Phytotoxic Ozone Dose-Response Relationships for Durum Wheat (Triticum durum, Desf.)

Ozone (O3) pollution poses a significant threat to global crop productivity, particularly for wheat, one of the most important staple foods. While bread wheat (Triticum aestivum) is unequivocally considered highly sensitive to O3, durum wheat (Triticum durum) was often found to be more tolerant. This study investigated the O3 dose-response relationships for durum wheat in the Mediterranean region, focusing mainly on grain yield losses, and utilizing the phytotoxic ozone dose (POD) metric to describe the intensity of the stressor. The results from two experiments with Open-Top Chambers performed in 2013 and 2014 on two relatively sensitive durum wheat cultivars confirmed that this wheat species is far more tolerant than bread wheat. The use of a local parameterization of a stomatal conductance model based on field measurements did not significantly improve the dose-response relationships obtained in comparison to the generic parameterization suggested by the Mapping Manual of the United Nations Economic Commission for Europe (UNECE). The POD6 critical level of 5 mmolO3 m-2 for 5% grain yield loss was remarkably higher than the one established for bread wheat with analogous experiments, highlighting that O3 risk assessments based on bread wheat may largely overestimate the damage in the Mediterranean region where durum wheat cultivation prevails.

Oxidative Stress Mitigation by Chitosan Nanoparticles in Durum Wheat Also Affects Phytochemicals and Technological Quality of Bran and Semolina

In our previous work, durum wheat cv. Fabulis was grown over two consecutive seasons (2016–2017 and 2017–2018) in an experimental field in the north of Italy. With the aim of mitigating oxidative stress, plants were subjected to four treatments (deionized water, CHT 0.05 mg/mL, CHT-NPs, and CHT-NPs-NAC) three times during the experiment. Chitosan nanoparticles (CHT-NPs) reduced symptom severity on wheat leaves and positively influenced the final grain yield. The present work aimed at investigating whether CHT treatments and particularly N-acetyl cysteine (NAC)-loaded or -unloaded CHT-NPs, while triggering plant defense mechanisms, might also vary the nutritional and technological quality of grains. For this purpose, the grains harvested from the previous experiment were analyzed for their content in phytochemicals and for their technological properties. The results showed that CHT increased the polyphenol and tocopherol content and the reducing capacity of bran and semolina, even if the positive effect of the nano-formulation remained still unclear and slightly varied between the two years of cultivation. The positive effect against oxidative stress induced by the chitosan treatments was more evident in the preservation of both the starch pasting properties and gluten aggregation capacity, indicating that the overall technological quality of semolina was maintained. Our data confirm the role of chitosan as an elicitor of the antioxidant defense system in wheat also at the grain level.

Contributions of Ultrastructural Studies to the Knowledge of Filamentous Fungi Biology and Fungi-Plant Interactions

Since the first experiments in 1950s, transmission electron microscopy (TEM) observations of filamentous fungi have contributed extensively to understand their structure and to reveal the mechanisms of apical growth. Additionally, also in combination with the use of affinity techniques (such as the gold complexes), several aspects of plant-fungal interactions were elucidated. Nowadays, after the huge of information obtained from -omics techniques, TEM studies and ultrastructural observations offer the possibility to support these data, considering that the full comprehension of the mechanisms at the basis of fungal morphogenesis and the interaction with other organisms is closely related to a detailed knowledge of the structural features. Here, the contribution of these approaches on fungal biology is illustrated, focusing both on hyphae cell ultrastructure and infection structures of pathogenic and mycorrhizal fungi. Moreover, a concise appendix of methods conventionally used for the study of fungal ultrastructure is provided.

The Fusarium graminearum FGSG_03624 Xylanase Enhances Plant Immunity and Increases Resistance against Bacterial and Fungal Pathogens

Fungal enzymes degrading the plant cell wall, such as xylanases, can activate plant immune responses. The Fusarium graminearum FGSG_03624 xylanase, previously shown to elicit necrosis and hydrogen peroxide accumulation in wheat, was investigated for its ability to induce disease resistance. To this aim, we transiently and constitutively expressed an enzymatically inactive form of FGSG_03624 in tobacco and Arabidopsis, respectively. The plants were challenged with Pseudomonas syringae pv. tabaci or pv. maculicola and Botrytis cinerea. Symptom reduction by the bacterium was evident, while no reduction was observed after B. cinerea inoculation. Compared to the control, the presence of the xylanase gene in transgenic Arabidopsis plants did not alter the basal expression of a set of defense-related genes, and, after the P. syringae inoculation, a prolonged PR1 expression was detected. F. graminearum inoculation experiments of durum wheat spikes exogenously treated with the FGSG_03624 xylanase highlighted a reduction of symptoms in the early phases of infection and a lower fungal biomass accumulation than in the control. Besides, callose deposition was detected in infected spikes previously treated with the xylanase and not in infected control plants. In conclusion, our results highlight the ability of FGSG_03624 to enhance plant immunity, thus decreasing disease severity.

