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Publikationen - Molekulare Signalverarbeitung

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Clarke, S.M.; Cristescu, S.M.; Miersch, O.; Harren, F.J.M.; Wasternack, C.; Mur, L.A.J. Jasmonates act with salicylic acid to confer basal thermotolerance in <i>Arabidopsis thaliana</i> New Phytol 182, 175-187, (2009) DOI: 10.1111/j.1469-8137.2008.02735.x

The cpr5-1 Arabidopsis thaliana mutant exhibits constitutive activation of salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) signalling pathways and displays enhanced tolerance of heat stress (HS). cpr5-1 crossed with jar1-1 (a JA-amino acid synthetase) was compromised in basal thermotolerance, as were the mutants opr3 (mutated in OPDA reductase3) and coi1-1 (affected in an E3 ubiquitin ligase F-box; a key JA-signalling component). In addition, heating wild-type Arabidopsis led to the accumulation of a range of jasmonates: JA, 12-oxophytodienoic acid (OPDA) and a JA-isoleucine (JA-Ile) conjugate. Exogenous application of methyl jasmonate protected wild-type Arabidopsis from HS. Ethylene was rapidly produced during HS, with levels being modulated by both JA and SA. By contrast, the ethylene mutant ein2-1 conferred greater thermotolerance. These data suggest that JA acts with SA, conferring basal thermotolerance while ET may act to promote cell death.

Stumpe, M.; Göbel, C.; Faltin, B.; Beike, A. K.; Hause, B.; Himmelsbach, K.; Bode, J.; Kramell, R.; Wasternack, C.; Frank, W.; Reski, R.; Feussner, I. The moss Physcomitrella patens contains cyclopentenones but no jasmonates: mutations in allene oxide cyclase lead to reduced fertility and altered sporophyte morphology New Phytol 188 (3), 740-749, (2010) DOI: 10.1111/j.1469-8137.2010.03406.x

Two cDNAs encoding allene oxide cyclases (PpAOC1, PpAOC2), key enzymes in the formation of jasmonic acid (JA) and its precursor (9S,13S)‐12‐oxo‐phytodienoic acid (cis‐(+)‐OPDA), were isolated from the moss Physcomitrella patens.Recombinant PpAOC1 and PpAOC2 show substrate specificity against the allene oxide derived from 13‐hydroperoxy linolenic acid (13‐HPOTE); PpAOC2 also shows substrate specificity against the allene oxide derived from 12‐hydroperoxy arachidonic acid (12‐HPETE).In protonema and gametophores the occurrence of cis‐(+)‐OPDA, but neither JA nor the isoleucine conjugate of JA nor that of cis‐(+)‐OPDA was detected.Targeted knockout mutants for PpAOC1 and for PpAOC2 were generated, while double mutants could not be obtained. The ΔPpAOC1 and ΔPpAOC2 mutants showed reduced fertility, aberrant sporophyte morphology and interrupted sporogenesis.

Farmer, E. E.; Gasperini, D.; Acosta, I. F. The squeeze cell hypothesis for the activation of jasmonate synthesis in response to wounding New Phytol 204, 282-288, (2014) DOI: 10.1111/nph.12897

Jasmonates are lipid mediators that control defence gene expression in response to wounding and other environmental stresses. These small molecules can accumulate at distances up to several cm from sites of damage and this is likely to involve cell‐to‐cell jasmonate transport. Also, and independently of jasmonate synthesis, transport and perception, different long‐distance wound signals that stimulate distal jasmonate synthesis are propagated at apparent speeds of several cm min–1 to tissues distal to wounds in a mechanism that involves clade 3 GLUTAMATE RECEPTOR‐LIKE (GLR) genes. A search for jasmonate synthesis enzymes that might decode these signals revealed LOX6, a lipoxygenase that is necessary for much of the rapid accumulation of jasmonic acid at sites distal to wounds. Intriguingly, the LOX6 promoter is expressed in a distinct niche of cells that are adjacent to mature xylem vessels, a location that would make these contact cells sensitive to the release of xylem water column tension upon wounding. We propose a model in which rapid axial changes in xylem hydrostatic pressure caused by wounding travel through the vasculature and lead to slower, radially dispersed pressure changes that act in a clade 3 GLR‐dependent mechanism to promote distal jasmonate synthesis.

Wasternack, C. A plant's balance of growth and defense - revisited New Phytol 215, 1291-1294, (2017) DOI: 10.1111/nph.14720

This article is a Commentary on Major et al., 215: 1533–1547.

Wasternack, C. The Trojan horse coronatine: the COI1–JAZ2–MYC2,3,4–ANAC019,055,072 module in stomata dynamics upon bacterial infection. New Phytol 213, 972-975, (2017) DOI: 10.1111/nph.14417

Coronatine (COR) is a phytotoxin produced by a plasmid-encoded operon of genes in several strains of Pseudomonas syringae (Bender et al., 1999). It is a mimic of the defense-associated phytohormone jasmonic acid isoleucine and delivered by the phytopathogenic bacterium to gain access to host plants through stomatal entry and to repress a specific sector of plant immunity. In this issue of New Phytologist (pp. 1378–1392) Gimenez-Ibanez et al. reveal exciting insights into the transcriptional regulation of COR/jasmonic acid isoleucine-governed transcriptional networks modulating stomatal aperture during bacterial invasion.
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