must fend off many herbivores, among them cockchafer larvae. The common cockchafer (Melolontha melolontha) spends the first three years of its life cycle underground as a grub feeding on the roots of different plants. One of its favorite foods is dandelion roots. Like many other plants, dandelions produce secondary metabolites to protect themselves against herbivores. Some of these defenses, such as terpenes and phenols, are of pharmaceutical interest and are considered promising anti-cancer agents. The most important dandelion metabolites are bitter substances which are especially found in a milky sap called latex, a substance found in almost ten percent of all flowering plants.

Why dandelion latex is bitter

Scientists from the Department of Biochemistry and their colleagues from the University of Bern have now taken a closer look at dandelion latex. The scientists found the highest concentrations of the bitter latex in the roots of dandelions. Dandelions need to protect their roots very fiercely because these are the main storage organs for nutrients which fuel growth early in the spring.

One single defensive chemical protects the plant

The scientists tested first whether latex compounds produced by dandelion roots were negatively associated with the development of cockchafer larvae. They also wanted to know whether these compounds had a positive effect on the fitness and reproductive success of dandelions under Melolontha melolontha attack. An analysis of the components of dandelion latex revealed that one single substance negatively influenced the growth of cockchafer larvae. This substance was identified as the sesquiterpene lactone, taraxinic acid β-D-glucopyranosyl ester (TA-G). When the purified substance was added to an artificial larval diet in ecologically relevant amounts, the grubs fed considerably less.

The researchers succeeded in identifying the enzyme and gene responsible for the formation of a precursor of TA-G biosynthesis, and so were able to engineer plants with lower TA-G. Roots of engineered plants with less TA-G were considerably more attacked by cockchafer larvae. The chemical composition of latex varies between different natural dandelion lines. A common garden experiment with different lines revealed that plants which produce higher amounts of TA-G maintained a higher vegetative and reproductive fitness when they were attached by cockchafer larvae. "For me, the biggest surprise was to learn that a single compound is really responsible for a defensive function," says Jonathan Gershenzon, the head of the Department of Biochemistry at the Max Planck Institute in Jena. "The latex of dandelions and other plants consists of such a mixture of substances that it didn't seem necessarily true that one chemical by itself had such a protective role against our study insect."

The combination of approaches as a key to success

"It was clearly the combination of techniques that was crucial for the success of our studies," explains Matthias Erb from the University of Bern who led the study. "Each approach has its weaknesses that were balanced by the strengths of the others. We think that this type of interdisciplinary research can be very powerful to understand biological systems."

The scientists are now planning further experiments study the co-evolution of dandelions and their root herbivores in order of find out whether the presence of root-feeding insects has shaped the plant defensive chemistry in the course of evolution and whether the insects show adaptations to dandelion defenses. [AO]
-end-
Original Publication:

Huber, M., Epping, J., Schulze Gronover, C., Fricke, J., Aziz, Z., Brillatz, T., Swyers, M., Köllner, T. G., Vogel, H., Hammerbacher, A., Triebwasser-Freese, D., Robert, C. A. M., Verhoeven, K., Preite, V. Gershenzon, J., Erb, M. (2016). A latex metabolite benefits plant fitness under root herbivore attack. PLOS Biology, DOI: 10.1371/journal.pbio.1002332. Open Access http://dx.doi.org/10.1371/journal.pbio.1002332

Further Information:

Meret Huber, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, Germany, +49 3641 57-1329, mhuber@ice.mpg.de

Matthias Erb, University of Bern, Institute of Plant Sciences, Altenbergrain 21, 3013 Bern, Switzerland, +41 31 631 8668, matthias.erb@ips.unibe.ch

Jonathan Gershenzon, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, Germany, +49 3641 57-1301, gershenzon@ice.mpg.de

Contact and Media Requests:

Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail overmeyer@ice.mpg.de

Download high-resolution images via http://www.ice.mpg.de/ext/downloads2016.html

Max Planck Institute for Chemical Ecology

Related Plants Articles from Brightsurf:

When plants attack: parasitic plants use ethylene as a host invasion signal
Researchers from Nara Institute of Science and Technology have found that parasitic plants use the plant hormone ethylene as a signal to invade host plants.

210 scientists highlight state of plants and fungi in Plants, People, Planet special issue
The Special Issue, 'Protecting and sustainably using the world's plants and fungi', brings together the research - from 210 scientists across 42 countries - behind the 2020 State of the World's Plants and Fungi report, also released today by the Royal Botanic Gardens, Kew.

New light for plants
Scientists from ITMO in collaboration with their colleagues from Tomsk Polytechnic University came up with an idea to create light sources from ceramics with the addition of chrome: the light from such lamps offers not just red but also infrared (IR) light, which is expected to have a positive effect on plants' growth.

How do plants forget?
The study now published in Nature Cell Biology reveals more information on the capacity of plants, identified as 'epigenetic memory,' which allows recording important information to, for example, remember prolonged cold in the winter to ensure they flower at the right time during the spring.

The revolt of the plants: The arctic melts when plants stop breathing
A joint research team from POSTECH and the University of Zurich identifies a physiologic mechanism in vegetation as cause for Artic warming.

How plants forget
New work published in Nature Cell Biology from an international team led by Dr.

Ordering in? Plants are way ahead of you
Dissolved carbon in soil can quench plants' ability to communicate with soil microbes, allowing plants to fine-tune their relationships with symbionts.

When good plants go bad
Conventional wisdom suggests that only introduced species can be considered invasive and that indigenous plant life cannot be classified as such because they belong within their native range.

How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.

Can plants tell us something about longevity?
The oldest living organism on Earth is a plant, Methuselah a bristlecone pine (Pinus longaeva) (pictured below) that is over 5,000 years old.

Read More: Plants News and Plants Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.