From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Thu Jul 25 2002 - 04:37:41 MDT
On Wed, 24 Jul 2002, Rafal Smigrodzki wrote:
> Robert's suggestion to increase the copy number of the genes involved
> in beta-carotene synthesis is a quick-and-dirty method, but it does
> have a chance of success. The only way of finding out is not armchair
> genetics but experimentation.
What one actually needs to know is where the rate limiting steps
are in the process. If one of the enzymes in the middle of the
synthesis chain is saturated, then my suggestion is reasonable.
If the downstream storage capacity for BC is saturated and it
is backing up the whole synthesis chain (as I think Harvey may
be suggesting), then he is correct that one needs to engineer
better storage facilities for BC that don't cause the synthesis
chain to slow down. If its an upstream problem of lack of BC
precursors, then one needs to add either "better" genes for
precursor synthesis or more of them. Since, to the best of
my knowledge, BC is entirely CHO (no N) and the starch in
rice grains is also CHO, there shouldn't be any raw material
problems turning the entire rice grain into BC (perhaps disolved
in a lipid carrier) with little or no starch at all.
One simply needs to engineer in the proper enzymes and their
abundance to do the proper conversions. Not an simple problem
mind you, but one that we should be able to resolve.
Robert
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