title: Phylloplanins of tobacco are defensive proteins deployed on aerial surfaces by short glandular trichomes.
abstract: In plants, defensive proteins secreted to leaf aerial surfaces have not previously been considered to be a strategy of pathogen resistance, and the general occurrence of leaf surface proteins is not generally recognized. We found that leaf water washes (LWW) of the experimental plant Nicotiana tabacum tobacco introduction (TI) 1068 contained highly hydrophobic, basic proteins that inhibited spore germination and leaf infection by the oomycete pathogen Peronospora tabacina. We termed these surface-localized proteins tobacco phylloplanins, and we isolated the novel gene T-Phylloplanin (for Tobacco Phylloplanin) and its promoter from N. tabacum. Escherichia coli-expressed T-phylloplanin inhibited P. tabacina spore germination and greatly reduced leaf infection. The T-phylloplanin promoter, when fused to the reporter genes beta-glucuronidase and green fluorescent protein, directed biosynthesis only in apical-tip cell clusters of short, procumbent glandular trichomes. Here, we provide evidence for a protein-based surface defense system in the plant kingdom, wherein protein biosynthesis in short, procumbent glandular trichomes allows surface secretion and deposition of defensive phylloplanins on aerial surfaces as a first-point-of-contact deterrent to pathogen establishment. As yet uncharacterized surface proteins have been detected on most plant species examined.
authors.affiliation: Plant Physiology, Biochemistry, Molecular Biology Program, Agronomy Department, University of Kentucky, Lexington, Kentucky 40546, USA.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Shepherd
authors.forename: W Troy
authors.initials: WT
authors.lastname: Bass
authors.forename: Robert L
authors.initials: RL
authors.lastname: Houtz
authors.forename: George J
authors.initials: GJ
authors.lastname: Wagner
mesh_terms: D017124:Conserved Sequence / Q000235:genetics; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D017930:Genes, Reporter / Q000235:genetics; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics; D019441:Plant Epidermis / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D011401:Promoter Regions, Genetic / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins