Legumes and breeding under abiotic stress: An overview - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 11

et al. (2001) reported 43 drought-responsive mRNA
transcripts differentially expressed in peanut under
water stress. Pnueli et al. (2002) applied suppression
subtractive hybridization screening (SSHS) in Retama
raetam, a C 3 drought-tolerant legume. The authors
revealed that dormancy, key to the survival of many
species in arid environments, was followed by
accumulation of transcripts encoding PR-10-like pro-
tein, a low-temperature-inducible dehydrin and a
WRKY transcription factor. Umezawa et al. (2002), by
using a modified c-DNA-AFLP technique in soybean,
revealed 140 differentially expressed cDNA fragments
by comparing control and iso-osmotic treated plants.
Some of the responsive genes encoded ion transporters,
transcription factors (TFs) and redox enzymes (Dita
et al., 2006). From the Arabidopsis database, Ishitani et al.
(2004) selected 100-200 genes, and revealed that at
least three DREB -like genes might be key transcriptional
regulators of drought and/or cold resistance in common
bean (Dita et al., 2006).

pressure on continued nodular SS activity during
drought stress (Arrese-Igor et al., 2011).
Proteome analysis of M. truncatula nodules provided
good evidence of drought stress affecting the enzyme Met
synthetase (Larrainzar et al., 2007). Depressed Met avail-
ability had a major effect on both protein synthesis and
sulphur metabolism in nodules (Arrese-Igor et al., 2011).
Aghaei et al. (2009) and Sobhanian et al. (2010) studied
the proteome of soybean under salt stress by using differ-
ent tissues. They identified a 50S ribosome protein that
was downregulated in leaves. Alam et al. (2010) studied
the proteome analysis of soybean root under water stress.
They indicated that two key enzymes involved in sugar
metabolism, UDP-glucose pyrophosphorylase and
2,3-biophosphoglycerate-independent phosphoglycerate
mutase, were downregulated under drought stress.
Cheng et al. (2010) reported 40 proteins (25 upregu-
lated and 15 downregulated) in soybean seeds exposed
to cold stress (4 °C). These proteins are involved in cell
growth/division, storage, cellular defences, energy pro-
tein synthesis, transcription and transport. Zhu et al.
(2006) reported that the activation of HSP70 in trans-
genic lines by its upstream gene HsfA1 improved soybean
tolerance under high temperature stress.

1.7.7 proteomics
A proteomics approach is used to investigate the path-
ways of biochemical activities and the different responses
of plants to stress (Aghaei & Komatsu, 2013). Plant stress
proteomics has the ability to identify possible candidate
genes that can be used for the genetic enhancement of
plants against stresses (Cushman & Bohnert, 2000;
Ngara, 2009; Rodziewicz et al., 2014).
In legumes, proteomic techniques have been applied
to cowpea, pea and lupin for identification of proteins
involved in responses to different abiotic stresses (Fecht-
Christoffers et al., 2003; Repetto et al., 2003; Kav et al.,
2004; Pinheiro et al., 2005; Cheng et al., 2010).
Proteomic analysis of M. truncatula under drought
stress reported that the decline in SS is one of the most
observable changes in plant function in root nodules
(Larrainzar et al., 2007). However, a plant system
approach including the proteome and metabolome
responses of M. truncatula nodules to drought revealed
that the decline in SS was not correlated with a decrease
in malate concentration (Larrainzar et al., 2009), in con-
trast to studies of nodules of grain legumes (González et
al., 2001; Gálvez et al., 2005). This relatively contrasting
behaviour of Medicago species to other legumes is
intriguing (Arrese-Igor et al., 2011). One theoretical
explanation is that in pasture legumes such as Medicago ,
grazing has produced a strong evolutionary selective

1.7.8 transgenomics
Transgenic technology is one of the many tools available
for modern plant improvement programmes (Jewell et
al., 2010). The use of transgenic approaches, or 'transge-
nomics', helps in understanding the mechanisms
governing stress tolerance, providing good ways for the
genetic enhancement of field crops, thereby alleviating
some of the major constraints to crop productivity in
developing countries (Sharma & Ortiz 2000; Reddy et
al., 2012). Transgenic plants or their germplasm can be
used as sources of new cultivars or as new sources of
variation in breeding programmes (Jewell et al., 2010).
When plants are subjected to abiotic stresses, a
number of genes are turned on causing increased levels
of several osmolytes and proteins that may be respon-
sible for conferring a certain degree of protection from
these stresses. Thus, it may be necessary to transfer sev-
eral potentially useful genes into the same plant in order
to obtain a high degree of tolerance to drought or salt
stress (Reddy et al., 2012).
There are several transgenic technologies for
improving stress tolerance involving the expression of
functional genes (Reddy et al., 2012), including those