CULT: in the news: freeze/thaw

Thought I would share this article while things are slow on iris-talk:

Plants have genetic alarm clock

Thu Jan 8, 5:27 AM ET

By Patricia Reaney

                    LONDON (Reuters) - Many plants have a genetic alarm
clock that
                    tells them when to wake from their winter slumber
and bloom in spring,
                    scientists say.

                                     Exactly how plants know when it is
time to
                                     flower is a subject that has
perplexed
                                     botanists for thousands of years.

                                     But two teams of scientists have
uncovered
                                     clues that may help explain why
certain
                                     plants need a cold spell to
stimulate
                                     flowering. The research could lead
to new
                    ways of increasing the productivity of crop plants.

                    Although several genes linked to flowering have
already been identified,
                    researchers at the University of Wisconsin-Madison
have found another,
                    called VIN3, that blocks the expression of a gene
known as FLC.

                    FLC encodes a protein that prevents flowering.

                    "It is part of the system that measures the duration
of cold," Professor
                    Richard Amasino, a biochemist at the university,
said in an interview on
                    Thursday.

                    The cold spell needed by many plants to stimulate
flowering is called
                    vernalisation. Certain plants grow in the autumn but
shut down in the
                    winter and need to make sure they are not tricked
into flowering too soon
                    during an early warm spell.

                    "VIN3 is a piece of the system designed to recognise
that it has been a
                    complete winter," Amasino said.

                    Amasino and Sibum Sung, who pinpointed VIN3, said it
goes into action
                    only after the plant has been exposed to the winter
cold. They found it by
                    studying a variety of Arabidopsis thaliana, a common
weed that takes
                    two seasons to bloom.

                    Mutant plants without VIN3 did not bloom at all. In
research reported in
                    the science journal Nature, Amasino and his team
explained that the
                    VIN3 protein is needed to alter proteins called
histones bound to the FLC
                    gene.

                    In the autumn, histones are modified so FLC is
highly expressed. But in
                    the spring, after vernalisation, they silence the
FLC gene and switch the
                    plant into a flowering state.

                    In a second study in the journal, scientists at the
John Innes Centre in
                    Norwich, England also studied Arabidopsis to
identify chemical changes
                    in plants that help them "remember" that they have
gone through a cold
                    period.

                    In previous research they showed that two genes,
VRN1 and VRN2,
                    were involved in flowering. In the latest study,
they discovered that the
                    genes caused chemical changes in a histone called H3
that makes the
                    plants remember they have had a long period of cold
to stimulate them
                    to flower in spring.

                    "In the depths of a British winter we are all
looking forward to the coming
                    of spring when we can forget the cold. But many
plants will be
                    remembering the winter cold to ensure that, come
spring, they flower at
                    the right time," said Professor Caroline Dean, the
leader of the research
                    team.

                    "Understanding this process is of tremendous
scientific importance but it
                    is also of practical interest as flowering time can
have a big effect on
                    crop yields," she added.
============
Not to mention a big effect on damage to iris blooms....

--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
talk archives: <http://www.hort.net/lists/iris-talk/>
photos archives: <http://www.hort.net/lists/iris-photos/>
online R&I <http://www.irisregister.com>

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