London, United Kingdom
April 20, 2007
A protein acting as a
long-distance signal from leaf to shoot-tip tells plants when to
flower, says new research published in Science Express on
Thursday 19 April 2007.
The study reveals the likely mechanism by which the Arabidopsis
plant flowers in response to changes in day length. Earlier
research had shown that plants' leaves perceived seasonal
changes in day length, which triggers a long-distance signal to
travel through the plant's vascular system from the leaf to the
shoot apex, where flowering is induced. However, the identity of
the long-distance signal remained unclear.
This new research, carried out by scientists at Imperial College
London and the Max Planck Institute for Plant Breeding Research
in Cologne, has led to the proposal that this signal is a
protein known as Flowering Locus T Protein (FT protein), which
is produced in leaves by the Flowering Locus T gene (FT gene).
It travels through the plant's vascular system to the shoot
apex, where it activates other genes, causing the plant to
flower. The research team were able to track the progress of the
protein through the plant by tagging it with a green fluorescent
protein originally isolated from jellyfish, allowing it to be
detected in living tissues using highly sensitive microscope
systems.
The team then grafted two plants together, only one of which
contained the gene for the fluorescent version of FT. This
allowed them to show conclusively that FT protein moved from
where it was produced in the leaves of one plant, across into
the other plant.
The FT protein is produced when the FT gene is switched on by
another gene known as CONSTANS. This is a key gene expressed in
leaves which reacts to changes in day length.
Dr Colin
Turnbull from Imperial
College London's Division of Biology, who carried out the
research, said: "This could be a really important breakthrough
in plant science. Since the 1930s when it first became clear
that something was communicating the perception of changes in
day length in leaves to the shoot apex, and causing flowering,
scientists have been trying to work out exactly how this
mechanism works.
"Over the past couple of years several labs made exciting
discoveries all pointing to the FT gene being central to
controlling flowering time. Now that we have been able to track
FT protein moving from its source in leaves to its destination
in the shoot tip, we have a plausible explanation for how plants
respond to day length. Parallel work in Japan shows very similar
mechanisms operating in rice, so there is immediate potential to
translate research into practical benefits for food crops. The
ability to control flowering is of enormous commercial
significance across food and non-food species, for example
extending production seasons or designing plants better adapted
to changing climate." |
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