Re: Gene That Gives Power to Flower Is Found

Stephen E. Jones (
Fri, 13 Aug 1999 06:17:44 +0800


Here is a New York Times article at:

reporting on yet another master gene that codes for all flowers! Note the
unconscious design language in the opening sentence:

"Whether an elaborate orchid, a simple daisy or a many-petaled
garden rose, the world's flowers are all variations on one simple

As David Berlinski said regarding the astonishing discovery that all
eyes are produced by the one master gene, "No one in possession of
these facts can imagine that they support the Darwinian theory":

"I am in agreement with Mr. Gross when he refers to "new and
astonishing evidence" about the origin of the eye. Herewith the facts.
Halder, Callaerts, and Gehring's research group in Switzerland
discovered that the ey gene in Drosophila is virtually identical to the
genes controlling the development of the eye in mice and men. The
doctrine of convergent evolution, long a Darwinian staple, may now
be observed receding into the darkness. The same group's more
recent paper, "Induction of Ectopic Eyes by Targeted Expression of
the Eyeless Gene in Drosophila" (Science 267, 1988) is among the
most remarkable in the history of biology, demonstrating as it does
that the ey gene is related closely to the equivalent eye gene in Sea
squirts (Ascidians), Cephalopods, and Nemerteans. This strongly
suggests (the inference is almost irresistible) that ey function is
universal (universal!) among multicellular organisms, the basic design
of the eye having been their common property for over a half-billion
years. The ey gene clearly is a master control mechanism, one
capable of giving general instructions to very different organisms.
No one in possession of these facts can imagine that they support the
Darwinian theory. How could the mechanism of random variation and
natural selection have produced an instrument capable of
anticipating the course of morphological development and controlling
its expression in widely different organisms?"
(Berlinski D., "Denying Darwin: David Berlinski and Critics",
Commentary, September 1996, pp28,30.
." )


August 3, 1999

Gene That Gives Power to Flower Is Found



Whether an elaborate orchid, a simple daisy or a many-petaled
garden rose, the world's flowers are all variations on one simple

According to this standard floral scheme, at the very center of a
flower lies the reason for its existence, the plant's reproductive
organs, surrounding which are whorls of petals, which are
themselves encircled by the leaf-like sepals that originally enclosed
the bud.

A normal Arabidopsis.

When the agamous gene is active everywhere, as in above, the
flower makes only reproductive organs: stamens and carpels.

Courtesy of Detlef Weigel

When the gene is inactivated, the flower makes no reproductive
organs, and produces only sepals and petals.

But despite an intense scientific interest in recent years in how this
blueprint gets realized in flowers, researchers had been unable to
find the gene that switched on the making of the different parts of a
blossom. Now, according to two new studies in a recent issue of
Science, researchers have identified the master gene that lays
down the architectural plan for the construction of a proper flower.

Known as leafy, this control gene turns on the sepal and petal-
forming genes at a flower's perimeter and the genes for the building
of reproductive organs that produce pollen, seeds and fruit, right
where they belong in the center.

The researchers say that by identifying a master switch gene for
the formation of a flower's reproductive organs -- the plant parts
that provide most of the world's food -- the new results will be of
particular interest to agricultural scientists.

In addition, they say the potential to control petal-formation will be
of interest to horticultural researchers, in an industry always looking
for more petals. The studies could even be a step toward such
things as trees that don't shed pollen.

"This is a real breakthrough," said Dr. Vivian Irish, a plant
developmental biologist at Yale University. Flower development, Dr.
Irish said, is one of the few systems in which both the master gene
and those genes that it controls have been identified. "It's going to
be a good paradigm for how these things work," she added.

The studies were carried out by two groups of plant developmental
biologists, both working with Arabidopsis, a plant whose genetics
are so well known that it is the botanical equivalent of the fruit fly.

One group was led by Dr. Elliot Meyerowitz at the California
Institute of Technology and the other by Dr. Detlef Weigel at the
Salk Institute for Biological Studies.

Based on previous research, biologists already knew that leafy was
a master control gene at a much higher level that could trigger the
growth of an entire flower, initiating the growth of blossoms where
there would only have been stem and leaves.

