Xanthomonas axonopodis pv. citri uses a plant natriuretic peptide-like protein to modify host homeostasis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 47; pp. 18631 - 18636
• Main Authors: Gottig, Natalia, Garavaglia, Betiana S, Daurelio, Lucas D, Valentine, Alex, Gehring, Chris, Orellano, Elena G, Ottado, Jorgelina
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 25.11.2008; National Acad Sciences
• Subjects: Bacteria; bacterial diseases of plants; bacterial natriuretic peptides; Bacterial proteins; Biological Sciences; Cell culture; Citrus; Flowers & plants; Gene expression; genes; Guard cells; Homeostasis - physiology; host-pathogen relationships; Infections; Inoculation; Leaves; Lesions; lesions (plant); Mutation; Natriuretic peptides; Natriuretic Peptides - physiology; pathogenesis; Pathogens; Peppers; Peptides; plant natriuretic peptides; plant physiology; Plant Proteins - chemistry; Plant Proteins - physiology; Plants; Plants - metabolism; Plants - microbiology; Plectranthus; Plectranthus ecklonii; signs and symptoms (plants); stomatal movement; transcription (genetics); Xanthomonas - physiology; Xanthomonas axonopodis; Xanthomonas axonopodis pv. citri
• DOI: 10.1073/pnas.0810107105
• ISSN: 0027-8424

Plant natriuretic peptides (PNPs) are a class of extracellular, systemically mobile molecules that elicit a number of plant responses important in homeostasis and growth. The bacterial citrus pathogen, Xanthomonas axonopodis pv. citri, also contains a gene encoding a PNP-like protein, XacPNP, that shares significant sequence similarity and identical domain organization with plant PNPs but has no homologues in other bacteria. We have expressed and purified XacPNP and demonstrated that the bacterial protein alters physiological responses including stomatal opening in plants. Although XacPNP is not expressed under standard nutrient rich culture conditions, it is strongly induced under conditions that mimic the nutrient poor intercellular apoplastic environment of leaves, as well as in infected tissue, suggesting that XacPNP transcription can respond to the host environment. To characterize the role of XacPNP during bacterial infection, we constructed a XacPNP deletion mutant. The lesions caused by this mutant were more necrotic than those observed with the wild-type, and bacterial cell death occurred earlier in the mutant. Moreover, when we expressed XacPNP in Xanthomonas axonopodis pv. vesicatoria, the transgenic bacteria caused less necrotic lesions in the host than the wild-type. In conclusion, we present evidence that a plant-like bacterial PNP can enable a plant pathogen to modify host responses to create conditions favorable to its own survival.