Gene Editing

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Key Knowledge:
  • The function of CRISPR-Cas9 in bacteria and the application of this function in editing an organism’s genome
  • Potential uses and applications of CRISPR-Cas9 technologies to improve photosynthetic efficiencies and crop yields


Gene editing involves the insertion, removal or replacement of DNA within the genome of a living organism

  • The most precise, efficient and flexible method of gene editing currently available involves the CRISPR editing system


CRISPR-Cas9 System

The CRISPR-Cas9 system functions naturally in bacteria to provide immunity against viral infections

  • When a virus infects a bacterial cell, snippets of viral DNA are pasted into palindromic sequences within the bacterial genome to form a CRISPR locus (CRISPR = ‘clustered regularly interspaced short palindromic repeats’), which act as a memory bank for viral infections
  • A CRISPR sequence is transcribed into an RNA strand that associates with a CRISPR-associated nuclease (e.g. Cas9)
  • The RNA and Cas nuclease drift throughout the cell until the RNA locates and binds with any complementary viral DNA
  • This enables the Cas nuclease to then destroy the viral DNA sequence and hence prevents any subsequent infection


Gene Editing

The CRISPR-Cas9 system has been modified to selectively remove any targeted sequence, allowing for precise gene editing

  • The Cas protein is complexed with a synthetically derived guide RNA molecule that is complementary to a target sequence
  • The guide RNA (gRNA) will bind to the target sequence, prompting its excision by the Cas nuclease
  • Following the removal of the target sequence, another sequence of DNA can be integrated in its place (gene editing)


gene editing


Practical Applications

Gene editing via the CRISPR-Cas9 system has been used to address a variety of agricultural issues associated with food production

  • Certain metabolic pathways have been enhanced to improve nutritional content (e.g. higher starch production)
  • Plant absorption spectra have been modified to increase photosynthetic efficiencies (e.g. new pigments introduced)
  • Higher tolerances to biotic pathogens (viral, bacterial, fungal) or abiotic stresses (cold, drought, salt) have been achieved
  • Resistance to particular herbicides have been incorporated into crops to allow for elimination of competing weed species
  • Improvements in photorespiration efficiencies has resulted in increased food production in a variety of common C3 plants


Genetic Modifications in Crop Species

GM crops