Helicases: Plant engineers in abiotic stresses Pal Lalita1, Dwivedi Vikas1,*, Tripathi Diwakar Mani2 1Agricultural Research Organization the Volcani Center, 68 HaMaccabim Road, P.O.B. 15159Rishon LeZion7505101, Israel 2Dr. Reddy’s Laboratories Ltd., Bachupally Qutubullapur, Medchal Malkajgiri, Telangana-500090, India *Email: dwivedivikas1989@gmail.com
Online Published on 16 September, 2023. Abstract Helicases are being ubiquitous in nature, has the property to break the hydrogen bonds between annealed nucleotide bases and used to separate strands of a DNA, RNA molecule. They are also being used in separation of the double-stranded RNA and RNA—DNA hybrids. In bacteria, helicases regulates different functions like DNA replication, repair, recombination, and transcription. The DnaB, primary replicative helicase involved in bacterial DNA replication. It helps to unwind the DNA duplex as well as attracting the DnaG primase towards the replication fork so that replication can start. It is known that DEAD-box and DEAH-box RNA helicases are involved in many processes including the modification of RNA secondary structures. They help in intermolecular RNA and RNA/protein interactions. Bacterial DEAD-box proteins regulate the ribosome biogenesis, RNA decay and translation initiation. Based on sequence information and protein structures RNA and DNA helicases are divided into six superfamilies All RNA helicases and some DNA helicases are present in SF1 and SF2 groups. SF3-6 group contains other DNA helicases, translocases, and AAA + proteins. RNA unwinding, removing of protein from RNA, RNA annealing, RNA-dependent ATPase, metabolite sensing, and RNA clamping are some major biochemical characteristics of DEAD-box helicases. In bacteria, DEAD-box are the key molecules that are required in many adverse conditions like for growth at low temperature, in low biofilm condition, providing resistance in oxidative stress, reduced catalase activity, upregulation of some genes, prey-independent growth condition, and reduced growth in iron deficient conditions. Now days, helicases are emerging as important targets for the generation of novel antiviral, antibiotic, and anticancer drugs. In this chapter, we will review about DNA and RNA helicases and their role in different developmental processes and stress responses. Top Keywords Abiotic stress, Helicases, Plant engineers. Top |
Introduction Helicases are universal molecular motor proteins which catalyze the unwinding of duplex DNA into single strand and regulating the RNA secondary structure through ATP hydrolysis. (Vashisht & Tuteja, 2006; Matson et al., 1994). Helicase helps in DNA replication by creating single-stranded template for DNA polymerase. They break the hydrogen bonds and noncovalent bonds between nucleic acids. They require 50 ATPs for this process (Tuteja & Tuteja, 1996). They are universal enzymes and regulates many cellular processes like DNA/RNA metabolism (replication, repair, transcription, and translation) and in modifying of RNA structures (Lohman & Bjornson 1996; Tuteja & Tuteja, 1996). In E. coli, DnaB is primary replicative helicase and require for cell viability (Matson, 1991). The helicases are classified in DNA helicases; unwind DNA, and RNA helicases; unwind RNA. There are few helicases that unwind hybrids of DNA: RNA duplex. DNA helicases were first isolated from E. coli and also known as the “DNA unwinding enzyme,” (Abdel-Monem et al., 1976). |
To date many DNA helicases have been isolated from various organisms across the kingdom, like bacteria, viruses, bacteriophages, yeasts, frogs, Drosophila, cows, calf thymuses, mice, plants and humans (Matson et al., 1994; Tuteja & Tuteja, 1996). According to their sequence and structures, RNA and DNA helicases can be disseminated into six superfamilies (Fairman-Williams et al., 2010). The superfamilies 1 and 2 possess RNA helicases. The DEAD and DEAH/RHA RNA helicases families falls within superfamily 2 (Fairman-Williams et al., 2010). |
There are seven helicase motifs named I, Ia, II, III, I V, V, and VI, bioinformatically analyse (Figure 1) (Gorbalenya & Koonin, 1993; Tanner & Linder, 2001). Due to the high conservation in 80 helicase sequences, it is assumed that the helicases are derived from a common ancestor. The SF1 and SF2 groups contains all the eukaryotic RNA helicases. Other groups like, SF3– SF5 belongs to viral and bacterial DNA helicases. The SF6 helicase includes helicase that maintains the ubiquitous mini-chromosome and MCM group. Usually, the SF1 and SF2 groups are monomeric in nature whereas SF3–SF6 are hexameric ring-form in nature. |
The 200-700 amino acids regions are present in SF1 and SF2. There are some low sequence conservation’s amino acids present in between conserved motifs. The divergent regions are responsible for individual protein functions while the conserved regions are regulating the helicase activity. Motifs I and II are, play a key role during binding of nucleotide cofactors, homologous to Walker A and B boxes. |
