Geoscience Reference
In-Depth Information
promoters:
precise tools for
controlling gene
expression in
environmental
stress
Gene expression changes during environmental stresses are
complex phenomena. Promoters are a very powerful tool in
genetic engineering and biotechnological applications because
the expression of genes operably linked to them can be regu-
lated to function at certain stages of development or a particular
cell/tissue or an external/internal stimulus under defined condi-
tions. Promoters regulate and fine tune the expression levels
and patterns of transgenic genes. The transgene plays a signifi-
cant role in determining the phenotypes of transgenic plants.
Promoters can be categorised into different categories such as
constitutive promoters (active constantly in most or all tissues/
parts), tissue-specific promoters (controlling gene expression in
a tissue-dependent manner), development-stage-specific pro-
moters (controlling gene expression at certain stages of devel-
opment), inducible promoters (regulated by the application of
an external chemical or physical signal), synthetic promoters
(
cis
-regulatory sequence of DNA that can be used to specifi-
cally control gene activity in any cell or tissue type of interest)
and bidirectional promoters (two genes that are transcribed in
opposite directions) (Peremarti et al., 2010).
In the perspective of environmental stress, necessities to
re-engineer the promoters that are induced in response to a
specific condition or change in the environment are predomi-
nantly valuable. These types of promoters are triggered by one
or more stimuli such as hormones (e.g. GA, ABA, JA, SA and
auxin), chemicals, environmental conditions (dehydration, heat,
water, salt, wounding etc.) and biotic stress (microbes, insects
and nematodes). Such promoters not only reduce the genetic
load to the plant but are also safe to environments. Table 13.1
provides different types of inducible promoters that have been
used to enhance the gene expression of plant transgenes during
varied stresses.
Differences in the expression patterns of genes during
stress are a result of the diverse architecture of the promoters
(Srivastava et al., 2014). Induction of the promoters is regulated
by transcription factors, activators and suppressors that bind to
cis
-regulatory elements present in the promoter regions (Priest
et al., 2009). Many such kinds of
cis
-regulatory elements have
been studied in response to the environmental signal. Even
with the differences in promoter architecture, functional dis-
section of the promoter regions has started to reveal the com-
mon
cis
-acting elements and has provided us with the tools to
identify distinct DNA-binding proteins required to modulate
transcription. A number of web-based and bioinformatic tools
have been developed to identify the potential plant
cis
-elements
