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Publikationen - Molekulare Signalverarbeitung

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Publikation

Schumann, N.; Navarro-Quezada, A.; Ullrich, K.; Kuhl, C.; Quint, M.; Molecular Evolution and Selection Patterns of Plant F-Box Proteins with C-Terminal Kelch Repeats Plant Physiol. 155, 835-850, (2011) DOI: 10.1104/pp.110.166579

The F-box protein superfamily represents one of the largest families in the plant kingdom. F-box proteins phylogenetically organize into numerous subfamilies characterized by their carboxyl (C)-terminal protein-protein interaction domain. Among the largest F-box protein subfamilies in plant genomes are those with C-terminal kelch repeats. In this study, we analyzed the phylogeny and evolution of F-box kelch proteins/genes (FBKs) in seven completely sequenced land plant genomes including a bryophyte, a lycophyte, monocots, and eudicots. While absent in prokaryotes, F-box kelch proteins are widespread in eukaryotes. Nonplant eukaryotes usually contain only a single FBK gene. In land plant genomes, however, FBKs expanded dramatically. Arabidopsis thaliana, for example, contains at least 103 F-box genes with well-conserved C-terminal kelch repeats. The construction of a phylogenetic tree based on the full-length amino acid sequences of the FBKs that we identified in the seven species enabled us to classify FBK genes into unstable/stable/superstable categories. In contrast to superstable genes, which are conserved across all seven species, kelch domains of unstable genes, which are defined as lineage specific, showed strong signatures of positive selection, indicating adaptational potential. We found evidence for conserved protein features such as binding affinities toward A. thaliana SKP1-like adaptor proteins and subcellular localization among closely related FBKs. Pseudogenization seems to occur only rarely, but differential transcriptional regulation of close relatives may result in subfunctionalization.
Publikation

Delker, C.; Pöschl, Y.; Raschke, A.; Ullrich, K.; Ettingshausen, S.; Hauptmann, V.; Grosse, I.; Quint, M.; Natural Variation of Transcriptional Auxin Response Networks in Arabidopsis thaliana Plant Cell 22, 2184-2200, (2010) DOI: 10.1105/tpc.110.073957

Natural variation has been observed for various traits in Arabidopsis thaliana. Here, we investigated natural variation in the context of physiological and transcriptional responses to the phytohormone auxin, a key regulator of plant development. A survey of the general extent of natural variation to auxin stimuli revealed significant physiological variation among 20 genetically diverse natural accessions. Moreover, we observed dramatic variation on the global transcriptome level after induction of auxin responses in seven accessions. Although we detect isolated cases of major-effect polymorphisms, sequencing of signaling genes revealed sequence conservation, making selective pressures that favor functionally different protein variants among accessions unlikely. However, coexpression analyses of a priori defined auxin signaling networks identified variations in the transcriptional equilibrium of signaling components. In agreement with this, cluster analyses of genome-wide expression profiles followed by analyses of a posteriori defined gene networks revealed accession-specific auxin responses. We hypothesize that quantitative distortions in the ratios of interacting signaling components contribute to the detected transcriptional variation, resulting in physiological variation of auxin responses among accessions.
Publikation

Hilpert, B.; Bohlmann, H.; Den Camp, R. o.; Przybyla, D.; Miersch, O.; Buchala, A.; Apel, K.; Isolation and characterization of signal transduction mutants of Arabidopsis thaliana that constitutively activate the octadecanoid pathway and form necrotic microlesions Plant J. 26, 435-446, (2001) DOI: 10.1046/j.1365-313X.2001.2641036.x

Thionins are a group of antimicrobial polypeptides that form part of the plant's defense mechanism against pathogens. The Thi 2.1 thionin gene of Arabidopsis thaliana has been shown to be inducible by jasmonic acid (JA), an oxylipin‐like hormone derived from oxygenated linolenic acid and synthesized via the octadecanoid pathway. The JA‐dependent regulation of the Thi 2.1 gene has been exploited for setting up a genetic screen for the isolation of signal transduction mutants that constitutively express the Thi 2.1 gene. Ten cet‐mutants have been isolated which showed a c onstitutive e xpression of the t hionin gene. Allelism tests revealed that they represent at least five different loci. Some mutants are dominant, others recessive, but all cet mutations behaved as monogenic traits when backcrossed with Thi 2.1‐GUS plants. Some of the mutants overproduce JA and its bioactive precursor 12‐oxophytodienoic acid (OPDA) up to 40‐fold while others have the same low levels as the control wildtype plants. Two of the mutants showed a strong induction of both the salicylic acid (SA)‐ and the JA‐dependent signaling pathways, while the majority seems to be affected only in the octadecanoid pathway. The Thi 2.1 thionin gene and the Pdf 1.2 defensin gene are activated independently, though both are regulated by JA. The cet‐mutants, except for one, also show a spontaneous leaf cell necrosis, a reaction often associated with the systemic acquired resistance (SAR) pathway.
Publikation

