Green leaf volatiles co-opt proteins involved in molecular pattern signalling in plant cells.

The green leaf volatiles (GLVs) Z-3-hexen-1-ol (Z3-HOL) and Z-3-hexenyl acetate (Z3-HAC) are airborne infochemicals released from damaged plant tissues that induce defenses and developmental responses in receiver plants, but little is known about their mechanism of action. We found that Z3-HOL and Z3-HAC induce similar but distinctive physiological and signaling responses in tomato seedlings and cell cultures. In seedlings, Z3-HAC showed a stronger root growth inhibition effect than Z3-HOL.

Dephosphorylation of the MAP kinases MPK6 and MPK3 fine-tunes responses to wounding and herbivory in Arabidopsis.

The Arabidopsis MAP Kinases (MAPKs) MPK6 and MPK3 and orthologs in other plants function as major stress signaling hubs. MAPKs are activated by phosphorylation and are negatively regulated by MAPK-inactivating phosphatases (MIPPs), which alter the intensity and duration of MAPK signaling via dephosphorylation. Unlike in other plant species, jasmonic acid (JA) accumulation in Arabidopsis is apparently not MPK6- and MPK3-dependent, so their role in JA-mediated defenses against herbivorous insects is unclear.

Survey of Sensitivity to Fatty Acid-Amino Acid Conjugates in the Solanaceae.

Plants perceive insect herbivores via a sophisticated surveillance system that detects a range of alarm signals, including herbivore-associated molecular patterns (HAMPs). Fatty acid-amino acid conjugates (FACs) are HAMPs present in oral secretions (OS) of lepidopteran larvae that induce defense responses in many plant species. In contrast to eggplant (Solanum melongena), tomato (S.

MAP kinases associate with high molecular weight multiprotein complexes.

Plant responses to the environment and developmental processes are mediated by a complex signaling network. The Arabidopsis thaliana mitogen-activated protein kinases (MAPKs) MPK3 and MPK6 and their orthologs in other plants are shared signal transducers that respond to many developmental and environmental signals and thus represent highly connected hubs in the cellular signaling network. In animals, specific MAPK signaling complexes are assembled which enable input-specific protein-protein interactions and thus specific signaling outcomes.

Methanol and ethanol modulate responses to danger- and microbe-associated molecular patterns.

Methanol is a byproduct of cell wall modification, released through the action of pectin methylesterases (PMEs), which demethylesterify cell wall pectins. Plant PMEs play not only a role in developmental processes but also in responses to herbivory and infection by fungal or bacterial pathogens. Molecular mechanisms that explain how methanol affects plant defenses are poorly understood.

The tomato kinome and the tomato kinase library ORFeome: novel resources for the study of kinases and signal transduction in tomato and solanaceae species.

Protein kinase-driven phosphorylation constitutes the core of cellular signaling. Kinase components of signal transduction pathways are often targeted for inactivation by pathogens. The study of kinases and immune signal transduction in the model crop tomato (Solanum lycopersicum) would benefit from the availability of community-wide resources for large scale and systems-level experimentation.

Many jobs for one good cop - the COP9 signalosome guards development and defense.

The COP9 signalosome (CSN) is a multiprotein complex that regulates the activity of CULLIN-RING E3 ubiquitin ligases (CRLs). CRLs ubiquitinate substrate proteins and thus target them for proteasomal degradation. This post-translational modification of proteins is arguably as important as reversible protein phosphorylation.

Wounding systemically activates a mitogen-activated protein kinase in forage and turf grasses.

Forage and turf grasses are continually cut and grazed by livestock, however very little is known concerning the perception or molecular responses to wounding. Mechanical wounding rapidly activated a 46 kDa and a 44 kDa mitogen-activated protein kinase (MAPK) in six different grass species. In the model grass species Lolium temulentum, the 46 kDa MAPK was rapidly activated within 5 min of wounding both locally and systemically in an adjacent unwounded tiller.

The COP9 signalosome controls jasmonic acid synthesis and plant responses to herbivory and pathogens.

The COP9 signalosome (CSN) is a multi-protein complex that regulates the activities of cullin-RING E3 ubiquitin ligases (CRLs). CRLs ubiquitinate proteins in order to target them for proteasomal degradation. The CSN is required for proper plant development.

Systemin and jasmonic acid regulate constitutive and herbivore-induced systemic volatile emissions in tomato, Solanum lycopersicum.

Transgenic tomato (Solanum lycopersicum) plants that overexpress the Prosystemin gene (35S::PS) and plants with a mutation in the JA biosynthetic pathway (def1) are known to exhibit a constitutive or reduced wound response, respectively. Here it is demonstrated that several independent 35S::PS lines emit high levels of specific volatiles in addition to increased accumulation of proteinase inhibitors (PIs). Furthermore, the temporal dynamics of systemically induced volatile compounds including green-leaf volatiles, terpenes, and shikimic acid-derivatives from 35S::PS and def1 plants in response to herbivore wounding and treatment with jasmonic acid (JA) are described.

Tissue-type specific systemin perception and the elusive systemin receptor.

