Evolutionary Implications of a Peroxidase with High Affinity for Cinnamyl Alcohols from Physcomitrium patens, a Non-Vascular Plant

Physcomitrium (Physcomitrella) patens is a bryophyte highly tolerant to different stresses, allowing survival when water supply is a limiting factor. This moss lacks a true vascular system, but it has evolved a primitive water-conducting system that contains lignin-like polyphenols. By means of a three-step protocol, including ammonium sulfate precipitation, adsorption chromatography on phenyl Sepharose and cationic exchange chromatography on SP Sepharose, we were able to purify and further characterize a novel class III peroxidase, PpaPrx19, upregulated upon salt and H₂O₂ treatments. This peroxidase, of a strongly basic nature, shows surprising homology to angiosperm peroxidases related to lignification, despite the lack of true lignins in P. patens cell walls. Moreover, PpaPrx19 shows catalytic and kinetic properties typical of angiosperm peroxidases involved in oxidation of monolignols, being able to efficiently use hydroxycinnamyl alcohols as substrates. Our results pinpoint the presence in P. patens of peroxidases that fulfill the requirements to be involved in the last step of lignin biosynthesis, predating the appearance of true lignin.

Overexpression of ZePrx in Nicotiana tabacum Affects Lignin Biosynthesis Without Altering Redox Homeostasis

Class III plant peroxidases (Prxs) are involved in the oxidative polymerization of lignins. Zinnia elegans Jacq. Basic peroxidase (ZePrx) has been previously characterized as capable of catalyzing this reaction in vitro and the role in lignin biosynthesis of several of its Arabidopsis thaliana homologous has been previously confirmed. In the present work, ZePrx was overexpressed in Nicotiana tabacum to further characterize its function in planta with particular attention to its involvement in lignin biosynthesis. Since Prxs are known to alter ROS levels by using them as electron acceptor or producing them in their catalytic activity, the impact of this overexpression in redox homeostasis was studied by analyzing the metabolites and enzymes of the ascorbate-glutathione cycle. In relation to the modification induced by ZePrx overexpression in lignin composition and cellular metabolism, the carbohydrate composition of the cell wall as well as overall gene expression through RNA-Seq were analyzed. The obtained results indicate that the overexpression of ZePrx caused an increase in syringyl lignin in cell wall stems, suggesting that ZePrx is relevant for the oxidation of sinapyl alcohol during lignin biosynthesis, coherently with its S-peroxidase nature. The increase in the glucose content of the cell wall and the reduction of the expression of several genes involved in secondary cell wall biosynthesis suggests the occurrence of a possible compensatory response to maintain cell wall properties. The perturbation of cellular redox homeostasis occurring as a consequence of ZePrx overexpression was kept under control by an increase in APX activity and a reduction in ascorbate redox state. In conclusion, our results confirm the role of ZePrx in lignin biosynthesis and highlight that its activity alters cellular pathways putatively aimed at maintaining redox homeostasis.

Changes in lignin biosynthesis and monomer composition in response to benzothiadiazole and root-knot nematode Meloidogyne incognita infection in tomato

Benzothiadiazole (BTH) acts as a priming agent in plant defence leading to a reduction in penetration and development of the root-knot nematode Meloidogyne incognita in susceptible tomato roots. Changes in lignin biosynthesis in the susceptible tomato cv. Roma following nematode infection and/or BTH treatment were investigated in comparison to the resistant cv. Rossol. Both untreated and BTH-treated susceptible infected roots (galls) showed an increased level of expression of lignin synthesis-related genes (PAL, C4H, HCT and F5H) at early times during infection (2-4 days post inoculation). Peroxidase (soluble and cell-wall bound, POX) enzyme activities increased after inoculation with M. incognita and the priming effect of BTH treatment was evident at later stages of infection (7 days post inoculation). As expected, the induction of PAL and POXs and lignin synthesis-related genes was faster and greater in resistant roots after infection. Histochemical analysis revealed accumulation of higher lignin levels at later infection stages in BTH-treated galls compared to untreated ones. Furthermore, the monomer composition of lignin indicated a different composition in guaiacyl (G) and syringyl (S) units in BTH-treated galls compared to untreated galls. The increase in G units made G/S ratio similar to that in the resistant genotype. Overall, lignin played a critical role in tomato defence to M. incognita in response to BTH.

Deciphering the role of the phenylpropanoid metabolism in the tolerance of Capsicum annuum L. to Verticillium dahliae Kleb

Verticillium dahliae is an economically relevant soilborne pathogen that causes vascular wilt in several crops, including pepper (Capsicum annuum). Fungal infection is usually visualized as a vascular browning, likely due to the onset of phenylpropanoid metabolism, which also seems to play a crucial role in the tolerance of some pepper varieties. In the current work, the potential function of distinct phenylpropanoid derivatives (suberin, lignin and phenolic compounds) in the pepper tolerance response against V. dahliae, was investigated. Histochemical and biochemical analyses ruled out suberin as a key player in the pepper-fungus interaction. However, changes observed in lignin composition and higher deposition of bound phenolics in infected stems seemed to contribute to the reinforcement of cell walls and the impairment of V. dahliae colonization. Most importantly, this is the first time that the accumulation of the hydroxycinnamic acid amide N-feruloyltyramine was reported in pepper stems in response to a vascular fungus. Fungitoxic activity for that hydroxycinnamate-tyramine conjugate was demonstrated as well.

Suppression of Arabidopsis peroxidase 72 alters cell wall and phenylpropanoid metabolism

Class III peroxidases are glycoproteins with a major role in cell wall maturation such as lignin formation. Peroxidases are usually present in a high number of isoenzymes, which complicates to assign specific functions to individual peroxidase isoenzymes. Arabidopsis genome encodes for 73 peroxidases, among which AtPrx72 has been shown to participate in lignification. Here, we report by using knock out peroxidase mutants how the disruption of AtPrx72 causes thinner secondary walls in interfascicular fibres but not in the xylem of the stem. This effect is also age-dependent, and AtPrx72 function seems to be particularly important when lignification prevails over elongation processes. Finally, the suppression AtPrx72 leads to the down-regulation of lignin biosynthesis pathway, as well as genes and transcription factors involved in secondary wall thickening.

