A secreted citrus protease cleaves an outer membrane protein of the Huanglongbing pathogen

McClelland, Alexander J., Hu, Bin, Xu, Yuantao, Fang, Xiaodong, Wang, Chunxia, Koch, Benjamin L., Lovelace, Amelia H., Hawara, Eva, Wang, Yuanchun, Pang, Zhiqian, De Francesco, Agustina, van Wier, Suzanne P., Beekman, Andrew M. ORCID: https://orcid.org/0000-0002-3056-6406, Levy, Amit, Wang, Nian, van der Hoorn, Renier A.L., Xu, Qiang and Ma, Wenbo (2026) A secreted citrus protease cleaves an outer membrane protein of the Huanglongbing pathogen. Proceedings of the National Academy of Sciences of the United States of America, 123 (15). ISSN 0027-8424

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Abstract

Plants secrete a variety of proteases as a defense response during infection by microbial pathogens. However, the relationship between their catalytic activities and antimicrobial functions remains largely unknown. Particularly, few biologically relevant substrates of these proteases have been identified. Huanglongbing (HLB) has been a major threat to the citrus industry worldwide. The HLB-associated bacterium, “Candidatus Liberibacter asiaticus” (Las), was previously shown to deploy an inhibitor of papain-like cysteine proteases (PLCPs) to promote disease in citrus. In this study, we identified an outer membrane protein (OMP) of Las, LasOMP1, as a substrate of the citrus PLCP CsRD21a. LasOMP1 is one of the most highly expressed genes in Las. CsRD21a cleaves LasOMP1 and produces cleaved peptide products, which could be detected in vitro and in HLB-diseased citrus plants. We found that CsRD21a targets the N-terminal portion of LasOMP1, potentially at an extracellular loop region. Importantly, transgenic sweet orange overexpressing CsRD21a showed reduced Las populations and improved plant growth, highlighting that engineering this protease is a promising strategy to enhance HLB resistance in citrus. Together, our work reveals a pathogen-derived substrate of plant PLCPs and suggests bacterial OMPs may be direct targets of plant defense.

Item Type: Article
Additional Information: Data, Materials, and Software Availability: RNA-seq data have been deposited in NCBI Bioproject (BioProject PRJEB82095/) (78).
Uncontrolled Keywords: bacterial pathogens,candidatus liberibacter,citrus greening disease,plant innate immunity,plant-pathogen interactions,general ,/dk/atira/pure/subjectarea/asjc/1000
Faculty \ School: Faculty of Science > The Sainsbury Laboratory
Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
Related URLs:
Depositing User: LivePure Connector
Date Deposited: 04 Aug 2026 15:10
Last Modified: 05 Aug 2026 14:22
URI: https://ueaeprints.uea.ac.uk/id/eprint/103981
DOI: 10.1073/pnas.2528641123

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