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 phaseoli pv. manihotis, the causal agent of cassava bacterial blight (CBB), uses transcription activator-like20 (TAL20) to induce expression of the S gene MeSWEET10a. In this work, we direct 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 decreased CBB symptoms while maintaining normal growth and development. This work therefore presents an epigenome editing approach useful for crop improvement.

Cassava molecular genetics and genomics for enhanced resistance to diseases and pests

“…Management of the disease involves cultural practices, varietal resistance, biological control and sanitation practices. However, no durable broad‐spectrum resistance genes are available to breeders (Veley et al., 2023 ).…”

CPK1‐HSP90 phosphorylation and effector XopC2–HSP90 interaction underpin the antagonism during cassava defense‐pathogen infection

“…Cassava (Manihot esculenta Crantz) is one of the most important tropical crops, feeding c. 1 billion in the tropical regions (Maxmen, 2019;Zierer et al, 2021). However, cassava bacterial blight (CBB) caused by Xanthomonas axonopodis pv manihotis (Xam) results in substantial yield losses world-wide (Maxmen, 2019;Veley et al, 2023). In order to successfully infect plant hosts, Xam has evolved complex functional pathogenicity mechanisms, such as type III effectors (Xanthomonas outer proteins (Xop) and transcription activator-like (TAL) effectors) to modulate host gene expression (Zierer et al, 2021).…”

Antimicrobial resistance in the wild: Insights from epigenetics

“…It is crucial to refine and improve these techniques, given that, in many cases, epigenetic editing is preferred over genetic editing. This preference relies on the reversible nature of epigenetic changes and their inducibility in specific tissues, developmental stages, or environmental conditions, often facilitated through the utilization of chemically inducible promoters (Thakore et al., 2016 ; Veley et al., 2023 ).…”

“…Cassava is widely cultivated for numerous purposes, including human and animal consumption, the production of flour, alcohol, starches, sweeteners, and textiles, and it is susceptible to a disease caused by the bacterium Xanthomonas phaseoli pv. manihotis (Veley et al., 2023 ). Research has shown that the pathogenic bacteria uses the TAL20 (transcription activator‐like effector) to induce expression of the susceptibility gene MeSWEET10a, which belongs to the sugar transporter family.…”