Location: Subtropical Plant Pathology ResearchTitle: Editing the CsDMR6 gene in citrus results in resistance to the bacterial disease citrus canker
|PARAJULI, SAROJ - University Of Florida|
|HUO, HEQIANG - University Of Florida|
|GMITTER, FRED - University Of Florida|
|LUO, FENG - Clemson University|
|DENG, ZHANAO - University Of Florida|
Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2022
Publication Date: 4/11/2022
Citation: Parajuli, S., Huo, H., Gmitter, F., Duan, Y., Luo, F., Deng, Z. 2022. Editing the CsDMR6 gene in citrus results in resistance to the bacterial disease citrus canker. Horticulture Research. 2. https://doi.org/10.1093/hr/uhac082.
Interpretive Summary: Citrus is one of the most important fruit crops in the world, grown in more than 114 countries with 146.6 million tons of production in 9.3 million hectares. Citrus production worldwide faces major challenges from multiple devastating bacterial diseases, including citrus canker and Huanglongbing (HLB). Citrus canker is caused by Xanthomonas citri ssp. citri (Xcc), and most citrus species and cultivars are susceptible to this disease. Improving resistance to citrus canker has been an important citrus breeding objective. In this study, we have demonstrated that disruptive (frameshift) mutagenesis of the DMR6 homolog (CsDMR6) in two citrus cultivars resulted in strong resistance to citrus canker. We also have shown that the hyper-accurate HypaCas9 mediated high frequencies of mutations in citrus. The guide RNAs designed in this study are expected to target DMR6 orthologs in multiple commercially important citrus species and cultivars. SA plays a central role in plant resistance to many pathogens. Functional knocking down of CsDMR6 increased SA accumulation and NPR1 expression in citrus, thus editing this gene may be an effective approach to improving citrus resistance to other pathogens.
Technical Abstract: Citrus canker is caused by Xanthomonas citri ssp. citri (Xcc), and most citrus species and cultivars are susceptible to this disease. In this study, we conducted CRISPR-Cas9 mediated mutagenesis of a DOWNY MILDEW RESISTANCE 6 (DMR6) ortholog (CsDMR6) in two citrus cultivars, ‘Duncan’ grapefruit (Citrus × paradisi) and Carrizo citrange (Citrus × sinensis × Poncirus trifoliata). The CsDMR6-edited lines of the two cultivars showed strong enhanced resistance to citrus canker caused by Xcc by significantly reduction of canker lesion size and bacterial titers. Furthermore, we have demonstrated the molecular mechanism underlying the enhanced resistance by revealing that functional knocking down of the CsDMR6 increased SA accumulation and NPR1 expression in edited citrus. These findings indicated editing the CsDMR6-gene may be an effective approach to improving citrus resistance to other important pathogens.