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Arabidopsis as a model

Rod Savidge savidge at unb.ca
Fri Nov 17 09:23:44 EST 1995

Dear Jose,
Sorry, but I've switched computers since the discussion and didn't save
those comments to my hard drive.  Fortunately, I did save the info received
as hard copies, so can give you some advice.

The primary justifications given for using Arabidopsis
thaliana as a model plant were that it grows quickly, has a rapid life
cycle, has a small genome (5 chromosome pairs, can be easily transformed
(e.g., by vacuum infiltration) or mutagenized, can be rapidly screened for
varied phenotypes, and requires little space (2000 seeds can be
screened on a 15 cm plate).  Somewhat cynically, I might paraphrase the
above to say that At enables `quick and dirty research'.

There seemed to be a consensus among those participating in the discussion
that At will be useful in answering questions about primary metabolism in
plants.  As one At researcher (Elliot Meyerowitz) put it to me:
"Arabidopsis is only intended as a model for those processes that are not
different between it and crops (or other plants)."   There certainly was
disagreement concerning its value in understanding developmental problems
related to crop productivity, some feeling that it will be helpful (at
least for the Brassicas) and others of the opinion that the At research
community is misguided.  Someone made the comment that a green alga would
probably be as useful as At in coming to grips with questions about primary
metabolism, a reasonable viewpoint I believe.

My personal perspective (I am not a geneticist or molecular biologist,
rather a physiologist) presently is that At is a highly evolved,
morphologically reduced dicot.  I interpret the small number of chromosomes
together with the smallness of the vegetative structure as evidence that At
has shed excess genetic baggage and become focussed on rapidly
and efficiently alternating between gametophytic and sphorophytic
generations.  In line with it having discarded or never acquired genes
which distract from the aim of self preservation, the At genome may well
harbour a complex set of genetic mechanisms - checks and balances - which
actively prevent it from functioning even in its primary metabolism in ways
identical to crop plants (which, of course, is not to say that At will
not have genes of primary metabolism homologous with those in crop
plants).  For example, the small size of At conceivably could be explained
in terms of metabolic inhibitors constantly checking metabolism.  Perhaps I
am overly skeptical, but I remain to be convinced that At is an appropriate
choice of a model system for even understanding primary metabolism in
higher plants.  

I hope this response helps.  As the original forum was on the Arabidopsis
listserver, I feel obligated to share your query and my response with the
members of that list.

Rod Savidge

In message Fri, 17 Nov 95 10:42:57 GMT,
  jose.feijo at bio.fc.ul.pt (Jose A. Feijo)  writes:

> Dear Rod:
> Some months ago you have leaded a discussion about Arabidopsis as a model,
> from which unfortunately I only caught your last resuming msg.
> I'm the professor of Plant Diferentiation and Morphogenesis at the
> University of Lisbon (Portugal), and I usually devote one lecture to model
> systems, and why they are chosen. Your discussion is of course highly
> interesting, and I was wondering if you kept the original msg's of the
> discussion. Many I wasn't able to download them.
> Thanks for your cooperation
> Jose
> ___________________________________________________________
> Jose A. Feijo, MS, Dr.Biol.
> Professor Auxiliar
> Dept. Biologia Vegetal, Fac. Ciencias Lisboa
> Ed. C2, Campo Grande, P-1700 LISBOA, PORTUGAL
> t. + 351.1.7500069  fax + 351.1.7500048
> e.mail  Jose.Feijo at bio.fc.ul.pt
> URL: http://www.fc.ul.pt/departs/biologia_vegetal/ejf.html
> ___________________________________________________________
   Rod Savidge, PhD, Professor      |         E-mail: savidge at unb.ca
   Faculty of Forestry and         \|/
      Environmental Management  \   |   /     Phone:  (506) 453-4919
   University of New Brunswick  _\/ | \/_
   Fredericton, NB CANADA          \|/        Fax:    (506) 453-3538
   E3B 6C2                          |

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