Ectopic lignification in primary cellulose-deficient cell walls of maize cell suspension cultures

Maize (Zea mays L.) suspension-cultured cells with up to 70% less cellulose were obtained by stepwise habituation to dichlobenil (DCB), a cellulose biosynthesis inhibitor. Cellulose deficiency was accompanied by marked changes in cell wall matrix polysaccharides and phenolics as revealed by Fourier transform infrared (FTIR) spectroscopy. Cell wall compositional analysis indicated that the cellulose-deficient cell walls showed an enhancement of highly branched and cross-linked arabinoxylans, as well as an increased content in ferulic acid, diferulates and p-coumaric acid, and the presence of a polymer that stained positive for phloroglucinol. In accordance with this, cellulose-deficient cell walls showed a fivefold increase in Klason-type lignin. Thioacidolysis/GC-MS analysis of cellulose-deficient cell walls indicated the presence of a lignin-like polymer with a Syringyl/Guaiacyl ratio of 1.45, which differed from the sensu stricto stress-related lignin that arose in response to short-term DCB-treatments. Gene expression analysis of these cells indicated an overexpression of genes specific for the biosynthesis of monolignol units of lignin. A study of stress signaling pathways revealed an overexpression of some of the jasmonate signaling pathway genes, which might trigger ectopic lignification in response to cell wall integrity disruptions. In summary, the structural plasticity of primary cell walls is proven, since a lignification process is possible in response to cellulose impoverishment.

Peroxidase 4 is involved in syringyl lignin formation in Arabidopsis thaliana

Syringyl lignins result from the oxidative polymerization of sinapyl alcohol in a reaction mediated by syringyl (basic) peroxidases. Several peroxidases have been identified in the genome of Arabidopsis thaliana as close homologues to ZePrx, the best characterized basic peroxidase so far, but none of these has been directly involved in lignification. We have used a knock-out mutant of AtPrx4, the closest homologue to ZePrx, to study the involvement of this basic peroxidase in the physiology of the plant under both long- and short-day light conditions. Our results suggest that AtPrx4 is involved in cell wall lignification, especially in syringyl monomer formation. The disruption of AtPrx4 causes a decrease in syringyl units proportion, but only when light conditions are optimal. Moreover, the effect of AtPrx4 disruption is age-dependent, and it is only significant when the elongation process of the stem has ceased and lignification becomes active. In conclusion, AtPrx4 emerges as a basic peroxidase regulated by day length with an important role in lignification.

New insights into Capsicum spp relatedness and the diversification process of Capsicum annuum in Spain

The successful exploitation of germplasm banks, harbouring plant genetic resources indispensable for plant breeding, will depend on our ability to characterize their genetic diversity. The Vegetable Germplasm Bank of Zaragoza (BGHZ) (Spain) holds an important Capsicum annuum collection, where most of the Spanish pepper variability is represented, as well as several accessions of other domesticated and non-domesticated Capsicum spp from all over the five continents. In the present work, a total of 51 C. annuum landraces (mainly from Spain) and 51 accessions from nine Capsicum species maintained at the BGHZ were evaluated using 39 microsatellite (SSR) markers spanning the whole genome. The 39 polymorphic markers allowed the detection of 381 alleles, with an average of 9.8 alleles per locus. A sizeable proportion of alleles (41.2%) were recorded as specific alleles and the majority of these were present at very low frequencies (rare alleles). Multivariate and model-based analyses partitioned the collection in seven clusters comprising the ten different Capsicum spp analysed: C. annuum, C. chinense, C. frutescens, C. pubescens, C. bacatum, C. chacoense and C. eximium. The data clearly showed the close relationships between C. chinense and C. frutescens. C. cardenasii and C. eximium were indistinguishable as a single, morphologically variable species. Moreover, C. chacoense was placed between C. baccatum and C. pubescens complexes. The C. annuum group was structured into three main clusters, mostly according to the pepper fruit shape, size and potential pungency. Results suggest that the diversification of C. annuum in Spain may occur from a rather limited gene pool, still represented by few landraces with ancestral traits. This ancient population would suffer from local selection at the distinct geographical regions of Spain, giving way to pungent and elongated fruited peppers in the South and Center, while sweet blocky and triangular types in Northern Spain.

A proteomic approach to Physcomitrella patens rhizoid exudates

The interaction between plants and the surrounding environment has been widely studied, specially the defence reactions and the plant-plant interactions. One of the most remarkable metabolic features of plant roots is the ability to secrete a vast array of compounds into the rhizosphere, not only of low molecular weight but also polysaccharides and proteins. Here, we took advantage of proteomics to study the rhizoid exudates of Physcomitrella patens at early and late development stages (7 and 28 days of culture in liquid medium). Samples were extracted, separated and detected with nanoLC-MALDI-TOF/TOF MS/MS, identifying 47 proteins at the development stage of 7 days, and 66 proteins at 28 days. Moreover, 21 proteins were common to the two analyzed periods. All the identified proteins were classified into 8 functional categories: response to stress, response to stimulus, oxido-reduction, cell wall modification, photosynthesis and carbohydrate metabolism, transport, DNA metabolic process and regulation/signalling. Our results show important differences in the protein expression profile along the development of P. patens, mainly at the level of regulation- and senescence-related proteins. Defence-related proteins, such as chitinases, thaumatins and peroxidases have a major role in the interaction of P. patens with the environment.

Molecular cloning of two novel peroxidases and their response to salt stress and salicylic acid in the living fossil Ginkgo biloba

BACKGROUND AND AIMS

Peroxidase isoenzymes play diverse roles in plant physiology, such as lignification and defence against pathogens. The actions and regulation of many peroxidases are not known with much accuracy. A number of studies have reported direct involvement of peroxidase isoenzymes in the oxidation of monolignols, which constitutes the last step in the lignin biosynthesis pathway. However, most of the available data concern only peroxidases and lignins from angiosperms. This study describes the molecular cloning of two novel peroxidases from the 'living fossil' Ginkgo biloba and their regulation by salt stress and salicylic acid.

METHODS

Suspension cell cultures were used to purify peroxidases and to obtain the cDNAs. Treatments with salicylic acid and sodium chloride were performed and peroxidase activity and gene expression were monitored.

