Biological and Clinical Sciences Research
Journal
Biol. Clin. Sci.
Res. J. Volume, 2020: e022
GENETIC
MODIFICATION FOR SALT AND DROUGHT TOLERANCE IN PLANTS THROUGH SODERF3
ALI M, RAFIQUE F,
*ALI Q, MALIK A
Institute of
Molecular Biology and Biotechnology, The University of
Lahore, Lahore, Pakistan
Corresponding
author email: saim1692@gmail.com
Abstract
Plants constitute the major part of the
ecosystem and maintain balance through their different roles in the stability
of the environment. As plants have an impact over environment; in the same
manner environment interacts with plants. These interactions bring some
productive results or sometimes may cause serious issues to plants. The environment
poses some serious threats to plants as it is changing drastically over the
course of years. Plants have been resistant to many of biotic and abiotic stresses naturally but now it is getting
challenging. The major issues faced by plants are drought, high salt
concentration, temperature and many other factors. These issues can be
compensated by engineering plants with such novel genes which cause the release
of ethylene responsive factor in the case of drought and salt intolerance. There
are various studies to engineer the stress sensitive plants with SodERF3, a novel sugarcane ethylene responsive factor
which causes promising tolerance in transgenic plants.
Keywords: salt, drought, SodERF3, sugarcane, genetic engineering,
transgenic plants
Introduction
There are countless problems
which are presented to plants, as if instance is taken, high salt
concentration, low temperature, flooding, dry spell, oxidative pressure, heat,
and considerable metal toxicity which ultimately impose stress to plants. Abiotic stress recurrently prompts impediment in plant
development. It has been evaluated that abiotic
stresses were the chief reason for diminishing the normal yield of significant
harvests by over half. To stand up to such natural hostilities, plants have
shown great potential of versatile reactions at physiological and sub-atomic
levels, which are triggered under such pressure conditions. Plants exhibit
various safeguard systems that have the capacity to maximize the resistance to
the unfavorable conditions caused by abiotic
stresses. A significant occasion noticed because of stress is the observation
and transduction of stress signals through flagging segments, which brings
about the initiation of various qualities that prove to be very effective in
stress conditions. The ability of possessing these qualities lead
to the release of plant hormones like ethylene and abscisic acid etc. (Quan et al., 2014). These hormones have the ability to start a
cycle of declining the stress that is being faced by them that ultimately
contribute to the overall reaction of plants towards stress. Ethylene end up being associated with plant pressure
reactions as a plant hormone which is vaporous, in spite of its jobs in natural
product maturing, germination, microbe reaction, senescence, organ abscission,
etc. A few reports proposed that
accretion of ethylene or its forerunner, the ACC
(aminocyclopropane-1-carboxylic corrosive) is incredibly prompted by abiotic stress boosts, for example, water pressure,
saltiness, and flooding (Borrαs-Hidalgo et al., 2004).
Plants
devote a large portion of their genome to genes that are involved in
transcription, as it can be illustrated by the Arabidopsis thaliana genome that
encodes about 1,500 transcription factors (TFs). Most of these TFs are grouped
in large families, some of which are unique to plants (Riechmann
et al. 2000). One group of
plant-specific transcription factors encompasses the so-called
ethylene-responsive factors (ERFs) that act at the last step of ethylene
signaling pathways, the first member of which was identified in tobacco. To
date, in different plant species ERFs have been found to be involved in growth,
development and regulation of metabolism, but also in the response to biotic
and abiotic stress. ERF proteins contain a very characteristic and
highly conserved plant-specific DNA-binding domain that consists mainly of
5859 amino acids structured as a three-stranded antiparallel
b-sheet and an a-helix in parallel to the b-sheet. Two similar cis-elements have been identified as binding sites in the
promoters of ERF controlled genes: the GCC box that is typically identified in
pathogenesis-related (PR) genes, and the C-repeat (CRT)/dehydration-responsive
element (DRE) motif in dehydration- and low-temperature-responsive genes. ERFs
belong to the large APETALA2 (AP2)/ERF TF super family that is unique to
plants. The AP2 domain group comprises 4150 ERF genes classified into two
subgroups A and B, each of which is further divided into six clusters based on
sequence conservation.