The amino acids ‘GxGKS/T’ is conserved in motif I and interact with cofactors (sugar and phosphates of nucleotides). The amino acid sequence, D-E-A-D (asp-glu-ala-glu) or D-E-A-H (asp-glu-ala-his) is distinctive to the Walker B Motif. The aspartate amino acid, present in motif II, works in abiotic stress in plants. The conserved glutamine residue of motif II regulates AT P hydrolysis. Due to these two residues, the helicase family is called DExx-box, or DEAD-box. The amino acid change in motifs I or II instigate weakened DNA-unwinding and ATPase activities of enzymes. In yeast, a Q motif presents upstream of motif I that regulate ATP hydrolysis and binding in eIF4a (Tanner et al., 2003). There are two model for study of the enzyme kinetics, binding data and DNA unwinding mechanism of helicases, the first one is “active rolling model” (Wong & Lohman, 1992) and the “inchworm model” (Lohman & Bjornson, 1996). The binding of helicase to the single-stranded or double-stranded DNA is dependent on kinetically favoured state of enzyme. There are two subunits of the enzyme are required for activity in the active rolling model, while in the inchworm model a monomer is required to unwind the DNA. Amino acid switches in motif III can stop the enzyme’s displacement activity but not NTPase activity. The DEAD-box helicases are very much in number (25 in yeast, 36 in humans) in organisms. However, bacteria have very less DEAD-box genes. They regulate many processes as transcription, translation initiation and termination, ribosome biogenesis, RNA export, splicing of pre-mRNA, organelle gene expression (Figure 2) (de la Cruz et al., 1998; Linder & Jankowsky 2011). |
Plants, being sessile, are persistently exposed to various stresses that damage the DNA as a result reduced genome stability, growth, and productivity in plants. The plants have different mechanism to cop up with these stresses like reverse excise or resistant to DNA damage products. In plants, abiotic stress regulates the expression of many important genes in many pathways, which distress the plant development and growth. To develop tolerance for these effects, plants develop both physical adaptation and interactive molecular and cellular process. The abiotic stresses can regulate by multigene family. The stress condition the extracellular signal is first recognized by the membrane receptors, and they activate signalling cascade. The signalling cascade activates multiple stress responsive genes family that provides stress tolerance. The many gene family also cross talk during stress condition. The genes involved in nucleic acid metabolism changes the expression during stresses like helicase. All the helicases possess intrinsic ATPase activity that is DNA-dependent, for the helicase action (Rocak et al., 2004). The unwinding of local RNA secondary structures catalyze by RNA helicases through ATP dependent manner and play crucial role in regulation of RNA structures (Luking et al., 1998, Tuteja et al., 2012). Multiple helicases are present in single cell at same time in each plant because of different substrate need to be catalyze for the development of plant. Many important crops and fruits like rice, wheat, maize, banana, tomato, and orange, are showing injured or killed by exposure to low (non-freezing) temperature. Low temperature induced the expression of multiple genes including helicases. These genes help plants to become tolerant to low temperature. |
The DEAD/ H-box helicase is largest number of genes among all the sequenced genomes including those of worm, humans, yeast, fly and Arabidopsis (Umate et al., 2010). In Arabidopsis 94 helicases reported that are regulated with various stress. |
Eukaryotic cells have many membrane less organelles that regulate the spatiotemporal aspects of multiple cellular activities. These organelles are created from liquid droplets of proteins and nucleic acids. Li et al. (2021) studied how membrane less nuclear dicing bodies (D-bodies), which are seen in Arabidopsis thaliana, arise and change. They discovered that three previously undiscovered D-body parts are RNA helicase 6 (RH6), RH8, and RH12. These helicases interact with and encourage the phase separation of SERRATE, a crucial component of D-bodies, and they are what cause liquidliquid phase separations (LLPSs), that lead to the formation of D-bodies. Following Turnip mosaic virus infections, the accumulation of these helicases in the nuclei reduces, which is accompanied by a reduction in D-bodies. |
Saifi et al. (2021) characterised the rice homolog of RuvBL1 (OsRuvBL1a). OsRuvBL1a has ATPase and helicase activities that may be necessary for carrying out cellular processes. |