KEY RESULTS

A novel peroxidase was purified, which preferentially used p-hydroxycinnamyl alcohols as substrates and was able to form dehydrogenation polymers in vitro from coniferyl and sinapyl alcohols. Two peroxidase full-length cDNAs, GbPrx09 and GbPrx10, were cloned. Both peroxidases showed high similarity to other basic peroxidases with a putative role in cell wall lignification. Both GbPrx09 and GbPrx10 were expressed in leaves and stems of the plant. Sodium chloride enhanced the gene expression of GbPrx09 but repressed GbPrx10, whereas salicylic acid strongly repressed both GbPrx09 and GbPrx10.

CONCLUSIONS

Taken together, the data suggest the participation of GbPrx09 and GbPrx10 in the developmental lignification programme of the cell wall. Both peroxidases possess the structural characteristics necessary for sinapyl alcohol oxidation. Moreover, GbPrx09 is also involved in lignification induced by salt stress, while salicylic acid-mediated lignification is not a result of GbPrx09 and GbPrx10 enzymatic activity.

Nitric oxide is required for determining root architecture and lignin composition in sunflower. Supporting evidence from microarray analyses

Nitric oxide (NO) is a signal molecule involved in several physiological processes in plants, including root development. Despite the importance of NO as a root growth regulator, the knowledge about the genes and metabolic pathways modulated by NO in this process is still limited. A constraint to unravel these pathways has been the use of exogenous applications of NO donors that may produce toxic effects. We have analyzed the role of NO in root architecture through the depletion of endogenous NO using the scavenger cPTIO. Sunflower seedlings growing in liquid medium supplemented with cPTIO showed unaltered primary root length while the number of lateral roots was deeply reduced; indicating that endogenous NO participates in determining root branching in sunflower. The transcriptional changes induced by NO depletion have been analyzed using a large-scale approach. A microarray analysis showed 330 genes regulated in the roots (p≤0.001) upon endogenous NO depletion. A general cPTIO-induced up-regulation of genes involved in the lignin biosynthetic pathway was observed. Even if no detectable changes in total lignin content could be detected, cell walls analyses revealed that the ratio G/S lignin increased in roots treated with cPTIO. This means that endogenous NO may control lignin composition in planta. Our results suggest that a fine tuning regulation of NO levels could be used by plants to regulate root architecture and lignin composition. The functional implications of these findings are discussed.

From Zinnia to Arabidopsis: approaching the involvement of peroxidases in lignification

Zinnia elegans constitutes one of the most useful model systems for studying xylem differentiation, which simultaneously involves secondary cell wall synthesis, cell wall lignification, and programmed cell death. Likewise, the in vitro culture system of Z. elegans has been the best characterized as the differentiation of mesophyll cells into tracheary elements allows study of the biochemistry and physiology of xylogenesis free from the complexity that heterogeneous plant tissues impose. Moreover, Z. elegans has emerged as an excellent plant model to study the involvement of peroxidases in cell wall lignification. This is due to the simplicity and duality of the lignification pattern shown by the stems and hypocotyls, and to the basic nature of the peroxidase isoenzyme. This protein is expressed not only in hypocotyls and stems but also in mesophyll cells transdifferentiating into tracheary elements. Therefore, not only does this peroxidase fulfil all the catalytic requirements to be involved in lignification overcoming all restrictions imposed by the polymerization step, but also its expression is inherent in lignification. In fact, its basic nature is not exceptional since basic peroxidases are differentially expressed during lignification in other model systems, showing unusual and unique biochemical properties such as oxidation of syringyl moieties. This review focuses on the experiments which led to a better understanding of the lignification process in Zinnia, starting with the basic knowledge about the lignin pattern in this plant, how lignification takes place, and how a sole basic peroxidase with unusual catalytic properties is involved and regulated by hormones, H2O2, and nitric oxide.

Bioinformatic and functional characterization of the basic peroxidase 72 from Arabidopsis thaliana involved in lignin biosynthesis

Lignins result from the oxidative polymerization of three hydroxycinnamyl (p-coumaryl, coniferyl, and sinapyl) alcohols in a reaction mediated by peroxidases. The most important of these is the cationic peroxidase from Zinnia elegans (ZePrx), an enzyme considered to be responsible for the last step of lignification in this plant. Bibliographical evidence indicates that the arabidopsis peroxidase 72 (AtPrx72), which is homolog to ZePrx, could have an important role in lignification. For this reason, we performed a bioinformatic, histochemical, photosynthetic, and phenotypical and lignin composition analysis of an arabidopsis knock-out mutant of AtPrx72 with the aim of characterizing the effects that occurred due to the absence of expression of this peroxidase from the aspects of plant physiology such as vascular development, lignification, and photosynthesis. In silico analyses indicated a high homology between AtPrx72 and ZePrx, cell wall localization and probably optimal levels of translation of AtPrx72. The histochemical study revealed a low content in syringyl units and a decrease in the amount of lignin in the atprx72 mutant plants compared to WT. The atprx72 mutant plants grew more slowly than WT plants, with both smaller rosette and principal stem, and with fewer branches and siliques than the WT plants. Lastly, chlorophyll a fluorescence revealed a significant decrease in ΦPSII and q L in atprx72 mutant plants that could be related to changes in carbon partitioning and/or utilization of redox equivalents in arabidopsis metabolism. The results suggest an important role of AtPrx72 in lignin biosynthesis. In addition, knock-out plants were able to respond and adapt to an insufficiency of lignification.

Purification and kinetic characterization of two peroxidases of Selaginella martensii Spring. involved in lignification

Two cationic peroxidases from Selaginella martensii Spring. (SmaPrx2 and SmaPrx3) were purified using a three-step protocol which includes ammonium sulfate precipitation, adsorption chromatography on phenyl sepharose and cationic exchange chromatography on SP sepharose. The molecular mass for SmaPrx2 and SmaPrx3 was calculated to be 36.3 kDa and 45.6 kDa, respectively, according to MALDI-TOF/TOF. The isoelectric points were estimated in 9.2 and 9.5 for SmaPrx2 and SmaPrx3, respectively, according to isoelectrofocusing. Both enzymes show a typical peroxidase UV-visible spectrum with a Soret peak at 403 nm for SmaPrx2 and 404 nm for SmaPrx3. The specific activities showed against several substrates and the kinetic parameters suggest SmaPrx2 and SmaPrx3 have specific roles in cell wall formation and especially in lignin biosynthesis. Several peptides from tryptic digestion of both peroxidases were identified through MALDI-TOF MS/MS. The presence in these peptides of structural determinants typical of syringyl peroxidases indicates these proteins show no structural restrictions to oxidize syringyl moieties. These data, along with the in vitro capacity of using sinapyl alcohol as substrate and the low K(m) in the μM range suggest these two peroxidases may be responsible for the oxidation of syringyl monolignols that leads to syringyl lignins biosynthesis.

