This site is not maintained. Click here for the new website of Richard Dawkins.

← Parasitic Plants Steal Genes from Their Hosts

Parasitic Plants Steal Genes from Their Hosts - Comments

Neodarwinian's Avatar Comment 1 by Neodarwinian

Interesting in and of itself even if no implications for bio-medicine are readily apparent. At one time people actually thought that parasites had " devolved " from some " higher " state of existence to a lower state of life. We can see by this article that is not even close to true.

Sun, 10 Jun 2012 02:44:47 UTC | #946684

zengardener's Avatar Comment 2 by zengardener

This will make that whole "complete tree of life" a little more complicated.

Sun, 10 Jun 2012 03:31:00 UTC | #946687

justinesaracen's Avatar Comment 3 by justinesaracen

If you can steal some of them, why not steal all of them?

Adds a whole new layer of meaning to 'the body snatchers'.

Sun, 10 Jun 2012 06:07:27 UTC | #946693

Susanne Desic's Avatar Comment 4 by Susanne Desic

I have to admit that before this article I didn't actually know about the existence of horizonal gene transfer so first of all thank you for posting these news. Indeed especially for the early stages of life this kind of gene transfer makes a completion of the tree of life more complicated. I'm currently reading this Wikipedia article on Horizontal gene transfer in evolution: http://en.wikipedia.org/wiki/Horizontal_gene_transfer_in_evolution which elaborates a bit on the problems scientists are facing. Very interesting for someone like me who has never heard about the topic before. Important quote in my eyes: "These approaches are enabling estimates of the relative frequency of HGT; the relatively low values that have been observed suggests that the 'tree' is still a valid metaphor for evolution – but the tree is adorned with 'cobwebs' of horizontally transferred genes." And since HGT is also limited to certain organisms which can exchange or "steal" genes from each other it won't really turn the model of a tree of life upside down as a whole.

Sun, 10 Jun 2012 08:26:01 UTC | #946700

mummymonkey's Avatar Comment 5 by mummymonkey

You could just as easily put it that the host's genes have infected the parasite. Either way it's win win for those particular genes.

Sun, 10 Jun 2012 08:38:17 UTC | #946702

Alan4discussion's Avatar Comment 6 by Alan4discussion

@OP - Researchers from Singapore, Malaysia and USA collaborated to systematically investigate the possibility of horizontal gene transfer between these two plants.

The reproductive cycles of plants clearly move at a slower pace than those of bacteria, so the horizontal gene-exchange will be more limited in plants.

Comment 4 by Susanne Desic - "These approaches are enabling estimates of the relative frequency of HGT; the relatively low values that have been observed suggests that the 'tree' is still a valid metaphor for evolution – but the tree is adorned with 'cobwebs' of horizontally transferred genes." And since HGT is also limited to certain organisms which can exchange or "steal" genes from each other it won't really turn the model of a tree of life upside down as a whole.

.+ Comment 2 by zengardener

We were discussing the implications of horizontal gene exchange for the tree of life diagram

on this earlier discussion. - http://richarddawkins.net/articles/646130-tree-of-life-project-aims-for-every-twig-and-leaf

Sun, 10 Jun 2012 10:57:17 UTC | #946719

Susanne Desic's Avatar Comment 7 by Susanne Desic

@Alan4discussion: Thanks for the link to the earlier discussion on this subject. Intresting points made there. Have to go through all the links to get a clearer picture on the extent to which HGT might change the idea of the usefulness of the tree structure as the basic model to illustrate evolution (beside all the other named occurrences like ring species etc. that show where the tree model comes to certain limits). Without having read all material posted in the discussion I would suppose despite all these occurrences the tree model is still a good model to show the basic tendencies - mapping each and every species with this model is surely another matter - and the whole complex world of bacteria another one ;).

Sun, 10 Jun 2012 14:38:02 UTC | #946732

Alan4discussion's Avatar Comment 8 by Alan4discussion

Comment 7 by Susanne Desic

Without having read all material posted in the discussion I would suppose despite all these occurrences the tree model is still a good model to show the basic tendencies - mapping each and every species with this model is surely another matter - and the whole complex world of bacteria another one ;).

I think the tree model is good for illustrating particular branches, or main branches, but to try to assemble a whole tree of life, will produce a diagram much too congested to be useful. - Rather like the congested multiple dichotomous 3D branching of this monstrose form of the normally cylindrical stems of this tree-like columnar cactus. ( as seen in the background)
... ... or sometimes simply fanning out like the analogy with a cristate branch of a tree or plant. - as illustrated by this Euphorbia.

Apart from horizontal gene exchanges , end species and ring species, species populations are not made up of individuals with identical genomes, but with a diverse range (as demonstrated in ring species) which with on-going evolution, are branching within the local constraints selection places on them, until geography or other forms of selection, separates them into different species going their separate ways.
A good example of this is plants which cover a range of altitudes. These often have dwarf forms in the higher wind-swept heights.