According to the functioning mechanism, OsRuvBL1a interacts with many proteins that, either directly or indirectly, help the plant withstand stress. Numerous physiological and biochemical studies revealed that transgenic lines overexpressing OsRuvBL1a performed better than WT plants under salinity and drought stress. |
In grapevine, Yang et al. (2022), showed a total of 40 DEAD-box genes and characterized their protein and gene structure. Nine candidate genes (VviDEADRH10c, -13, -22, -25a, -25b, -33, -34, -36, and -39) were screened and the overexpression of the candidate genes (VviDEADRH25a) resulted in more sensitivity of the transgenic plants to drought stress. |
A genome-wide analysis across the chickpea genome led to the identification of a total of 150 RNA helicase genes which included 50 DEAD, 33 DEAH and 67 DExD/H-box genes. These were distributed across all the eight chromosomes, with highest number on chromosome 4 (26) and least on chromosome 8 (8). The two genotypes were chosen of the cultivated variety ICC 8261 (kabuli, C. arietinum), and the wild accession ILWC 292 (C. reticulatum) and, showed the least percentage (%) loss in relative water content (RWC) and membrane stability index (MSI) for the drought stressed plants after withholding water for 24 days compared to the control or well-watered plants. Chickpea RNA helicase genes that respond to drought include CaDEAD50 and CaDExD/H66. One of the CLSY (CLASSY) proteins from A. thaliana and the protein that the CaDExD/H66 gene encodes have a high degree of similarity (Yadav et al., 2022). |
Top Mechanism of Helicases The helicases are acted at two possible positions: (i) at the level of gene transcription or translation to increase protein in cells and (ii) they form complex with DNA to alter gene expression. The expression of gene (transcription or translation) is affected by environmental stress. The DEAD-box RNA helicase could facilitate transcription by deteriorated the structure of nascent RNA. This RNA can stimulate reinitiation and/or elongation. The translation initiation is affected by cold stress and the RNA helicases helps to start the translation machinery (Figure 3) (Iost and Dreyfus 1994). |
The ribosome expression also affected by temperature change like in cold temperature a greater number of monosomes present specially 70 S and free 30 S subunit. |
The mRNA structure also affects protein synthesis under temperature variability. The 5’ untranslated region (5’ UTR) structure can hide the ribosome binding site. During stress, the stress-induced RNA helicase(s) recognized non-functional RNAs secondary structures and unwound the structures, which leads to the translation initiation. |
The DEAD-box helicases are conserved in nature and can be a prominent molecule to understand stress signalling in plants. Helicases are involved in translocation and unwinding of bases through NTP binding and NTP ligation states. Helicases are monomeric and oligomeric in nature. In monomeric confirmational changes are control by single NTPase site. Ring shaped helicases can hydrolyze six NTPs. The changing environmental conditions continuously threaten the genomic integrity of all living organisms. The integrity of genome can be maintain by robust DNA repair and recombination pathways that leads to repair/remove or to tolerate genomic lesions throughout evolutionary history (Singh et al., 2010). |
Top Bacterial Helicases The direct evolutionary ancestors of plant chloroplasts are cyanobacteria (Margulis, 1981; Ponce-Toledo et al., 2017). A cyanobacterium’s endosymbiosis has a considerable influence on the structure of the plant nuclear genome in addition to producing the chloroplast (Martin et al., 2002). The higher plant level can therefore benefit from knowledge gained from studying gene function in cyanobacteria. The DEAD-box RNA helicase CrhR, for cyanobacterial RNA helicase redox, is encoded by the unicellular cyanobacterium Synechocystis sp. PCC 6803 (hence referred to as Synechocystis) (Rosana et al., 2012). CrhR is the archetype protein of a new clade in the DEAD-box RNA helicase family, and it is identified by a 50 amino acid sequence pattern (Whitford et al., 2021). Contrary to plants and many other bacteria, only CrhR (crhR/slr0083) is a DEAD-box RNA helicase encoded in Synechocystis (Redder et al., 2015). |
In addition to low temperatures, a variety of abiotic stressors that weaken the electron transport chain (ETC) also cause crhR, independent of temperature changes (Vinnemeier and Hagemann, 1999; Ritter et al., 2020). It shares a dicistronic operon with the gene rimO (slr0082), whose putative protein product shares 38% identity with RimO, a ribosomal protein S12 methyl thiotransferase (UniProtKB P0AEI4), and 29% identity with the paralogous tRNA methylthiolase MiaB (Uni-ProtKB P0AEI1) from E. coli (Rosana et al., 2020). |