Distribution of lignin monomers and the evolution of lignification among lower plants

Through application of chemical, biochemical and histochemical analyses, we provide new data on the absence/presence of syringyl lignins in the algal species Mastocarpus stellatus, Cystoseira baccata and Ulva rigida, the bryophytes Physcomitrella patens and Marchantia polymorpha, the lycophytes Selaginella martensii, Isoetes fluitans and Isoetes histrix, the sphenophyte Equisetum telmateia, the ferns Ceratopteris thalictroides, Ceratopteris cornuta, Pteridium aquilinum, Phyllitis scolopendrium and Dryopteris affinis, and the angiosperm Posidonia oceanica. Lignins, and especially syringyl lignins, are distributed from non-vascular basal land plants, such as liverworts, to lycopods and ferns. This distribution, along with the already reported presence of syringyl lignins in ginkgoopsids, suggests that syringyl lignin is a primitive character in land plant evolution. Here, we discuss whether the pathway for sinapyl alcohol recruitment was iterative during the evolution of land plants or, alternatively, was incorporated into the earliest land plants and subsequently repressed in several basal liverworts, lycopods, equisetopsids and ferns. This last hypothesis, which is supported by recent studies of transcriptional regulation of the biosynthesis of lignins, implies that lignification originated as a developmental enabler in the peripheral tissues of protracheophytes and would only later have been co-opted for the strengthening of tracheids in eutracheophytes.

The Ve-mediated resistance response of the tomato to Verticillium dahliae involves H2O2, peroxidase and lignins and drives PAL gene expression

BACKGROUND

Verticillium dahliae is a fungal pathogen that infects a wide range of hosts. The only known genes for resistance to Verticillium in the Solanaceae are found in the tomato (Solanum lycopersicum) Ve locus, formed by two linked genes, Ve1 and Ve2. To characterize the resistance response mediated by the tomato Ve gene, we inoculated two nearly isogenic tomato lines, LA3030 (ve/ve) and LA3038 (Ve/Ve), with V. dahliae.

RESULTS

We found induction of H2O2 production in roots of inoculated plants, followed by an increase in peroxidase activity only in roots of inoculated resistant plants. Phenylalanine-ammonia lyase (PAL) activity was also increased in resistant roots 2 hours after inoculation, while induction of PAL activity in susceptible roots was not seen until 48 hours after inoculation. Phenylpropanoid metabolism was also affected, with increases in ferulic acid, p-coumaric acid, vanillin and p-hydroxybenzaldehyde contents in resistant roots after inoculation. Six tomato PAL cDNA sequences (PAL1 - PAL6) were found in the SolGenes tomato EST database. RT-PCR analysis showed that these genes were expressed in all organs of the plant, albeit at different levels. Real-time RT-PCR indicated distinct patterns of expression of the different PAL genes in V. dahliae-inoculated roots. Phylogenetic analysis of 48 partial PAL cDNAs corresponding to 19 plant species grouped angiosperm PAL sequences into four clusters, suggesting functional differences among the six tomato genes, with PAL2 and PAL6 presumably involved in lignification, and the remaining PAL genes implicated in other biological processes. An increase in the synthesis of lignins was found 16 and 28 days after inoculation in both lines; this increase was greater and faster to develop in the resistant line. In both resistant and susceptible inoculated plants, an increase in the ratio of guaiacyl/syringyl units was detected 16 days after inoculation, resulting from the lowered amount of syringyl units in the lignins of inoculated plants.

CONCLUSIONS

The interaction between the tomato and V. dahliae triggered a number of short- and long-term defensive mechanisms. Differences were found between compatible and incompatible interactions, including onset of H2O2 production and activities of peroxidase and PAL, and phenylpropanoid metabolism and synthesis of lignins.

The presence of sinapyl lignin in Ginkgo biloba cell cultures changes our views of the evolution of lignin biosynthesis

Suspension cell cultures (SCCs) from one of the oldest seed plants, Ginkgo biloba, show unpredictable alterations in the nature of the lignins, such as is the recruitment of sinapyl alcohol for lignin biosynthesis, compared with the woody tissues of the same species, which lack syringyl (S) lignins. These results show that, in this gymnosperm, the genes involved in sinapyl alcohol biosynthesis are latent and that their regulatory regions respond, by initiating gene expression, to the developmental signals and the environmental clues, which condition its in vitro culture. G. biloba SCCs not only synthesize S lignins but also their extracellular proteome contains both class III peroxidases capable of oxidizing sinapyl alcohol and enzymes involved in H2O2 production, observation which suggests that the peroxidase branch for the oxidative coupling of sinapyl alcohol units into lignins is operative. The incomplete knowledge of the G. biloba peroxidase-encoding genes led us to purify, characterize and partially sequence the peroxidase responsible for monolignol oxidation. When the major peroxidase from G. biloba SCCs (GbPrx) was purified to homogeneity, it showed absorption maxima in the visible region at 414 (Soret band), and at 543 and 570 nm, which calls to mind those shown by low-spin ferric peroxidases. However, the results also showed that the paraperoxidase-like character of GbPrx is not an obstacle for oxidizing the three monolignols compared with high-spin ferric peroxidases. Taken together, these results mean that the time at which the evolutionary gain of the segment of the route that leads to the biosynthesis of S lignins took place in seed plants needs to be revised.

Varietal differences among the flavonoid profiles of white grape cultivars studied by high-performance liquid chromatography

In order to develop a method that allows to distinguish between white grape cultivars, the flavonoid profiles of 10 white accessions from the "Misión Biológica de Galicia" germplasm collection were studied during years 2003, 2004 and 2005 by high-performance liquid chromatography (HPLC). Twenty-four flavonoids (15 flavonols and 9 dihydroflavonols) were totally or partly identified, and significant differences between the studied flavonoid markers were found. With this method all the cultivars examined could be easily distinguished from each other, and we may conclude that this has been proved to be of great value for white grape cultivar recognition.

