**7. Genome editing strategy (CRISPR/Cas9) for transgenic plants**

Different genome editing strategies are being used to develop transgenic-resistant crops to deal with food insecurity issues. CRISPR/Cas9 is the most powerful system to develop a genetically engineered crop system that is able to adapt to different climate change-induced stresses more effectively. It also helps in producing high-yielding and stress-resistant crops. It is environment friendly, fast, rapid, accurate and economical. SgRNA/Cas9 construct is established to target the specific genome sequence of a plant. This construct is introduced in the targeted crop by means of various transformation methods, such as Agrobacterium-mediated transformation and protoplast transfection, to produce abiotic stress-resistant variety [61]. *B. napus* was modified with CRISPR technology to downregulate the expression of CLVTA3*.* Transgenic *B. napus* showed more seed production. TaGW2 gene's expression was knocked down using the CRISPR system in wheat. This modification helped in increasing the seed size of wheat. Overexpression of SlMAPK3 gene by CRISPR/Cas9 in *S. lycopersicon* showed improved drought tolerance. Knocking down the expression of Osann3 by CRISPR/Cas9 in rice produced more cold stress tolerance [62]. CRISPR/Cas9-mediated genome editing technology is very efficient to develop transgenic crops, which are environment-friendly and able to adapt to climate changes efficiently. A short review of the application of CRISPR/Cas9 in abiotic stress tolerance has been summarized in **Table 6**.

### **8. Conclusion**

In this chapter, molecular responses of transgenic plants to different types of abiotic stresses have been discussed. This review has thrown light on the effects of


#### **Table 6.**

*Genetic engineering of plants through CRISPR/Cas9 to adapt abiotic stress.*

climate change-induced stress factors for plants and how genetic engineering can help to develop transgenic plants that are able to respond to these stresses at the molecular level. Climate change is a major threat factor for the agricultural sector as it causes lower yield and productivity. It causes increased food demand leading to hunger and starvation. Drought stress, salinity stress, temperature stress, and heavy metal stress are major types of abiotic stresses that cause retarded and stunted growth, lower yield, and productivity. Molecular adaptations through genetic engineering can be achieved by expressing stress-related genes, accumulation of compatible solutes, activation of signaling pathways, activation of transcriptional factors, action of various transporters, synthesis of heat-shock proteins and secondary metabolites, and enzymatic and nonenzymatic defense mechanisms, etc. through various genome editing tools, such as CRISPR/Cas9. This review has covered a detailed analysis of each type of abiotic stress and responses of transgenic plants at the molecular level.

Most of the studies of transgenic plants are based on Arabidopsis, rice, and tobacco. Further studies are required by using model plants on different staple crops, such as wheat, cereals, and legumes. to meet food requirements. Climate is changing very rapidly and it has adverse effects on plant growth, productivity, and yield. Climate change-induced stress factors can cause famine and starvation. Different technologies and genome editing tools are being used worldwide to produce resistant transgenic crops, such as CRISPR/Cas9, OMICS, TALEN, QTL, nanobiotechnology, and miRNAs/siRNAs. These technologies focus on genome editing of transcription factors and stress-responsive genes to introduce novel modifications in the plant genome. The development of transgenic crops through genetic engineering is a need of time and demands serious efforts.

*Molecular Mechanisms and Strategies Contributing toward Abiotic Stress Tolerance in Plants DOI: http://dx.doi.org/10.5772/intechopen.109838*
