Agriculture Reference
In-Depth Information
in chickpea. It has been reported that chickpea was able
to allocate more roots to the deeper soil layers under
conditions of stress than other legumes (Benjamin &
Nielsen, 2005), or than more sensitive genotypes
(Kashiwagi
et al.,
2006). However, this was so only
when the phenology of the genotype was well suited to
the test environment. For example, the chickpea geno-
types K1189 and ICC898 had adequate root length
density (RLD) compared to ICC4958 (Vadez
et al.,
2007).
It is assumed that pigeon pea is deep-rooted and that
confers drought tolerance because the crop is usually
grown on deep soils and completes its life cycle on
residual moisture (Vadez
et al.,
2007).
was in
Arabidopsis thaliana
(Park
et al.,
2002; Reinhart &
Bartel, 2002). Since then they have been isolated from
a wide range of species via genetic screening (Lee
et al.,
1993; Wightman
et al.,
1993), direct cloning after isola-
tion of small RNAs (Fu
et al.,
2005; Lu
et al.,
2005) and
computational prediction strategies (Wang
et al.,
2005;
Jones-Rhoades
et al.,
2006).
Mantri
et al.
(2013) in their review reported that miR-
NAs play an important role in drought tolerance. These
include conserved miRNAs such as miR164, miR169,
miR171, miR396, miR398, miR399, miR408 and
miR2118 (Liu
et al.,
2008). Their expression patterns
vary with legumes species. For example, miR169 was
downregulated in
M. truncatula
(Trindade
et al.,
2010)
but upregulated in common bean (in response to
abscisic acid treatment) (Zhao
et al.,
2009). In
M. trun-
catula
, miR398a,b and miR408 were strongly
upregulated in shoots and roots under drought stress
(Trindade
et al.,
2010). The miR398 and miR408 repress
the
COX5b
,
CSD1
and plantacyanin genes (Trindade
et al.,
2010). Under drought and ABA treatments,
Arenas-Huertero
et al.
(2009) identified a number of
novel legume miRNAs in
Phaseolus vulgaris
. Among
them pvu-miRS1, pvu miR1514a, miR159.2, pvu-
miR2118 and pvu-miR2119 accumulated upon drought
and ABA treatments. Novel miRNAs may target
regulatory elements for cellular processes that may be
unique to legumes (Arenas-Huertero
et al.,
2009). Forty-
four drought-associated miRNAs (30 were upregulated
in drought conditions and 14 were downregulated)
were identified in cowpea under drought stress (Barrera-
Figueroa
et al.,
2011). Wang
et al.
(2011) in their study
on
M. truncatula
subjected to drought stress, identified
22 members of four miRNA families that were upregu-
lated and 10 members of six miRNA families that were
downregulated. Among the 29 new miRNAs/new mem-
bers of known miRNA families, eight miRNAs were
responsive to drought stress of which four each were
upregulated and downregulated. The drought-respon-
sive miRNAs were found to be involved in diverse
cellular processes including development, transcription,
protein degradation, detoxification, nutrient status and
cross-adaptation (Mantri
et al.,
2013).
Mantri
et al.
(2013) in their review reported that
legumes express a variety of miRNAs in response to salt
stress. In cowpea under salinity stress, Paul
et al.
(2011)
identified 18 conserved miRNAs belonging to 16 miRNA
families. Fifteen miRNAs were predicted and identified
1.7 Biotechnology approaches
Plant biotechnology offers new ideas and techniques
applicable to agriculture. It uses the conceptual frame-
work and technical approaches of plant tissue culture
and molecular biology to develop commercial processes
and products (Sharma & Lavanya, 2002). These tech-
niques enable the selection of successful genotypes,
better isolation and cloning of favourable traits, and the
creation of transgenic crops of importance to agricul-
ture. This ability has moved agriculture from a
resource-based to a science-based industry (Sharma &
Ortiz, 2000; Sharma & Lavanya, 2002).
Legumes can face the threat posed by abiotic stress
through several genetic improvement strategies, from
classical breeding to more direct physiological genetic
approaches.
1.7.1 MicrorNas
MicroRNAs (miRNAs) play major roles in plant growth
and development (Jones-Rhoades
et al.,
2006;
Khraiwesh
et al.,
2012; Mantri
et al.,
2013) as well as in
regulating the synthesis of polypeptides from different
mRNAs including those that act as transcription factors
(Mantri
et al.,
2013). They help plants to thrive under
abiotic stresses such as drought, salinity and high/low
temperature by regulating the expression of thousands
of genes (Mantri
et al.,
2013).
Next Generation Sequencing (NGS) technology has
greatly accelerated the discovery and characterization of
miRNAs in a range of diverse plant species (Sunkar &
Jagadeeswaran, 2008; Zhao
et al.,
2010; Chen
et al.,
2011; Mantri
et al.,
2013). The first isolation for miRNAs
Search WWH ::
Custom Search