either the endogenous imprecise Nonhomologous End-Joining (NHEJ) or the highfidelity Homology-Directed Repair (HDR) pathways. NHEJ can induce small
insertions or deletions at the repair junction while HDR stimulates precise sequence
alterations, including programmed sequence correction as well as DNA fragment
insertion, when a DNA repair template is exogenously supplied. The system has
been successfully tested in staple crops, such as maize, wheat, rice, and soybean (Cai
et al. 2015; Du et al. 2016; Sun et al. 2016; Svitashev et al. 2015; Wang et al. 2014;
Zhou et al. 2014a, 2015c).
The recent availability of genome editing tools provides ample opportunity to
introduce targeted modifications in the genome efficiently to study the functional
aspects of various components of the genome in diverse plants and offers potential
avenues for production of drought-tolerant soybeans. Genome editing tools provide
a method for introducing targeted mutation, insertion/deletion (indel), and precise
sequence modification using customized nucleases in a wide variety of organisms.
CRISPR-Cas9 mediated genome engineering can enable manipulation of nearly any
sequence in the genome. Abiotic stress is a complex trait, which is governed by
multiple genes. There is a substantial interaction between components of several
signaling, regulatory and metabolic pathways, which lead to abiotic stress response/
adaptation (Nakashima et al. 2009; Garg et al. 2014; Mickelbart et al. 2015). Further,
plants have undergone whole genome duplication events and a large fraction of
genes are represented by multi-gene families with functional redundancy. Many
times knock-out of a single gene may not produce desired phenotype, thus making it
difficult to reveal its function. Due to ease of design and high efficiency of sgRNAs,
multiple genes can be targeted simultaneously using CRISPR-Cas9 system, which
can overcome the problem posed by functional redundancy of genes. Multiplex
genome editing has been successfully implemented in model and crop plants
(Li et al. 2013a; Mao et al. 2013; Zhou et al. 2014a). Such approaches can allow
deciphering the role of multiple and functionally redundant genes involved in the
same biological process such as drought stress response. Another approach could be
the pyramiding/stacking of multiple genes involved in a stress response pathway or
regulatory network via HDR-mediated gene targeting. The genes involved in
drought stress-related gene regulatory network, signal transduction, and metabolite
production may be targeted via CRISPR-Cas9 technologies for production of
drought tolerant soybeans.
4.9.4 Rhizobial Inoculation to Enhance The Drought Stress
Tolerance in Soybean
Symbiotic association between legume plants and N2 fixing microbes like rhizobium
has always been one of the fascinating areas for the researchers across the world
since decades. Soybean, a legume plant makes the symbiotic association with soil
bacterium, Rhizobium species by which plant can harness the benefit of biologically
fixed nitrogen which helps the host plant for achieving growth and development. In
return, rhizobia species get food and shelter inside the root nodules of a legume
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G. K. Satpute et al.
insertions or deletions at the repair junction while HDR stimulates precise sequence
alterations, including programmed sequence correction as well as DNA fragment
insertion, when a DNA repair template is exogenously supplied. The system has
been successfully tested in staple crops, such as maize, wheat, rice, and soybean (Cai
et al. 2015; Du et al. 2016; Sun et al. 2016; Svitashev et al. 2015; Wang et al. 2014;
Zhou et al. 2014a, 2015c).
The recent availability of genome editing tools provides ample opportunity to
introduce targeted modifications in the genome efficiently to study the functional
aspects of various components of the genome in diverse plants and offers potential
avenues for production of drought-tolerant soybeans. Genome editing tools provide
a method for introducing targeted mutation, insertion/deletion (indel), and precise
sequence modification using customized nucleases in a wide variety of organisms.
CRISPR-Cas9 mediated genome engineering can enable manipulation of nearly any
sequence in the genome. Abiotic stress is a complex trait, which is governed by
multiple genes. There is a substantial interaction between components of several
signaling, regulatory and metabolic pathways, which lead to abiotic stress response/
adaptation (Nakashima et al. 2009; Garg et al. 2014; Mickelbart et al. 2015). Further,
plants have undergone whole genome duplication events and a large fraction of
genes are represented by multi-gene families with functional redundancy. Many
times knock-out of a single gene may not produce desired phenotype, thus making it
difficult to reveal its function. Due to ease of design and high efficiency of sgRNAs,
multiple genes can be targeted simultaneously using CRISPR-Cas9 system, which
can overcome the problem posed by functional redundancy of genes. Multiplex
genome editing has been successfully implemented in model and crop plants
(Li et al. 2013a; Mao et al. 2013; Zhou et al. 2014a). Such approaches can allow
deciphering the role of multiple and functionally redundant genes involved in the
same biological process such as drought stress response. Another approach could be
the pyramiding/stacking of multiple genes involved in a stress response pathway or
regulatory network via HDR-mediated gene targeting. The genes involved in
drought stress-related gene regulatory network, signal transduction, and metabolite
production may be targeted via CRISPR-Cas9 technologies for production of
drought tolerant soybeans.
4.9.4 Rhizobial Inoculation to Enhance The Drought Stress
Tolerance in Soybean
Symbiotic association between legume plants and N2 fixing microbes like rhizobium
has always been one of the fascinating areas for the researchers across the world
since decades. Soybean, a legume plant makes the symbiotic association with soil
bacterium, Rhizobium species by which plant can harness the benefit of biologically
fixed nitrogen which helps the host plant for achieving growth and development. In
return, rhizobia species get food and shelter inside the root nodules of a legume
112
G. K. Satpute et al.