Why are Some Alkaloids So Ubiquitous and Others Found Only in 1 Plant

[daddysgone]

Well....the title says it all.
This is probably a very complicated and difficult (if not impossible) question to answer, but perhaps some of the minds here have even, a partial answer.

It just seems odd to me that certain alkaloids are found in many, many, seemingly unrelated species. And then there are some alkaloids which seem to only appear in one plant on the planet.
For instance, caffeine is found in varying quantities in a good number of plants. DMT even more so. Compare this with something like morphine, which as far as I know, is found only in one or two poppy varieties. Is there any known mechanism which accounts for this?

It would seem to me that any particular secondary metabolite, either benefits the plant or it doesn't. If it doesn't then the process of evolution will eventually phase out this trait, as it offers no benefit, but is energy demanding.
So, for a secondary metabolite like morphine, which I will assume benefits the plant due to its role as a sort of natural pesticide, why has this particular defense mechanism only been developed in an isolated species? If this phenomenon (an alkaloid found in only one species) was universal, meaning that if each particular alkaloid was always only found in one species, this could make sense to me.
But it just seems odd that for certain alkaloids, you find them present in a whole host of unrelated species (caffeine, DMT, etc.), and then you have alkaloids which seem to only exist in a single, specific species.
Any ideas that would explain this phenomenon?-DG

 

[vecktor]

morphine is not a good example as it is found in diverse plants including lettuce.

the more interesting thing is the idifference in alkaloidal compositions of closely related plants, they all have the same basic enzymatic pathways but for example the various coca plants contain very different proportions of cocaine type alkaloids.

last time I was talking to god I asked her about it, and she said that it was done to baffle and confuse man

the simple alkaloids like caffeine and DMT should be more widespread, and the super complex ones that require much more specialised enzymatic machinery should be less ubiquitous,

that is not an proper answer but I don't think there is a answer.

 

[amanitadine]

yeah and *how* do they get those little ships in the tiny bottles anyway?! ;D

 

[daddysgone]

morphine is not a good example as it is found in diverse plants including lettuce.

the more interesting thing is the idifference in alkaloidal compositions of closely related plants, they all have the same basic enzymatic pathways but for example the various coca plants contain very different proportions of cocaine type alkaloids.

last time I was talking to god I asked her about it, and she said that it was done to baffle and confuse man

the simple alkaloids like caffeine and DMT should be more widespread, and the super complex ones that require much more specialised enzymatic machinery should be less ubiquitous,

that is not an proper answer but I don't think there is a answer.

Ok, so perhaps morphine isn't the best example, but you get my point. How about cocaine? Are there any other plants, other then the few related varieties of coca trees? In any case, even on the spot, I can't name an alkaloid which is only found in one plant-we can all agree that there are cases such as this, and then their are the things like caffeine and DMT.

Im curious vecktor, why do you assert that alkaloids like caffeine and DMT are "simple", but something like morphine is super complex?

I do agree with you that it is quite interesting that plants with almost identical enzymatic pathways, can often have vastly different alkaloid profiles. My guess is that these drastic differences are mainly due to the action of genes turning on and off, specific proteins. -DG

 

[vecktor]

Ok, so perhaps morphine isn't the best example, but you get my point. How about cocaine? Are there any other plants, other then the few related varieties of coca trees? In any case, even on the spot, I can't name an alkaloid which is only found in one plant-we can all agree that there are cases such as this, and then their are the things like caffeine and DMT.

Im curious vecktor, why do you assert that alkaloids like caffeine and DMT are "simple", but something like morphine is super complex?

I do agree with you that it is quite interesting that plants with almost identical enzymatic pathways, can often have vastly different alkaloid profiles. My guess is that these drastic differences are mainly due to the action of genes turning on and off, specific proteins. -DG

DMT two enzymatic steps from the ubiquitous tryptophan

caffeine 3-4 steps from the common purines.

morphine on the other hand appears o me to be far more complex.

for me a complex alkaloid is something like strychnine or aconitine those are stunningly complex.

 

[Quanta]

^ agree with the above. Ultimately though does it not have to do with the gene expression profile within a certain species resultant from an evolutionary timescale and be very dependant on environmental influences and purposes? In general is it not accepted that secondary metabolites are generally present as some sort of protective value to the plant?

 

[amanitadine]

you've gotta look at the alkaloid/whatever content of a plant as a morphological feature.....ie much like its appearance it evolved that way, and just as plants evolved to look physically distinct they also are unique in chemical constituents once you get past the basic necessities for survival. its a trait, much like color, shape, etc.....

 

[Hammilton]

I'm not sure I understand the importance of the above comment. The question is why some alkaloids seem to be everywhere, and others are pretty rare.

Things that are easier to produce biosynthetically are more likely to occur randomly. The more complicated, the less likely it'll occur randomly.

Either way though, if they're beneficial, they'll be retained, if they're not, they'll be dropped. Obviously morphine is worth the work to produce for p. somni. Something like DMT doesn't need to offer as big an advantage because it's easier to produce, meaning less energy is spent on it.

