Omics approaches and abiotic stress tolerance in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 220

first being the identification of the proteome profile of
a given cell, tissue, organ, organism or population, and
the second being differential proteomics in which the
proteome of an organism under study conditions is
compared with that of the organism under control con-
ditions. Since the proteome mirrors the actual state or
response of a cell, it is the bridge between the transcrip-
tome and the metabolome. The proteins expressed are
key players in the biochemical processes, which implies
that they must be closer to the phenotypic expression
than DNA markers. The responses of plants to stress
have mostly been studied at the DNA and RNA levels,
and though this has provided great insights to improve
the understanding of stress tolerance, the proteomics
approach can paint a picture to evaluate the response.
The mRNA levels are not always reflective of the protein
expression because many proteins undergo post-transla-
tional modifications like glycosylation, phosphorylation
and ubiquitinylation, which have major influences on
protein function (Jorrin et al., 2006). The ability of a
plant to cope with a variety of abiotic stresses therefore
greatly depends on the fluctuation in the number of pro-
teins, which are either upregulated or downregulated
due to alterations in gene expression. These proteins are
either key players in signal transduction pathways or
help in the plant's adaptation processes, like stress repair
mechanisms. They thus help the plant to recover from
the stress and aid in its survival (Hakeem et al., 2012).
Two laboratory techniques are widely used for pro-
teomics studies: protein electrophoresis and mass
spectrometry. Differential proteomics has been exten-
sively applied study the responses of legumes to several
abiotic stresses.

cell defence and cell rescue, actively participate in the
molecular mechanisms responsible for tolerance to dehy-
dration in chickpea plants.
In another study, Pandey et al. (2008) observed the
changes in the nuclear proteome profile in 3-week-old
chickpea seedlings. These seedlings were progressively
dehydrated by withdrawing water and the changes in the
nuclear proteome were examined by two-dimensional
gel electrophoresis. The number of differentially regulated
proteins was approximately 205, and mass spectrometry
analysis identified 147 differentially expressed proteins.
These proteins are presumably involved in various cellular
functions including gene transcription, DNA replication,
cell signalling pathways and chromatin remodelling as
well as acting as molecular chaperones. The chickpea
nuclear proteome, as a result of the dehydration exposure,
revealed a coordinated response, involving both func-
tional and regulatory proteins. Hence this study provided
an insight into the complexity of the metabolic network
that operates in the nucleus during dehydration.

13.4.2 soybean
Swigonska and Weidner (2013) studied the effects of abi-
otic stress on the germination of soybean seeds.
Germination in soybean greatly depends on environ-
mental factors like temperature and water availability.
This also makes them highly sensitive to fluctuating or
harsh environmental conditions; prolonged exposure to
such abiotic stresses can not only greatly diminish the
crop yield but also cause poor or delayed germination.
Proteomics analysis was employed in this study to
observe the effects of osmotic and cold stress on the
germinated soybean seeds' roots. The seeds were germi-
nated under one of three continuous conditions: osmotic
stress (+25 °C/−0.2 MPa), cold stress (+10 °C/H 2 O), and a
combination of cold and osmotic stress (+10 °C/−0.2 MPa).
The proteome map that was constructed for the control
samples and stress-treated samples showed 1272 spots.
In total, 59 proteins were present in stress-treated sam-
ples as well as in the control samples, and when divided
into functional categories, the following breakdown was
achieved: nine in plant defence, 10 in various metabolic
pathways of carbohydrates and eight in storage.
Furthermore, quite a few proteins were also involved in
electron transport, protein synthesis, signal transduction,
secondary metabolism, embryogenesis, development,
cellular transport, cellular translocation and storage.
Upon analysis of the differences in the expression

13.4.1 Chickpea
A proteomics approach was used in a study to identify
the dehydration-responsive proteins in the extracellular
matrix (ECM) proteins of chickpea (Bhushan et al.,
2007). The dehydration tolerance of several commercial
chickpea varieties was screened using various biochemical
and physiological indexes. The temporal changes of ECM
proteins after dehydration in JG-62, a tolerant chickpea
variety, showed 186 proteins with a variance at a 95%
significance level. Upon comparative proteomics anal-
ysis, 134 differentially expressed proteins were identified.
It was demonstrated in this study that more than 100
ECM proteins, which are also involved in processes like
cell wall modification, metabolism, signal transduction,