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Crop Biotech Update

Engineering Broad-Spectrum Bacterial Blight Resistance in Rice Using CRISPR-Cas9

September 25, 2019

Bacterial blight is one of the most destructive diseases of rice worldwide. It is caused by Xanthomonas oryzae pv. oryzae (Xoo), which recruits transcription activator-like effectors (TALEs) to promote the expression of OsSWEET genes which are vital in sugar transport and disease susceptibility. To develop broad-spectrum bacterial blight resistance, scientists from Shanghai Jiao Tong University in China used CRISPR-Cas9 to break the TALE-binding elements of the susceptibility genes, OsSWEET11 and OSSWEET14 in rice.

The resulting rice line MS14K showed broad-spectrum resistance to most Xoo strains, which may imply that the compatible strains may have new TALEs. They found two types of PthXo2-like TALEs that function as major virulence factors in the compatible Xoo strains. Xoo encodes 5 types of PthXo2-like effectors. Since PthXo2/PthXo2.1 target OsSWEET13 for transcriptional activation, the genomes of 3,000 rice varieties were analyzed for variations of TALE-binding elements (EBE). The two PthXo2-like TALEs were found to bind slightly different EBE sequences and activated their expression. Then CRISPR-Cas9 was used to produce insertions and deletions in the EBE of OsSWEET13 promoter in the mutant MS14K. This led to the development of new germplasm with tree edited OsSWEET EBEs and broad-spectrum resistance against Xoo.

The research shows how to develop broad-spectrum resistance through the loss of effector-triggered susceptibility in plants.

Read the research article in Molecular Plant.

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