Preliminary analysis of the A and B subgroups
based on data from overexpression experiments and
transcriptional activation suggests that TFs belonging to subgroup A are involved in abiotic stress
responses, while those ones involved in disease resistance responses are found
in the B subgroup. Sugarcane (Saccharum officinarum L.) is a tropical grass that has been
cultivated for 44,000 years. In recent years, sugarcane cultivation occurs
worldwide in tropical and subtropical regions and contributes 460% of the world
sugar production. Importantly, sugarcane biomass is also increasingly used for
the production of bioethanol as an alternative to
petroleum-derived fuels. Despite its economic importance, sugarcane genetics is
still in its infancy, which is largely due to the poor availability of genetics
tools for Saccharum spp..
This may be explained by the complexity of the sugarcane genome, which exceeds
that of any other crop plant. Although a large amount of DNA sequence
information for sugarcane was released into the public domain as expressed
sequence tags (ESTs) derived from cDNA libraries, few
genes that govern biotic or abiotic stress responses
have been molecularly characterized from this crop to date. It is well known
that phytohormones mediate development and stress
response by modulating the expression of specific subsets of hormone-responsive
genes. Ethylene, for example, affects the expression of a group of genes
related to pathogen attack, wounding, abnormal temperatures and drought stress
Our search for sugarcane genes involved in ethylene responses led to the
identification of a new sugarcane member of the ERF transcription factor
family, named SodERF3, with the predicted characteristic DNA-binding domain, a
nuclear localization signal (NLS) and a C-terminal ERF-associated amphiphilic repression (EAR)-like motif. A detailed phylogenetic analysis with other members of the AP2/ERF TFs
indicates that SodERF3 belongs to subgroup VIII together with class II ERFs
containing an EAR motif. Constitutive expression of the SodERF3 gene in tobacco
did not lead to phenotypical changes in plant growth
and development, but enhanced drought and salt tolerance, a desired trait for
crop engineering.
SodERF3, a sugarcane (Saccharum officinarum L. cv Ja60-5) cDNA that
encodes a 201-amino acid DNA-binding protein that acts as a transcriptional
regulator of the ethylene responsive factor (ERF) superfamily.
Like other ERF transcription factors, the SodERF3 protein binds to the GCC box,
and its deduced amino acid sequence contains an N-terminal putative nuclear
localization signal (NLS). In addition, a C-terminal short hydrophobic region
that is highly homologous to an ERF-associated amphiphilic
repression-like motif, typical for class II ERFs, was found. Northern and
Western blot analysis showed that SodERF3 is induced by ethylene. In addition,
SodERF3 is induced by ABA, salt stress and wounding. Greenhouse-grown
transgenic tobacco plants (Nicotiana tabacum L. cv. SR1) expressing SodERF3 were found to
display increased tolerance to drought and osmotic stress.
Figure 1: A general pathway showing
the improvement in the tolerance of sugarcane plants.
