www.checkbiotech.org ; www.raupp.info ; www.czu.cz

Using genetic engineering, researchers at the Max Planck Institute have
started to decipher the chemical vocabulary of inter-plant communication,
February 2006 translated by Mark Hucko, Checkbiotech.

As an answer to an insect attack, plants release volatile scents.
Scientists at the Max-Planck Institute for Chemical Ecology in Jena, Germany
have been investigating chemical-scent exchange between neighboring plants.

Preliminary laboratory research hinted at the first evidence, however these
lab results did not necessarily reflect field conditions. Thus, the
Max-Planck researchers have investigated (with field trials as well) the
defense reaction of the wild tobacco plant (Nicotiana attenuate) to an
insect pest attack, after it had received scent-signals from a neighboring
and wounded plant - the Great Basin Sage Brush (Artemisia tridentata).

They found that the tobacco plants that had the opportunity to eavesdrop on
the Great Basin Sage Brush, could quickly and efficiently fight off the
insects, when compared to other tobacco plants which did not have this
opportunity (Oecologia, February 2006). This phenomena is called ?priming.?

With the help of genetically modified plants, the Jena scientists have
started to identify the scents that allow neighboring plants fight off an
insect attack. With their studies, the researchers were able to show that
tobacco plants were able to increase their defenses only after they had been
actually attacked, and not right after they had received the signals from
wounded, neighboring plants.

This behavior makes sense for the plant. If it had reacted to the
scent-signal to convert its valuable resources into defense-molecules, this
would put the plant at a disadvantage, because it would have invested energy
into defense mechanisms that might not be needed since it had not actually
been attacked.

One of the defense-substances are the so-called proteinase-inhibitors
(TPIs), which hamper the digestion of caterpillars. One question that
remains to be answered is to which extent does this communication between
tobacco and sage brush play a role in the ecology of both species.

Scientists at the Max-Planck Institute in Jena now want to explain the
details of inter-plant communication within one single species. A first
interesting result materialized, when the researchers were able to
demonstrate that wild tobacco plants (Nicotiana attenuate) could ?smell? and
recognize the entire scent-bouquet of other tobacco plants of the same
species. These scents are made up of various volatile chemicals.

With the help of genetically altered plants (or a so-called ?silent? plant),
which could no longer produce selected scents, the researchers showed that
the scent composition is very important. With the absence of certain
substances in the scent of the silent, ?broadcasting? plants, the
neighboring receiver-plants reacted differently than if the scent-bouquet
were complete.

During their investigation the biologists made an effort to combine
laboratory and field experiments in order to make all laboratory experiments
as realistic as possible. Traditionally, the plants were enclosed in
relatively confined glass containers during the scent-analysis in the
laboratory. This artificially increased the concentration of gas-forming
molecules from the plants. In addition, after the plants had been enclosed
in these glass containers, they suffered from CO2 deficiency.

?To compensate for this deficiency, the plant opens up its stomata, through
which CO2 and more scent-molecules can pass into the interior of the plant.
Due to this, the receiver-plant?s reaction can be artificially amplified or
distorted,? explains Dr. Anja Paschold.

In her work, Dr. Paschold had researched the scent-communication between
tobacco plants under ?realistic? conditions on the one hand, and then she
also used the help of ?silent? transgenic plants as a contrast. She found
that neither the complete scent-profile of wild-type plants, nor the
partially reduced profile of genetically engineered plants influenced the
defense mechanisms of the receiver-plants. She also noticed that nicotine,
jasmonic-acid, and proteinase inhibitors were practically unchanged and that
the priming effect could not be determined.

However an analysis of the gene expression showed that clearly more genes in
the receiver-plants were turned on when the scent-bouquet lacked
leaf-alcohols and aldehydes, which for example produce the well known scent
of freshly mowed grass. When the partial scent-bouquet again was
complemented with synthetic leaf-alcohols and leaf-aldehydes, then the genes
were turned off.

Apparently, at least in one species, various groups of genes could be turned
on and off as a result of inter-plant scent signals. The function of the
majority of these genes is not yet clear, and is now being further
investigated.

With the example of wild tobacco, the scientists under Dr. Ian Baldwin?s
direction want to eventually systematically research the ?chemical language?
that plants use for communication. Beside using ?silent?
broadcasting-plants, further tests will look at ?deaf? receiver-plants,
which cannot recognize certain scent molecules, because they lack the
corresponding receptor. The researchers note that this ground-breaking
research would not be possible without biotechnology.

[www.max-planck.de]

------------------------------------------
Posted to Phorum via PhorumMail