Chickpea: Role and responses under abiotic and biotic stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 72

(Gupta et al., 2002a,b). These PCs are part of the detoxi-
fying mechanism for heavy metals in higher plants
(Mehra & Tripathi, 2000; Cobbett & Goldsbrough,
2002). PCs are low-molecular-weight peptides chemi-
cally related to glutathione (GSH) that make complexes
with metals and metalloids and sequester them into vac-
uoles and thus detoxify the cell (Grill et al., 2006); hPCs
contain homoglutathione instead of GSH, having the
N-terminal β-alanine (Grill et al., 2006). Manifestation
of such metal-binding peptides in plants could be an
important biochemical indicator of heavy metal con-
tamination under various environments (Gupta et al.,
2002a,b), even if their changes in response to various
metal ions have not been fully examined. Several
reports have revealed that arsenic induces the synthesis
of PCs as well as hPCs (Gupta et al., 2004; Tripathi et al.,
2007), and complexes of arsenic with PCs and GSH have
also been demonstrated in various plants (Raab et al.,
2004, 2005).

under dehydration. Mass spectrometry analysis
allowed the identification of 147 differentially expressed
proteins, presumably involved in a variety of functions
including gene transcription and replication, molecular
chaperones, cell signalling and chromatin remodelling.
The dehydration-responsive nuclear proteome of
chickpea revealed a coordinated response, which
involves both regulatory and functional proteins
(Reddy et al., 2012).

4.6.2 transcriptomics
Transcriptomes are defined as the set of all the
messenger RNAs (mRNAs) in a cell/tissue/organism,
and investigation of populations of mRNAs is thus
called 'transcriptomics'. Genome-wide expression pro-
filing is a useful tool for studying genes involved in
various biological phenomena, identifying the candi-
date genes, and revealing the molecular cross-talk of
gene regulatory networks among abiotic stress responses
(Reddy et al., 2012).
Transcriptional profiling in chickpea under drought,
cold and high salinity was undertaken using cDNA
microarray analysis to look at the gene expression in the
leaf, root and/or flower tissues in tolerant and suscep-
tible genotypes (Mantri et al., 2007). The transcripts
differentially expressed in response to each particular
stress were analysed and a transcriptional change of
over two-fold was pronounced for 109, 210 and 386
genes after drought, cold and high-salinity treatments,
respectively. Among these, 2, 15 and 30 genes were dif-
ferentially expressed between tolerant and susceptible
genotypes studied for drought, cold and high salinity,
respectively. The differentially expressed genes coded
for various functional and regulatory proteins, high-
lighting the multiple gene control and complexity of
abiotic stress response mechanisms in chickpea (Reddy
et al., 2012).

4.6 Chickpea and abiotic stress:
the 'omics' approach

The 'omics' include proteomics, transcriptomics, geno-
mics and transgenomics. Recent advances in these areas
have contributed greatly to a better understanding of
the molecular and genetic bases of stress responses,
which has been an important bottleneck for molecular
and transgenic breeding (Reddy et al., 2012). Here we
summarize significant progress in chickpea research
regarding abiotic stress tolerance.

4.6.1 proteomics
Proteomics is the systematic analysis of the proteins
expressed by the genome. It not only describes entire
proteomes at the cell, organ or tissue level (Porubleva
et al., 2001) but also compares proteomes under differ-
ent stressful environmental factors (Ahsan et al., 2007).
Comparative proteomics analysis in JG-62, a
drought-tolerant variety of chickpea, resulted in the
identification of 134 differentially expressed proteins
that include predicted and novel dehydration-respon-
sive proteins (Bhushan et al., 2007). Another study
provided insights into the complex metabolic network
operating in the nucleus during dehydration in the
chickpea (Pandey et al., 2008). Approximately 205
protein spots were found to be differentially regulated

4.6.3 Genomics
The use of genetic and genomic analysis to assist in
identifying DNA regions tightly linked to agronomic
traits in crops, the so-called 'molecular markers, can
assist breeding strategies for crop enhancement.
Genomics includes the development of molecular
markers for genetic diversity analysis and it provides
novel opportunities to manipulate quantitative trait loci
(QTL) via marker-assisted selection (MAS) to develop
improved cultivars (Reddy et al., 2012).