Plants Growth and role of different hormones
Plant growth regulating hormones play vital
role in meristmetic activities of roots (Orlowska et al.,
2012).It has been reported that antagonistic activity of auxin and cytokinin helps in maintainance of root growth through cell division (Anderson et al.,
2010). During active divisions of cells in roots cytokinin
stimulate ARRI which triger the sypocotoyl
by suppressing the auxin signals (Kloepper
et al., 2004).It has been cited that Cytokinin oxidase4 helps in root growth by mixing ratio of
both auxin and cytokinin. (mith, 2008).Earlier it was
considered that rice variety WOX11 was involved in growth of crown root (part
of a root system from
which a stem arises). The proliferation of crown root requires the presence of
WOX11 transcriptional factor by bringing change in
genes of signaling hormones (Jackson et
al., 2012). ERF protein was identified in rice which was in interaction
with WOX11 in crown roots. Results revealed that ERF3 and excessive quantity of
RR2 (response regulator 2) were in direct contact with crown root growth. From
this research it might be proposed that ERF3 might deal with cytokinin but its collaboration with WOX11 can affect crown
root by increasing or suppressing the function of signaling molecules. This
technique can induce resistance in infectious pathogens through ISR (integrated
stress response). In this way plants increase their defensive mechanism (which
might include merging of cell wall, various enzymes etc) against various
pathogens (Alkalaeva et al., 2006). Activation of ISR proved to be useful in fighting
with pathogens, irrespective of decline in population of bacteria. Crop yield
of potato can also be enhanced by trigging the establishment of MIR (mycorrhizal-induced resistance) with AMF (Arbuscular
mycorrhizal
fungi) ( Salas et al., 2004).
Most
of the higher plants and symbiotic association of AMF have basic farming crops i.e potato. In their association they obtain carbohydrates
from plants and in return give them phosphorus and water. In plants SA(Salicylic acid),
JA (Jasmonic acid) and ethylene are directly involved
in inducing resistance mechanism. Jasmonic acid and
ethylene induction helps in ISR regulation (integrated
stress response) which eventually lead towards
defense in plants.SAR (systemic acquired resistance) is also found in plants
and stimulated against infectious agents which promote easily offending
response in leaves of plants (Shoemaker et
al., 2004). Tissues at infectious site have shown long term resistance
towards disease causing agents.At initial stage PR1
protein (Pathogenesis-related)
and these are used against pathogens is used in order to express those genes
which were induced earlier through salicylic acid which is
an important plant hormone
that regulates many aspects of plant growth
and development, as well as resistance to abiotic
stress and pathogenic attacks. Those phytohormones which are being used in defense mechanism are
basically identified through the nature of infectious agents.In
various circumstances it has been observed that ISR stimulate those pathways
which were dependent on salicylic acid. When resistance inducers work in
collaboration they showed improved regulatory mechanism in plants (Eurwilaichitr et al.,
1999). Successful attempts were made to increase the efficiency of ISR by
combining of defense bioprimers with various
bacterial strains (Cheng et al.,
2009). In order to boost up RMISR (root-microbe
interactions regulators) and yield
in plants various strategies including bacterial combination with AMF etc were
utilized. Whereas, bacterial associations with plants at molecular level
remained indefinable and is still under consideration for certain diseases in
crops (Merkulova et
al., 1999).
Crop Yield Increase
One of the major challenges being faced now a days is to fulfill the nutritional demand of
population. In order to obtain desirable outcome of crops various enzymes are
being used. For this purpose RubisCO enzyme is taken
under consideration for converting carbondioxode into
useful organic compounds (Georges et al.,
2014). Carbondioxide, water and 2 molecules of 3-PG
from RuBP were generated because of carboxylase activity of RubisCO.
The oxidation reaction reduces the ability of carbon fixation. Few plants suppress
the oxygenase activity with the help of their system
in order to enhance the level of carbon dioxide where RubisCO
can act on C4 plants which are plants that cycles carbon dioxide into four-carbon sugar compounds
to enter into the Calvin cycle which include
sugarcane etc. (Taylor et al., 2012).
As we all are familiar that C3 plants have greater level of photorespiration
and spend greater energy on it which ultimately lead towards slow growth.So, RubisCO engineering
with the enhanced kinship of carbondioxide might be
important for overall outcomes of crops (Gross et al., 2007).
