Utilizing the multiple multicomponent macrocyclization including bifunctional building blocks (MiB) strategy, a library of nonracemic, nonrepetitive peptoid-containing steroid−biaryl ether hybrid macrocycles was built. Up to 16 new bonds, including those of the macrocyclization, can be formed in one pot simultaneously while introducing varied elements of diversity. Functional diversity is generated primarily by choosing Ugi-reactive functional building blocks, bearing the respective recognition or catalytic motifs. These appear attached to the peptoid backbone of the macrocyclic cavity, similar to side chains of amino acids found in enzyme active sites. Likewise, skeletal diversity is based on the variation of defined bifunctional building blocks which allow the parallel formation of macrocyclic cavities that are highly diverse in shape and size and thus perspectively in function. This straightforward approach is suitable to generate multifunctional macrocycles for applications in catalysis, supramolecular, or biological chemistry.

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Cultured cells of Eschscholzia californica respond to a yeast glycoprotein elicitor by producing benzophenanthridine alkaloids, which are excreted into the cell wall and the outer medium. These compounds, preferentially sanguinarine, are efficient phytoalexins because of their ability to intercalate double‐stranded DNA (dsDNA), penetrate membranes and inhibit various enzymes containing SH‐groups. Externally added sanguinarine is rapidly taken up by intact cells and converted to dihydrosanguinarine, which is substituted intracellularly according to the biosynthetic route. A 29.5 kDa soluble enzyme that catalyses the reduction of sanguinarine and chelerythrine by either NADPH or NADH has been isolated and purified to homogeneity. Benzophenanthridines that accumulate in the outer medium, mainly 10‐OH‐chelerythrine, chelirubine and macarpine, are converted by the isolated enzyme and by intact cells at much slower rates than sanguinarine. The cellular capacity of uptake and conversion of sanguinarine largely surpasses the rate of alkaloid production. We conclude that the sanguinarine produced by intact cells, after excretion and binding to cell wall elements, is rapidly reabsorbed and reduced to the less toxic dihydrosanguinarine, which then undergoes further biosynthetic reactions. This recycling process would allow the presence of the toxic phytoalexin at the cellular surface without taking the risk of injuring the producing cell.

Toxic effects of both essential and non‐essential heavy metals are well documented in plants. Very little is known, however, about their modes of toxicity, about tolerance mechanisms and the signalling cascades involved in mediating transcriptional responses to toxic metal excess. We analysed transcriptome changes upon Cd2+ and Cu2+ exposure in roots of Arabidopsis thaliana and the Cd2+‐hypertolerant metallophyte Arabidopsis halleri . Particularly, three categories of genes were identified with the help of this comparative approach: (1) common responses, which might indicate stable and functionally relevant changes conserved across plant species; (2) metallophyte‐specific responses as well as transcripts differentially regulated between the two species, representing candidate genes for Cd2+ hypertolerance; and (3) those specifically responsive to Cd2+ and therefore indicative of toxicity mechanisms or potentially involved in signalling cascades. Our data define, for instance, Arabidopsis core responses to Cd2+ and Cu2+. In addition, they suggest that Cd2+ exposure very rapidly results in apparent Zn deficiency, and they show the existence of highly specific Cd2+ responses and distinct signalling cascades. Array results were independently confirmed by real‐time quantitative PCR, thereby further validating cross‐species transcriptome analysis with oligonucleotide microarrays.

Plants respond to mechanical wounding or herbivore attack with a complex scenario of sequential, antagonistic or synergistic action of different signals leading to defense gene expression. Tomato plants were used as a model system since the peptide systemin and the lipid-derived jasmonic acid (JA) were recognized as essential signals in wound-induced gene expression. In this review recent data are discussed with emphasis on wound-signaling in tomato. The following aspects are covered: (i) systemin signaling, (ii) JA biosynthesis and action, (iii) orchestration of various signals such as JA, H2O2, NO, and salicylate, (iv) local and systemic response, and (v) amplification in wound signaling. The common occurrence of JA biosynthesis and systemin generation in the vascular bundles suggest JA as the systemic signal. Grafting experiments with JA-deficient, JA-insensitive and systemin-insensitive mutants strongly support this assumption.

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The reactions of [PtMe3(OAc)(bpy)] (4) with the N,S and S,S containing heterocycles, pyrimidine-2-thione (pymtH), pyridine-2-thione (pytH), thiazoline-2-thione (tztH) and thiophene-2-thiol (tptH), resulted in the formation of the monomeric complexes [PtMe3(-κS)(bpy)] ( = pymt, 5; pyt, 6; tzt, 7; tpt, 8), where the heterocyclic ligand is coordinated via the exocyclic sulfur atom. In contrast, in the reactions of [PtMe3(OAc)(Me2CO)x] (3, x = 1 or 2) with pymtH, pytH, tztH and tptH dimeric complexes [{PtMe3(μ-)}2] (μ- = pymt, 9; pyt, 10; tzt, 11) and the tetrameric complex [{PtMe3(μ3-tpt-κS)}4] (12), respectively, were formed. The complexes were characterized by microanalyses, 1H and 13C NMR spectroscopy and negative ESI-MS (12) measurements. Single-crystal X-ray diffraction analysis of [PtMe3(pymt-κS)(bpy)] (5) exhibited a conformation where the pymt ligand lies nearly perpendicular to the complex plane above the bpy ligand that was also confirmed by quantum chemical calculations on the DFT level of theory.

Reactive oxygen intermediates (ROI) are closely related to defence reactions of plants against pathogens. A prominent role in the production of ROI has been attributed to the plant respiratory burst oxidase homologues (RBOH) of the human phagocyte GP91(phox). A barley RBOH, which encodes a putative superoxide (O2·−) producing NADPH oxidase, is described here. Histochemical analysis of the barley-Blumeria graminis f. sp. hordei (Bgh) interaction showed that O2·− is produced locally at the site of penetration. In contrast, hydrogen peroxide (H2O2) is produced in non-penetrated cell wall appositions. A barley RBOHA cDNA was isolated and a minor induction of expression of RBOHA was observed during the interactions of barley with Bgh. Transient RNA interference-mediated gene silencing of HvRBOHA during the penetration process of Bgh led to an increase of basal penetration resistance. The results support a potential role of HvRBOHA in cellular accessibility to Blumeria graminis.

Nicotianamine is an important metal ligand in plants. Surprisingly, recent genome sequencing revealed that ascomycetes encode proteins with similarity to plant nicotianamine synthases (NAS). By expression in a Zn2+‐hypersensitive fission yeast mutant we show for a protein from Neurospora crassa that it indeed possesses NAS activity. Using electrospray‐ionization‐quadrupole‐time‐of‐flight mass spectrometry we prove the formation of nicotianamine in N. crassa . Transcript level is strongly upregulated under Zn deficiency as shown by real‐time PCR. These findings demonstrate that nicotianamine is more widespread in nature than anticipated and provide further evidence for a function of nicotianamine as a cytosolic chelator of Zn2+ ions.

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