Structural motifs of syringyl peroxidases predate not only the gymnosperm-angiosperm divergence but also the radiation of tracheophytes

* The most distinctive variation in the monomer composition of lignins in vascular land plants is that found between the two main groups of seed plants. Thus, while gymnosperm lignins are typically composed of guaiacyl (G) units, angiosperm lignins are largely composed of similar levels of G and syringyl (S) units. * However, and contrary to what might be expected, peroxidases isolated from basal (Cycadales and Ginkgoales) and differentially evolved (Coniferales and Gnetales) gymnosperms are also able to oxidize S moieties, and this ability is independent of the presence or absence of S-type units in their lignins. * The results obtained led us to look at the protein database to search for homologies between gymnosperm peroxidases and true eudicot S-peroxidases, such as the Zinnia elegans peroxidase. * The findings showed that certain structural motifs characteristic of eudicot S-peroxidases (certain amino acid sequences and beta-sheet secondary structures) predate the gymnosperm-angiosperm divergence and the radiation of tracheophytes, since they are found not only in peroxidases from basal gymnosperms, ferns and lycopods, but also in peroxidases from the moss Physcomitrella patens (Bryopsida) and the liverwort Marchantia polymorpha (Marchantiopsida), which, as typical of bryophytes, do not have xylem tissue nor lignins.

Characterization of the last step of lignin biosynthesis in Zinnia elegans suspension cell cultures

The last step of lignin biosynthesis in Zinnia elegans suspension cell cultures (SCCs) catalyzed by peroxidase (ZePrx) has been characterized. The k(3) values shown by ZePrx for the three monolignols revealed that sinapyl alcohol was the best substrate, and were proportional to their oxido/reduction potentials, signifying that these reactions are driven exclusively by redox thermodynamic forces. Feeding experiments demonstrate that cell wall lignification in SCCs is controlled by the rate of supply of H(2)O(2). The results also showed that sites for monolignol beta-O-4 cross-coupling in cell walls may be saturated, suggesting that the growth of the lineal lignin macromolecule is not infinite.

Cellulase Activity in Isolates of Verticillium dahliae Differing in Aggressiveness

Ten Verticillium dahliae isolates from different Galician locations were classified by degree of aggressiveness. High variability exists independent of locality of origin. Two isolates differing in aggressiveness were evaluated for cellulase production on several carbon sources. V. dahliae is able to degrade crystalline cellulose (Avicel) and, therefore, has the three enzymes necessary for its hydrolysis. The two isolates behaved similarly in the presence of soluble cellulose, but the most aggressive isolate had greater β-1,4-glucosidase (EC. 3.2.1.21) and endo-β-1,4-glucanase (EC. 3.2.1.4) activity. The less aggressive isolate needed more time to degrade crystalline cellulose. Cellulases may not be the determining factor for aggressiveness and symptom expression; however, they may play a role in penetration.

Varietal differences among the anthocyanin profiles of 50 red table grape cultivars studied by high performance liquid chromatography

In order to develop a method that allows to distinguish between grape cultivars, the anthocyanin profiles of 50 accessions from the "Misión Biológica de Galicia" germplasm collection were studied by high performance liquid chromatography (HPLC). Nineteen anthocyanins were totally or partly identified and significant quantitative differences between the studied anthocyanin markers were found. With this method all 50 cultivars examinated could be easily distinguished from each other. In addition, the HPLC fingerprints and the relative-area anthocyanins plot for every cultivar has been elaborated and stored in a database. To test the validity of this method, several unknown samples have been analysed comparing their anthocyanin profile with the fingerprint database, and we may conclude that this has been proved to be of great value for grape cultivar recognition.

Changes in stem lignins (monomer composition and crosslinking) and peroxidase are related with the maintenance of leaf photosynthetic integrity during Verticillium wilt in Capsicum annuum

•  Verticillium dahliae is a soilborne pathogen that causes vascular wilt in pepper (Capsicum annuum var. annuum). Here we study to what extent changes in the lignification response of peppers condition tolerance of wilt. •  For this, the quantum yield (Φ_PSII ), the linear electron transport rate (ETR), and the lignification response (monomer composition and crosslinking) were studied in three C. annuum cultivars differing in degree of tolerance. •  The results showed that in tolerant cultivars (Padrón and Yolo Wonder), both Φ_PSII and ETR showed significantly higher levels at saturating photosynthetically active radiation values. This was not, however, the case for cv. Luesia, which showed a significant decrease in Φ_PSII , ETR and nonphotochemical quenching values, suggesting that photochemical processes are strongly damaged in this cultivar as a consequence of the disease. The analysis of stem lignins in tolerant cultivars revealed that they were mainly composed of p-hydroxyphenyl units, while levels of β-O-4-linked coniferyl and sinapyl alcohols were significantly lower. •  It is concluded that through the observed changes in stem lignins (monomer composition and crosslinking) peppers retard, since they maintain leaf photosynthetic integrity, but do not stop (since wilt symptoms are not avoided) V. dahliae fungal hyphae penetration.

Zinnia elegans uses the same peroxidase isoenzyme complement for cell wall lignification in both single-cell tracheary elements and xylem vessels

The nature of the peroxidase isoenzyme complement responsible for cell wall lignification in both Zinnia elegans seedlings and Z. elegans tracheary single-cell cultures have been studied. Results showed that both hypocotyls and stems from lignifying Z. elegans seedlings express a cell wall-located basic peroxidase of pI approximately 10.2, which was purified to homogeneity. Molecular mass determination under non-denaturing conditions showed an M(r) of about 43 000, similar to that of other plant peroxidases. The purified Z. elegans peroxidase showed absorption maxima at 403 (Soret band), and at 496-501 and 632-635 (alpha and beta absorption bands), indicating that this enzyme is a high spin ferric haem protein, belonging to the plant peroxidase superfamily, the prosthetic group being ferric protoporphyrin IX. The N-terminal amino acid sequence of this Z. elegans basic peroxidase was KVAVSPLS (peptide motif in bold), which shows strong homologies with the N-amino acid terminus of other strongly basic plant peroxidases. Isoenzyme and western blot analyses showed that this peroxidase isoenzyme is also expressed in trans-differentiating Z. elegans tracheary single-cell cultures. The results also showed that Z. elegans tracheary single-cell cultures not only express the same peroxidase isoenzyme as the Z. elegans lignifying xylem, but that this peroxidase isoenzyme acts as a marker of tracheary element differentiation in Z. elegans mesophyll single-cell cultures. From these results, it may be concluded that Z. elegans uses a single programme, i.e. an identical peroxidase isoenzyme complement, for lignification of the xylem, regardless of the existence of different ontogenesis pathways from either mesophyll cells (in the case of tracheary elements) or cambial derivatives (in the case of xylem vessels).

