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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