Omics approaches and abiotic stress tolerance in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 224

Marker-assisted selection has been deployed at
ICRISAT in order to introgress the QTL alleles in
chickpea that are associated with large root size (Saxena
et al., 2002). Drought has a dire effect on the yield of the
crop, hence this approach could facilitate the
development of a crop line having a deep root system,
thus having a positive impact on the yield.

a major role in the strigolactone pathway ( CCD7 and
CCD8 ) were notably increased when treated with ABA.
This provides further proof that ABA is somehow
involved in the regulation of strigolactone metabolism.
Hence it was deduced that all the carotenoid oxygenase
genes present in soybean are involved in its abiotic stress
physiology, and ABA is presumably a core regulatory
substance. These results have further provided insights
into the mechanism involved in the regulation of abiotic
stress response and tolerance in soybean.

13.6.2 soybean
In a study conducted by Li et al. (2005), the isolation of
the DREB homologue genes, GmDREBa, GmDREBb and
GmDREBc , from soybean was carried out. The protein
deduced from each of the genes was found to contain
an AP2 domain consisting of 64 amino acids. It was
revealed by yeast one-hybrid assay that all three of the
dehydration-responsive element binding proteins bind
specifically to the dehydration-responsive element.
Upon analysing these proteins with respect to their
transcriptional activation abilities, it was shown that
GmDREBa and GmDREBb could lead to the activation
of a reporter gene, whereas GmDREBc was unable to do
so. Salt, cold and drought stresses induced the transcrip-
tion of GmDREBa and GmDREBb in the leaves of soybean
seedlings. There was no significant change in the tran-
scription of GmDREBc in leaves but its transcription in
roots was probably induced by drought, salt and abscisic
acid treatment. In the light of these results, it can be
suggested that these three genes participate in the
response of soybean to abiotic stress.
In another study, the genes for carotenoid oxygenase
in soybean were identified to assess their phylogenetic
relationships as well as their transcriptional response
to four abiotic stresses: NaCl, PEG, and high and low
temperature (Wang et al., 2013). Their response to
abscisic acid (ABA) treatment was also studied. All these
responses were investigated to characterize the poten-
tial role they could play in a plant's resistance against
these stresses. An adaptive evolution was indicated
in the clades studied as the branches favoured the
selection of NCED (9- cis -epoxycarotenoid oxygenase),
carotenoid cleavage dioxygenase ( CCD1 ) and CCD8 .
Eight genes for carotenoid oxygenase were identified
in soybean. On assessment with qPCR, almost all of
these genes showed significant alteration under ABA
treatment and stress. The most notable changes were
noticed in CCD1 and CCD4. These genes are also known
for the key role they play in norisoprenoid metabolism.
Moreover, the transcription levels of two genes that play

13.7 transgenomics

One of the most famous techniques employed in life
sciences and medicine to develop novel phenotypes
with beneficial characteristics is transgenomics. Novel
phenotypes are generated using numerous genetic engi-
neering techniques, which confer changes in the genetic
code of the target organism, i.e. the transgenic organism
(Correa et al., 2012; Tzfira et al., 2012). Non-native or
foreign DNA that codes for a novel trait or an agricul-
turally relevant characteristic, from various sources
including plants, animals, bacteria and viruses, is trans-
ferred into the target organism's germ line. In case of
legumes and other plants, the transgenes are capable of
increasing the levels of certain proteins and osmolytes,
namely osmoprotectants (Tarczynski et al., 1993), late
embryogenesis proteins (Xu et al., 1996), detoxification
enzymes, etc., that enable defence and amplify toler-
ance against abiotic stresses. Two of the most efficient
methods employed for the purpose of successfully trans-
forming crops include the Agrobacterium -mediated gene
transfer and particle bombardment technique (Pratap
et al., 2010).

13.7.1 soybean
Being an important crop throughout the world, the
soybean plant has been the focus for countless researches
in recent times (Agarwal et al., 2013; Pinto et al., 2013;
Wu et al., 2013). Genetic engineering techniques such as
Agrobacterium -mediated gene transfer, electric discharge
particle acceleration, electroporation, etc. have been
used widely to generate transgenic fertile soybean plants
since the first successful attempt (Hinchee et al., 1988).
For instance, the AtMYB44 gene stimulates the abscisic
acid signalling pathway, which in turn triggers stomatal
closure and culminates in drought tolerance as well as