Peroxidase: a multifunctional enzyme in grapevines

Peroxidases are heme-containing enzymes that catalyse the one-electron oxidation of several substrates at the expense of H₂O₂. They are probably encoded by a large multigene family in grapevines, and therefore show a high degree of polymorphism. Grapevine peroxidases are glycoproteins of high thermal stability, whose molecular weight usually ranges from 35 to 45 kDa. Their visible spectrum shows absorption bands characteristic of high-spin class III peroxidases. Grapevine peroxidases are capable of accepting a wide range of natural compounds as substrates, such as the cell wall protein extensin, plant growth regulators such as IAA, and phenolics such as benzoic acids, stilbenes, flavonols, cinnamyl alcohols and anthocyanins. They are located in cell walls and vacuoles. These locations are in accordance with their key role in determining the final cell wall architecture, especially regarding lignin deposition and extensin insolubilization, and the turnover of vacuolar phenolic metabolites, a task that also forms part of the molecular program of disease resistance. Although peroxidase is a constitutive enzyme in grapevines, its levels are strongly modulated during plant cell development and in response to both biotic and abiotic environmental factors. To gain an insight into the metabolic regulation of peroxidase, several authors have studied how grapevine peroxidase and H₂O₂ levels change in response to a changing environment. Nevertheless, the results obtained are not always easy to interpret. Despite such difficulties, the response of the peroxidase-H₂O₂ system to both UV-C radiation and Trichoderma viride elicitors is worthy of study. Both UV-C and T. viride elicitors induce specific changes in peroxidase isoenzyme / H₂O₂ levels, which result in specific changes in grapevine physiology and metabolism. In the case of T. viride-elicited grapevine cells, they show a particular mechanism for H₂O₂ production, in which NADPH oxidase-like activities are apparently not involved. However, they offer a unique system whereby the metabolic regulation of peroxidase by H₂O₂, with all its cross-talks and downstream signals, may be elegantly dissected.

H(2)O(2) generation during the auto-oxidation of coniferyl alcohol drives the oxidase activity of a highly conserved class III peroxidase involved in lignin biosynthesis

Characterization of lignified Zinnia elegans hypocotyls by both alkaline nitrobenzene oxidation and thioacidolysis reveals that coniferyl alcohol units are mainly found as part of 4-O-linked end groups and aryl-glycerol-beta-aryl ether (beta-O-4) structures. Z. elegans hypocotyls also contain a basic peroxidase (EC 1.11.1.7) capable of oxidizing coniferyl alcohol in the absence of H(2)O(2). Results showed that the oxidase activity of the Z. elegans basic peroxidase is stimulated by superoxide dismutase, and inhibited by catalase and anaerobic conditions. Results also showed that the oxidase activity of this peroxidase is due to an evolutionarily gained optimal adaptation of the enzyme to the microM H(2)O(2) concentrations generated during the auto-oxidation of coniferyl alcohol, the stoichiometry of the chemical reaction (mol coniferyl alcohol auto-oxidized/mol H(2)O(2) formed) being 0.496. These results therefore suggest that the H(2)O(2) generated during the auto-oxidation of coniferyl alcohol is the main factor that drives the unusual oxidase activity of this highly conserved lignin-synthesizing class III peroxidase.

O-4-Linked coniferyl and sinapyl aldehydes in lignifying cell walls are the main targets of the Wiesner (phloroglucinol-HCl) reaction

The nature and specificity of the Wiesner test (phloroglucinol-HCl reagent) for the aromatic aldehyde fraction contained in lignins is studied. Phloroglucinol reacted in ethanol-hydrochloric acid with coniferyl aldehyde, sinapyl aldehyde, vanillin, and syringaldehyde to yield either pink pigments (in the case of hydroxycinnamyl aldehydes) or red-brown pigments (in the case of hydroxybenzaldehydes). However, coniferyl alcohol, sinapyl alcohol, and highly condensed dehydrogenation polymers derived from these cinnamyl alcohols and aldehydes did not react with phloroglucinol in ethanol-hydrochloric acid. The differences in the reactivity of phloroglucinol with hydroxycinnamyl aldehydes and their dehydrogenation polymers may be explained by the fact that, in the latter, the unsubstituted (alpha,beta-unsaturated) cinnamaldehyde functional group, which is responsible for the dye reaction, is lost due to lateral chain cross-linking reactions involving the beta carbon. Fourier transform infrared spectroscopy and thioacidolysis analyses of phloroglucinol-positive lignifying plant cell walls belonging to the plant species Zinnia elegans L., Capsicum annuumvar. annuum, Populus albaL., and Pinus halepensisL. demonstrated the presence of 4- O-linked hydroxycinnamyl aldehyde end groups and 4- O-linked 4-hydroxy-3-methoxy-benzaldehyde (vanillin) end groups in lignins. However, given the relatively low abundance of 4- O-linked vanillin in lignifying cell walls and the low extinction coefficient of its red-brown phloroglucinol adduct, it is unlikely that vanillin contributes to a great extent to the phloroglucinol-positive stain reaction. These results suggest that the phloroglucinol-HCl pink stain of lignifying xylem cell walls actually reveals the 4- O-linked hydroxycinnamyl aldehyde structures contained in lignins. Histochemical studies showed that these aldehyde structures are assembled, as in the case of coniferyl aldehyde, during the early stages of xylem cell wall lignification.

