Wageningen, The Netherlands
August 12, 2008
Strigolactones also play a major
role outside the plant
Scientists from the Wageningen
University Laboratory of Plant Physiology and an
international team of scientists have discovered a new group of
plant hormones, the so-called strigolactones. This group of
chemicals is known to be involved in the interaction between
plants and their environment. The scientists have now proven
that strigolactones, as hormones, are also crucial for the
branching of plants. The discovery will soon be published in
Nature and is of great importance for innovations in
agriculture. Examples include the development of cut flowers or
tomato plants with more or fewer branches. These crops are of
major economic and social importance worldwide.
The growth and development of plants is largely controlled by
plant hormones. Plants produce these chemicals themselves, thus
controlling the growth and development of roots and stems, for
example. A number of plant hormones, such as auxins, giberellins
and cytokinins, were discovered by scientists decades ago. Now a
new group of hormones has been found: The so-called
strigolactones.
Previous research by institutes including Wageningen UR has
shown that strigolactones plays a major part in the interaction
between plants and their environment. As plants cannot move,
they commonly use their own chemicals to control the environment
as best as they can.
Strigolactones are of major importance to the interaction
between plants and symbiotic fungi, for example. These fungi
live in a symbiotic relationship with plants, lthat is mutually
beneficial. They transport minerals from the soil to the plant,
while the plant gives the fungi sugars ‘in return’.
Unfortunately, the strigolactones have also been “hijacked” by
harmful organisms: They help seeds of parasitic plants to
germinate when plant roots are in the vicinity. The seedlings of
the parasite attach to the root of the plant and use the plant’s
nutrients for their own growth and reproduction. Unlike the
symbiotic fungi, however, they do not give anything in return.
On the contrary, the parasitism often causes the host plant to
die, eventually.
The international research team consisting of French, Australian
and Dutch scientists, coordinated in France, found mutants of
pea that were branching without restraint. It turned out that
these pea plants were not capable of producing strigolactones.
When the plants were administered strigolactones, the
unrestrained branching stopped. The same effect occurred in an
entirely different plant, thale cress. The mutant plants also
caused a significant lower germination of the parasitic plant
seeds and induced less interaction with symbiotic fungi.
The scientists also showed that a specific ‘receptor reaction’
for the strigolactones occurs in plants, a phenomenon that is
characteristic for plant hormones. Although some previously
discovered plants with unrestrained branching turned out to be
producing strigolactones themselves, their receptor connection
was disturbed: Strigolactones administered from the outside
could not stop the uncontrolled branching.
It has also been shown that the plants are capable of
transporting strigolactones internally and that the chemicals
work at very low concentrations, two other typical
characteristics of plant hormones.
The importance of this discovery of a new group of plant
hormones is emphasised by the fact that Nature is publishing an
article by a Japanese team in the same issue in which similar
results are presented. It is expected that this new knowledge
will be applied in agriculture and horticulture, for example in
breeding and the development of branching regulators.
Cut flower varieties and potted plants with either more or less
branching may have special ornamental value, while crops with
more or less branching may be beneficial in cultivation. Tomato
plants in which less branching occurs can benefit the greenhouse
horticulture, for instance.
Plant breeding and greenhouse horticulture are key agricultural
industries in the Netherlands and strongly focussed on
innovation. |
|
