The sweet orange (Citrus sinensis) event GE-LOB1 Orange was developed with CRISPR/Cas9 technology. Small DNA deletions were induced in the lob1 gene to knockout this gene.
The intended effect of the modification is to confer resistance to citrus canker to the plant.
lob1 is a member of the Lateral Organ Boundaries Domain (LBD) gene family of plant transcription factors and is directly targeted by the Xanthomonas citri ssp. citri virulence effector PthA4.
A plasmid carrying the Cas9 nuclease and the Lob1 guide RNA was introduced into Citrus sinensis protoplasts by PEG-mediated transformation and was transiently expressed. No selection marker was used.
GE-LOB1 Orange does not contain any foreign DNA sequences as verified by PCR and genome sequencing.
What is more, the developer described the development of a Duncan grapefruit with similar trait. In the grapefruit the first exon of the lob1 gene was modified using CRISPR/Cas9 to confer resistance to citrus canker; JIA et al. (2017). Plant Biotechnol J. 15, 817-823