 

[daddysgone]

Thanks for the responses.
It now occurs to me that there is a related question to the one I originally posed, which seems to be more of a mystery.

Namely, why do these more complex and/or energy demanding secondary metabolites exist, when there are a wide array of simpler, less energy demanding alkaloids which could provide the same protection and function as these more complex metabolites?

Why would the poppy plant, for example, have evolved mechanisms and pathways to create more complex secondary metabolites like morphine, when evolution could have selected much simpler and less energy demanding metabolites to serve as an effective pesticide and protection for this plant? Metabolites dont necessarily have to be complex and energy demanding in order for them to serve a function (such as acting as a insect/animal deterrent).
The poppy/morphine example might not be the best example to use here, since I believe humans were instrumental in shaping the alkaloidal makeup of this plant through selective breeding. But still, you get my point.-DG

 

[amanitadine]

hammilton- to clarify, what i was *attempting* to say what that the bulk of the physical characteristics present in any given plant species are responses per se to the environment which spawned them. Some of these environments have a lot in common, like, say, the sun, and we have the prevalence of chlorophyll throughout....other traits are more specialized, due to the specialized circumstances which created them. And much as say an orchid has evolved a certain flower type to be pollinated by a specific species of moth, some plants have developed unique and bizarre chemical constituents, whether or not the "role" is clear to us. And then there are the wild cards, the genetic baggage that gets passed on simply because it isnt directly harmful. Evolution. You touch on it yrself. :D

 

[onmyway]

wait a minute....lettuce has a pathway for morphine? I smell an interesting opportunity for playing around with transgenic lettuce (if you have lots of time and money). I wonder if one could find a way to sneak a more active transcription factor into the lettuce genome?

Anyway, I wonder if some of those ubiquitous alkaloids may have come from gene transposition via viruses over the last few million years?

 

[Hammilton]

hammilton- to clarify, what i was *attempting* to say what that the bulk of the physical characteristics present in any given plant species are responses per se to the environment which spawned them. Some of these environments have a lot in common, like, say, the sun, and we have the prevalence of chlorophyll throughout....other traits are more specialized, due to the specialized circumstances which created them. And much as say an orchid has evolved a certain flower type to be pollinated by a specific species of moth, some plants have developed unique and bizarre chemical constituents, whether or not the "role" is clear to us. And then there are the wild cards, the genetic baggage that gets passed on simply because it isnt directly harmful. Evolution. You touch on it yrself. :D

You're starting from a faulty place and ending with a similarly flawed conclusion.

It's actually quite literally backwards. You're starting with the idea that things evolve for reasons.

They don't.

mutations are kept for reasons, they happen by random chance.

Chlorophyll isn't ubiquitous because most environments have light. Chlorophyll is ubiquitous because some very distant ancestor evolved it through random chance and the mutation was retained because it offered such a big benefit to that ancestor. It seems that you believe that chlorophyll popped up randomly millions of times. That's wrong. It popped up once and just hasn't left.

I guess I thought that this conversation was about why some alkaloids appear frequently in unrelated plants and why others appear only once or twice in unrelated plants.

The conservation would be pointlessly dull if we're talking about related species, which can be explained by genetic similarity.

Why is DMT produced by dozens of unrelated species? It's easy to make so it could occur by chance easily. It has a benefit so it's likely to be retained. So, A + B = high chance that it will appear

Genetics and evolution is incredibly complicated but also so very simple.

 

[amanitadine]

No i am most definitely not saying things evolve for a reason. Im saying that in the random game of genetics we only see what worked. We dont see all the failures. Ie chlorophyll....no where did i make the argument that all these plants developed chlorophyll independently; its just a unifying factor in the myriad influences that develop a plants genome. Hence its prevalence. Somebody mutated, it was a big hit, and those that didn't hit the backseat. Same goes for any other trait, be it chemical composition or whatever. I have a grasp on evolutionary biology, as do you apparently. I think you are misunderstanding me.

 

[seep]

Just have to chime in and say that plants didn't develop chlorophyl--cyanobacteria did. These prokaryotes were later engulfed by aquatic protists and became chloroplasts. Only billions of years later did these eventually speciate into terrestrial plants.

As for plants revising their genome to minimize work: this is a bit of an oversimplification. The engine that drives natural selection is powered by reproductive success. Whether you have to go across the street or across the planet to impregnate the mother of your children, the outcome is the same. This spatial analogy applies to evolution as well. As long as plants can mature and disperse gamettes, it doesn't matter if they are the amorphophallus or the crabgrass.

Not every product has to have a role in protecting the plant. Many plants benefit from being torn to shreds, so long as they can reach reproductive maturity before being torn to shreds. Add to this the complication that plants "use" animals (and more recently humans, oh poppy) to propagate. Add to this the extra complication that artificial selection has entered the equation ever since agriculture was developed.

