Publikationen - Molekulare Signalverarbeitung

Recognition of pathogen-associated molecular patterns (PAMPs) induces multiple defense mechanisms to limit pathogen growth. Here, we show that the Arabidopsis thaliana tandem zinc finger protein 9 (TZF9) is phosphorylated by PAMP-responsive mitogen-activated protein kinases (MAPKs) and is required to trigger a full PAMP-triggered immune response. Analysis of a tzf9 mutant revealed attenuation in specific PAMP-triggered reactions such as reactive oxygen species accumulation, MAPK activation and, partially, the expression of several PAMP-responsive genes. In accordance with these weaker PAMP-triggered responses, tzf9 mutant plants exhibit enhanced susceptibility to virulent Pseudomonas syringae pv. tomato DC3000. Visualization of TZF9 localization by fusion to green fluorescent protein revealed cytoplasmic foci that co-localize with marker proteins of processing bodies (P-bodies). This localization pattern is affected by inhibitor treatments that limit mRNA availability (such as cycloheximide or actinomycin D) or block nuclear export (leptomycin B). Coupled with its ability to bind the ribohomopolymers poly(rU) and poly(rG), these results suggest involvement of TZF9 in post-transcriptional regulation, such as mRNA processing or storage pathways, to regulate plant innate immunity.

Jasmonates are lipid-derived compounds which are signals in plant stress responses and development. They are synthesized in chloroplasts and peroxisomes. An endogenous rise occurs upon environmental stimuli or in distinct stages of development such as that of anthers and trichomes or in root growth. Hydroxylation, carboxylation, glucosylation, sulfation, methylation, or conjugation of jasmonic acid (JA) leads to numerous metabolites. Many of them are at least partially biologically inactive. The most bioactive JA is the (+)-7-iso-JA–isoleucine conjugate. Its perception takes place by the SCFCOI1-JAZ-co-receptor complex. At elevated levels of JAs, negative regulators such as JAZ, or JAV are subjected to proteasomal degradation, thereby allowing positively acting transcription factors of the MYC or MYB family to switch on JA-induced gene expression. In case of JAM negative regulation takes place by anatagonism to MYC2. JA and COI1 are dominant signals in gene expression after wounding or in response to necrotrophic pathogens. Cross-talk to salicylic acid, ethylene, auxin, and other hormones occurs. Growth is inhibited by JA, thereby counteracting the growth stimulation by gibberellic acid. Senescence, trichome formation, arbuscular mycorrhiza, and formation of many secondary metabolites are induced by jasmonates. Effects in cold acclimation; in intercropping; during response to herbivores, nematodes, or necrotrophic pathogens; in pre- and post-harvest; in crop quality control; and in biosynthesis of secondary compounds led to biotechnological and agricultural applications.