Targeted editing of OsSWEET11 promoter for imparting bacterial leaf blight resistance in rice

Abstract

Rice is one of the most cultivated cereal crops worldwide and its productivity is affected by several biotic and abiotic factors. The gram-negative bacterium, Xanthomonas oryzae pv. oryzae (Xoo) severely impacts rice productivity by causing bacterial leaf blight disease. During infection, Xoo secretes a TALe protein which binds to effector binding element (EBE) present in the promoter sequence of susceptible genes, such as SWEET genes in order to make the plants vulnerable to infection. Mutations in EBE were shown to prevent binding of TALe and in turn result in enhanced resistance to the pathogen. In an attempt to engineer resistance in ASD16 to Xoo strains that secrete PthXo1, the EBE of promoter of SWEET11 gene was edited through CRISPR/Cas9 tool. Genome editing of ASD16, through Agrobacterium-mediated transformation resulted in seventeen transgenic events. Thirty one plants belonging to thirteen independent transgenic events turned out to be mutants possessing biallelic or homozygous mutations. Bioassay studies on twelve T0 mutant plants against Xoo revealed that eleven mutant plants were found to be resistant/ moderately resistant to the Xoo strain, indicating the potential of CRISPR technology in creating allelic variations which could be exploited in disease resistance breeding programmes.

Keywords

• rice
• bacterial leaf blight
• xanthomonas oryzae pv. oryzae
• effector binding element
• crispr/cas9