Tree's leaves genetically different from its roots

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Steve Galehouse
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Re: Tree's leaves genetically different from its roots

Post by Steve Galehouse » Sun Sep 02, 2012 9:17 pm

This seems to be a spontaneous chimera---really interesting!

Steve
every plant is native somewhere

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gnmcmartin
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Re: Tree's leaves genetically different from its roots

Post by gnmcmartin » Mon Sep 03, 2012 1:54 pm

Wow, this is interesting.

Here is a question, followed by a thought. First, the question: is this degree of genetic variation within one tree greater, or more common with black cottonwood than with other trees? And if so, how much more common? I doubt anyone would have an answer to that question yet.

Anyway, here is the thought: there are a great many trees sold as grafted clones. Cuttings are taken from a "parent" tree, then grafted onto a rootstock, and then sold as a clonal variety, or "cultivar." Genetic identity is assumed. I have a collection of these, including a bunch of Norway spruce cultivars. But, if there are commonly mutations throughout a tree, the cuttings may not all have the same genetic makeup.

I once found a very unusual and beautiful Norway spruce tree, and twice had someone do custom grafting for me. Unfortunately, I lost most of the grafts due to one accident or another, but four remain. I am not sure that any of those really represent the tree from which I got the cuttings. I always thought this was strange, and had some explanations in mind. Well, now I have another potential explanation. Some of the cuttings I took were from epicormic sprouts from low down on the trunk, which if there is genetic diversity within the tree, would increase the chance that I may have got a sample genetically different from what the upper parts of the tree were expressing.

I have been a member of the Gardenweb tree forums for years, and there has been a fair amount of discussion of the identity/confusion about some of the clonal varieties. I have always thought it was because of some pervasive carelessness in the trade. For one example, at two different times I bought a cultivar called Norway spruce 'Pendula Major.' But the trees are growing in very different forms, and can't be "clones." Is this because of some confusion or carelessness? Or could it be somewhere along the line someone took cuttings properly and kept them properly identified, all with good provenance, but there was an unsuspected mutation involved, resulting in a tree quite different from the parent?

Most dwarf conifer clones originate as branch mutations, usually expressing themselves as witches brooms--obvious cases of an intra-tree mutation. But other mutations may not be so obvious, but may still result in noticeable, and sometimes significant differences in growth of the grafted tree.

--Gaines

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edfrank
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Re: Tree's leaves genetically different from its roots

Post by edfrank » Mon Sep 03, 2012 2:36 pm

Gaines,

I ask myself the same questions when reading the post about the degree of variation between the roots and branches and whether it was more prevalent in black cottonwood than other species. I would think if it had been a dramatic difference it would have been noted previously. I also consider the case of some of the clonal colonies, such as the box huckleberry plants estimated to be 11,000 years old. These have been shown in literature to be the same plant across its many acre spread based upon genetic testing. http://naldc.nal.usda.gov/catalog/17706 So... where does this lead us...
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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gnmcmartin
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Re: Tree's leaves genetically different from its roots

Post by gnmcmartin » Mon Sep 03, 2012 6:07 pm

Here is another thing that may apply here, but again, I have to plead that I know little or nothing about the cause:

Sometimes a grafted clonal variety, or "cultivar" will have a chance reversion back to the normal type. Two specific times I have seen this happen with a cultivar of white spruce, sometimes called Dwarf Alberta Spruce, or Picea glauca 'conica.' I saw one of these at the National Arboretum, and one on one of my own trees. On my tree, I cut it out, and it has not grown back.

Now here is what makes me think this is strange--why a reversion to the original type? Now I obviously didn't do any genetic testing, but these shoots looked like regular white spruce. Of course they could be a mutation to some third genetic "type," that includes undoing the dwarfism. Possible, but to me this seems like a stretch.

