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Flores, R.; Gago-Zachert, S.; Serra, P.; Sanjuán, R.; Elena, S. F. Viroids: Survivors from the RNA World? Annual Rev Microbiol 68, 395 - 414, (2014) DOI: 10.1146/annurev-micro-091313-103416

Because RNA can be a carrier of genetic information and a biocatalyst, there is a consensus that it emerged before DNA and proteins, which eventually assumed these roles and relegated RNA to intermediate functions. If such a scenario—the so-called RNA world—existed, we might hope to find its relics in our present world. The properties of viroids that make them candidates for being survivors of the RNA world include those expected for primitive RNA replicons: (a) small size imposed by error-prone replication, (b) high G+ C content to increase replication fidelity, (c) circular structure for assuring complete replication without genomic tags, (d) structural periodicity for modular assembly into enlarged genomes, (e) lack of protein-coding ability consistent with a ribosome-free habitat, and (f) replication mediated in some by ribozymes, the fingerprint of the RNA world. With the advent of DNA and proteins, those protoviroids lost some abilities and became the plant parasites we now know.

Floková, K.; Tarkowská, D.; Miersch, O.; Strnad, M.; Wasternack, C.; Novak, O. UHPLC-MS/MS based target profiling of stress-induced phytohormones Phytochemistry 105, 147-157, (2014) DOI: 10.1016/j.phytochem.2014.05.015

Stress-induced changes in phytohormone metabolite profiles have rapid effects on plant metabolic activity and growth. The jasmonates (JAs) are a group of fatty acid-derived stress response regulators with roles in numerous developmental processes. To elucidate their dual regulatory effects, which overlap with those of other important defence-signalling plant hormones such as salicylic acid (SA), abscisic acid (ABA) and indole-3-acetic acid (IAA), we have developed a highly efficient single-step clean-up procedure for their enrichment from complex plant matrices that enables their sensitive quantitative analysis using hyphenated mass spectrometry technique. The rapid extraction of minute quantities of plant material (less than 20 mg fresh weight, FW) into cold 10% methanol followed by one-step reversed-phase polymer-based solid phase extraction significantly reduced matrix effects and increased the recovery of labile JA analytes. This extraction and purification protocol was paired with a highly sensitive and validated ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method and used to simultaneously profile sixteen stress-induced phytohormones in minute plant material samples, including endogenous JA, several of its biosynthetic precursors and derivatives, as well as SA, ABA and IAA.

Schilling, S.; Stenzel, I.; von Bohlen, A.; Wermann, M.; Schulz, K.; Demuth, H.-U.; Wasternack, C. Isolation and characterization of the glutaminyl cyclases from Solanum tuberosum and Arabidopsis thaliana: implications for physiological functions Biol. Chem 388, 145-153, (2007) DOI: 10.1515/BC.2007.016


Abel, S.; Nguyen, M.D.; Theologis, A. The PS-IAA4/5-like family of early auxin-inducible mRNAs in Arabidopsis thaliana Journal of Biological Chemistry 270, 19093-19099, (1995)

1-Aminocyclopropane-1-carboxylic acid (ACC) synthase is the key regulatory enzyme in the biosynthetic pathway of the plant hormone ethylene. The enzyme is encoded by a divergent multigene family in Arabidopsis thaliana, comprising at least five genes, ACS1-5 (Liang, X., Abel, S., Keller, J. A., Shen, N. F., and Theologis, A.(1992) Proc. Natl. Acad. Sci. U. S. A. 89, 11046-11050). In etiolated seedlings, ACS4 is specifically induced by indoleacetic acid (IAA). The response to IAA is rapid (within 25 min) and insensitive to protein synthesis inhibition, suggesting that the ACS4 gene expression is a primary response to IAA. The ACS4 mRNA accumulation displays a biphasic dose-response curve which is optimal at 10 μM of IAA. However, IAA concentrations as low as 100 nM are sufficient to enhance the basal level of ACS4 mRNA. The expression of ACS4 is defective in the Arabidopsis auxin-resistant mutant lines axr1-12, axr2-1, and aux1-7. ACS4 mRNA levels are severely reduced in axr1-12 and axr2-1 but are only 1.5-fold lower in aux1-7. IAA inducibility is abolished in axr2-1. The ACS4 gene was isolated and structurally characterized. The promoter contains four sequence motifs reminiscent of functionally defined auxin-responsive cis-elements in the early auxin-inducible genes PS-IAA4/5 from pea and GH3 from soybean. Conceptual translation of the coding region predicts a protein with a molecular mass of 53,795 Da and a theoretical isoelectric point of 8.2. The ACS4 polypeptide contains the 11 invariant amino acid residues conserved between aminotransferases and ACC synthases from various plant species. An ACS4 cDNA was generated by reverse transcriptase-polymerase chain reaction, and the authenticity was confirmed by expression of ACC synthase activity in Escherichia coli.
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