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Publikationen - Molekulare Signalverarbeitung

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Publikation

Biondi, E.; Branciamore, S.; Fusi, L.; Gago, S.; Gallori, E.; Catalytic activity of hammerhead ribozymes in a clay mineral environment: Implications for the RNA world Gene 389, 10-18, (2007) DOI: 10.1016/j.gene.2006.09.002

The hypothesized RNA-based world would have required the presence of a protected environment in which RNA, or an RNA-like molecule, could originate and express its biological activity.Recent studies have indicated that RNA molecules adsorbed/bound on clay minerals are able to persist in the presence of degrading agents, to interact with surrounding molecules, and to transmit the information contained in their nucleotide sequences.In this study, we assessed the ability of RNA molecules with catalytic activity to perform a specific reaction in a mineral environment. For this purpose, we investigated the self-cleavage reaction of the hammerhead ribozyme of the Avocado Sun Blotch Viroid (ASBVd), both in the monomeric and in dimeric forms. The monomeric transcript was tightly bound on the clay mineral montmorillonite to form a stable complex, while the behaviour of the dimeric transcript was studied in the presence of the clay particles in the reaction mixture.The results indicated that the hammerhead ribozyme was still active when the monomeric transcript was adsorbed on the clay surface, even though its efficiency was reduced to about 20% of that in solution. Moreover, the self-cleavage of clay-adsorbed molecule was significantly enhanced (∼ four times) by the presence of the 5′ reaction product.The self-cleavage reaction of the dimeric transcript in the presence of montmorillonite indicated that the mineral particles protected the RNA molecules against aspecific degradation and increased the rate of cleavage kinetics by about one order of magnitude.These findings corroborate the hypothesis that clay-rich environments would have been a good habitat in which RNA or RNA-like molecules could originate, accumulate and undergo Darwinian evolutionary processes, leading to the first living cells on Earth.
Publikation

Calderon-Villalobos, L. I. A.; Nill, C.; Marrocco, K.; Kretsch, T.; Schwechheimer, C.; The evolutionarily conserved Arabidopsis thaliana F-box protein AtFBP7 is required for efficient translation during temperature stress Gene 392, 106-116, (2007) DOI: 10.1016/j.gene.2006.11.016

In eukaryotes, E3 ubiquitin ligases (E3s) mediate the ubiquitylation of proteins that are destined for degradation by the ubiquitin–proteasome system. In SKP1/CDC53/F-box protein (SCF)-type E3 complexes, the interchangeable F-box protein confers specificity to the E3 ligase through direct physical interactions with the degradation substrate. The vast majority of the approximately 700 F-box proteins from the plant model organism Arabidopsis thaliana remain to be characterized. Here, we investigate the previously uncharacterized and evolutionarily conserved Arabidopsis F-box protein 7 (AtFBP7), which is encoded by a unique gene in Arabidopsis (At1g21760). Several apparent fbp7 loss-of-function alleles do not have an obvious phenotype. AtFBP7 is ubiquitously expressed and its expression is induced after cold and heat stress. When following up on a reported co-purification of the eukaryotic elongation factor-2 (eEF-2) with YLR097c, the apparent budding yeast orthologue of AtFBP7, we discovered a general defect in protein biosynthesis after cold and heat stress in fbp7 mutants. Thus, our findings suggest that AtFBP7 is required for protein synthesis during temperature stress.
Publikation

Feussner, I.; Wasternack, C.; Lipoxygenase catalyzed oxygenation of lipids Fett/Lipid 100, 146-152, (1998) DOI: 10.1002/(SICI)1521-4133(19985)100:4/5<146::AID-LIPI146>3.0.CO;2-D

Lipoxygenases (LOXs) and other LOX pathway enzymes are potentially able to form a large set of compounds being of commercial interest. Among them are conjugated dienic acids, jasmonates, and volatile aldehydes. Additionally, fatty acid hydroperoxides, formed by LOX, can serve as precursors for further transformation by either enzymes of the so‐called LOX pathway or by chemical reactions. In the case of linoleic acid more than one hundred products generated from its LOX‐derived fatty acid hydroperoxides have been described. Many of these products exhibit biological activity, suggesting a significant biological function of LOXs. This will be described for two different 13‐LOXs. (I) In various oilseeds we found that specific 13‐LOXs are localized at the lipid body membrane. They are capable of oxygenating esterified polyenoic fatty acids, such as triacylglycerols and phospho‐lipids. In addition, they form with arachidonic acid as substrate preferentially either 8‐ or 11‐hydroperoxy eicosatetraenoic acid, which is a very unusual positional specificity for plant LOXs. (II) From barley leaves we isolated another linoleate 13‐LOX form, which is localized within chloroplasts and is induced by jasmonic acid methyl ester. It is suggested, that this LOX form is capable of oxygenating linolenic acid residues of galactolipids. Examples will be presented for barley leaves of oxygenated derivatives of linolenic acid and compounds resulting from the hydroperoxide lyase‐branch of the LOX pathway.
Publikation

Wasternack, C.; Miersch, O.; Kramell, R.; Hause, B.; Ward, J.; Beale, M.; Boland, W.; Parthier, B.; Feussner, I.; Jasmonic acid: biosynthesis, signal transduction, gene expression Fett/Lipid 100, 139-146, (1998) DOI: 10.1002/(SICI)1521-4133(19985)100:4/5<139::AID-LIPI139>3.0.CO;2-5

Jasmonic acid (JA) is an ubiquitously occurring plant growth regulator which functions as a signal of developmentally or environmentally regulated expression of various genes thereby contributing to the defense status of plants [1–5]. The formation of jasmonates in a lipid‐based signalling pathway via octadecanoids seems to be a common principle for many plant species to express wound‐ and stressinduced genes [4, 5].There are various octadecanoid‐derived signals [3]. Among them, jasmonic acid and its amino acid conjugates are most active in barley, supporting arguments that β‐oxidation is an essential step in lipid‐based JA mediated responses. Furthermore, among derivatives of 12‐oxophytodienoic acid (PDA) carrying varying length of the carboxylic acid side‐chain, only those with a straight number of carbon atoms are able to induce JA responsive genes in barley leaves after treatment with these compounds. Barley leaves stressed by treatment with sorbitol solutions exhibit mainly an endogenous rise of JA and JA amino acid conjugates suggesting that both of them are stress signals. Data on organ‐ and tissue‐specific JA‐responsive gene expression will be presented and discussed in terms of “JA as a master switch” among various lipid‐derived signals.
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