Ana P. C. Ribeiro

Coffee (Coffea arabica L.) genes early expressed during infection by the rust fungus (Hemileia vastatrix)

SUMMARY The beverage cash crop coffee (Coffea arabica L.) is subject to severe losses caused by the rust fungus Hemileia vastatrix. In naturally resistant coffee plants, a specific hypersensitive reaction (HR) may be elicited early to stop fungal infection. To isolate host genes involved in HR, we undertook an expressed sequence tags (ESTs) analysis. Two cDNA libraries were constructed using suppression subtractive hybridization (SSH) and 527 non-redundant ESTs were generated from 784 randomly picked clones. Classification of the ESTs into several functional categories showed that more than one-quarter of the predicted proteins might encode disease resistance (R) proteins, stress- and defence-proteins, and components of signal transduction pathways. Twenty-eight differentially screened sequences (DSSs) were selected after differential hybridization of 1000 cDNA clones from each library. Investigation of the expression patterns of a subset of 13 DSSs showed higher levels of gene expression in inoculated plants compared with control plants. HR-up-regulation of transcript accumulation occurred for 9 out of the 13 genes 24 and 48 h after H. vastatrix challenge. Two genes encoded homologues of the Arabidopsis DND1 and NDR1 proteins, suggesting conservation of resistance signalling pathways in perennial plants. Other HR-regulated sequences matched receptor kinases, AP2 domain- and WRKY transcription factors, cytochromes P450, heat shock 70 proteins, glucosyltransferases and proteins of unknown function. The ESTs reported here provide a useful resource for studying coffee resistance responses and for improving C. arabica for durable disease resistance.

Nitrogen metabolism in actinorhizal nodules of Alnus glutinosa: expression of glutamine synthetase and acetylornithine transaminase.

Two nodule cDNA clones representing genes involved in Alnus glutinosa nitrogen metabolism were analysed. ag11 encoded glutamine synthetase (GS), the enzyme responsible for ammonium assimilation, while ag118 encoded acetylornithine transaminase (AOTA), an enzyme involved in the biosynthesis of citrulline, the nitrogen transport form in Alnus. GS mRNA was found at highest levels in root nodules, where it was present in the infected cells as well as in the cells of the pericycle of the vascular system. AOTA transcripts were found at high levels in nodules, confined to the infected cells, suggesting that in nodules of A. glutinosa, citrulline biosynthesis takes place mainly in the infected cells.

Highly efficient and reusable CNT supported iron(II) catalyst for microwave assisted alcohol oxidation

The highly efficient eco-friendly synthesis of ketones (yields over 99%) from secondary alcohols is achieved by combination of [FeCl2{η(3)-HC(pz)3}] (pz = pyrazol-1-yl) supported on functionalized multi-walled carbon nanotubes and microwave irradiation, in a solvent-free medium. The carbon homoscorpionate iron(ii) complex is the first one of this class to be used as catalyst for the oxidation of alcohols.

Progress on research on actinorhizal plants

In recent years, our understanding of the plant side of actinorhizal symbioses has evolved rapidly. No homologues of the common nod genes from rhizobia were found in the three Frankia genomes published so far, which suggested that Nod factor-like molecules would not be used in the infection of actinorhizal plants by Frankia. However, work on chimeric transgenic plants indicated that Frankia Nod factor equivalents signal via the same transduction pathway as rhizobial Nod factors. The role of auxin in actinorhizal nodule formation differs from that in legume nodulation. Great progress has been made in the analysis of pathogenesis-related and stress-related gene expression in nodules. Research on nodule physiology has shown the structural and metabolic diversity of actinorhizal nodules from different phylogenetic branches. The onset of large-scale nodule transcriptome analysis in different actinorhizal systems will provide access to more information on the symbiosis and its evolution.

Actinorhizal plant defence-related genes in response to symbiotic Frankia

Actinorhizal plants have become increasingly important as climate changes threaten to remake the global landscape over the next decades. These plants are able to grow in nutrient-poor and disturbed soils, and are important elements in plant communities worldwide. Besides that, most actinorhizal plants are capable of high rates of nitrogen fixation due to their capacity to establish root nodule symbiosis with N2-fixing Frankia strains. Nodulation is a developmental process that requires a sequence of highly coordinated events. One of these mechanisms is the induction of defence-related events, whose precise role in a symbiotic interaction remains to be elucidated. This review summarises what is known about the induction of actinorhizal defence-related genes in response to symbiotic Frankia and their putative function during symbiosis.