Transcription factors and their role in plants
Transcription factors are
considered to play significant role at transcription level. They either
suppress or activate the genes under various diverse conditions. Transcription
factors account for nearly 7% coding capacity of vascular plant genome as they
regulate genes at the level of transcription. In plants, thousands of
transcription factors have been identified. From the major families of TFs one
is AP2/ERF and are mediated by various different
signaling transduction pathways. They are being utilized for coping up both the
biotic and abiotic stress. Still a lot of research
needs to be done for identifying the applications of transcription factor genes, these genes are helpful to produce stress resistant
crops having high productivity, so that the food security can be ensured (Alcazar-Roman et al., 2010). There are some advance gene editing tools like
CRISPR/Cas9 and these tools can be explored in the near future. Due to the
complex polypoid genome of Saccharum, several transcription factors like MYB, NAC and AP2/ERF
transcription factors have not been identified yet. Today, there is dire need
to employ molecular breeding tools for improving the sugarcane yield for
farmers having crops with small genetic variances. Moreover, epigenetics is considered for better understanding the
natural procedures during environment stresses. This technique involves DNA methylation, histone alteration,
chromatin remodeling and non-coding RNA (Bolger et al., 2008).
Issue of salinity in plants
Salinity is considered as
chief abiotic stress that limits growth as well as
productivity of plants in several areas around the world. It is increasing
because of elevated usage of poor quality water for both soil salinization and irrigation. Various complex physiological
traits, molecular or genetic networks and metabolic pathways are involved for
development of tolerance in plants against salinity stress. Development of salt
tolerance in salt affected areas involve several molecular tools along with
physiological and biochemical techniques. All these techniques are imperative
for developing tolerance. Adaptive responses have been identified for salinity
stress at different levels i-e metabolic, cellular,
molecular and physiological (Bolger et al.,
2008).
Changes in physiological and
metabolic processes are involved under salinity stress. This depends upon both
the duration and severity of the stress, which in turns inhibit crop production. Primarily soil salinity represses the growth of plant in
the osmotic stress form, which is later followed by ion toxicity (Khoshnevis et al., 2010). During the early phases of stress, capacity of roots to absorb
water declines and water loss from the leaves increases because of osmotic
stress of high salt accumulation in the soil and plants. Thus, salinity stress
is also considered as hyperosmotic stress as well as hyperionic stress (Mikhailovaet al., 2017).
Osmotic stress in the early stages of salinity stress is involved in causing
several physiological changes like nutrient imbalance, membrane interruption,
lowered photosynthetic activity, difference in antioxidant enzymes and
reduction in stomatal aperture (Beznoskova et al., 2013). Accumulation of sodium and chloride ions in plant tissues are
ultimately released in soil. Soil with high sodium chloride concentration is
considered as one of the most damaging effects of salinity stress. Entrance of
both sodium and chloride ion in the cells leads to severe ionic imbalance and
the excess uptake can also cause major physiological disorder. Uptake of
potassium ion is inhibited by high concentration of sodium ion. Potassium is
essential for both growth and development that later results in decreased
productivity and can lead to death (Tieg et al.,
2013). As a result of salinity stress,
ROS production like singlet oxygen, hydroxyl radical, and hydrogen peroxide is
increased. This can result in oxidative damages in several cellular components
like lipids, proteins and DNA which later affects the chief cellular functions
of the plants (Noble et
al., 2011).
Genetic variations and tolerance in plants:
Genetic variations in salt tolerance
have been noticed, and the extent of salt tolerance changes with species of
plants as well as varieties within a specie. Among key crops, a greater degree
of salt tolerance has been shown by barley as compared to wheat and rice. This
degree of variation is even more noticed in dicotyledons
cases that range from Arabidopsis thaliana which is extremely sensitive to
salinity, to halophytes like Atriplex sp., Mesembryanthemum crystallinum
and Thellungiella salsuginea.
In order to understand the mechanism of salt tolerance in Arabidopsis, excessive research has been done in the past two
decades. Now biologists can study or identify the physiological mechanisms,
gene products and sets of genes by genetic variations as well as differential
responses to salinity stress in plants. These sets of genes are involved in
elevating stress tolerance and incorporating them in suitable species so that
they can yield salt tolerant varieties (Neumann et al., 2016).
