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Yini Huang

Second Green Revolution--Gene Editing

Traditional Breeding: At first, researchers obtained homozygous offspring by crossing the preferred variation and unfavourable variation based on the existence of genetically modified phenomena in nature, such as cross-pollination, natural hybridization, natural transgene of Agrobacterium, etc.

Figure 1 Traditional Breeding.

GM: Researchers developed Genetic Modification (GM) based on the principles of natural breeding. GM integrates the desired target genes into the plant genome after artificial isolation and recombination and modifies the crop genome to optimize the existing traits or induce new excellent traits.

Figure 2 Key steps of agrobacterium-mediated genetic modification.

Gene editing: To avoid introducing foreign DNAs and to just edit the site-specific clusters. Gene editing relies on genetically engineered nucleases to produce site-specific double-strand breaks (DSBS) at specific locations in the genome, inducing the host to repair the DSB via either nonhomologous end junction (NHEJ) or homologous directed repair (HDR), and the errors generated during this repair process lead to targeted mutations, which are gene editing.

Figure 3 Mechanism of  CRISPR/Cas9.

 Figure 4 CRISPR/Cas9 reagents delivery.

The common method is inserting a transgenic CRISPR/Cas9 construct into the host genome and then crossing it out again to obtain transgene-free progeny still requires multiple rounds of selection.The typical gene-edited crops are regenerated from callus or protoplasts by tissue culture which means that every time getting a gene-edited crop needs go through this process.

Advanced gene editing research field: VIGE

Figure5 VIGE

VIGE: Virus-Introduced Plant Genome Editing. Use virus infect plants without tissue culture to get transgene free plants.

Difficulty: Let virus enter SAM(shoot apical meristem) to get gene edited seeds.

Second Green Revolution

  • Reason: Excessive use of fertilisers and irrigation changes the natural biota in the soil and the salinity of the soil leads to soil degradation. Pesticides, herbicides and other chemicals that were widely used in agricultural production not only damage the ecological environment, but also have adverse effects on human health, and even lead to poisoning, disease and death. To maintain crop yields, save degraded soils and achieve ecosystem sustainability.
  • Methods: Gene engineering.