calcimycin and methyl-jasmonate

A homology-based cloning strategy yielded two cDNA clones designated Am-cam-1 and Am-cam-2, presumably encoding calmodulin protein from a callus culture derived from the leaf tissues of Aquilaria microcarpa. An appreciable increase in the transcriptional activity of Am-cam-1 was reproducibly observed by exposure of the cell culture to methyl jasmonate, as analyzed by a reverse-transcription polymerase chain reaction. The expression level of the gene also increased when the cells were treated with yeast extract. The transcription of Am-cam-2 was similarly stimulated by the treatment with methyl jasmonate and yeast extract, however, the intensities of the enhanced expression appeared to be lower as compared with that of Am-cam-1. In contrast, Ca(2+)-ionophore A23187 did not show inducing activity for the expression of these two calmodulin genes. These results suggest that Am-cam-1 and Am-cam-2 and their products play important roles in signal transduction processes in methyl jasmonate- and yeast extract-treated cells of A. microcarpa, accompanying the change in the transcriptional activities.

Topics: Acetates; Calcimycin; Calmodulin; Cloning, Molecular; Cyclopentanes; DNA, Complementary; Gene Expression; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Plant Leaves; Plant Somatic Embryogenesis Techniques; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Thymelaeaceae; Transcriptional Activation; Yeasts

A homology-based cloning strategy yielded a cDNA clone, designated Sd-cam, encoding calmodulin protein from Scoparia dulcis. The restriction digests of genomic DNA of S. dulcis showed a single hybridized signal when probed with the fragment of this gene in Southern blot analyses, suggesting that Sd-cam occurs as a sole gene encoding calmodulin in the plant. The reverse-transcription polymerase chain reaction analysis revealed that Sd-cam was appreciably expressed in leaf, root and stem tissues. It appeared that transcription of this gene increased transiently when the leaf cultures of S. dulcis were treated with methyl jasmonate and calcium ionophore A23187. These results suggest that transcriptional activation of Sd-cam is one of the early cellular events of the methyl jasmonate-induced responses of S. dulcis.

Topics: Acetates; Amino Acid Sequence; Blotting, Southern; Calcimycin; Calmodulin; Cells, Cultured; Cloning, Molecular; Cyclopentanes; DNA, Complementary; Gene Expression; Ionophores; Molecular Sequence Data; Oxylipins; Plant Growth Regulators; Plant Leaves; Plant Roots; Plant Stems; Protein Structure, Tertiary; Reverse Transcriptase Polymerase Chain Reaction; Scoparia; Transcription, Genetic

The biosynthesis of a phytoalexin, beta-thujaplicin, in Cupressus lusitanica cell cultures can be stimulated by a yeast elicitor, H(2)O(2), or methyl jasmonate. Lipoxygenase activity was also stimulated by these treatments, suggesting that the oxidative burst and jasmonate pathway may mediate the elicitor-induced accumulation of beta-thujaplicin. The elicitor signalling pathway involved in beta-thujaplicin induction was further investigated using pharmacological and biochemical approaches. Treatment of the cells with calcium ionophore A23187 alone stimulated the production of beta-thujaplicin. A23187 also enhanced the elicitor-induced production of beta-thujaplicin. EGTA, LaCl(3), and verapamil pretreatments partially blocked A23187- or yeast elicitor-induced accumulation of beta-thujaplicin. These results suggest that Ca(2+) influx is required for elicitor-induced production of beta-thujaplicin. Treatment of cell cultures with mastoparan, melittin or cholera toxin alone or in combination with the elicitor stimulated the production of beta-thujaplicin or enhanced the elicitor-induced production of beta-thujaplicin. The G-protein inhibitor suramin inhibited the elicitor-induced production of beta-thujaplicin, suggesting that receptor-coupled G-proteins are likely to be involved in the elicitor-induced biosynthesis of beta-thujaplicin. Indeed, both GTP-binding activity and GTPase activity of the plasma membrane were stimulated by elicitor, and suramin and cholera toxin affected G-protein activities. In addition, all inhibitors of G-proteins and Ca(2+) flux suppressed elicitor-induced increases in lipoxygenase activity whereas activators of G-proteins and the Ca(2+) signalling pathway increased lipoxygenase activity. These observations suggest that Ca(2+) and G-proteins may mediate elicitor signals to the jasmonate pathway, and the jasmonate signalling pathway may then lead to the production of beta-thujaplicin.

Topics: Acetates; Calcimycin; Calcium; Cells, Cultured; Cholera Toxin; Cupressus; Cyclopentanes; Egtazic Acid; Fungi; GTP Phosphohydrolases; GTP-Binding Proteins; Hydrogen Peroxide; Intercellular Signaling Peptides and Proteins; Lanthanum; Lipoxygenase; Monoterpenes; Oxylipins; Peptides; Plant Growth Regulators; Signal Transduction; Suramin; Tropolone; Verapamil; Wasp Venoms