methyl-jasmonate and sclareol

Plant pathogens cause huge yield losses. Plant defense often depends on toxic secondary metabolites that inhibit pathogen growth. Because most secondary metabolites are also toxic to the plant, specific transporters are needed to deliver them to the pathogens. To identify the transporters that function in plant defense, we screened

Topics: Acetates; Alternaria; Arabidopsis; Arabidopsis Proteins; ATP Binding Cassette Transporter, Subfamily G; Biological Transport; Botrytis; Cyclopentanes; Diterpenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Green Fluorescent Proteins; Indoles; Mutation; Oxylipins; Phenotype; Phylogeny; Plant Diseases; Plant Leaves; Signal Transduction; Thiazoles

Expression of NpABC1, a gene encoding a plasma membrane ATP binding cassette (ABC) transporter in Nicotiana plumbaginifolia, is induced by sclareol, an antifungal diterpene produced at the leaf surface, as well as by sclareolide, a close analog. A genomic fragment including the 1282-bp region upstream of the NpABC1 transcription start was fused to the reporter beta-glucuronidase (gus) gene and introduced into N. tabacum BY2 cells for stable transformation. A 25-fold increase in gus expression was observed when cells were treated with sclareolide and some other terpenes. The combined use of 5'-deletion promoter analysis, gel mobility shift assays, DNase I footprinting, and site-directed mutagenesis allowed us to identify three cis-elements (sclareol box 1 (SB1), SB2, and SB3) located, respectively, within nucleotides -827 to -802, -278 to -243, and -216 to -190 upstream of the NpABC1 transcription start. In vivo evaluation of these elements on sclareolide-induced expression showed that mutation of SB1 reduced expression by twofold, while that of SB2 had no effect. On the other hand, SB3 had a marked effect as it completely abolished sclareolide-mediated expression. NpABC1-gus expression was not induced by the stress signals, salicylic acid and ethylene, but was mediated, to some extent, by methyl jasmonate, which is known to promote diterpene synthesis.

Topics: Acetates; ATP-Binding Cassette Transporters; Base Sequence; Cell Line; Cyclopentanes; Deoxyribonuclease I; Diterpenes; DNA Footprinting; DNA Mutational Analysis; Electrophoretic Mobility Shift Assay; Ethylenes; Gene Expression Regulation, Plant; Glucuronidase; Molecular Sequence Data; Nicotiana; Oxylipins; Plant Proteins; Promoter Regions, Genetic; Recombinant Fusion Proteins; Regulatory Sequences, Nucleic Acid; Salicylic Acid; Sequence Deletion; Sequence Homology, Nucleic Acid

The ATP-binding cassette (ABC) transporters are encoded by large gene families in plants. Although these proteins are potentially involved in a number of diverse plant processes, currently, very little is known about their actual functions. In this paper, through a cDNA microarray screening of anonymous cDNA clones from a subtractive library, we identified an Arabidopsis gene (AtPDR12) putatively encoding a member of the pleiotropic drug resistance (PDR) subfamily of ABC transporters. AtPDR12 displayed distinct induction profiles after inoculation of plants with compatible and incompatible fungal pathogens and treatments with salicylic acid, ethylene, or methyl jasmonate. Analysis of AtPDR12 expression in a number of Arabidopsis defense signaling mutants further revealed that salicylic acid accumulation, NPR1 function, and sensitivity to jasmonates and ethylene were all required for pathogen-responsive expression of AtPDR12. Germination assays using seeds from an AtPDR12 insertion line in the presence of sclareol resulted in lower germination rates and much stronger inhibition of root elongation in the AtPDR12 insertion line than in wild-type plants. These results suggest that AtPDR12 may be functionally related to the previously identified ABC transporters SpTUR2 and NpABC1, which transport sclareol. Our data also point to a potential role for terpenoids in the Arabidopsis defensive armory.

Topics: Acetates; Arabidopsis; Arabidopsis Proteins; ATP-Binding Cassette Transporters; Cloning, Molecular; Cyclopentanes; Diterpenes; DNA, Complementary; Ethylenes; Fungi; Gene Expression Regulation, Plant; Germination; Immunity, Innate; Membrane Transport Proteins; Mutation; Oligonucleotide Array Sequence Analysis; Oxylipins; Plant Diseases; Salicylic Acid; Seeds; Sequence Analysis, DNA; Signal Transduction