Sun, 10 Jun 2012 17:45:55 UTC | #946746

All About Meme's Avatar Comment 9 by All About Meme

Comment 2 by zengardener

This will make that whole "complete tree of life" a little more complicated.

Ha! That's an understatement.

The discovery of this Malaysian beauty is the death knell for the Neo-Darwinian synthesis.

Which means Dawkins is totally wrong.

Which means the bible is true.

Which means God exists.

Which means y'all are going to Hell.

Which makes me very happy.

Now if you'll excuse me, I'm late for Sunday services.

Jesus loves you!

Sun, 10 Jun 2012 17:54:44 UTC | #946748

Quine's Avatar Comment 10 by Quine

Perhaps in the future we will have a Tree of DNA, that maps sequences back in time, and just happens to note the species that were nominally the carriers at any given point.

Sun, 10 Jun 2012 18:25:44 UTC | #946751

kev_s's Avatar Comment 11 by kev_s

Re: All About Meme

Masterly!

Sun, 10 Jun 2012 18:26:17 UTC | #946752

Alan4discussion's Avatar Comment 12 by Alan4discussion

@OP- New research published June 8 in BioMed Central's open access journal BMC Genomics reveals that the Malaysian parasitic plant Rafflesia cantleyi, with its 50cm diameter flowers, has 'stolen' genes from its host Tetrastigma rafflesiae.

... ..

Comment 9 by All About Meme - The discovery of this Malaysian beauty is the death knell for the Neo-Darwinian synthesis.

Fundies probably could not work out horizontal gene transfer, but the discovery of Rafflesia its self is not new!

Rafflesia, among the world's largest flowers, belong to the family Rafflesiaceae. The plant family Rafflesiaceae has eight genera which includes the genus Rafflesia. Rafflesia arnoldi, that grows up to 150 cm in diameter, is the largest flower in the world. It was discovered by Sir Stamford Raffles and Dr Joseph Arnold on 19 May 1818. - http://infopedia.nl.sg/articles/SIP_38_2005-01-22.html

Rafflesia is found in tropical rainforests of Malaysia, Singapore, Indonesia and Philippines. It occurs only in certain habitats as a parasite on the Tetrastigma species of woody vines. Rafflesia is a very rare flower, difficult to reproduce in the lab and its dried specimen is difficult to preserve. Other species of Rafflesia can measure between 36 to 42 in. in diameter and weigh between 9 to 12 kg.

Description

The first description of Rafflesia arnoldi was given by Robert Brown. Taxonomic classification of plant family Rafflesiaceae has not been thoroughly decided as yet. At least 55 species in eight genera however have been identified. The genera of Rafflesiaceae plant family are Apodanthes, Bdallophyton, Cytinus, Mitrastemon, Pilostyles, Rafflesia, Rhizanthes and Sapria. Since all the plants of this family are parasitic, they therefore do not have any roots, stems or leaves. Individual flowers or buds simply sprout on the species of Tetrastigma woody vines. They lack chlorophyll. Some flowers are monoecius, with both sexes in the same flower. All flowers of the family Rafflesiaceae may not carry the same parts and traits.

Re. Comment 7 by Susanne Desic:-

Taxonomic classification of plant family Rafflesiaceae has not been thoroughly decided as yet. At least 55 species in eight genera however have been identified.

With 55 species of these alone and the classification unclear, this illustrates the point about the difficulty in constructing diagrams of huge evolutionary trees, rather than limiting diagrams to specialist local branches!

Sun, 10 Jun 2012 21:39:26 UTC | #946780

OHooligan's Avatar Comment 13 by OHooligan

From the article:

Bacteria use horizontal gene transfer to exchange resistance to antibiotics.

Which goes along with the whole "gene-stealing" theme of the article, but reinforces the "intentional evolution" meme if you like, the one that says that a species "adapts" to its environment like its something deliberate and planned. "Hey, it snows a lot. I think I'll encourage the kids to grow white fur..".

Saying that the host genes have infected the parasite seems much better. No deceptive baggage of "intent".

And the bacteria statement? How about "Antibiotic resistance in bacteria spreads via horizontal gene transfer". No need for "use...to" as if there was intention, purpose, guidance.

Sloppy writing like the above simply makes things easier for the Intelligent Design Creationists.

ps: A few years back in the NZ Parliament, a Green MP speaking on the topic of Genetic Engineering, raised concerns about Horizontal Gene Transfer. Other members sniggered like schoolboys. Clearly they had a different mechanism in mind.