Gene Transformation Technologies
Quality exchange can be accomplished
in unsurprising way by hereditary change innovation. In this manner, these
strategies would be valuable in controlling the pathways related to osmoprotectants biosynthesis to collect those particles
that can demonstration by searching ROS protein (Kispal
et al., 2005). Numerous
investigations directed in the past draw attention to the plant alteration
system that assists with improving saltiness resistance, and furthermore center
around the qualities that control particle transport since sodium take-up's
guideline is altogether significant for endurance of plants under saltiness
stress. Numerous qualities that control this component have additionally been
distinguished. It has been seen that building plants for over-expressing
qualities that encode antiporters are recognized as
viable technique to produce salt resistant plants (Strunk
et al., 2012). Quality expression
focuses on those promoters which are constitutive. These convey just restricted
genetic data. When these were contrasted
with the use of inducible expression factors or cell type open expression
factors, it may be said that the determination of expression factors can
enormously influence the outcomes from transgenic control. Subsequently,
building of salt lenient yields should be possible by fruitful adjusting of
pressure reaction through designing of novel administrative targets; total
comprehension of post-translational changes which are useful in managing the
development of plants under pressure conditions. There is support of hormone
homeostasis in plants for keeping away from pleiotropic
impacts under pressure; and by use of plants some specific techniques for
improving methodologies of hereditary structure transfers are applied (Preis et al.,
2014). Responses at molecular, cellular, metabolic
and physiological level have been observed in salinity tolerance. Extensive
research on these responses has depicted several responses or strategies for
controlling osmotic regulation, ion uptake, hormone metabolism, and stress
signaling play significant role in adapting salinity stress in plants. Now,
scientists are advancing in the field of proteomics, transcriptomics,
genomics and metabolomics techniques, and they are
now able to focus on the development of complete gene and protein profiles, and
metabolites that are responsible for dissimilar method of salinity tolerance in
different species of plants (Barthelme & Pisarev,
2012).
Regulation factors
It has been studied that a
large portion of plant genome is devoted to their genes that play role in
transcription. The same mechanism has also been observed in Arabidopsis
thaliana genome which encodes approximately 1500 transcription factors.
Majority of the transcription factors are usually grouped in large family,
whereas some of these are unique to plants.
Out of all, one group of TFs covers so called ethylene responsive
factors that usually act upon the end step of ethylene signaling pathways. Its
first member was identified in tobacco (Anderson et al., 2004). Till today, ethylene responsive factors in various
plant species have been identified to have role in growth, development as well
as metabolism regulation. The agricultural production worldwide highly depends
on the plants ability to tolerate salt as well as drought conditions. The
elevated understanding regarding regulatory networks that control drought
stress response has led to practical methods in order to engineer drought and
salt tolerance in the plants (Casu et al., 2004)
Figure 2: Shows ERF genes playing key role in
hormonal regulation against the condition of stress for plants
A supposed protein having a
DNA binding domain generally present in EREBP/ AP2-type TFs was found by an
expressing sequence tag. From the excised library, a full length cDNA clone i-e SodERF3 was
isolated. It has been found that SodERF3 codes DNA binding protein for 240 amino acid (Cavalcante et al.,
2007). However, it was also originated that it possesses ERF linked amphiphilic suppression like motif which is not real one.
It is a short C-terminal hydrophobic region. The protein binds to GGC box, where
SodERF3 binds, and its deduced amino acid sequence contains an
N-terminal putative nuclear localization signal and N terminal putative nuclear localization signal was
observed in the deduced amino acid sequence of the protein. In sugarcane
leaves, SodERF3 is induced by the ethylene, salt stress, abscisic
acid and wounding as judged by western and northern blot assays. These were
grown in greenhouse (Nicotiana tabacum L.
cv. SR) that expressed SodERf3 were observed to show elevated tolerance to
osmotic stress and drought, and no visible phenotypic change in growth and
development was observed in them. Results showed that SodERF3 will act as
valuable tool in assisting the manipulation of plants thus they can improve
their tolerance of stress (Grivet et al.,
2002).
