indicating the positive role of JA in the plant salinity response and that the
α-linolenic acid metabolism pathway governs this response.
Contrary to these findings, there are some reports which proposed that salinity
tolerance is due to reduction in jasmonic acid level or its inactivation in plants.
Kurotani et al. (2015) in their finding observed that transgenic rice expressing
transgene OsCYP94C2b resulted in decreased sensitivity to salinity and enhanced
the survival rate. This gene encodes an enzyme that catalyses the conversion of
jasmonoyl isoleucine to inactive form. Guo et al. (2019) reported that transcription
factor GarWRKY5 regulates salinity stress in Arabidopsis on its overexpression by
jasmonic or salicylic acid-mediated signalling pathway.
Some reports suggested that SA may enhance the formation of ROS which leads
to increased oxidative damage during salinity. Cao et al. (2009) reported transgenic
Arabidopsis expressing NahG showed better tolerance to moderate salinity and have
higher glutathione/oxidised glutathione ratio and the ascorbate/dehydroascorbate
ratio than wild type plants but not under severe stress.
9.4.3 Genome Editing for Salinity Stress Alleviation
Genomics has emerged progressively over the last decade and has a tremendous
contribution to the agricultural field particularly by providing crucial information for
crop improvement. With its help, we can identify novel genes involved in salinity
tolerance and have been able to use them for enhancing tolerance of our crops.
Genome editing is targeted mutagenesis of genomes that allows us to introduce
specific changes at specific sites in the genome. It utilises DNA cleavage reagents
and cellular DNA repair pathways (Orellana et al. 2010). The DNA cleavage
reagents are mostly nucleases (engineered) that cleave the target DNA site at a
specific site and the double-stranded breaks so generated are repaired by non–
homologous end joining, NHEJ or homologous recombination, HR (Carroll 2014)
Zinc finger nucleases (ZFNs), the Transcription activator-like effector nucleases
(TALENs), the Meganucleases are used to create breaks in targeted double-stranded
DNA at or close to place of the target gene and DNA can be exploited to make
specific changes like insertion or deletion and repaired by non-homologous end
joining or homologous recombination (Curtin et al. 2012; Carroll 2014). The
CRISPR/Cas RNA-guided system is recently identified which has provided newer
and faster means for the production of precisely engineered crops.
This newly emerging technology CRISPR/Cas has immense potential in improving the stress tolerance ability of our crop plants and several researchers are working
on developing stress-tolerant plant species. Recently, Zhang et al. (2019a) succeeded
in enhancing salinity tolerance in rice via CRISPR/Cas9 targeted mutagenesis of
OsRR22 (Oryza sativa response regulator 22) gene. Bo et al. (2019) observed that
targeted mutagenesis of NAC (NAM, ATAF and CUC) transcription factor coding
gene, OsNAC041 resulted in salt sensitivity in rice which pointed out the role of
OsNAC041 gene in imparting salinity tolerance in rice. Zhang et al. (2019b) in their
study produced knockout of the SUMO protease, OsOTS1 (Rice OVERLY
9 Phytohormones: A Promising Alternative in Boosting Salinity Stress Tolerance in. . .
291
α-linolenic acid metabolism pathway governs this response.
Contrary to these findings, there are some reports which proposed that salinity
tolerance is due to reduction in jasmonic acid level or its inactivation in plants.
Kurotani et al. (2015) in their finding observed that transgenic rice expressing
transgene OsCYP94C2b resulted in decreased sensitivity to salinity and enhanced
the survival rate. This gene encodes an enzyme that catalyses the conversion of
jasmonoyl isoleucine to inactive form. Guo et al. (2019) reported that transcription
factor GarWRKY5 regulates salinity stress in Arabidopsis on its overexpression by
jasmonic or salicylic acid-mediated signalling pathway.
Some reports suggested that SA may enhance the formation of ROS which leads
to increased oxidative damage during salinity. Cao et al. (2009) reported transgenic
Arabidopsis expressing NahG showed better tolerance to moderate salinity and have
higher glutathione/oxidised glutathione ratio and the ascorbate/dehydroascorbate
ratio than wild type plants but not under severe stress.
9.4.3 Genome Editing for Salinity Stress Alleviation
Genomics has emerged progressively over the last decade and has a tremendous
contribution to the agricultural field particularly by providing crucial information for
crop improvement. With its help, we can identify novel genes involved in salinity
tolerance and have been able to use them for enhancing tolerance of our crops.
Genome editing is targeted mutagenesis of genomes that allows us to introduce
specific changes at specific sites in the genome. It utilises DNA cleavage reagents
and cellular DNA repair pathways (Orellana et al. 2010). The DNA cleavage
reagents are mostly nucleases (engineered) that cleave the target DNA site at a
specific site and the double-stranded breaks so generated are repaired by non–
homologous end joining, NHEJ or homologous recombination, HR (Carroll 2014)
Zinc finger nucleases (ZFNs), the Transcription activator-like effector nucleases
(TALENs), the Meganucleases are used to create breaks in targeted double-stranded
DNA at or close to place of the target gene and DNA can be exploited to make
specific changes like insertion or deletion and repaired by non-homologous end
joining or homologous recombination (Curtin et al. 2012; Carroll 2014). The
CRISPR/Cas RNA-guided system is recently identified which has provided newer
and faster means for the production of precisely engineered crops.
This newly emerging technology CRISPR/Cas has immense potential in improving the stress tolerance ability of our crop plants and several researchers are working
on developing stress-tolerant plant species. Recently, Zhang et al. (2019a) succeeded
in enhancing salinity tolerance in rice via CRISPR/Cas9 targeted mutagenesis of
OsRR22 (Oryza sativa response regulator 22) gene. Bo et al. (2019) observed that
targeted mutagenesis of NAC (NAM, ATAF and CUC) transcription factor coding
gene, OsNAC041 resulted in salt sensitivity in rice which pointed out the role of
OsNAC041 gene in imparting salinity tolerance in rice. Zhang et al. (2019b) in their
study produced knockout of the SUMO protease, OsOTS1 (Rice OVERLY
9 Phytohormones: A Promising Alternative in Boosting Salinity Stress Tolerance in. . .
291