Biology Reference
In-Depth Information
plant species. For example, prolamins exist only in the herbaceous
plant species and cereals as the major storage proteins, whereas only
fractions of albumin, globulin, and glutelin are found in sugarbeet [
4
].
Eighteen years after the Osborne work, in 1994, Marc R.
Wilkins coined the term proteome [
5
,
6
]; this being the beginning
of a paradigm shift in the protein studies from protein chemistry/
biochemistry to proteomics. This change was possible thanks to
the progress in genome sequencing projects, the applicability of
mass spectrometry to the analysis of peptide and proteins, and the
development of bioinformatic tools for protein identifi cation and
data analysis. The potential of proteomics in plant biology research
is extensively validated with the number of original papers and revi-
sions, some of them dealing with plant seeds, devoted to different
purposes: descriptive studies, cataloguing of genotypes, phyloge-
netic studies, seed germination, development, and responses
against biotic and abiotic stresses [
7
-
12
]. The full potential of pro-
teomics, however, is far from being fully exploited in biological
research, due to the inherent diffi culty of research with proteins,
together with techniques and equipment limitations. We should
highlight that the number of protein species is much higher than
the number of genes, they are quite different physicochemically
from each other, its dynamic range is of up nine orders of magni-
tude, and there is no possibility of being amplifi ed, as it occurs with
DNA. For all the above reasons, it is impossible to capture in just
one experiment all or most of the total set of protein species that
constitute the cell's proteome. Thus, according to our results, and
considering that they depend on the experimental system carried
out (plant, yeast, fungi, or bacteria), the best protein extraction
protocol yielded less than 20 % of the total amount of proteins as
determined by the Kjeldahl method [
13
]. For this reason, the pro-
teome characterization and the protein species cataloguing require
the use of fi rstly fractionation techniques at the cellular, subcellu-
lar, protein or peptide level; and secondly, the use of complemen-
tary approaches.
We have optimized for Holm oak seeds an experimental work-
fl ow in which the Osborne sequential protein extraction is com-
bined with downstream electrophoretic separation or shotgun MS
analysis. Up to now, most analyses of plant seed proteomic have
been based on a total protein extract, and also with some examples
of a similar strategy [
4
,
14
-
17
].
In our current project on
Quercus ilex
subsp.
ballota
, we aim to
obtain a full description of the seed proteome, in order to: (1)
search for proteins of practical interest (i.e., enzymes); (2) identify
possible allergens; (3) characterize the acorn nutritional quality;
(4) catalog populations; and (5) carry out studies of seed germina-
tion and responses to stresses. The optimized workfl ow is schema-
tized in Fig.
1
.
