CRISPR/Cas9 generatedMeSWEET10amutants show reduced susceptibility to cassava bacterial blight and produce viable seed

Abstract

AbstractBacteria from the genusXanthomonasare prolific phytopathogens that elicit disease in over 400 plant species. Xanthomonads carry a repertoire of specialized proteins called transcription activator-like (TAL) effectors that promote disease and pathogen virulence by inducing expression of host susceptibility (S) genes.Xanthomonas phaseolipv.manihotis(Xpm) causes bacterial blight on the staple food crop, cassava. The Xpm effector, TAL20, induces ectopic expression of the S gene,MeSWEET10a, a sugar transporter that contributes to cassava bacterial blight susceptibility. We used CRISPR/Cas9 to generate multiple cassava lines with edits to theMeSWEET10aTAL20 effector binding site and/or coding sequence. In several of the regenerated lines,MeSWEET10aexpression was no longer induced byXpmand in these cases, we observed reduced cassava bacterial blight disease symptoms post Xpm infection.MeSWEET10ais expressed in cassava flowers. Therefore, we investigated flower development and reproductive function in anMeSWEET10amutant line. We found that theMeSWEET10amutant produced phenotypically wildtype cassava flowers and viable F1 seed. Thus, blockingMeSWEET10ainduction is a viable strategy for decreasing cassava susceptibility to CBB.