O-4-Linked coniferyl and sinapyl aldehydes in lignifying cell walls are the main targets of the Wiesner (phloroglucinol-HCl) reaction

The nature and specificity of the Wiesner test (phloroglucinol-HCl reagent) for the aromatic aldehyde fraction contained in lignins is studied. Phloroglucinol reacted in ethanol-hydrochloric acid with coniferyl aldehyde, sinapyl aldehyde, vanillin, and syringaldehyde to yield either pink pigments (in the case of hydroxycinnamyl aldehydes) or red-brown pigments (in the case of hydroxybenzaldehydes). However, coniferyl alcohol, sinapyl alcohol, and highly condensed dehydrogenation polymers derived from these cinnamyl alcohols and aldehydes did not react with phloroglucinol in ethanol-hydrochloric acid. The differences in the reactivity of phloroglucinol with hydroxycinnamyl aldehydes and their dehydrogenation polymers may be explained by the fact that, in the latter, the unsubstituted (alpha,beta-unsaturated) cinnamaldehyde functional group, which is responsible for the dye reaction, is lost due to lateral chain cross-linking reactions involving the beta carbon. Fourier transform infrared spectroscopy and thioacidolysis analyses of phloroglucinol-positive lignifying plant cell walls belonging to the plant species Zinnia elegans L., Capsicum annuumvar. annuum, Populus albaL., and Pinus halepensisL. demonstrated the presence of 4- O-linked hydroxycinnamyl aldehyde end groups and 4- O-linked 4-hydroxy-3-methoxy-benzaldehyde (vanillin) end groups in lignins. However, given the relatively low abundance of 4- O-linked vanillin in lignifying cell walls and the low extinction coefficient of its red-brown phloroglucinol adduct, it is unlikely that vanillin contributes to a great extent to the phloroglucinol-positive stain reaction. These results suggest that the phloroglucinol-HCl pink stain of lignifying xylem cell walls actually reveals the 4- O-linked hydroxycinnamyl aldehyde structures contained in lignins. Histochemical studies showed that these aldehyde structures are assembled, as in the case of coniferyl aldehyde, during the early stages of xylem cell wall lignification.

Capsaicinoids in vegetative organs of Capsicum annuum L. in relation to fruiting

Pepper (cv. Padrón) shows a spatial gradient in the content of phenolic compounds, and particularly of capsaicinoids, along the stem. These compounds were consistently more abundant in apical fruits than in fruits belonging to middle and basal segments. Analysis of the two principal capsaicinoids in fruits showed that the proportion of capsaicin was always higher than that of dihydrocapsaicin. Capsaicinoids were also found to be present in vegetative organs, such as stem and leaves. In this case, the proportion of individual capsaicinoids was different than that in fruits, and dihydrocapsaicin was found to be more abundant. To find out whether the capsaicinoids in vegetative organs came from the fruits, the floral buds were removed and fruit formation was prevented. Capsaicinoids were not detected in the stem and leaves of floral bud-deprived plants, suggesting that they did originate from the fruit.

In situ characterization of a NO-sensitive peroxidase in the lignifying xylem of Zinnia elegans

The lignifying xylem from Zinnia elegans stems gives an intense reaction with 3,3',5,5'-tetramethylbenzidine (TMB), a reagent previously reported to be specific for peroxidase/H2O2. However, the staining of lignifying xylem cells with TMB is apparently the result of two independent mechanisms: one, the catalase-sensitive (H2O2-dependent) peroxidase-mediated oxidation of TMB, and the other, the catalase-insensitive oxidation of TMB, probably mediated by xylem oxidases which are specific from lignifying tissues. The catalase-insensitive oxidation of TMB by the Z. elegans xylem was sensitive to sodium nitroprusside (SNP), a nitric oxide (NO)-releasing compound that, when used at 5.0 mM, is capable of sustaining NO concentrations of 6.1 &mgr;M in the aqueous phase. This effect of SNP was totally reversed by 150 &mgr;M 2-phenyl-4,4,5,5-tetramethyl imidazoline-1-oxyl-3-oxide (PTIO), an efficient NO scavenger in biological systems, so the above-mentioned effect must be ascribed to NO, and not to other nitrogen oxides. This response of the catalase-insensitive TMB-oxidase activity of the lignifying Z. elegans xylem was similar to that shown by a basic peroxidase isolated from the intercellular washing fluid, which showed TMB-oxidase activity, and which was also inhibited by 5 mM SNP, the effect of SNP also being reversed by 150 &mgr;M PTIO. These results suggest that peroxidase was the enzyme responsible for the NO-sensitive catalase-insensitive TMB-oxidase activity of the lignifying Z. elegans xylem. Further support for this statement was obtained from competitive inhibitor-dissected histochemistry, which showed that this stain responded to peroxidase-selective competitive inhibitors, such as ferulic acid and ferrocyanide, in a similar way to the Z. elegans basic peroxidase. From these results, we conclude that this NO-sensitive catalase-insensitive oxidation of TMB is apparently performed by the Z. elegans basic peroxidase, and that the regulation of this enzyme by NO may constitute an intrinsically programmed event during the differentiation and death of the xylem.

Oxidation of cinnamyl alcohols and aldehydes by a basic peroxidase from lignifying Zinnia elegans hypocotyls

The xylem of 26-day old Zinnia elegans hypocotyls synthesizes lignins derived from coniferyl alcohol and sinapyl alcohol with a G/S ratio of 43/57 in the aryl-glycerol-beta-aryl ether core, as revealed by thioacidolysis. Thioacidolysis of Z. elegans lignins also reveals the presence of coniferyl aldehyde end groups linked by beta-0-4 bonds. Both coniferyl and sinapyl alcohols, as well as coniferyl and sinapyl aldehyde, are substrates of a xylem cell wall-located strongly basic peroxidase, which is capable of oxidizing them in the absence and in the presence of hydrogen peroxide. This peroxidase shows a particular affinity for cinnamyl aldehydes with kappa(M) values in the mu(M) range, and some specificity for syringyl-type phenols. The affinity of this strongly basic peroxidase for cinnamyl alcohols and aldehydes is similar to that shown by the preceding enzymes in the lignin biosynthetic pathway (microsomal 5-hydroxylases and cinnamyl alcohol dehydrogenase), which also use cinnamyl alcohols and aldehydes as substrates, indicating that the one-way highway of construction of the lignin macromolecule has no metabolic "potholes" in which the lignin building blocks might accumulate. This fact suggests a high degree of metabolic plasticity for this basic peroxidase, which has been widely conserved during the evolution of vascular plants, making it one of the driving forces in the evolution of plant lignin heterogeneity.

