Multiplex Cas9-based excision of CLCuV betasatellite and DNA-A revealed reduction of viral load with asymptomatic cotton plants

MAIN CONCLUSION

Multiplexed Cas9-based genome editing of cotton resulted in reduction of viral load with asymptomatic cotton plants. In depth imaging of proteomic dynamics of resulting CLCuV betasatellite and DNA-A protein was also performed. The notorious  cotton leaf curl virus (CLCuV), which is transmitted by the sap-sucking insect whitefly, continuously damages cotton crops. Although the application of various toxins and RNAi has shown some promise, sustained control has not been achieved. Consequently, CRISPR_Cas9 was applied by designing multiplex targets against DNA-A (AC2 and AC3) and betasatellite (βC1) of CLCuV using CRISPR direct and ligating into the destination vector of the plant using gateway ligation method. The successful ligation of targets into the destination vector was confirmed by the amplification of 1049 bp using a primer created from the promoter and target, while restriction digestion using the AflII and Asc1 enzymes determined how compact the plasmid developed and the nucleotide specificity of the plasmid was achieved through Sanger sequencing. PCR confirmed the successful introduction of plasmid into CKC-1 cotton variety. Through Sanger sequencing and correlation with the mRNA expression of DNA-A and betasatellite in genome-edited cotton plants subjected to agroinfiltration of CLCuV infectious clone, the effectiveness of knockout was established. The genome-edited cotton plants demonstrated edited efficacy of 72% for AC2 and AC3 and 90% for the (βC1) through amplicon sequencing, Molecular dynamics (MD) simulations were used to further validate the results. Higher RMSD values for the edited βC1 and AC3 proteins indicated functional loss caused by denaturation. Thus, CRISPR_Cas9 constructs can be rationally designed using high-throughput MD simulation technique. The confidence in using this technology to control plant virus and its vector was determined by the knockout efficiency and the virus inoculation assay.

Development of Virus Resistance Transgenic Cotton Using Cotton Leaf Curl Virus Antisense ßC1 Gene

Cotton (Gossypium hirsutum L.) is the most economically important crop in the world and produced 90% of the total natural cellulose fiber which is utilized to make cotton fabrics. The production of cotton is affected by many several diseases, and among them, viral disease, especially leaf curl, is the most destructive disease caused by a begomovirus transmitted by whiteflies vector. Plant biotechnology has provided an opportunity to develop transgenic plant with variable traits against biotic and abiotic stress such as resistance against pathogens, yield, quality, and salinity. Transgenic cotton (Gossypium hirsutum L., cv. Coker 312) plants were raised against leaf curl disease using bC1 gene in antisense orientation through Agrobacterium-mediated transformation somatic embryogenesis system. In this chapter, a standardized protocol will be given to raise virus resistance transgenic cotton.