Miersch, O.; Bohlmann, H.; Wasternack, C.; Jasmonates and related compounds from Fusarium oxysporum Phytochemistry 50, 517-523, (1999) DOI: 10.1016/S0031-9422(98)00596-2

The culture filtrate of Fusarium oxysporum f sp matthiolae was inspected on the occurrence of jasmonates and related compounds. Among compounds described for the first time of biological origin are 7-iso-cucurbic acid, (1S,2S)- and (1S,2R)-3-oxo-2-pentylcyclopentane-1-butyric acid, (1S,2S)- and (1S,2R)-3-oxo-2-(2Z-pentenyl)cyclopentane-1-hexanoic acid, (1S,2S)- and (1S,2R)-3-oxo-2-pentylcyclopentane-1-hexanoic acid, (1S,2S)-3-oxo-2-(2Z-pentenyl)cyclopentane-1-octanoic acid, (1S,2S)-3-oxo-2-pentylcyclopentane-1-octanoic acid and N-[9,10-dihydro-7-iso-jasmonoyl]-(S)-isoleucine. The following metabolites were identified for the first time for this fungus: (−)-Jasmonic acid, 9,10-dihydrojasmonic acid and N-[(−)-jasmonoyl-(S)]-isoleucine were major constituents of the culture filtrate, whereas as minor metabolites occurred N-[9,10-dihydrojasmonoyl]-(S)-isoleucine, cucurbic acid and 3-oxo-2-(2Z-pentenyl)cyclopentane-1-butyric acid, 3-oxo-2-(2Z-pentenyl)cyclopentane-1-octanoic acid and 3-oxo-2-pentylcyclopentane-1-octanoic acid. All cyclopentanones found carried a cis- or trans-attached side chain. Didehydro-jasmonates, hydroxylated jasmonates or 12-oxophytodienoic acid could not be detected in the culture filtrate.
Publikation

Bohlmann, H.; Vignutelli, A.; Hilpert, B.; Miersch, O.; Wasternack, C.; Apel, K.; Wounding and chemicals induce expression of the Arabidopsis thaliana gene Thi2.1, encoding a fungal defense thionin, via the octadecanoid pathway FEBS Lett. 437, 281-286, (1998) DOI: 10.1016/S0014-5793(98)01251-4

In seedlings of Arabidopsis thaliana the thionin gene Thi2.1 is inducible by methyl jasmonate, wounding, silver nitrate, coronatine, and sorbitol. We have used a biochemical and genetic approach to test the signal transduction of these different inducers. Both exogenously applied jasmonates and jasmonates produced endogenously upon stress induction, lead to GUS expression in a Thi2.1 promoter-uidA transgenic line. No GUS expression was observed in a coi1 mutant background which lacks jasmonate perception whereas methyl jasmonate and coronatine but not the other inducers were able to overcome the block in jasmonic acid production in a fad3-2 fad7-2 fad8 mutant background. Our results show conclusively that all these inducers regulate Thi2-1 gene expression via the octadecanoid pathway.
Publikation

Vignutelli, A.; Wasternack, C.; Apel, K.; Bohlmann, H.; Systemic and local induction of an Arabidopsis thionin gene by wounding and pathogens Plant J. 14, 285-295, (1998) DOI: 10.1046/j.1365-313X.1998.00117.x

The Arabidopsis Thi2.1 thionin gene was cloned and sequenced. The promoter was fused to the uidA gene and stably transformed into Arabidopsis to study its regulation. GUS expression levels correlated with the steady‐state levels of Thi2.1 mRNA, thus demonstrating that the promoter is sufficient for the regulation of the Thi2.1 gene. The sensitivity of the Thi2.1 gene to methyl jasmonate was found to be developmentally determined. Systemic and local expression could be induced by wounding and inoculation with Fusarium oxysporum f sp. matthiolae . A deletion analysis of the promoter identified a fragment of 325 bp upstream of the start codon, which appears to contain all the elements necessary for the regulation of the Thi2.1 gene. These results support the view that thionins are defence proteins, and indicate the possibility that resistance of Arabidopsis plants to necrotrophic fungal pathogens is mediated through the octadecanoid pathway.
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