So here is another speculation--yeah, maybe a bit "far-out"--but recently there has been a lot of interest in epigenetics, or ways in which the phenotype (the physical structure of a grown plant) can be significantly different because of factors that influence gene expression, and these can be inherited even though they are not a part of the plant's DNA. So, I am wondering why there is such a common "reversion" in Picea glauca "conica." Yes, apparently it is common--I have seen it twice, and others have seen the same thing.

So, could this "Dwarf Alberta Spruce" be simply a form that is expressing epigenetic factors, not true genetic ones in the DNA? The frequency of the reversions makes me wonder. There is some question about how long inherited epigenetic factors can be passed on to offspring. But this difficulty does not apply here, because the Picea glauca 'conica' is propagated by grafted cuttings.

My first question in trying to solve this question would be to find out what the origin of this cultivar was. Was it a witches broom, which would indicate, I would think, a genetic mutation? Or a chance seedling growing in some special environment that may have brought into play some epigenetic factors?

Well, lots of ideas for someone who is looking for a plant genetics dissertation topic.

Anyway, just as an aside here--you all know I am fascinated by Norway spruce. A professor at Michigan State University once told me that Norway spruce has a very, very large genome, and it is/was(?) thought that much of this is "junk" DNA. Well, having observed the apparent genetic diversity of the species--or at least the phenotype diversity--and the tree's great adaptability, I have wondered if the "junk" DNA is really junk, or if it is in some sense "dormant" until some epigenetic factors come into play.

OK, I know, too much speculation, too many questions, about something I know too little about to really discuss sensibly. Anyway, maybe someone knows something, or would like to do some "unbuttoned" speculation along with me.

--Gaines

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edfrank
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Re: Tree's leaves genetically different from its roots

Post by edfrank » Mon Sep 03, 2012 6:14 pm

Gaines,

In some animals, and I assume some plant species there are certain genes that can be turned on or off by various environmental factors. The genetic code is there for two different forms, but only one is turned on at a time.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Don
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Re: Tree's leaves genetically different from its roots

Post by Don » Mon Sep 03, 2012 9:25 pm

While attending Northern Arizona University specializing in Ecological Forest Restoration, we had only to look up at the San Francisco Peaks at the north edge of Flagstaff, Arizona to find another reason to ponder this issue.
At mid-slope around most of The Peaks, quaking aspens had established a transitional position in the classic C. Hart Merriam Life Zone model that informed ecologists for more than a century. The colors of the aspen's seasonal change was a palette of colors ranging from yellow to gold to almost scarlet, not so much in an elevational or temporal gradient, as defining clonal groups, or so the speculation ran among the forest academics.
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

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View my Alaska Big Tree List Webpage at:
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TN_Tree_Man
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Re: Tree's leaves genetically different from its roots

Post by TN_Tree_Man » Tue Sep 04, 2012 8:33 am

Gaines,

This is an interesting topic. Attached are a couple of pics of a Dwarf Alberta spruce that has reverted back. Both of these trees were the same size and age at planting. One has reverted while the other has not.
Reverted Dwarf Alberta spruce; the tree is about 10 feet tall now; notice it's cohort to the side
Reverted Dwarf Alberta spruce; the tree is about 10 feet tall now; notice it's cohort to the side
Closer view of the reverted Dwarf Alberta spruce
Closer view of the reverted Dwarf Alberta spruce
[/attachment]
Dwarf Alberta spruce
Dwarf Alberta spruce
My understanding is that this cultivar was indeed discovered and propagated from a "witches broom" growing on White spruce. Witches brooms are unpredictable and usually considered as genetic anomallies caused by different variables including unstable dominant alleles, environmental factors and/or other reactionary responses (chance?).


Steve Springer
"One can always identify a dogwood tree by it's bark."