Not to mention that a lot of the genes that encode for the alkaloids we pay attention to are lucky enough to be at a locus near a gene that nature selects for--and thus the alkaloid is preserved. Take also into account that some common ancestors have speciated exponentially while others have not speciated much but survive nevertheless (say gingko). Also relevant is that plants don't fossilize as well as animals and therefore paleobotany is more challenging than animal paleontology. Lastly, the greatest diversity of species are in parts of the world that are currently suffering bitter environmental degredation and we are in the middle of a mass extinction.

Excellent question though.

/ends rant/

 

[tryp2fun]

Don't forget that many of these alkaloids are made in animals as well as plants, though they likely have different roles. Morphine is made in the human body, not just in poppies, and there is a class of opiate receptors that seems to be quite specific for morphine, not enkephalins or endorphins. Not to mention DMT is the ligand for the sigma receptor and bufotenin is also produced in our brains. So, did these products arise prior to the divergence of animals and plants, or are they the result of convergent evolution?

 

[seep]

So, did these products arise prior to the divergence of animals and plants, or are they the result of convergent evolution?

There never was a "divergence of animals and plants." Animals are unikonts and much more closely related to fungus.

See this diagram and follow choanoflagellata back to the central stalk. If the fossil record were intact then I'd wager we could dismiss convergent evolution in this case, but systematic DNA comparison is rather telling. If you have library access account and can wade through incredibly technical genetic terminology, read the article "Rooting the Eukaryote Tree by Using a Derived Gene Fusion".

 

[mad_scientist]

This entire thread seems to be built on a fairly shaky premise. Actually there are relatively few alkaloids that are produced exclusively by a single plant (organism, whatever), but most of them are only produced in very small quantities.

Morphine for instance is made in the highest quantities by certain strains of the opium poppy and this is effectively the only viable source for commercial production. However if you look for tiny traces of morphine being produced then you will find it all over the place, it is even produced endogenously by neuroblast cells in human brain.

Similarly while strychnine may be famous as coming from the Strychnos nux-vomica tree, it is produced in smaller quantities by most of the plants in the Strychnos family, and even by some unrelated species.

In general any "unique" alkaloid unless produced by a plant which is the only species in its genus, will be found in at least trace amounts in other closely related species.

Naturally there will be exceptions to this, but at least when referring to all the more well known alkaloids used by humans, you shouldn't confuse "the only commercially viable source" with being "the only source whatsoever"...

 

[Hammilton]

Similarly while strychnine may be famous as coming from the Strychnos nux-vomica tree, it is produced in smaller quantities by most of the plants in the Strychnos family, and even by some unrelated species.

This is my point - within a family you'll likely find many relatives producing the same alkaloid at varying levels, which makes counting close relatives as individual appearances pointless. These should be counted as one appearance, and that's it. The appearance of an alkaloid within unrelated plants and animals is the only issue worth looking at here.

 

[daddysgone]

^^^^^^^^^^^
Yes. If you look at my first post, you will see that I made a point to focus on the phenomenon of certain alkaloids appearing in many, completely unrelated species-and then contrasting this with the fact that there are other alkaloids which seem only to appear in one plant. Obviously its not very interesting to discuss or study the fact that morphine can be found in a few, related species of poppy. The mystery, to me, would be if morphine was discovered also to be made by tulip plants, for example.

Mad-Scientist I believe it was, did make an interesting point that many of the alkaloids which I consider to be found only in 1 species, or a few species of closely related plants, are in fact found in many other plants, but in much smaller quantities. It is therefore, untrue, to say assert that something like morphine is only found in a few related poppy species.

Still, the fact remains that there are certain things, like DMT, which are found in significant quantities in totally unrelated species, and in fairly high quantities. And then there are the alkaloids which for all practical purposes, are really only found (in any functional amounts) in one plant.

Does this discrepancy simply result from the fact that some alkaloids are much simpler in structure, and thus more likely to be found in a wide array of species, as compared to the alkaloids which are more complex and require more enzymes and subsequent steps to synthesize?

And getting back to Mad-Scientists point about alkaloids like morphine, which I submitted as being found only in 1 or 2 related species, actually being found in many more species, but in minute quantities:
If this is indeed the case (and I believe it is), what possible function could the synthesis of the MINUTE quantities of morphine in something like lettuce, serve this plant? The production of morphine in poppy species perform a very concrete and important function- they act as a natural pesticide for the plant. But in something like lettuce, which apparently produces barely detectable quantities of morphine, what possible benefit does the synthesis of morphine offer this species? I can't imagine that these truly minute quantities of morphine could act as an effective pesticide. So, why would such a plant have evolved these enzymes and pathways, and expend the energy to produce something which is not made in high enough concentrations to be useful? The only thing I can imagine is that my assumption about these low quantities of morphine not being in high enough concentrations to be effective, turns out to be untrue. Is it possible that these miniscule quantities of morphine could in fact as an effective pesticide against small insects?

Well thats all for now. Thanks-DG

 

[fastandbulbous]

that is not an proper answer but I don't think there is a answer.

It's about as proper as I'd venture to offer


Most alkaloids originate from amino acid modification, so the closer to the amino acid (tryptophan in the case of DMT) the more likely to be widespread