Characterization of four defense-related genes up-regulated in root nodules of Casuarina glauca

Actinorhizal plants are capable of high rates of nitrogen fixation, due to their capacity to establish a root-nodule symbiosis with N2-fixing actinomycetes of the genus Frankia. Nodulation is an ontogenic process which requires a sequence of highly coordinated events. One of these mechanisms is the induction of defense-related events, whose precise role during nodulation is largely unknown. In order to contribute to the clarification of the involvement of defense-related genes during actinorhizal root-nodule symbiosis, we have analysed the differential expression of several genes with putative defense-related functions in Casuarina glauca nodules versus non-inoculated roots. Four genes encoding a chitinase (CgChi1), a glutathione S-transferase (CgGst), a hairpin-inducible protein (CgHin1) and a peroxidase (CgPox4) were found to be up-regulated in mature nodules compared to roots. In order to find out to which extend were the encoded proteins involved in nodule protection, development or both, gene regulation studies in response to SA and wounding as well as phylogenetic analysis of the protein sequences were performed. These were further characterized through expression studies after SA-treatment and wounding, and by phylogenetic analysis. We suggest that CgChi1 and CgGst are involved in defense or microsymbiont control and CgPox4 is involved in nodule development. For CgHin1 the question “defense, development or both” remains open.

N2O-Free single-pot conversion of cyclohexane to adipic acid catalysed by an iron(II) scorpionate complex

The highly efficient eco-friendly synthesis of adipic acid (96% yield, 98% selectivity, TONs up to 1.8 × 103) directly from cyclohexane is achieved by using ozone and [FeCl2{κ3-HC(pz)3}] (pz = pyrazol-1-yl) in a solvent-, heating-, radiation- and N2O-free new protocol.

Nickel (ii)-2-amino-4-alkoxy-1,3,5-triazapentadienate complexes as catalysts for heck and henry reactions

Nickel(II)-triazapentadienate complexes, [Ni(tap)2], are synthesized and found to act as catalysts in the Heck reaction of deactivated aryl halides. The use of room-temperature ionic liquids instead of organic solvents allows easy separation of the catalyst from the products and substrates. The synthesized complexes also catalyse the Henry reaction of benzaldehydes with nitroethane, at 25 °C, leading to the corresponding nitroalkanols with diastereoselectivity in favour of the anti isomer.

Carbon dioxide-to-methanol single-pot conversion using a C-scorpionate iron(II) catalyst

The highly efficient eco-friendly synthesis of methanol (44% yield, TONs up to 2.3 × 103) directly from carbon dioxide is achieved by using H2 and the iron(II) scorpionate catalyst [FeCl2{κ3-HC(pz)3}] (pz = pyrazol-1-yl) in a solvent- or amine-free mild new protocol.

ZnII and CdII MOFs based on an amidoisophthalic acid ligand: synthesis, structure and catalytic application in transesterification

Solvothermal reaction of zinc(II) and cadmium(II) salts with 5-propionamidoisophthalic acid (H2L1) and 5-benzamidoisophthalic acid (H2L2) in the presence or absence of an auxiliary ligand gives rise to a series of 1D, 2D and 3D Zn(II) or Cd(II) self-assembled metal–organic frameworks as revealed by X-ray diffraction structural analyses: [Zn(μ-L1-μ-1κOO′:2κO′′)(formamide)2]n (1), [{Zn2(μ-L1-1κO:2κO′)2(4,4′-bipyridine)2(H2O)}·2(DMF)·5(H2O)]n (2), [Cd(μ-L1-μ-1κO2O′:2κO′′2O′′′)(DMF)]n (3), [{Zn(μ-L2-1κO:2κO′)(4,4′-bipyridine)(H2O)}·(H2O)]n (4) and [{Cd(μ-L2-μ-1κO2O′:2κO′′2O′′′)(formamide)(4,4′-bipyridine)}·(formamide)]n (5), which are also characterized by elemental analysis, IR spectroscopy and thermogravimetric analysis. The different architectures found in 1–5 result from the coordination modes of the carboxylate groups, which can assume nonbridging monodentate (in 1, 2 and 4), bridging bidentate (also in 1), bridging chelate (in 3 and 5) and chelate bidentate (also in 5) coordination. While 1 and 5 possess one dimensional double chain type structures, 3 has a 1D cyclic type structure and 2 and 4 have 2D or 3D wave-like structures, respectively. Topological analysis has shown that 1 and 5 have a 3-connected uninodal net with a topological type SP1-periodic net, 2 has a 2,4-connected binodal net, 3 has a 4-connected uninodal net structure and 4 has a more complex 2,2,2,4-connected tetranodal net. Frameworks 1–5 act as heterogeneous catalysts for the transesterification reaction of different carboxylate esters, with 4 showing the highest activity. These heterogeneous catalysts can be recycled without losing activity.