Top Plant Helicases Arabidopsis LOS4 helicase (AtRH38) The los4-1 was isolated from mutant screening in Arabidopsis which showed a decreased RD29A-LUC expression under cold, but it is not showing in ABA or high salt stress. The CBF gene shows reduced expression in los4-1 mutant plants under cold. It was also showing that los4-1 mutant plants become less developed under chilling temperature in dark. The constitutive expression of the CBF-3 gene in los4-1 mutant plants showed resistant to the chilling temperature. The map-based cloning was used to isolate LOS4 gene, encode for a DEAD-box RNA helicase protein (AtRH38). It is localized both in cytoplasm and in nucleus (Gong et al., 2002). Another Arabidopsis mutant los4-2 is isolated that has ATPase activity which is RNA-dependent and showed defective mRNA export. los4-2 is highly expressed in nucleus. The both los4-1 and los4-2 regulate the chilling temperature in vice versa manner, one is sensitive and other is tolerant. The los4-1 decrease mRNA export at warm and low temperature, but los4-2 decrease RNA export at warm and high temperature. LOS4 helicase regulates mRNA export from the nucleus to the cytoplasm under cold stress conditions and provide tolerance (Gong et al., 2005, Zhu et al., 2007). LOS4 helicase is also regulate ABA hypersensitivity of los4-2 and plant development like early flowering in los4 mutant. Arabidopsis STRS1 and STRS2 These DEAD-box RNA helicases, named stress response suppressor 1 (STRS1) and STRS2 were downregulated during abiotic stresses in Arabidopsis. The mutated plants of these helicases resulted in increased tolerance than wild type to various abiotic stress like salt, osmotic, and heat stresses. They showed higher expression of stress-responsive transcription factors that further regulates the downstream genes. The STRSs can be regulated by both ABA-dependent and -independent stress signalling networks (Figure 4). RNA helicases can control stress responsive genes (Kant et al., 2007). Sorghum HVD1 helicase In sorghum, a DEAD-box RNA helicase dependent on ATP energy and accumulated under salt stress, cold stress, and ABA treatment. This is called HVD1 (Hordeum vulgare DEAD-box protein). They are conserved and encodes protein with five repeats of RGG that is known as RNA recognition motif. They also possess helicase domain. This also has hydrophilic C terminus region. The transcript abandoned in chloroplast proved by immunogold blotting. Thus, it is shown that HVD1 protein regulates the function of transcript(s) of salt tolerance or photosynthetic genes in chloroplast (Nakamura et al., 2004). Pea helicases DNA helicase The pea DNA helicases 45 and 47 (PDH 45 and PDH47) in number and belongs to DEAD-box helicase and shows high homology to eIF4A (eukaryotic translation initiation factor 4A) (Vashisht et al., 2005). They showed DNA and RNA helicase activity that are ATP-dependent and also DNA-dependent ATPase activity. The PDH45 is upregulated under salt stress whereas PDH47 upregulated under cold and salt stresses. PDH45 also upregulated under dehydration stress but PDH 47 showed no effect under dehydration effect. The PDH 45 controls the Na+ ions level in cells under salinity. The PDH45 transcript was induced by the phytohormone, ABA, which suggested that ABA-mediated stress effect under drought. The PDH47 possess both the 30-50 and 50-30 directional helicase activities but PDH45 don’t show both activities. The PDH47 protein exhibited higher protein synthesis. Single-subunit MCM6 helicase The DNA is replicated one time in a cell division cycle and governed by Pre-PC (prereplicative complex) and heterohexameric minichromosome maintenance (MCM2-7) proteins. This MCM complex is unwind the DNA. The MCM6 forms homohexamer and works as DNA helicase. AS MCM worked in cell division, so it expressed under stress condition. This helicase upregulated under salinity and cold stresses but not affected by heat, ABA, and drought. The transgenic plants showed higher chlorophyll content, net photosynthetic rate, and thus more dry matter accumulation and yield under 200 mM of NaCl condition as compared to wild type (Dang et al., 2011). Dogbane helicase The AvDH1 isolated from the halophyte dogbane (Apocynum venetum), is a salt-responsive helicase. There are nine conserved DEAD-box helicase motifs in AvDH1, and this is single copy gene. It also contains both ATP-dependent DNA and RNA helicase activities and DNA- or RNA dependent ATPase activities. This is upregulated under salt and cold conditions but not under drought and ABA stress. (Liu et al., 2008) Alfalfa helicase The M. sativa helicase 1 (MH1) from alfalfa is homologous to PDH45. This was found to be expressed in leaves, roots, and stems. It was upregulated in various stress response like under mannitol (drought), NaCl, or H2O2 treatments. The