Basically the term 'chimera' means " also spelled Chimaera, in
botany, a plant or plant part that is a mixture of two or more
genetically different types of cells..... Chimeras may also arise by a
mutation in cells of a growing region. The new kind of tissue may be
conspicuously different from the old" (encyclopedia Britanica)
The original chimera plants did have two plant genomes mixed together.
But this usage has changed over time. Now it can be just one base
pair, leading to a new codon and a new amino acid in a protein
structure. And anywhere in between these two extremes.
The interesting flower chimera are 'sectoral somatic mutations'.
That is they occur in part of the flower, but not in the germ line.
These sectors have nice smoth edges and are usually triangular in
shape with narrow base nearest center of flower. These are a result
of turning off or turning on of a previously silenced gene. Usually
through some form of mutation. Could be just abase pair, a gene segment
, or a rearrangement of a section of gene through a mistake in cell
production. All of the cells originating from this cell outwards, have
this mutation, hence the sectors. Cells can divide sidewise and then
length wise. And thus sector gets wider.
The versicolor flower shown has classic sector features, gets wider
and has smooth edge. So thus a 'one off'' chimera and not a germline
sector mutant. Thus likely only flower on plant like this. Could be a
colour change (ie; loss of cartenoid pigment) or could be removal of
'OH" molecule on anthrocyanin molecule or loss of a sugar attachment
on the base anthrocuyanin molecule. Both of these later changes will
change colour of pigment.
I have seen this where it was in floral meristem, and then you get a
number of flowers on stalk with same pattern but this is very rare.
The broken colour flowers have a 'jumping' gene, called a transposon.
This involves a sector of gene being cut and moved to a new location
randomly. AS this happens a gene is turned off with insertion and
turned back on when inserted gene section is removed. In these cases
pattern is irregular and random. No smooth edges and no wedge. This
is genetic and gene will be passed on to some offspring. So not
really a gene change so much as a change in gene _expression_.
Chuck Chapman
-----Original Message-----
From: David Ferguson manzano57@msn.com [iris-species]
<iris-species@yahoogroups.com>
To: iris-species <iris-species@yahoogroups.com>
Sent: Sat, Feb 7, 2015 6:57 pm
Subject: RE: [iris-species] unusual forms in species
Some thoughts on chimeras,
Â
I'm not sure howÂyou could be sure if this photo is of a true chimera,
or just something weird happening within the tissues of theÂindividual
plant itself. We have a number of Iris cultivars that do this sort of
thing routinely, and they are not chimeras. A chimera would involve
tissue of two genetically distinct individual plants combined into one,
but not completely integrated, and some patches of tissue being of one
and some of the other, and perhaps some mixed. Usually this would
occur in early embryonic development, but it can happen with
intermixing of tissue through a graft as well. It happens in both
plants and animals. However, other things can cause a similar
appearance. When something happens in some tissue, but not all,
perhaps aÂgenetic mutation,Âthat switches on or off or altersÂsome
visibly expressed trait, the affect can look similar to a chimera , but
it doesn't mean it is truly a chimera. Variegates can pop up this way
too, and inÂuni-sexual organismsÂwe can get gynandromorphs (part male,
part female).ÂÂPigment and pattern mutations seems to happen moderately
often in Iris, especially in hybrids between species (especially those
involving Iris variegata). Sometimes we get a particular
pigmentÂpresent in one part, but not another (such as this one),
sometimes broken patterns, and sometimes other weird color patterns.Â
We also get sports, where part of a plant starts to produce foliageÂor
flowers with different characteristics than the rest of the plant
(oftenÂinvolving coloration).
Â
IÂsuspect that the plant in the photo has someÂinstability affecting
the production of yellow pigments in the flowers, and that each flower
might look different, with pattern distribed in varying broken
patches. It could be that part of the plant has lost or gained the
capability of producing the yellow pigments in the flower, and this
particular flowerÂgot caught right at the dividing lineÂbetween
tissues. Regardless, I suspect that it is not a true chimera (though
it could be). I doubt a true chimera would have everything so
perfectly matched in the different parts (size, shape, pattern,Âetc.),
with only the lack or presence ofÂyellow pigment affected.
Â
Dave
Â
----------------------------------------------------------
To: iris-species@yahoogroups.com
From: iris-species@yahoogroups.com
Date: Sat, 7 Feb 2015 22:31:10 +0000
Subject: Re: [iris-species] unusual forms in species
Â
Sean,
What about the iris in this picture: SIGNA: The Species Iris Group of
North America
It's labelled as a chimera.
I'm wondering if it was just that one flower or were all the flowers on
that plant like that?
[I never will forget the first time I saw a picture of the 'Twin
Sisters' or 'Twin Beauties' peony cultivar.
Each flower o n the plant was half one color and half another.
Thanks,
Anita Clyburn
Â
Â
Â
Â
Â
Â
Â
< span class="ecxlink-enhancr-element ecxicon ecxicon-shrink
ecxlink-enhancr-toggle">SIGNA: The Species Iris Group of North America
Species Iris Group of North America About Us Membershi p Publications
Seed Exchange Species Database Spec-X Add Comments Iris versicolor #26
of 43
View on www.signa.org
Preview by Yahoo
Â
On Saturday, February 7, 2015 5:01 PM, "Sean Zera zera@umich.edu
[iris-speci es]" <iris-species@yahoogroups.com> wrote:
Â
I've seen thousands of plants of the three iris species native to
Michigan, but only once found one of an unusual color. Plenty of normal
variation, though (see hereÂfor example). Conversely, I found about a
dozen variegated plants in the wild just this past year alone, as well
as a few albinos. No irises yet.
The way to increase your chances of finding unusual variation is to
examine many, many plants, either by roaming the wild or raising lots
of seed in the garden.ÂSearching in the wild means nature does most of
the work and you don't have to grow bazillions of seedlings yourself,
but most of the unusual forms will have been weeded out by natural
selection.
Sean Z
Zone 6a
SE Michigan