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Bart Bouricius
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Re: Tree's leaves genetically different from its roots

Post by Bart Bouricius » Wed Sep 05, 2012 8:55 am

Gaines,

Here is some more "unbuttoned" speculation
This is a very interesting subject and may help explain why some early research showed more similarity between the DNA of some white and red oaks in I believe Wisconsin? than between Red Oaks in North Carolina and Wisconsin. There may have been flaws with this research which was done at the very beginning of gene sequencing technology, but much of this may be explained by HGT (horizontal gene transfer) which is now said to account for significantly more genetic change in organisms as a whole than does mutation. Epigenetic explanations certainly play a role here, but there are probably more factors at play.

When one of my favorite evolutionists Richard Dawkins, asked Lynn Margulis in a debate (paraphrasing here), why we needed more than mutation and adaptation through natural selection, straight forward and parsimonious, to explain evolution, Lynn replied "because it exists". Lynn was talking about the myriad of ways that genetic material moves or is moved from one organism to another and how organisms often combine together to form new organisms. She also championed the notion that organisms often evolve as guilds or interlocking systems rather than as simply individuals and I remember her telling me that she believed that very little of "junk DNA" was actually junk.

Now I have probably gotten way beyond the scope of this thread, but don't kill the messenger when new information, in this case about genes in trees, shows up. Should you not believe "your lying eyes" just because you do not know the mechanism, or should you search more broadly for a different mechanism. Sorry for the rambling thoughts.

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gnmcmartin
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Re: Tree's leaves genetically different from its roots

Post by gnmcmartin » Wed Sep 05, 2012 6:58 pm

Bart:

Yes, yes, yes. And I have read that viruses can be the transfer mediums for genes. And, I actually remember seeing something about genes being transferred from dogs--or was it cats--to their owners, or the reverse. I have no idea if any of this was true, but I could do a quick web search to see what I can find.

And, as coincidence would have it--about the "junk" DNA: there was a report on the NBC evening news, of all places, about the "junk" DNA and it said that the DNA that the DNA directly responsible for the structure of proteins was previously thought to be the only acting DNA, but the report tonight said that the "junk" DNA actually is the switches that control the activity of the other genes and/or their effects. One point the report made is that the new way of understanding our DNA may lead to medical breakthroughs.

I am not sure I caught the report completely or accurately. But I assume that it is not really "breaking news," but it does seem to overlap somewhat what I have read about the epigenetic factors. It is exciting that we are beginning to sort these things out.

--Gaines

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Don
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Re: Tree's leaves genetically different from its roots

Post by Don » Mon Sep 17, 2012 2:42 am

Gaines/Bart-
My favorite ecologist was Aldo Leopold, with his most quotable wisdom "The first law of intelligent tinkering is to save all the parts." Who I think may have had John Muirs similar thought in mind at the time.
In any case, I just recently sent to NTS in the General Science section, which I'd like to paste here, as it seems to me to address some if not most of the issues you have raised. My earlier post follows:

I'd like to explain that the title comes from John Muir's original and elegant quote, "When we try to pick out anything by itself we find that it is bound fast by a thousand invisible cords that cannot be broken, to everything in the universe. "

While that's a big undertaking, Northern Arizona University's has taken a smaller bite in their "A Thousand Different Cords: Connecting Genes to Ecosystems" PowerPoint presentation. It's audience is probably most appropriately an academic one, but a lay person can pick up many of the basics.

Gaines, Bart, it explains (without mentioning) "resilience", the value of biodiversity, relates individuals to populations, to communities in ways you may not have thought of before...this will be a powerful tool for informing climate change concerns, forest restoration, and far more complex issues.
I hope that at the very least, this will provide you with food for thought and discussion!

View this fairly large Powerpoint file by going to: http://athousandinvisiblecords.org/education
navigating to Downloads, and clicking on Lecture Notes (in either Powerpoint or *.pdf formats).

It will take several minutes (4 on my laptop/cable connection) to download and more to view.
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

BJCP Apprentice Beer Judge

View my Alaska Big Tree List Webpage at:
http://www.akbigtreelist.org

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