enhanced stress tolerance was due to higher superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities and proline. (Luo et al., 2009). GmRH from soybean An RNA helicase, containing bipartite lysine-rich nuclear localization signal (NLS) at the N-terminal variable region isolated from soybean, called GmRH. It is upregulated under cold and salt stress but unaffected under Abscisic acid and drought stress. It might play role in RNA processing during abiotic stress (Chung et al., 2009). Dead-box helicase Different abiotic stress affects the yield in different crops. The plants have several mechanisms to encounter these stresses. Many researchers have done various study in abiotic stress field and found that somatic embryogenesis is increased under stress condition (Pandey et al., 2019). During abiotic stress the dedifferentiation of cells occurs which is followed by change in chromatin structure that is an active open conformation thus finally increase the expression of stress responsive genes (Koroleva et al., 2009; Ma et al., 2016). When plants feel abiotic stress, some signalling molecules activate transcription factors which regulate the promoter region of stress responsive genes during abiotic stress (Asensi-Fabado et al., 2017). The higher AMP (adenosine monophosphate) expression during stressed condition inhibits the RNA binding and RNA unwinding activity of the many helicases like eIF4A, Ded1p and Mss116p in yeast (Putnam & Jankowsky, 2013). The Arabidopsis AtRH7 DEAD-box gene regulates cold tolerance (Huang et al., 2016). During stress condition plant revert back in dedifferentiation condition to acclimatize in stress. This condition reduces protein synthesis, nucleolus structure and conformational changes of chromatin. A putative DEAD box gene in tomato called SlDEAD31 has been conferred drought tolerance and upregulate the stress related genes expression (Zhu et al., 2015). Some brassica dehydrin genes like BnDHN1, ERD10, ERD15, Bn115 and COR25 found to be upregulated under drought (Keshaviah et al., 2014). Temperature is also a very important factor for growth and development of plants. During reproductive stage, the temperature plays crucial role that leads to develop good fruit. If there will be higher temperature so there will less fruits in plant. Increase in temperature causes membrane damage and enzymatic inhibition in plants. The RNA helicases in rice, Thermo-tolerant Growth Required1 (TOGR1) improve yield under high temperature (Wang et al., 2016). In tomato, SlDEAD31 showed higher expression in heat stress and provide tolerance to plant (Zhu et al., 2015). The LOS4 mutant in Arabidopsis showed sensitivity under heat stress. Many transcription factors and proteins involved in abiotic stress and regulate helicases either positively or negatively. The DRD1, DC13 and RDR2 help STRS2 helicase to execute RNA directed DNA methylation (RdDM). The mutated HD2C cause deformed localization of STRS1 under stresses (Yang et al., 2014). The EMB3108 and PDE340, two Arabidopsis RNA helicases has been reported to be downregulated by various stresses like cold, salt and osmotic stresses (Macovei et al., 2012). The DRH1 expression was increased under cold stress in Arabidopsis (Macovei et al., 2012). The AtRH9, DDB1, LHP1 and RD29A (responsive to dehydration 29A) regulates multiple abiotic stress responses (Kim et al., 2008; Exner et al., 2009; Lata & Prasad, 2011; To et al., 2011; Zhu et al., 2015). Helicase genes under abiotic stress There are several helicase genes involved in various stresses such as anoxia, genotoxic, drought, cold, hypoxia, osmotic, heat, oxidative, wounding, and salt reported (Tuteja & Tuteja, 2004). There are different helicases express under various condition like the RH55, SDE3 and chromatin remodelling 31, expresses for helicase domain-containing proteins, while RH11 and RH18 expressed in drought stress. The RecQl3, CHR31 and MCM8 expressed in genotoxic stress. In hypoxia, MEE29, RH42, helicase domain-containing protein, SNF2, RH55, and MER3 is expressed. The MEE29, CHR31, RH55 and RH45 helicases showed higher expression in osmotic stress, while RH28, SDE3, RH37 and RNA helicase DRH1 were overexpressed in oxidative stress. The genes that overexpressed in salt stress were MEE29, SNF2, CHR9, DRH1, EDA16, RH30, RH55, CHR31 and RH40. The CHR42, MER3, PIF1 and SNF2 showed increased expression in wounding stress. As RNA form more secondary structures so they require RNA chaperones for their proper functioning (Umate et al., 2010). DEAD/ H-box RNA helicases, RNA chaperones use ATP energy to regulate RNA structures (folding) (Umate et al., 2010). The expression of gene crhR (a cyanobacterial RNA helicase) is regulated RNA stability through controlled manner at transcription level controlled by redox reaction. RNA helicase would regulate the crhR