Figure 3: Increasing changes in the climate and weather
patterns are making it urgent
To increase the tolerance in plant using the technique of
SodERF3
Several developments have
been made in the recent understanding of gene expression, signal transduction
and transcriptional regulation in plants regarding their salinity and drought
tolerance. Moreover, gene discovery has been facilitated by molecular as well
as genomic analysis. Both of these have enabled the genetic engineering (a
field of gene discovery) in activating or repressing specific or broad pathways
to drought and salinity tolerance in the plants by utilizing various regulatory
or functional genes (Liu et al.,
1998). Transcription factors that are concerned in ethylene responsive factors
confer tolerance to various abiotic as well as biotic
stresses. These Tfs upon
activation by ethylene biosynthesis pathway either elevate or decrease the
genes activation regarding stress and vegetative development (Cheng et al., 2013)
Strategy
used in the working
Figure 4: Tobacco plant showing SodERF3 expression to
exhibit tolerance towards drought and salt after the process of transgenesis (Trujillo et al., 2008)
Stress
Factors
There are different stress mechanisms which are being shown
at different levels in plants under stress response conditions. Transcription
factors are considered as important regulators to control the gene expression
in every living organism and therefore take part in significant growth of
plants, cycling in cell and sign for stress reaction (American association,
1986). Transcription factors are thought to modulate the expression of genes by
binding to the local and distal factors which are used as marking genes and
later play role in influencing the genomic features, structure of DNA and
transcription factor interactions. Inplant,
approximately 10% of genes at various stages encode the transcription factors,
thus they can regulate specific signaling mediated functions. There are
different main families of transcription factors like NAC, MYB, ERF and WRKY
which are used as important regulators for management of stress (Zuo et al.,
2007). These later contribute in ideal choice for genetic engineering for elevating
resistance of plants against various stress stimuli (Kasuga
et al., 2004). It is important to
note that till today 44 NAC, 73 AP2/ERF, 38 MYB and 39 WRKY gene families of
Transcription factors have been identified in sugarcane (Murashige
et al., 1962). In sugarcane,
SodERf3 expression is induced by hormones that are involved in both biotic and abiotic stresses. The presence of SodERF3 transcripts in
higher quantities are easily detectable in leaves of the sugarcane. It was
experimented with a help of stimulus which is quite weak in the presence of
treatment of salicylic acid. It was observed that the expression of SodERF3 can
be observed by timeline of different experiments as it was shown with ethephon. After ethephon
treatment in the span of 1 hour, expression of SodERF3 were
noticed in higher quantities (DHont et al., 2001). The synthesis of protein
and its accumulation also occured gradually after
sugarcane leaf disc was treated with ethephon as
monitored through western blot. The ethylene responsive part of sugarcane which
is being activated by ethephon treatment plays major
role in abiotic as well as biotic signaling pathways
(Banno et al.,
2001)
Classification & Diversification of AP2/ERF Gene Family
Alanine at position 9 and aspartate at
position 14 directs the cis elements binding.
AP2/ERF is categorized in 5 major groups on the basis of number of domain
numbers present in genes. These groups include: DREB (Dehydration responsive
element binding protein) AP2, RAV (Related to AB13/VP1), ERF (Ethylene
responsive factors). To date, various AP2/ERF transcription factors were
identified in many species of plants such as 6 in number factors of AP2/ERF
transcription factors in sugarcane (Benson
et al., 2002).
