Re: Re: Re: Epigenome-sidebar

Chuck,
 
I've seen that term, demethylation, in the checklists... thanks for
clearing up the meaning.  I had inferred that it was probably not a "natural"
process, so I'm glad to have conformation.
 
Thanks
Christian



-----
Original Message ----
From: "irischapman@aim.com" <irischapman@aim.com>
To:
iris@hort.net
Sent: Wednesday, September 3, 2008 10:39:02 PM
Subject: [iris]
Re: Re: Epigenome genetics

I've looked at at some of the information on
epigenome  genetics. 
Basically it refers to the effects of environment on
expression or non 
expression of certain genetic characteristics.
Vernalisation is an example of this. Exposure to low temperatures for a
certain time ( temp and duration varies for cultivars and species)  
results
in a permanent change in  plant, enabling or increasing ability 
and speed of
flowering.  This way the environment  changing  the 
genetics. It can be
turned off by  bio-chemical response (speculation)  
from blooming parent
rhizome.  The specific  condition is turned on and 
off  regularly. this
turning off and on does not result in any change 
in  genetics or epigenetics
of plant. Just the current condition of the 
plant.

The same is true of any
changes from acclimatization.  The plant can be 
sent back to original garden,
grown for a couple of years and be sent 
back, have to go through
acclimatization . This can be done forever  
and  ther is no change to the
genetics and epigentic composition. The 
plant still responds the same way,
set and reset.. It doesn't matter 
what the condition of plant is when it sets
seed. the inheritance of  
genes and epigenes will proceed the same . Any
effects of epigentics 
will continue to set and reset regardless of initial
stage, according 
to prevailing conditions.  For example plant  will be in
bloom 
readiness  when vernalized and not ready when vernalized.  (of course
I'm referring to oncers, spring only)

The Study showing inherited change
refers to the change that was  
induced by chemical trauma (demethayliation) 
and not to any change 
induced by epigenetic  condition at seed set. That is 
the  change was 
induced by the chemical and was inherited as the change
occurred to DNA.

Another example of inherited chemical change is my iris
'Canadian 
Streaker', a variegated foliage plant.  It was produced by spraying
some abandoned  seedlings  in a weed patch with roundup. This  modified 
the
plastids  and can be inherited through maternal inheritance. 
Chemicals are
often used to produce  mutations, this was one of them.

Basically,  there is
nothing to support the idea (at this time)  that  
there would be anything
different from inheritance of seeds under 
different conditions.  There may be
some changes of seed viability 
caused by maternal effects, but this is a
different situation. Maternal 
effect is the ability of the seed to germinate
and grow based on energy 
contained in seed embryo. A plant that is
acclimatised would naturally 
have  more energy in embryo  then one that is
not properly 
acclimatized.

( Paul, any of your experiments would need to
account and control  for 
maternal  effects)

The opposite is also true. Any
rhizome that comes in from another 
climate  could be more hardy the first
summer in the garden and weaker 
after that. This is because plant comes in
with energy  obtained from 
where it was grown. Many plants from Oregon  do
well here the first 
summer (with their store of energy)  but not afterward. 
Sort of 
reverse acclimatization . One good example of this is 'Isn't This
something'  Every couple of years I order some plants in to use for
breeding.  The first summer here it produces lovely blooms and bloom 
stalks.
But never again. After that they  are wimpy plants that barely 
survive and
eventually fade away. Sometimes producing a few sparse 
blooms  in second
summer.

The length of summer , degree days, warmth of summer , day and night
temperatures etc.  all effect the storage of energy and setting of 
flower
bud  differentiation.  New climate, new conditions, new plant 
response.
Chuck Chapman
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