title: Pathogen challenge, salicylic acid, and jasmonic acid regulate expression of chitinase gene homologs in pine.
abstract: To better understand the molecular regulation of defense responses in members of the genus Pinus, we tested the expression of various chitinase homologs in response to pathogen-associated signals. PSCHI4, a putative extracellular class II chitinase, was secreted into liquid medium by pine cells and was also secreted by transgenic tobacco cells that ectopically expressed pschi4. Extracellular proteins of pine were separated by isoelectric focusing; PSCHI4 was not associated with fractions containing detectable beta-N-acetylglucosaminidase or lysozyme activities. However, other fractions contained enzyme activities that increased markedly after elicitor treatment. The pschi4 transcript and protein accumulated in pine seedlings challenged with the necrotrophic pathogen Fusarium subglutinans f. sp. pini, with the protein reaching detectable levels in susceptible seedlings concomitant with the onset of visible disease symptoms. Additional chitinase transcripts, assigned to classes I and IV based on primary sequence analysis, were also induced by pathogen challenge. Jasmonic acid induced class I and class IV but not class II chitinase, whereas salicylic acid induced all three classes of chitinase. These results show that multiple chitinase homologs are induced after challenge by a necrotrophic pathogen and by potential signaling molecules identified in angiosperms. This suggests the potential importance of de novo pathogenesis-related (PR) gene expression in pathogen defense responses of pine trees.
authors.affiliation: School of Forest Resources and Conservation, and Plant Molecular and Cellular Biology Program, University of Florida, Gainesville 32611, USA. jmdavis@ufl.edu
authors.forename: John M
authors.initials: JM
authors.lastname: Davis
authors.forename: Haiguo
authors.initials: H
authors.lastname: Wu
authors.forename: Janice E K
authors.initials: JE
authors.lastname: Cooke
authors.forename: Jon M
authors.initials: JM
authors.lastname: Reed
authors.forename: K Scott
authors.initials: KS
authors.lastname: Luce
authors.forename: Charles H
authors.initials: CH
authors.lastname: Michler
mesh_terms: D000595:Amino Acid Sequence; D002688:Chitinases / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003517:Cyclopentanes / Q000494:pharmacology*; D004926:Escherichia coli / Q000235:genetics; D005658:Fungi / Q000254:growth & development*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D054883:Oxylipins; D028223:Pinus / Q000187:drug effects / Q000235:genetics* / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology; D010937:Plant Growth Regulators / Q000494:pharmacology; D020156:Salicylic Acid / Q000494:pharmacology*; D017385:Sequence Homology; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism
chemical_list: D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; C011006:jasmonic acid; D002688:Chitinases; D020156:Salicylic Acid