Mon, 11 Jun 2012 00:00:03 UTC | #946791

Susanne Desic's Avatar Comment 14 by Susanne Desic

Comment 8 by Alan4discussion :

Comment 7 by Susanne Desic

Without having read all material posted in the discussion I would suppose despite all these occurrences the tree model is still a good model to show the basic tendencies - mapping each and every species with this model is surely another matter - and the whole complex world of bacteria another one ;).

I think the tree model is good for illustrating particular branches, or main branches, but to try to assemble a whole tree of life, will produce a diagram much too congested to be useful.

Yes. Main branches were what I had in mind when I wrote "basic tendencies".

Mon, 11 Jun 2012 04:49:01 UTC | #946809

Susanne Desic's Avatar Comment 15 by Susanne Desic

I have to agree that the wording that the parasite "stole" the genes could be misleading for some readers. Not only because you could read some intent into it but also because one could think the parasite literally stole the genes away from the host (instead of copying them), meaning the host does not have the genes anymore afterwards. I don't know if it would have been better if the OP had written about infection by the host? Unfortunately I don't know about the details of HGT, but I would think the parasite triggered the gene copying process and not the host, so "infection" would be also a bit misleading in my opinion - it would sound as if the host was the "active" part in the process that freely "gifted" its genes to the parasite without any signal from it (how altruistic...).

Mon, 11 Jun 2012 05:03:20 UTC | #946810

Alan4discussion's Avatar Comment 16 by Alan4discussion

Comment 13 by OHooligan

From the article: - Bacteria use horizontal gene transfer to exchange resistance to antibiotics.

Which goes along with the whole "gene-stealing" theme of the article, but reinforces the "intentional evolution" meme if you like, the one that says that a species "adapts" to its environment like it's something deliberate and planned.

Sloppy writing can confuse "mechanism" with "intention"!

Saying that the host genes have infected the parasite seems much better. No deceptive baggage of "intent".

The parasite acquiring host genes, could help it escape the host's defences, and access the host's resources, - hence it would have a selective advantage over individuals without this feature. The process would initially be random, but could with selective advantage in successful cases, have evolved a function in time, which would have aided it in spreading to related species of host.

And the bacteria statement? How about "Antibiotic resistance in bacteria spreads via horizontal gene transfer". No need for "use...to" as if there was intention, purpose, guidance.

There is "guidance" towards survival and expansion, in the form of natural selection by the antibiotic medicines eliminating or reducing, vulnerable competitor bacteria, and giving the resistant strains an open field in which to rapidly expand their numbers and take over, replacing the others.
Natural selection, is the guiding force in evolution. Under dosing, and failure to complete a course of antibiotics, encourages the development of resistant strains, by only killing the more vulnerable bacteria.

Mon, 11 Jun 2012 09:20:13 UTC | #946837

This Is Not A Meme's Avatar Comment 17 by This Is Not A Meme

I'm so glad I saw this before the new Alien movie (Prometheus).

Mon, 11 Jun 2012 10:13:23 UTC | #946842

Greyman's Avatar Comment 18 by Greyman

Comment 16 by Alan4discussion :

Comment 13 by OHooligan

And the bacteria statement? How about "Antibiotic resistance in bacteria spreads via horizontal gene transfer". No need for "use...to" as if there was intention, purpose, guidance.

There is "guidance" towards survival and expansion, in the form of natural selection by the antibiotic medicines eliminating or reducing, vulnerable competitor bacteria, and giving the resistant strains an open field in which to rapidly expand their numbers and take over, replacing the others. Natural selection, is the guiding force in evolution. Under dosing, and failure to complete a course of antibiotics, encourages the development of resistant strains, by only killing the more vulnerable bacteria.

Gravity is the guiding force of water running down a hill. That doesn't mean it actually conspires to pull water down the steepest gradients.

It's so easy imply an "intention" instead of a "tendency". It's like an expectation of conscious agency is built into our language.

Wait.

Mon, 11 Jun 2012 13:42:45 UTC | #946862

Alan4discussion's Avatar Comment 19 by Alan4discussion

Comment 18 by Greyman

Gravity is the guiding force of water running down a hill.

Indeed! and it interacts with the strata and/or the Coriolis effect, to arrive at the routes taken - above or below ground.

That doesn't mean it actually conspires to pull water down the steepest gradients.

Very much so! Anthropomorphism should be avoided when looking at functions of natural forces.

It's so easy imply an "intention" instead of a "tendency". It's like an expectation of conscious agency is built into our language.

Anthropomorphism reads "intention" into possibilities of nature. It is the non-random nature of natural selection, that from exploration of multiple options, competitive possible options are selected, and those which do not work or compete, fail & die out.

Antibiotic resistance in bacteria, is effectively human malpractice (unintentionally) guiding the development resistant strains, - while natural selection works as usual, we use a misdirected aim, to "shoot ourselves in the foot"!

Mon, 11 Jun 2012 14:52:36 UTC | #946871