A secreted citrus protease cleaves an outer membrane protein of the Huanglongbing pathogen
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 Cs RD21a. LasOMP1 is one of the most highly expressed genes in Las. Cs RD21a cleaves LasOMP1 and produces cleaved peptide products, which could be detected in vitro and in HLB-diseased citrus plants. We found that Cs RD21a targets the N-terminal portion of LasOMP1, potentially at an extracellular loop region. Importantly, transgenic sweet orange overexpressing Cs RD21a 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.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (18)
Alexander J. McClelland
The Sainsbury Laboratory, University of East Anglia
Bin Hu
Yuantao Xu
Xiaodong Fang
BGI Research, Hangzhou, China.
Chunxia Wang
Citrus Research and Education Center, Department of Plant Pathology, Microbiology and Cell Science, University of Florida/Institute of Food and Agricultural Sciences
Benjamin L. Koch
The Sainsbury Laboratory, University of East Anglia
Amelia H. Lovelace
The Sainsbury Laboratory, University of East Anglia
Eva Hawara
Department of Microbiology and Plant Pathology, University of California Riverside
Yuanchun Wang
Citrus Research and Education Center, Department of Plant Pathology, Microbiology and Cell Science, University of Florida/Institute of Food and Agricultural Sciences
Zhiqian Pang
Citrus Research and Education Center, Department of Plant Pathology, Microbiology and Cell Science, University of Florida/Institute of Food and Agricultural Sciences
Agustina De Francesco
Department of Microbiology and Plant Pathology, University of California Riverside
Suzanne P. van Wier
School of Chemistry, Pharmacy and Pharmacology, University of East Anglia
Andrew M. Beekman
School of Chemistry, Pharmacy and Pharmacology, University of East Anglia
Amit Levy
Citrus Research and Education Center, Department of Plant Pathology, Microbiology and Cell Science, University of Florida/Institute of Food and Agricultural Sciences
Nian Wang
Citrus Research and Education Center, Department of Plant Pathology, Microbiology and Cell Science, University of Florida/Institute of Food and Agricultural Sciences
Renier A. L. van der Hoorn
Plant Chemetics Laboratory, Department of Biology, University of Oxford
Qiang Xu
Key Laboratory of Material Simulation Methods & Software of Ministry of Education, College of Physics
Wenbo Ma
The Sainsbury Laboratory, University of East Anglia