Fruit development in Capsicum annuum: changes in capsaicin, lignin, free phenolics, and peroxidase patterns

Pepper fruits, of Capsicum annuum cv. Padron, undergo changes in content of capsaicinoids, lignin, and free phenolics during the maturation process. Although capsaicinoids increase with development, the maximal levels of free phenolics and lignin are observed during the early stages of development. A decrease of peroxidase activity was observed during maturation, and this was related with a decrease in other physiological parameters studied, namely chlorophylls and pH. Subcellular fractionation studies reveal that most peroxidase activity is localized in the soluble fraction throughout development. The changes in the peroxidase activity were accompanied by changes in the different isoenzymes. Acidic isoenzymes increased whereas the basic isoenzymes decreased over the same period, and the changes in these isoenzymes were related with capsaicin metabolism.

Gastric antisecretory and antiulcer activities of an ethanolic extract of Bidens pilosa L. var. radiata Schult. Bip

Bidens pilosa var. radiata Schult. Bip. is used in folk medicine to treat stomach disorders including peptic ulcers. The ethanolic extract (0.5-2 g/kg) decreased the gastric juice volume, acid secretion, as well as pepsin secretion in pylorus ligated rats. B. pilosa extract showed antiulcer activity against indomethacin-induced gastric lesions. The extract effectively inhibited gastric haemorrhagic lesions induced by ethanol, and with an effective dose of 2 g/kg being more potent than sucralfate (400 mg/kg). In contrast, ranitidine (50 mg/kg) failed to reduce these lesions. These results indicate that B. pilosa ethanolic extract exerts a cytoprotective effect in addition to its gastric antisecretory activity that could be due, partly at least, to the presence of flavonoids of which quercetin was identified by HPLC.

Stenting in a patient with a single coronary artery and myocardial infarction

The single coronary artery is an uncommon congenital defect. We report on a patient admitted to our hospital with an acute myocardial infarction and a single coronary artery arising from the left sinus of Valsalva who was treated with coronary angioplasty and stent implantation. We have not found an identical report of stenting in such an anomaly in the medical literature.

[Differential characteristics and survival of women with acute myocardial infarction. Registry of Acute Myocardial Infarctions of the City of Valencia (RICVAL). Researchers of the RICVAL]

INTRODUCTION AND OBJECTIVES

The prevalence of women who are admitted to the hospital after acute myocardial infarction is lower to that of men and their prognosis is worse. The reason for these differences is unclear. We studied the demographic and historical variables, the evolution, treatment and early survival in 269 women included in the Register of Acute Myocardial Infarctions of the City of Valencia (RICVAL) and compared them with the 855 men included in the same Register.

PATIENTS AND METHODS

Register of patients admitted into a Coronary Care Unit in the City of Valencia since December, 1st, 1993 until November 30th, 1994.

RESULTS

23.9% of the patients were women with a mean age of 71.9 +/- 9 years; 46.8% of them were diabetics, 55.4% hypertensives, and 6.7% smokers. The women arrived for treatment later than men and 34.9% of them were thrombolised. The incidence in women of severe heart failure (Killip III and IV) was 40.1% and the mortality 29.7%. In women with thrombolytic treatment the mortality was 29.8%. In the logistic regression model performed, female sex predicted a higher mortality rate (odds ratio [OR] = 1.30; confidence interval [CI], 1.05-1.61).

CONCLUSIONS

Early mortality in women after acute myocardial infarction is higher than in men in the RICVAL Register. The longer delay in initiating medical care and thrombolysis might be the cause for the higher proportion of heart failure among women and explain their worse prognosis after an acute myocardial infarction compared to men.

Functional and ultrastructural alterations of canine myocardium subjected to very brief coronary occlusions

The effects of very brief and recurrent coronary occlusions on myocardial regional shortening and its ultrastructure have been analysed. Ultrasonic crystals were implanted in the left ventricular subendocardium of 23 anaesthetized dogs with the thorax open, to measure the shortening fractions of an ischaemic and a control segment. Twenty 2 min total occlusions were provoked in the left anterior descending coronary artery, with 3 min recovery intervals (reperfusion) between occlusions. The shortening fraction decreased progressively with each occlusion, reaching a value 18.9% lower than the basal after the last ischaemic episode (P < 0.05); 32.3% after 4 h of reperfusion (P < 0.01), and 28.6% after 24 h (P < 0.01). Qualitative and quantitative ultrastructural analysis showed an increase in the mitochondrial volume of the ischaemic tissue (158% vs control, P < 0.001) with significant damage to the cell components (7.7-fold increases vs control mitochondria). These results show that when the myocardium is subjected to very brief and repeated coronary occlusions, there is progressive deterioration of systolic function with structural alterations, mainly at the mitochondrial level. These modifications are still observable 24 h after the end of ischaemic stimulation and could be the cause of transitory and/or chronic systolic dysfunctions in the absence of previous heart attack.

[Acute hepatic lesion caused by Giardia lamblia]

A study was made of 20 rats infested by Giardia muris in which a histologic study was made of the liver, as well as of 25 patients with giardiasis and elevated alanine-aminotransferase levels. Patients with positive A or B hepatitis markers, cholelithiasis or history of drug or alcohol use were excluded. Tests of liver function and liver biopsy were performed and antiparasite therapy was given during three months of follow-up, after which the liver biopsy was repeated. Humoral alterations were compared to those of 30 patients with acute viral hepatitis (15 type A and 15 type B) over the same periods of time. In 20% of the rats, nonspecific liver lesions were found. In the patients liver enzymes and the thymol test normalized a month after treatment and serum bile acids became normal in the third month. The liver biopsy demonstrated hepatic damage in 94% of the patients (in 20 cases cell lesions and in 12 cases inflammatory lesions) which regressed in the third month, the follow-up biopsy being normal after eradication of the parasite was confirmed. The comparative study with viral hepatitis showed highly significant differences in all the variables studied during the follow-up stage. Emphasis is placed on the importance of this lesion and its differential diagnosis to prevent its progression to chronic liver disease.

[Anomalous origin of the left coronary artery from the pulmonary artery in adults]

A 24 year old male with anomalous origin of the left coronary artery from the pulmonary artery was surgically treated with aortocoronary bypass with saphenous vein graft. The clinical signs and pathophysiology of this cardiopathy are reviewed, with emphasis on the great importance of collateral circulation in its prognosis.