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present only in root hairs, while CDPK:calmodulin-like domain
protein kinase isoenzyme
, phosphoenolpyruvate carboxylase, and
ascorbate peroxidase 2 appeared more abundant in root hairs than
in stripped roots. This work opened new avenues for further pro-
teomic study of the legume-
Rhizobium
symbiotic interactions.
Recently, Salavati et al. [
16
] have analyzed the early symbiotic
response in the roots of super-nodulating (En-b0-1) and non-
nodulating (En1282) varieties, and their parental normal-
nodulating variety (Enrei). The nanoLC MS/MS analysis identifi ed
56 proteins from 48 differentially expressed protein spots in
normal-nodulating soybean variety after bacterial inoculation.
Proteins involved in metabolism and energy production were
shown to be increased in super-nodulating and decreased in non-
nodulating varieties compared to normal-nodulating variety. The
super-nodulating and non-nodulating varieties responded oppo-
sitely to bacterial inoculation. Seven proteins out of 11 were
decreased in super-nodulating varieties, while expression of protea-
some subunit alpha type 6, gamma glutamyl hydrolase, glucan
endo-1,3-beta glucosidase, and nodulin 35 were increased in
En-b0-1 compared to non-nodulating En1282. Results suggest
that suppression of the autoregulatory mechanism in the super-
nodulating soybean variety might be due to negative regulation of
defense and signal transduction related processes.
β
4
Subcellular Proteomics of Soybean
Proteomic analysis of subcellular organelle provides fundamental
information about the plants response to a given stress at the func-
tional level and thus refi nes our knowledge about plant stress
related signaling pathways. We have recently reviewed plant cell
organelle proteomics in response to abiotic stress [
38
]. In this sec-
tion, signifi cant contributions of only soybean proteomic works
related to abiotic stress responses are summarized.
In plants, cell wall is the fi rst compartment that responds to envi-
ronmental stress. Signals are then transmitted to the cell interior to
trigger the plants defense cascade. Change in cell wall proteome in
response to fl ooding stress was investigated in detail in soybean cul-
tivar Enrei [
39
]. The CaCl
2
-extracted cell wall proteins were iso-
lated via sucrose gradient centrifugation and analyzed using
gel-based proteomic techniques. All together 16 protein spots out
of 204 showed changes in abundance under fl ooding stress. Of the
identifi ed proteins, methionine synthases and copper amine oxidase
were found to be increased. Interestingly, proteins related to ligni-
fi cation, such as lipoxygenases, germin-like protein precursors, stem
31 kDa glycoprotein precursors, Cu-Zn-superoxide dismutase, and
copper amine oxidase were decreased by fl ooding. Furthermore,
4.1 Cell Wall
Proteomics
