Improving cassava bacterial blight resistance by editing the epigenome

Abstract

Pathogens rely on expression of host susceptibility (S) genes to promote infection and disease. As DNA methylation is an epigenetic modification that affects gene expression, blocking access to S genes through targeted methylation could increase disease resistance. Xanthomonas axonopodis pv. manihotis, the causal agent of cassava bacterial blight (CBB), uses transcription activator-like20 (TAL20) to induce expression of the S gene MeSWEET10a. We directed methylation to the TAL20 effector binding element within the MeSWEET10a promoter using a synthetic zinc-finger DNA binding domain fused to a component of the RNA-directed DNA methylation pathway. We demonstrate that this methylation prevents TAL20 binding, blocks transcriptional activation of MeSWEET10a in vivo and that these plants display increased resistance to CBB while maintaining normal growth and development. This work establishes epigenome editing as a new strategy for crop improvement.

Engineering bacterial blight-resistant plants through CRISPR/Cas9-targeted editing of theMeSWEET10apromoter in cassava

“…However, these mutations often affect plant fitness with reduced growth, fertility, yield, and abiotic stress tolerance (Zaidi et al, 2018). Recently, Veley et al (2022) has been reported that directed methylation to EBE TALE20 region of MeSWEET10a promoter of TME419 in 60444 cassava cultivar, the plants displayed an increased resistance to Xam668 strain, meanwhile, they maintained normal growth and development (Veley et al, 2022). In our results, there were no significant differences in tuber root traits and starch content between the EBE TALE20 mutated lines and the wild type plants when grown under normal conditions (Fig.…”