expression to modulate RNA secondary structure so electron flow can elicit. RNA unwinding activity induced by crhR could remove secondary structures that inhibit ef–cient translation of mRNAs. In response to abiotic stress, Owttrim (2006), gives a general overview of the control of RNA helicase gene expression or enzymatic activity. It also investigates the variety of biochemical processes and physiological roles attributed to these environmentally controlled RNA helicases. Top Helicase Promoters and Stress Tolerance Several studies used constitutively active promoters with helicase under different stress condition. Sometimes higher expression of helicases beyond the limit, cause the negative impact on yield so it is better to use native promoters. In rice, OsXPB2 promoter has been identified and it showed higher expression under abiotic stress. It is with different cis-elements like CACGTG, CACG, GTAACG, CGTCA, and CCGCCGCGCT that are active under various abiotic stresses such as cold, salt, dehydration, MeJA, and ABA, respectively (Briolat et al., 2002). A pea helicase, Psp68 possess cis regulatory elements such as E-box, GATA-box, GAAAA, AGAAA, ACGT, and GTCTC (Banu et al., 2014). The PDH45, pea helicase contains ABRE, MBS, G-box, GARE motif, CCAAT box, and TGA element (Sanan et al., 2005). |
Top Conclusion and Future DEAD-box proteins were found expressed in many different stresses. In some Inactive DEAD-box proteins in bacteria leads to a cold sensitivity (e.g., ΔsrmB or ΔcsdA in E. coli; ΔcshA, ΔcshB in Firmicutes; ΔcrhC in cyanobacteria) indicating that at low temperatures, these proteins are required for stress tolerance. Mutation in bacterial DEAD-box proteins, do not lead to growth deficiency (e.g., Δrhlb, ΔrhlE, ΔdbpA in E. coli). To edit various abiotic stress responsive DEAD-box RNA helicase genes and develop sustainable multiple abiotic stress tolerance in crop plants for sustainable crop productivity under various stresses to adapt to climate change, target specific multiplex and multigene CRISPR/ Ca9 genome editing would be the best method. |
Diverse studies have amply shown that overexpression of these helicases confers abiotic stress tolerance on plants. DEAD box helicases frequently exhibit higher expression in the presence of varied stress situations. Utilizing the cutting-edge CRISPR/Cas9 genome editing method, it is possible to successfully design plants with innate stress tolerance. Adopting these approaches might make it possible to create knockout lines of DEAD box helicases that are down regulated under different stress circumstances. Future research initiatives that could expedite the potential application of DEAD box helicases in modifying the stress tolerance of various plants include the ones listed below: |
It has been discovered that a certain group of plant DEAD box helicases has a lot of promise for resistance to various abiotic stresses. For the development of multiple stress tolerant plants, the homologs of such helicases can be used in economically significant crop plants. Some DEAD box helicases may have cumulative effects when co-expressed with other stress-responsive genes, enabling resistance to a variety of stresses. A better choice would be to isolate DEAD box helicases from robust plants that can survive in adverse environments and employ them to create plants that can withstand stress because they are likely to produce higher levels of stress resistance. However, the DEAD box helicases that have been discovered so far mainly provide abiotic stress tolerance. Some helicases offer both abiotic and biotic stress tolerance or resistance. As a result, more helicases must be found while under stress. There are a few RNA helicases with well-established functions in RNA metabolism and stress resistance. Plants under stress may benefit from their ability to function well under adversity. Plant DEAD box helicases’ structure-function studies may aid in understanding the various helicases’ molecular pathways, enabling plants to better withstand stress. |
Top Figures Figure 1:: Diversification of helicases and their characteristic domain present in SF1 and SF2 that share most similarity including Walker A, Walker B and arginine finger (VI) motifs
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| Figure 2:: DNA/RNA helicases play various role in regulating various biological processes in plant growth and development
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| Figure 3:: Schematic representation of helicases mechanism regulating gene expression under the stress condition
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| Figure 4:: Diagrammatic view of mechanism showing upregulation and downregulation of STRS (DEAD-box RNA helicases) under abiotic stress condition in Arabidopsis.
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