Glycosidase and glycan polymorphism control hydrolytic release of immunogenic flagellin peptides

• Published in: Science (American Association for the Advancement of Science) 2019-04, Vol.364 (6436)
• Main Authors: Buscaill, Pierre, Chandrasekar, Balakumaran, Sanguankiattichai, Nattapong, Kourelis, Jiorgos, Kaschani, Farnusch, Thomas, Emma L, Morimoto, Kyoko, Kaiser, Markus, Preston, Gail M, Ichinose, Yuki, van der Hoorn, Renier A L
• Format: Article
• Language: English
• Subjects: Angiosperms; Animals; Apoplast; Bacteria; beta-Galactosidase - genetics; beta-Galactosidase - metabolism; Buried structures; Cell surface; Computational fluid dynamics; DNA probes; Flagella; Flagellin; Flagellin - immunology; Flagellin - metabolism; Flowers & plants; Fluids; Fragmentation; Fragments; Galactosidase; Gene polymorphism; Genome editing; Genomes; Glycan; Glycosidases; Glycosylation; Host-Pathogen Interactions - immunology; Hydrolysis; Immune response; Immune system; Immunity; Immunogenicity; Infections; Microorganisms; Mutants; Nicotiana - enzymology; Nicotiana - genetics; Nicotiana - immunology; Nicotiana - microbiology; Nicotiana benthamiana; Organic chemistry; Pathogens; Peptides; Plant immunity; Plant tissues; Polymers; Polymers - metabolism; Polymorphism; Polysaccharides; Polysaccharides - chemistry; Polysaccharides - metabolism; Protease inhibitors; Proteinase inhibitors; Proteins; Pseudomonas syringae; Pseudomonas syringae - immunology; Pseudomonas syringae - pathogenicity; Reactive oxygen species; Recognition; Regulators; Rhamnose; Shielding; Strains (organisms); Thermal stability; Tomatoes; Virulence; β-Galactosidase
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aav0748

Plants and animals recognize conserved flagellin fragments as a signature of bacterial invasion. These immunogenic elicitor peptides are embedded in the flagellin polymer and require hydrolytic release before they can activate cell surface receptors. Although much of flagellin signaling is understood, little is known about the release of immunogenic fragments. We discovered that plant-secreted β-galactosidase 1 (BGAL1) of promotes hydrolytic elicitor release and acts in immunity against pathogenic strains only when they carry a terminal modified viosamine (mVio) in the flagellin -glycan. In counter defense, pathovars evade host immunity by using BGAL1-resistant -glycans or by producing a BGAL1 inhibitor. Polymorphic glycans on flagella are common to plant and animal pathogenic bacteria and represent an important determinant of host immunity to bacterial pathogens.