Systemin is a wound signaling peptide from tomato that is important for plant defenses against herbivory. The systemin receptor was initially identified as the tomato homolog of the brassinosteroid receptor BRI1, but genetic evidence argued against this finding. However, we found that BRI1 may function as an inappropriate systemin binding protein that does not activate the systemin signaling pathway.

The tomato brassinosteroid receptor BRI1 increases binding of systemin to tobacco plasma membranes, but is not involved in systemin signaling.

The tomato wound signal systemin is perceived by a specific high-affinity, saturable, and reversible cell surface receptor. This receptor was identified as the receptor-like kinase SR160, which turned out to be identical to the brassinosteroid receptor BRI1. Recently, it has been shown that the tomato bri1 null mutant cu3 is as sensitive to systemin as wild type plants.

Micro-electrode flux estimation confirms that the Solanum pimpinellifolium cu3 mutant still responds to systemin.

In this study, we introduce the Micro-Electrode Ion Flux Estimation technique as a sensitive and accurate technique to study systemin-induced changes in ion fluxes from isolated nearly intact plant tissues. Our results demonstrate the effectiveness and value of the Micro-Electrode Ion Flux Estimation technique to monitor and characterize those elicitor-induced ion flux changes from intact tissues. We used the method to monitor the systemin-induced changes in ion fluxes from leaf tissue of various plant species, including wild-type and cu3 mutant tomato (Solanum pimpinellifolium) plants, and confirm previous observations, but now in intact leaf tissue.

Tomato MAPKs LeMPK1, LeMPK2, and LeMPK3 function in the systemin-mediated defense response against herbivorous insects.

Systemin is a wound-signaling peptide that mediates defenses of tomato plants against herbivorous insects. Perception of systemin by the membrane-bound receptor SR160 results in activation of MAPKs, synthesis of jasmonic acid (JA), and expression of defense genes. To test the function of MAPKs in the response to systemin, we used virus-induced gene silencing (VIGS) in plants that overexpress the systemin precursor prosystemin (35S::prosys plants).

Tomato mitogen-activated protein kinases LeMPK1, LeMPK2, and LeMPK3 are activated during the Cf-4/Avr4-induced hypersensitive response and have distinct phosphorylation specificities.

Tomato (Solanum lycopersicum) plants with the Cf-4 resistance gene recognize strains of the pathogenic fungus Cladosporium fulvum that secrete the avirulence protein Avr4. Transgenic tomato seedlings coexpressing Cf-4 and Avr4 mount a hypersensitive response (HR) at 20 degrees C, which is suppressed at 33 degrees C. Within 120 min after a shift from 33 degrees C to 20 degrees C, tomato mitogen-activated protein (MAP) kinase (LeMPK) activity increases in Cf-4/Avr4 seedlings.

Changes in extracellular pH are neither required nor sufficient for activation of mitogen-activated protein kinases (MAPKs) in response to systemin and fusicoccin in tomato.

Leaf wounding and the wound signaling peptide systemin induce expression of wound response genes while the fungal toxin fusicoccin (FC) induces expression of pathogenesis-related genes. Consistent with their functional differences, FC and systemin regulate the extracellular pH in opposite ways, with systemin inducing an alkalinization and FC an acidification response. Here we show that systemin, wounding and FC activate the same mitogen-activated protein kinases (MAPKs; MPKs) MPK1 and 2 in tomato (Lycopersicon esculentum) leaves and L.

Plant respiratory burst oxidase homologs impinge on wound responsiveness and development in Lycopersicon esculentum.

Plant respiratory burst oxidase homologs (Rboh) are homologs of the human neutrophil pathogen-related gp91(phox). Antisense technology was employed to ascertain the biological function of Lycopersicon esculentum (tomato) Rboh. Lines with diminished Rboh activity showed a reduced level of reactive oxygen species (ROS) in the leaf, implying a role for Rboh in establishing the cellular redox milieu.

Convergence of signaling pathways induced by systemin, oligosaccharide elicitors, and ultraviolet-B radiation at the level of mitogen-activated protein kinases in Lycopersicon peruvianum suspension-cultured cells.

We tested whether signaling pathways induced by systemin, oligosaccharide elicitors (OEs), and ultraviolet (UV)-B radiation share common components in Lycopersicon peruvianum suspension-cultured cells. These stress signals all induce mitogen-activated protein kinase (MAPK) activity. In desensitization assays, we found that pretreatment with systemin and OEs transiently reduced the MAPK response to a subsequent treatment with the same or a different elicitor.

Long distance run in the wound response--jasmonic acid is pulling ahead.

When plants are wounded, a long-distance signal is produced that activates the wound response in unwounded leaves. Recent work by Gregg Howe's group suggests that jasmonic acid is the long-distance wound signal. Previously, many data indicated that the signaling peptide systemin might function as the systemic wound signal.

Ultraviolet-B activates components of the systemin signaling pathway in Lycopersicon peruvianum suspension-cultured cells.

Among the early responses of Lycopersicon peruvianum suspension-cultured cells to the polypeptide wound signal systemin are the alkalinization of the culture medium and the activation of a 48-kDa mitogen-activated protein kinase (MAPK). Here, we report that both responses are induced in the cells by exposure to ultraviolet-B (UV-B) radiation. Suramin, an inhibitor of systemin receptor function, strongly inhibited the UV-B-induced medium alkalinization and MAPK activity.