Biology Reference
In-Depth Information
6
The Debate Continues
Proteome investigations in plants are a step behind animal pro-
teomes and since very sophisticated technologies developed for ani-
mals are readily available one should see in the near future a rapid
progress in this domain. The identifi cation of proteins in plants still
suffers from the unavailability of genome sequences even if it is pos-
sible to work by analogy with other plants. One of the most investi-
gated plants is Arabidopsis thaliana for which the genome sequence
revealed the presence of about 30,000 genes. In spite of this very
large number only a modest number of unique proteins are detected
[ 44 ] for reasons explained earlier in this chapter. At this point in time
it is largely possible to detect many more proteins after treatment
with CPLL, as this can easily be evidenced by 2D electrophoresis,
but the formal identifi cation is the major technical diffi culty. With
more plant genomes sequenced this situation is likely to be improved
in the next coming years. The presence of very few proteins present
in massive amount among others that are very numerous and of low
abundance makes plant protein extracts particularly suitable for
CPLL treatments. Detecting differences in protein expression may
not have a big interest in plant diagnostic, but it can be an elegant
way to detect frauds or even genetically modifi ed vegetables through
the differential expression of low-abundance proteins.
Diffi culties of plant protein extraction may need to devise spe-
cifi c procedure and components that are or are not compatible
with CPLL. If so modifi ed, CPLL could be used accordingly. On
another level, specialized CPLL could also be designed in order to
meet plant protein requirements. These specialized beads could
also be designed in order to be specifi c only for categories of pro-
teins or even modifi ed to avoid nonspecifi c binding for undesired
materials. If such developments will be made they would largely
simplify the treatment of crude extracts, which would not need any
preliminary treatment prior to fractionation.
On this note, we add here a fi nal paragraph describing recent
progress in the fi eld. We felt that extra efforts were sorely needed to
study recalcitrant tissues and in general any plant proteome. This
extra effort has materialized in more than one extraction protocol,
i.e., under native and denaturing conditions, in both cases followed
by capture with CPLLs of the extracted proteins. This novel strategy
has been applied recently in the case of two recalcitrant fruit tissues,
namely, avocado and banana [ 45 , 46 ]. In both cases about 1 % total
protein is embedded either in solid oil (avocado) or in huge amounts
of polysaccharides (banana). In order to improve discovery of low-
abundance species, in parallel with the standard, native condition
extraction, a denaturing solubilization protocol has been imple-
mented, based on 3 % boiling SDS, an anathema in CPLL treat-
ments, since it would completely inhibit the capture. Yet, there are
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