related CPK genes such as TaCPK 7 and TaCPK 12 in wheat show diversity
wherein, the former responds to various stresses such as temperature (low), salinity,
drought, H 2 O 2 , whereas the latter responds only through ABA signalling (Geng et al.
2011; Atif et al. 2019).
As transcription factors act as key stress tolerance mediators, they can be
modified to increase the stress tolerance in various crops. Many studies have been
conducted on five major cereal crops such as barley, maize, sorghum, rice, and
wheat. Gene modification through these transcription factors (TFs) can improve
stress tolerance in transgenic plants. Although boosting tolerance level through TFs
is not so easy and is a complicated procedure, as one TF gene during downregulation may promote or suppress other genes. Various TFs families may be
involved in one or multiple stress responses, thus making TF responses very
complex and complicated and might have cross-talk between different signal
pathways. There are millions of TF at molecular level, and identifying, modifying
each TF is a bit challenging task. Application of CRISPR/Cas 9, a gene editing tool
is being used to improve the stress tolerance in plants (Baillo et al. 2019).
Abiotic stress also enhances the production, synthesis, and transcription of heat
shock proteins (HSPs) in comparison to other normal proteins. Post transcriptional
modifications of proteins such as microRNA and alternating splicing also help to
cope with abiotic stress. The HSPs have been categorized based on molecular weight
into Large (68,000–104,000 Da), Intermediate (20,000–23,000 Da), and Small
(15,000–18,000 DA) (Hughes and Dunn 1990). It has now been established that
HSPs help newly synthesized protein’s folding and protect them during stress.
Therefore HSPs are also known as molecular chaperones (Ul Haq et al. 2019).
HSPs are also present in cell and cellular compartments during standard environmental conditions and studies have confirmed their role in normal growth and
development apart from being stress responsive (Eck et al. 2007). HSPs not only
develop during heat stress but are also found to be present in other abiotic stresses.
HSPs express differentially in different species. Genes encoding HSPs, are
present in different cell compartments and thus they are expressed differently and
may also be specific depending on the stress intensity (Liu et al. 2006; Ul Haq et al.
2019). Under temperature stress high molecular weight HSPs (HSP 118, À114,
À110, À108, À104, À103, À101, À100, and À97) are formed. In Arabidopsis and
maize HSPs À100 and À101 are expressed and responsive against the high temperature stress and thermo-tolerance (Queitsch et al. 2000; Nieto-Sotelo et al. 2002). In
Pea low molecular weight HSPs 18.1 and À17.9 accumulates after 4 h treatment
(Dupuis and Dumas 1990). Low temperature also induces the expression of HSPs in
rice, maize, and Arabidopsis to protect them against cold stress (Bae et al. 2003;
Kosova et al. 2011; Hlavackova et al. 2013). HSPs have also found to be present
during drought stress. Mostly HSPs 70 are upregulated as evident from studies on
rice, Arabidopsis, sugar cane, cotton, maize, Cicer sp. (Subba et al. 2013; Reddy
et al. 2014; Yer et al. 2018). In Chenopodium rubrum under high light stress HSP
23 gets upregulated (Korotaeva et al. 2001). In marine ecosystems low light stress
induced accumulation of HSP 70, ClpBi, and HSP 60 (Kumar et al. 2017). Similarly
1 Abiotic Stress in Plants: An Overview
11
wherein, the former responds to various stresses such as temperature (low), salinity,
drought, H 2 O 2 , whereas the latter responds only through ABA signalling (Geng et al.
2011; Atif et al. 2019).
As transcription factors act as key stress tolerance mediators, they can be
modified to increase the stress tolerance in various crops. Many studies have been
conducted on five major cereal crops such as barley, maize, sorghum, rice, and
wheat. Gene modification through these transcription factors (TFs) can improve
stress tolerance in transgenic plants. Although boosting tolerance level through TFs
is not so easy and is a complicated procedure, as one TF gene during downregulation may promote or suppress other genes. Various TFs families may be
involved in one or multiple stress responses, thus making TF responses very
complex and complicated and might have cross-talk between different signal
pathways. There are millions of TF at molecular level, and identifying, modifying
each TF is a bit challenging task. Application of CRISPR/Cas 9, a gene editing tool
is being used to improve the stress tolerance in plants (Baillo et al. 2019).
Abiotic stress also enhances the production, synthesis, and transcription of heat
shock proteins (HSPs) in comparison to other normal proteins. Post transcriptional
modifications of proteins such as microRNA and alternating splicing also help to
cope with abiotic stress. The HSPs have been categorized based on molecular weight
into Large (68,000–104,000 Da), Intermediate (20,000–23,000 Da), and Small
(15,000–18,000 DA) (Hughes and Dunn 1990). It has now been established that
HSPs help newly synthesized protein’s folding and protect them during stress.
Therefore HSPs are also known as molecular chaperones (Ul Haq et al. 2019).
HSPs are also present in cell and cellular compartments during standard environmental conditions and studies have confirmed their role in normal growth and
development apart from being stress responsive (Eck et al. 2007). HSPs not only
develop during heat stress but are also found to be present in other abiotic stresses.
HSPs express differentially in different species. Genes encoding HSPs, are
present in different cell compartments and thus they are expressed differently and
may also be specific depending on the stress intensity (Liu et al. 2006; Ul Haq et al.
2019). Under temperature stress high molecular weight HSPs (HSP 118, À114,
À110, À108, À104, À103, À101, À100, and À97) are formed. In Arabidopsis and
maize HSPs À100 and À101 are expressed and responsive against the high temperature stress and thermo-tolerance (Queitsch et al. 2000; Nieto-Sotelo et al. 2002). In
Pea low molecular weight HSPs 18.1 and À17.9 accumulates after 4 h treatment
(Dupuis and Dumas 1990). Low temperature also induces the expression of HSPs in
rice, maize, and Arabidopsis to protect them against cold stress (Bae et al. 2003;
Kosova et al. 2011; Hlavackova et al. 2013). HSPs have also found to be present
during drought stress. Mostly HSPs 70 are upregulated as evident from studies on
rice, Arabidopsis, sugar cane, cotton, maize, Cicer sp. (Subba et al. 2013; Reddy
et al. 2014; Yer et al. 2018). In Chenopodium rubrum under high light stress HSP
23 gets upregulated (Korotaeva et al. 2001). In marine ecosystems low light stress
induced accumulation of HSP 70, ClpBi, and HSP 60 (Kumar et al. 2017). Similarly
1 Abiotic Stress in Plants: An Overview
11