Expression
of Abiotic Stresses
It was observed that the identified AP2/ERF transcription
factors that are mostly involved in abiotic tolerance
belong to Arabidopsis. Increase in tolerance against heat, salt and drought
stress in Arabidopsis was displayed by overexpression
of sugarcane SodERF3 gene (Gu et al., 2002).
It was observed by another study that BnaERF-B3-hy15mu3 mutant gene when over-expressed
increases cold resistance in transgenic Arabidopsis
which is considered as the model organism against which characteristics of
resistance in sugarcane are defined. The action genes if get mutated at the
point where GCC box elements are involved then resistance get compromised in
sugarcane. From Brassica napus, two
groups i.e., DREB I and II regulated
the signaling pathway being mediated by DRE synergistically by Trans inactive
and active in viable mode (Denekamp et al., 2003). There is an increase in measurement of antioxidants
levels, on the other hand lower MDA malondialdehyde
values are also observed because of up regulation of the two cold responsive
genes in sugarcane. These two cold responsive genes are VaERF080 and VaERF087
in Arabidopsis. It is observed that overexpression of
BpERF13 in sugarcane led to elevated antioxidants, decreased ROS (reactive
oxygen species) and improved tolerance against cold. But it has not shown
crucial elevation in salt or drought tolerance .In many plant species, the
AP2/ERF transcription factors, have been both identified and characterized for waterlogging (He et
al., 2001) . The sugarcane ariel
roots that are growing in the stress caused by waterlogging
help to maintain the advanced root growth and also a better concentration of
ethylene. This concentration contributes in increasing formation of aerenchym (Dey et al., 2015).
Populuseuphraticas expression analysis showed that upregulated
expression of PeDREBa depicted much increased values for physio-morphological traits. It also showed high values for
signal responsive regulation of both salt stress and drought
. Another gene in soyabeani-e GmDREB1 was
involved in activating the expression of various soyabean
specific stress responsive gene. When transcriptomic analysis was done, it was foundthat AP2si6 was more expressed in transgenic Sesamumindicum, so that it can cope up with deficiency
of water . When AtDREB2A
CA and OsDREP1 were overexpressed, they were found to be conferred to drought
endurance in sugarcane and rice respectively. TaDREB1 gene was induced through DRE-binding protein, thus it was
helpful to improve the sugarcane plants tendency for tolerating the osmotic
variations. Two DREB/CBF genes in sugarcane i-e TaDREB3 and TaCBF5L depicted elevated tolerance. This happened under presence
of strain receptive promoters HDZI-4 and
HDZI-3. The presence of ABA gene,
wounding and salt stress in sugarcane induced the SodERF3s expression (Guo et al., 2009).
ERF and stresses from environment
AP2/ERF transcription factors were involved in regulating
disease resistance in plants. Studies showed that when TaPIE1, Soly106,
OsEREBP1, OsREF83, and GmERF113 genes were overexpressed,
they proved to be effective against the pathogenic infections. Dual regulatory
functions of HvRAF (novel AP2/ERF transcription
factor) were observed under biotic as well as abiotic
stress. Overexpression of TaPIEPI
in wheat was majorly induced in Bipolarissorokiniana infection. When TaPIEPI
was overexpressed in transgenic plants, it showed
much higher resistance against fungal pathogenic infections. Various AP2/ERF3
transcription factors were expressed differently in both susceptible and
resistant tomato cultivars concerning TYLCV (Hanna-Rose et al.,
1996). Another AP2/ERF3 transcription
factor i-e CaERF5 participate
in a significant role to protect transgenic tobacco plants. There are expression which are Ectopic of apple MdERF11 in rejoinder to Botryosphaeriadothidea was observed and it played
significant role in higher resistance in Arabidopsis. Thus, it can be said that
AP2/ERF transcription factors collectively play significant role in enduring
biotic and abiotic stress by various stress mediated
signal transduction pathways (Gutterson et al., 2004).
Figure 6: ERFs role in stress
tolerance.
Conflict of
interest
The authors declare absence of any
conflict of interest.
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