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Re:RE: OT Plant cell biology - red

Dave, I get the impression that the recognition of a specific gene working
backwards from isolated enzymes of known function is already or almost a
reality.  That's a question we might pose to Dr. Meckenstock, as he is an
active researcher in studies somewhat akin to this question.  At least he
could point us toward research that is along this line.

From a paper that Dan Meckenstock has written, a couple of specific genes have
been identified that are two of the steps toward red.  His work is in JI's,
but much of the same genetic foundation for some of the pigments in JI's may
also occur in Eupogons, including our familiar garden varieties.

It is not impossible that the genes we need for true red are already floating
at random through our modern populations (collections).  Being recessives,
getting four copies of two or more genes that would render Delphinidin as
Pelargonidin or Peonidin is astronomically improbable if we depend only on
accidental associations.

Perhaps breeding with the warmest anthocyanin colors we can find that <don't>
depend on a light dose of yellow to warm them up and inbreeding with them
might move us toward red.

Dr. Spoon's article about red in the last *Bulletin* mentions Keppel's SOCIAL
GRACES as apparently having an anthocyanin variant that the "I" dominant
inhibitor does not affect.   (At least we have interpreted the effect as the
result of a dominant inhibitor, but a challenge to that interpretation has
been raised.  The question and its resolution do not affect what we are
looking at here).

Don Spoon suggests that pigment present with an intense, near-spectrum red
version of Lycopene, provided no beta Carotene is present with it, could
produce true spectrum red if a cooling reddest-possible form of our familiar
Delphinidin were also present in a very light dosage.

It also has been suggested elsewhere that anthocyanins alone might be produced
that would have the same spectrum red color--with genes we already have.

If the enzyme a gene results in is known, its chemical sequence of amino acids
reveals the sequence of the nucleotides in the DNA strand.  There isn't a
one-to-one correspondence, however, as most amino acids result from either of
two DNA 3-base pair codes, and in one case, an amino acid results from six
different, but very similar 3-base pair codes.  Such a set of base-pairs is
called a "codon" incidentally.

The problem is, these enzyme catalysts can have an extremely long set of amino
acids in their construction, and have more than amino acids involved, if I am
not mistaken.

A specific pigment is constructed by a sequence of chemical events, each step
mediated by one or more of these enzyme proteins.

The problem with all this is compounded.  There are many chemical steps in the
construction of an anthocyanin.  Research with Gladiolus pigments (to which I
referred some months ago either on Iris-talk or Iris-photos) suggests the
process is on the order of twenty steps long.

In effect--the set of genes we are looking for is probably millions of
base-pairs long.

We might as well go fishing as to try to identify the whole sequence.  If we
know <which> step(s) is/are the one(s) that will shift the synthesis from
Delphinidin to Peonidin or Pelargonidin, the colors found in peonies and
"geraniums," we would have our color.

The enzymes can be identified--or already have been, I think--and from this it
is technically possible to determine the sequences of amino acids in the
enzymes which spell out what the codons could be.  Then they can be identified
on the chromosomes.

Or, using the same information, cultvars can be identified which <already>have
the enzyme in their genome, and we don't have to breed at random.  We have
target varieties.  This still would be tedious and expensive, but far easier
than the above approach.

Dr. Spoon's method is to go after target varieties using the phenotypes he
described in his article.  That is far simpler than what is described above,
but will not happen over night unless extremely good fortune accompanies his
enthusiasm and intuition.

The approach I'm suggesting would cost megabucks, but might have an even
better "red" at the end than that suggested by Spoon.

In any event, any method for "red" development will probably take generations
of breeding, culling thousands of seedlings, and in the meantime produce some
awesome spin-offs.

Oh what fun this is all going to be!  We live in a marvelous time, we do.

Neil Mogensen   z 7 western NC mountains

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