Editing of the MeSWEET10a promoter yields bacterial blight resistance in cassava cultivar SC8

Yajie Wang, Mengting Geng, Ranran Pan, Tong Zhang, Xiaohua Lu, Xinghou Zhen, Yannian Che, Ruimei Li, Jiao Liu, Yinhua Chen, Jianchun Guo, Yuan Yao

Molecular Plant Pathology; 29 September 2024;

https://doi.org/10.1111/mpp.70010

Abstract

Cassava starch is a widely used raw material for industrial production and food source for people. However, cassava bacterial blight (CBB) caused by Xanthomonas axonopodis pv. manihotis (Xam) results in severe yield losses and is the most destructive bacterial disease in all worldwide cassava-growing regions. Xam11 is a highly pathogenic subspecies from China that infects the Chinese local cassava South China No. 8 (SC8) cultivar with marked symptoms. This study showed that the transcription activator-like effector TALE20_Xam11 of Xam11 strain regulates the expression of disease-susceptibility gene MeSWEET10a by binding to the EBE_TALE20 region of the MeSWEET10a promoter in cassava cultivar SC8. CRISPR/Cas9-generated mutations of the EBE_TALE20 region resulted in a significant reduction in MeSWEET10a expression after infection by Xam11, correlating with reduced disease symptoms, smaller lesion sizes and decreased bacterial proliferation compared with the wild type. Importantly, the edited plants maintained normal growth, development and yield characteristics under greenhouse conditions. The results lay a research foundation for breeding resistant cassava cultivar SC8 to bacterial blight.

See https://bsppjournals.onlinelibrary.wiley.com/doi/10.1111/mpp.70010

Figure 1. Schematic representation of repeat variable diresidue (RVD) in TALE20_Xam11 recognizes the EBE_Xam11 on MeSWEET10a promoter from cassava cultivar South China No. 8. (a) The C-terminus of TALE20_Xam11 has two nuclear localization signals (NLS) and an acidic activation domain (ADD). TALE20_Xam11 directly activates MeSWEET10a expression through the effector-binding element (EBE) region. (b) SK: pGreen II62-SK vector (control vector); TALE20: pGreen II62-SK-TALE20_Xam11 vector; pSWEET10a: pGreen II0800-pMeSWEET10a-LUC vector; pSWEET10a-EBE: pGreen II0800-pMeSWEET10a-EBE_TALE20-LUC vector (deletion of EBE_TALE20 from MeSWEET10a promoter). Data are displayed from three biological repeats (Student's t test, **p < 0.01).