methyl-jasmonate and diphenyleneiodonium

We analyze, for the first time, the early signal transduction pathways triggered by methyl jasmonate (MJ) and cyclodextrins (CDs) in tobacco (Nicotiana tabacum) cell cultures, paying particular attention to changes in cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)), the production of hydrogen peroxide (H(2)O(2)) and nitric oxide (NO), and late events like the induction of capsidiol. Our data indicate that MJ and CDs trigger a [Ca(2+)](cyt) rise promoted by Ca(2+) influx through Ca(2+)-permeable channels. The joint presence of MJ and CDs provokes a first increase in [Ca(2+)](cyt) similar to that observed in MJ-treated cells, followed by a second peak similar to that found in the presence of CDs alone. Moreover, oxidative burst induced by MJ is more pronounced when tobacco cells are incubated with CDs alone or in combination with MJ. The presence of both elicitors provokes H(2)O(2) production similar to that found in CD-treated cells, and a sustained response similar to that found in MJ-treated cells. In all treatments, H(2)O(2) production is dependent on Ca(2+) influx and protein phosphorylation events. Similarly, the joint action of both elicitors provokes NO accumulation, although to a lesser extent that in MJ-treated cells because CDs alone do not trigger this accumulation. This NO production is dependent on Ca(2+) influx but independent of both H(2)O(2) production and staurosporine-sensitive phosphorylation events. Taken as a whole, these results suggest the existence of different intracellular signaling pathways for both elicitors. Likewise, CDs might act by regulating the signaling pathway triggered by MJ since, in the presence of both compounds, CDs neutralize the strong oxidative and nitrosative bursts triggered by MJ and therefore, they regulate both H(2)O(2) and NO levels.

Topics: Acetates; Calcium; Cells, Cultured; Culture Media; Cyclodextrins; Cyclopentanes; Cytosol; Hydrogen Peroxide; Molecular Structure; Nicotiana; Nitric Oxide; Onium Compounds; Oxylipins; Phosphorylation; Plant Cells; Respiratory Burst; Sesquiterpenes; Signal Transduction

The plant cell wall is a dynamic and complex structure whose functional integrity is constantly being monitored and maintained during development and interactions with the environment. In response to cell wall damage (CWD), putatively compensatory responses, such as lignin production, are initiated. In this context, lignin deposition could reinforce the cell wall to maintain functional integrity. Lignin is important for the plant's response to environmental stress, for reinforcement during secondary cell wall formation, and for long-distance water transport. Here, we identify two stages and several components of a genetic network that regulate CWD-induced lignin production in Arabidopsis (Arabidopsis thaliana). During the early stage, calcium and diphenyleneiodonium-sensitive reactive oxygen species (ROS) production are required to induce a secondary ROS burst and jasmonic acid (JA) accumulation. During the second stage, ROS derived from the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D and JA-isoleucine generated by JASMONIC ACID RESISTANT1, form a negative feedback loop that can repress each other's production. This feedback loop in turn seems to influence lignin accumulation. Our results characterize a genetic network enabling plants to regulate lignin biosynthesis in response to CWD through dynamic interactions between JA and ROS.

Topics: Acetates; Arabidopsis; Arabidopsis Proteins; Calcium; Cell Wall; Cyclopentanes; Gene Expression Regulation, Plant; Genes, Plant; Lignin; Models, Biological; Mutation; Onium Compounds; Oxylipins; Phenotype; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Seedlings; Signal Transduction

Arachidonic acid, linolenic acid and methyl jasmonate (MeJA) were found to be strong triggers of an oxidative burst in the kelp Laminaria digitata. These findings constitute the first report of an oxidative burst in an algal system induced by free fatty acids. The source of reactive oxygen species can be at least partially inhibited by diphenylene iodonium (DPI). Treatment with arachidonic acid increases the levels of a number of free fatty acids [including myristic (C14:0), linoleic (C18:2), linolenic (C18:3) and eicosapentaeneoic (C20:5) acids] and hydroxylated derivatives [such as 15-hydroxyeicosatetraenoic acid (15-HETE), 13-hydroxyoctadecatrienoic acid (13-HOTE) and 15-hydroxyeicosapentaenoic acid (15-HEPE)]. Similar to a previous report of the function of an alginate oligosaccharide-triggered oxidative burst in the establishment of resistance in L. digitata against infection by its brown algal endophyte Laminariocolax tomentosoides, C20:4- and MeJA-induced oxidative bursts seem to be involved in establishing the same protection in L. digitata. Altogether, this study supports the notion that lipid oxidation signaling plays a key role in defense induction in marine brown algae.

Topics: Acetates; alpha-Linolenic Acid; Arachidonic Acid; Cyclopentanes; Fatty Acids, Nonesterified; Hydrogen Peroxide; Laminaria; Onium Compounds; Oxylipins; Respiratory Burst

Chitinase is a pathogenesis-related protein that hydrolyzes chitin, a major component of fungal cell walls. Two-week-old rice seedling leaf, leaf sheath and root tissues responded to an exogenous treatment by jasmonic acid (JA) with induction of the chitinases as determined by immunoblot analysis using an anti-endochitinase antibody. Induced accumulation of these chitinases was observed within 24 to 48 h in the leaf sheaths, leaves and roots. Besides, ethylene generator ethephon and abiotic stressor copper could also induce chitinases accumulation among various plant hormones and stress agents examined. Cycloheximide effectively blocked their accumulation by JA, suggesting that de novo protein synthesis is required. Partial blockage of the induced accumulation of chitinases by NADPH oxidase inhibitor and free radical scavengers suggested involvement of reactive oxygen species. Moreover, induced accumulation of these chitinases also by methyl jasmonate and certain protein phosphatase inhibitors indicated their potential importance and wider role in rice seedlings.

Topics: Acetates; Chitinases; Cycloheximide; Cyclopentanes; Enzyme Inhibitors; Ethylenes; Onium Compounds; Organophosphorus Compounds; Oryza; Oxylipins; Phosphoprotein Phosphatases; Plant Growth Regulators; Plant Structures; Reactive Oxygen Species