Cadmium is a major environmental pollutant that enters human food via accumulation in crop plants. Responses of plants to cadmium exposure—which directly influence accumulation rates—are not well understood. In general, little is known about stress-elicited changes in plants at the proteome level. Alterations in the root proteome of hydroponically grown Arabidopsis thaliana plants treated with 10 μM Cd2+ for 24 h are reported here. These conditions trigger the synthesis of phytochelatins (PCs), glutathione-derived metal-binding peptides, shown here as PC2 accumulation. Two-dimensional gel electrophoresis using different pH gradients in the first dimension detected on average ∼1100 spots per gel type. Forty-one spots indicated significant changes in protein abundance upon Cd2+ treatment. Seventeen proteins found in 25 spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Selected results were independently confirmed by western analysis and selective enrichment of a protein family (glutathione S-transferases) through affinity chromatography. Most of the identified proteins belong to four different classes: metabolic enzymes such as ATP sulphurylase, glycine hydroxymethyltransferase, and trehalose-6-phosphate phosphatase; glutathione S-transferases; latex allergen-like proteins; and unknown proteins. These results represent a basis for reverse genetics studies to better understand plant responses to toxic metal exposure and to the generation of internal sinks for reduced sulphur.

The first 3-fold multicomponent macrocyclizations of trifunctional building blocks were developed to produce, in one pot, cryptands, cages, and cryptophanes with peptoid tethers carrying additional recognition motifs. The straightforward, efficient, and diversity-oriented fashion by which these complex macromulticycles are obtained is suitable for building combinatorial libraries of synthetic receptors with potential applicability in catalysis and supramolecular and coordination chemistry. The strategy also easily allows creation of asymmetric macromulticyclic cavities, with up to 20 new bonds formed in one pot.

Barley plants are known to produce various PR-5 proteins. Transcripts encoding eight different barley PR-5 proteins (TLPs 1–8, TLP for thaumatin-like protein) were identified and cloned – seven from infected leaves and one from developing grains. Here, we describe the cDNA sequences of four of these TLP isoforms. Moreover, the TLPs from the infected leaves (TLPs 1, 2, and TLPs 4–8) were subjected to MALDI-TOF mass spectrometric measurements that resulted in protein fragments consistent with their deduced peptide sequences. Multiple sequence alignment analysis revealed that the TLPs in barley fall into two groups: long-chain proteins (TLPs 5–8) having 16 cysteine residues and short-chain proteins (TLPs 1–4) with only 10 cysteine residues. Finally, modelling experiments highlighted the effects of sequence differences between the TLP isoforms in terms of their secondary structures and their molecular electrostatic potentials. We propose that these sequence differences have implications for the target preferences of the different isomers.

We show that oomycete-derived Nep1 (for necrosis and ethylene-inducing peptide1)–like proteins (NLPs) trigger a comprehensive immune response in Arabidopsis thaliana, comprising posttranslational activation of mitogen-activated protein kinase activity, deposition of callose, production of nitric oxide, reactive oxygen intermediates, ethylene, and the phytoalexin camalexin, as well as cell death. Transcript profiling experiments revealed that NLPs trigger extensive reprogramming of the Arabidopsis transcriptome closely resembling that evoked by bacteria-derived flagellin. NLP-induced cell death is an active, light-dependent process requiring HSP90 but not caspase activity, salicylic acid, jasmonic acid, ethylene, or functional SGT1a/SGT1b. Studies on animal, yeast, moss, and plant cells revealed that sensitivity to NLPs is not a general characteristic of phospholipid bilayer systems but appears to be restricted to dicot plants. NLP-induced cell death does not require an intact plant cell wall, and ectopic expression of NLP in dicot plants resulted in cell death only when the protein was delivered to the apoplast. Our findings strongly suggest that NLP-induced necrosis requires interaction with a target site that is unique to the extracytoplasmic side of dicot plant plasma membranes. We propose that NLPs play dual roles in plant pathogen interactions as toxin-like virulence factors and as triggers of plant innate immune responses.

Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) proteins also function as auxin receptors, a potentially complete, and surprisingly simple, signaling pathway from perception to transcriptional response is now before us. However, understanding how this seemingly simple pathway controls the myriad of specific auxin responses remains a daunting challenge, and compelling evidence exists for SCFTIR1/AFB-independent auxin signaling pathways.

Four new spirostanes functionalized with the butyrolactone moiety were efficiently synthesized and submitted to preliminary biological tests. Two practical synthetic routes were designed to enable the incorporation of the γ-lactone functionality into rings A and B. Butyrolactones 5 and 10 showed a promising plant growth-promoting activity which renders them good candidates for further biological studies.

