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Researchers at the Umea Plant Science Centre at the Swedish University of
Agricultural Sciences (SLU), Sweden, report about a breakthrough in our
understanding of how plants control their flowering. In an article published
in the international journal Science, Thursday 11th, they show how a small
molecule that is formed in the plant leaves is transported to the shoot tips
where it induces the formation of flowers. This knowledge can lead to the
development of new tools that can be used to control the timing of plant
flowering, something that is of central importance in both agriculture and
forestry, August 2005.

We are all familiar with the fact that different plants flower at
different times of the year. Daffodils in spring, roses in summer and other
plants in fall. It is absolutely vital for the plant survival to flower at
exactly the right time to secure that it can pollinate, or be pollinated, by
other plants of the same species. How then does the plant know when to
flower?

Intense Florigen hunt

Already in the 30-ies scientists found out that plants can tell whether they
are growing in spring, summer or fall by measuring the length of the day.
One could also show that plants use their leaves to sense the length of the
day. By grafting leaves from plants that had been induced to flower on
non-induced plants one could show that the induced leaves produce a
substance that is transported to the shoot tips where it induces the
formation of flowers. In the 30-ies a Russian scientist called this
mysterious substance "Florigen". During the following 70 years scientists
have been involved in an intense hunt trying to find out the true nature of
"Florigen" which has been described as something of a "Holy Grail" for plant
physiology. The reason is that the nature of "Florigen" is central for our
understanding of how plant flowering is controlled. All attempts to identify
a single substance carrying the properties of "Florigen" have failed, until
now.

Messenger molecule

A research group led by Professor Ove Nilsson at the Ume? Plant Science
Centre at the Swedish University of Agricultural Sciences has now identified
a "messenger molecule" that fulfills all the classical properties of
Florigen. A gene called "FT" produces the "messenger molecule". This gene is
active in leaves and its activity is controlled by the length of the day.
When the gene is activated, a messenger molecule is produced that is
transported to the shoot tips where it very efficiently induces the "gene
programs" that control the formation of flowers. These groundbreaking
results are published "online" on Aug 11 in the international journal
Science. Together with other data published at the same time, it shows
convincingly that the "messenger molecule" produced by FT either is
florigen, or an important component of florigen.

The researchers have used the small plant model species Arabidopsis in their
research. But the group of Ove Nilsson has also other data showing that
these results can be directly applied to other species, such as poplar
trees. Ove Nilsson says: "With the help of this knowledge plant breeders
will get a new tool to control and adopt the flowering of plants, something
that has been of great importance for agriculture but that can also lead to
the development of efficient tree breeding for forestry".

[www.eurekalert.org]

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