death cap & amanitin-resistance genes

[Ken Kinman]

Dave and Brian,
     Although it is certainly true that gut microflora can often be an
important consideration in metazoan digestion, I am not sure that it is that
important in this particular case.
     I did a quick check on some Internet sources, and it seems that
resistance to this toxin (amanitin) is genetic.  Apparently an
amanitin-resistance gene has been identified in C. elegans mutants which
makes these worm 20,000 times more resistance to this toxin than non-mutant
forms.
     The question now in my mind is whether such a gene is widespread among
rodents and rabbits (and apparently in various Artiodactyls as well), and
whether or not such a gene spreads to other animals (by horizontal gene
transfer) often or only rarely.  Does it occur in some humans???
     The gene protects against this toxin by producing a resistant form of
RNA polymerase II.  Therefore, I have a feeling that the amanitin
cyclopeptide is probably only poisonous because it is NOT readily digested.
Although it is possible certain types of gut flora might be able to digest
it and protect the host animal, I haven't found any evidence yet that would
point in that direction.
     I think it would be very exciting if there turned out to be such a
resistance gene found only in Glires (and apparently at least sporadically
in some groups of artiodactyls and invertebrates).  But that is perhaps
being too optimistic, and such mutant genes might turn out to be more common
that we think.
     Could some humans have such a gene that makes them resistant to death
cap toxin, somewhat in a similar to the way sickle-cell genes protect
against malaria?  These are all interesting questions, but does anyone out
there know the answers?
                     Cheers, Ken Kinman
********************************************************
>From: "B. J. Tindall" <bti at DSMZ.DE>
>Reply-To: "B. J. Tindall" <bti at DSMZ.DE>
>To: TAXACOM at USOBI.ORG
>Subject: Re: death cap & Gliriform mammals
>Date: Fri, 7 Apr 2000 16:05:31 +0200
>
>Dave Jefferies wrote:
>
> >However far more interesting is this:
> >Is the molecule fragmented by secretions from the human stomach or is it
>split by the action of the gut flora? When we start to look at the human
>being
>as an ecosystem (I remember from one microbiology lecture that there are
>ten
>times as many non-human cells on a human body as there are human cells
>within it) life gets interesting.
> >
> >Should we look at an organism, or more importantly groups of organisms at
>both the species and at higher levels, as supplying the necessary
>conditions for
> >other organisms, that are themselves closely (or should that be
>functionally)
> >related? The ability of organisms to function is at least moderated by
>their
> >symbionts (using the word in the broad sense). How this affects a
>taxonomic view
> >I will leave to others.
> >
> >Dave Jefferies
> >
>You hit the mail on the head. You really move into other dimensions when
>you no longer consider that an animal or plant is part of an ecosystem, but
>is an ecosystem in itself for bacteria, fungi, protozoa etc. The breakdown
>of cellulose in ruminants, for example is carried out not by the animal,
>but by its microflora. Then there are cases when the symbionts of certain
>insects seem to influence the sex life of the host. Instead of
>investigating the biodiversity of tropical rain forsets one could also do
>the "biodiversity of the cow".
>Best wishes
>Brian
>
>
>
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