Genome editing made it possible for the world's most important food crop to become resistant to a destructive bacterial disease.
Xanthomonas oryzae pathovar oryzae (Xoo) causes bacterial blight in rice, a stable food for billions of people worldwide. To combat the devastating infection, Ricardo Oliva and his team at the International Rice Research Institute (IRRI) explored on Xoo genes that encode proteins called transcription-activator-like effectors (TALEs). Xoo use TALEs to switch on SWEET genes in rice plants, which are necessary for disease susceptibility. Thus, when the SWEET genes are expressed, Xoo gets access to the nutrients in the rice plants' leaves.
The researchers analyzed 63 Xoo strains and found that each strain has one or more versions of TALEs. Each version can turn on at lease on of the three SWEET genes. To modify the SWEET genes, the researchers used the genome editing tool CRISPR-Cas9. This led to edited SWEET genes that cannot be activated by the bacterial TALEs. The rice plants with edited genes were found to be resistant to at least 95 Xoo strains.
The findings indicate that genome editing could be an effective tool in enhancing disease resistance of rice, particularly to bacterial blight.
Xoo use these proteins to turn on the plant's SWEET genes, which produce sugar-transporting molecules. This gives the bacteria access to nutrients in the plants' leaves.