Geranylgeranyl diphosphate phosphatase is an enzyme catalyzing the dephosphorylation of geranylgeranyl diphosphate (GGPP) to form geranylgeraniol (GGOH). The enzyme activity of GGPP phosphatase was detected in leaves of Croton stellatopilosus, a Thai medicinal plant containing plaunotol, a commercial anti-peptic acyclic diterpenoid. Enzymological studies of GGPP phosphatase in C. stellatopilosis leaves revealed that the enzyme is a membrane-bound protein that could be removed from 20,000g pellet by 0.1% Triton X-100 without significant loss of enzyme activity. The solubilized enzyme preparation was separated into two activity peaks, PI and PII, by BioGel A gel filtration chromatography. PI and PII were both partially purified and characterized. PI appeared to be a tetrameric enzyme with its native molecular mass of 232 kDa and subunit size of 58 kDa, whereas PII was a monomeric enzyme with a molecular mass of 30–34 kDa. Both phosphatases utilized GGPP as the preferred substrate over farnesyl and geranyl diphosphates. The apparent Km values for GGPP of PI and PII appeared to be 0.2 and 0.1 mM, respectively. Both activities were Mg2+ independent and exhibited slightly acidic pH optima, 6.0–6.5 for PI and 6.5–7.0 for PII. The catalytic activities of PII was strongly inhibited by 1.0 mM of Zn2+, Mn2+ and Co2+, whereas that of PI was not affected. Both enzyme preparations were very stable upon storage at −20 °C for 45 days without significant loss of phosphatase activity. The presence of GGPP phosphatase enzymes in C. stellatopilosus is consistent with its putative involvement in the biosynthetic pathway of plaunotol although whether PI or PII is the actual enzyme involved in the pathway remains to be clarified.

Salicylic acid (SA) has been proposed to antagonize jasmonic acid (JA) biosynthesis and signaling. We report, however, that in salicylate hydroxylase-expressing tobacco (Nicotiana tabacum) plants, where SA levels were reduced, JA levels were not elevated during a hypersensitive response elicited by Pseudomonas syringae pv phaseolicola. The effects of cotreatment with various concentrations of SA and JA were assessed in tobacco and Arabidopsis (Arabidopsis thaliana). These suggested that there was a transient synergistic enhancement in the expression of genes associated with either JA (PDF1.2 [defensin] and Thi1.2 [thionin]) or SA (PR1 [PR1a-β-glucuronidase in tobacco]) signaling when both signals were applied at low (typically 10–100 μm) concentrations. Antagonism was observed at more prolonged treatment times or at higher concentrations. Similar results were also observed when adding the JA precursor, α-linolenic acid with SA. Synergic effects on gene expression and plant stress were NPR1- and COI1-dependent, SA- and JA-signaling components, respectively. Electrolyte leakage and Evans blue staining indicated that application of higher concentrations of SA + JA induced plant stress or death and elicited the generation of apoplastic reactive oxygen species. This was indicated by enhancement of hydrogen peroxide-responsive AoPR10-β-glucuronidase expression, suppression of plant stress/death using catalase, and direct hydrogen peroxide measurements. Our data suggests that the outcomes of JA-SA interactions could be tailored to pathogen/pest attack by the relative concentration of each hormone.

Fruitbodies of the genus Hygrophorus (Basidiomycetes) contain a series of anti‐biologically active compounds. These substances named hygrophorones possess a cyclopentenone skeleton. LC/ESI‐MS/MS presents a valuable tool for the identification of such compounds. The mass spectral behaviour of typical selected members of this group under positive and negative ion electrospray conditions is discussed. Using the ESI collision‐induced dissociation (CID) mass spectra of the [M + H]+ and [M − H]− ions, respectively, the compounds can be classified with respect to the substitution pattern at the cyclopentenone ring and the type of oxygenation at C‐6 (hydroxy/acetoxy or oxo function) of the side chain. The elemental composition of the fragment ions was determined by ESI‐QqTOF measurements. Thus, in case of the negative ion CID mass spectra an unusual loss of CO2 from the deprotonated molecular ions could be observed.

We have analyzed plastid proliferation in root cortical cells of Medicago truncatula colonized by arbuscular mycorrhizal (AM) fungi by concomitantly labeling fungal structures, root plastids, a protein involved in plastid division (FtsZ1) and a protein involved in the biosynthesis of AM-specific apocarotenoids. Antibodies directed against FtsZ1 have been generated after heterologous expression of the respective gene from M. truncatula and characterization of the gene product. Analysis of enzymatic activity and assembly experiments showed similar properties of this protein when compared with the bacterial proteins. Immunocytological experiments allowed two phases of fungal and plastid development to be clearly differentiated and plastid division to be monitored during these phases. In the early phase of arbuscule development, lens-shaped plastids, intermingled with the arbuscular branches, divide frequently. Arbuscule degradation, in contrast, is characterized by large, tubular plastids, decorated by a considerable number of FtsZ division rings.