Researchers also knew that each of three genes in a group known
as the ABC genes could turn on the making of particular flower
parts. Working from the outside in, the A genes switch on sepals at
the outer edge and the petals that come next. B genes, whose work
overlaps with A and C, turn on petals and the pollen-producing
stamens that form the next circle. Finally, C genes control the
stamens and lastly, in the flower's absolute center, the fruit and
seed-producing carpels.

But what levels of genetic control lay between leafy's authority to
initiate a flower and the detail work done within each flower by the
ABC genes remained unknown.

The situation is comparable to a corporate C.E.O., in charge of the
operation but probably not making detailed decisions in every
department. Dr. Weigel said researchers had figured that it was
impossible for a master control gene like leafy to be working on
defining individual flower parts.

As a result, he said he and his team spent years looking for the
genes that the high-ranking leafy switched on that ultimately
switched on the lower-level ABC genes.

"We were trying to find what was in between," said Dr. Weigel,
"until we realized there wasn't anything in between."

Dr. Weigel and his colleagues discovered that the protein produced
by the leafy gene latched directly onto a particular sequence of
DNA within a C gene, turning on the production of stamens and
carpels. This C gene, also known as the agamous gene, is so
called because plants that carry nonfunctional agamous genes lack
sexual organs ("a" meaning "without" and "gamous" meaning
"reproductive organs"). Such a defect can be rather attractive in a
flower as stamens and carpels become petals.

Other mutant plants in which the agamous gene is turned on not
only in the center of the flower but everywhere become a display of
sexual organs entirely unadorned by petals.

In the other study, Dr. Meyerowitz's group showed that leafy could
also turn on one of the A genes, those that control the development
of sepals and petals. In addition, Dr. Irish said her group had some
evidence that leafy might be controlling B genes in a similar
manner, putting leafy in control of the entire show.

But researchers note that while leafy can turn on these genes, it is
not acting alone. Biologists say they are already on the hunt for
other proteins that must be working in concert with leafy not only to
switch the ABC genes on but to switch them on in the right places
and at the right times.

"Leafy's in the middle of a lot of things," said Dr. Tom Jack,
molecular geneticist at Dartmouth College. He notes that in addition
to turning on genes and coordinating with other proteins, leafy is
also outranked by genes that can turn it on and off.

Researchers now are particularly interested in those highest-
ranking genes, since they are the ones that can control the timing
of flowering in a plant.

"The long-term application is the control of when crops flower,
which is very important," Dr. Meyerowitz said, "because when a
crop flowers determines where it can and can't be grown."

Other researchers may take an interest in the new research as a
step toward turning off the production of pollen altogether.

Because of increasing concerns about genetically engineered
plants and their pollen, which contains foreign genes, researchers
say the new studies are particularly interesting. Conceivably, the
information could lead to the elimination of stamen and pollen
production in genetically engineered trees, which can live for many
years dispersing pollen over long distances.

Scientists are only now beginning to identify the genes that
determine what parts grow where in a flower. In nature, however,
evolution has been experimenting with these genes for eons to help
produce the world's diversity of flowers. One species of Clarkia, for
example, a flower in the evening primrose family, has in place of
petals what look like sepals.

Finding the key to biological authority and delegation in the making
of a flower.

Another, which Dr. Meyerowitz is studying along with colleagues
who discovered the plant in Mexico, is a bizarre plant without
leaves or roots, but with flowers in which stamens and carpels have
switched places.

Plant breeders have unknowingly become adept at fiddling with
these very same genes. Petal-filled roses and other cultivated
flowers are mutants in which reproductive parts have been replaced
by attractive petals, probably as the result of a C or agamous gene

Researchers say these beautiful genetic experiments are probably
alterations in the C gene, which controls the production of
reproductive parts.

Breeders have even toyed with plant genes to the point that such
oddities as the green rose, in which all of the flower parts have
been replaced by leaves, can be found.

Such experiments in floral architecture are nothing new. In ancient
Greece, there were reports of mutant flowers like a rose with a
hundred petals.

And Chinese records from the ninth century mention double
peonies, a mutant that carries many extra petals in place of
reproductive parts.


Copyright 1999 The New York Times Company

"It is not surprising that large evolutionary innovations are not well
understood. None has ever been observed, and we have no idea whether
any may be in progress. There is no good fossil record of any. Because
they are difficult, evolution has occupied billions, not hundreds of
thousands of years." (Wesson R.G., "Beyond Natural Selection," [1991],
MIT Press: Cambridge MA, 1994, reprint, p206)