Chitosan Nanoparticles Loaded with N-Acetyl Cysteine to Mitigate Ozone and Other Possible Oxidative Stresses in Durum Wheat

Modern durum wheat cultivars are more prone to ozone stress because of their high photosynthetic efficiency and leaf gas exchanges that cause a greater pollutant uptake. This, in turn, generates an increased reactive oxygen species (ROS) production that is a challenge to control by the antioxidant system of the plant, therefore affecting final yield, with a reduction up to 25%. With the aim of mitigating oxidative stress in wheat, we used chitosan nanoparticles (CHT-NPs) either unloaded or loaded with the antioxidant compound N-acetyl cysteine (NAC), on plants grown either in a greenhouse or in an open field. NAC-loaded NPs were prepared by adding 0.5 mg/mL NAC to the CHT solution before ionotropic gelation with tripolyphosphate (TTP). Greenhouse experiments evidenced that CHT-NPs and CHT-NPs-NAC were able to increase the level of the leaf antioxidant pool, particularly ascorbic acid (AsA) content. However, the results of field trials, while confirming the increase in the AsA level, at least in the first phenological stages, were less conclusive. The presence of NAC did not appear to significantly affect the leaf antioxidant pool, although the grain yield was slightly higher in NAC-treated parcels. Furthermore, both NAC-loaded and -unloaded CHT-NPs partially reduced the symptom severity and increased the weight of 1000 seeds, thus showing a moderate mitigation of ozone injury.

Effect of high frequency ultrasound pre-treatment on nutritional and technological properties of tomato paste

This study investigates the separate effect of sonication (US, carried out for 5 and 15 min) and thermal treatment (90 °C for 5 min) on nutritional and technological properties of tomato paste. US treatments did not affect the colour parameters and decreased the level of total acidity. Ascorbic acid content was slightly reduced after 5 min US but halved by pasteurization, while total carotenoids (TCC) and lycopene (LC) decreased in non-pasteurized samples after 15 min US. Neither the TCC nor the LC significantly changed in US-pasteurized samples if compared to controls. Microscopic analyses suggested a possible increased bioaccessibility of lycopene in US treated samples due to an enhancement of free lycopene clusters. Viscosity decreased as a consequence of thermal stress, although sonication contributed as well. The present findings suggest that 5 min sonication before pasteurization can enhance the nutritional characteristics of tomato paste, besides improving its texture.

New Insight into Justicidin B Pathway and Production in Linum austriacum

Lignans are the main secondary metabolites synthetized by Linum species as plant defense compounds but they are also valuable for human health, in particular, for novel therapeutics. In this work, Linum austriacum in vitro cultures, cells (Cc), adventitious roots (ARc) and hairy roots (HRc) were developed for the production of justicidin B through elicitation with methyl jasmonate (MeJA) and coronatine (COR). The performances of the cultures were evaluated for their stability, total phenols content and antioxidant ability. NMR was used to identify justicidin B and isojusticidin B and HPLC to quantify the production, highlighting ARc and HRc as the highest productive tissues. MeJA and COR treatments induced the synthesis of justicidin B more than three times and the synthesis of other compounds. RNA-sequencing and a de novo assembly of L. austriacum ARc transcriptome was generated to identify the genes activated by MeJA. Furthermore, for the first time, the intracellular localization of justicidin B in ARc was investigated through microscopic analysis. Then, HRc was chosen for small-scale production in a bioreactor. Altogether, our results improve knowledge on justicidin B pathway and cellular localization in L. austriacum for future scale-up processes.

GUN1 influences the accumulation of NEP-dependent transcripts and chloroplast protein import in Arabidopsis cotyledons upon perturbation of chloroplast protein homeostasis

Correct chloroplast development and function require co-ordinated expression of chloroplast and nuclear genes. This is achieved through chloroplast signals that modulate nuclear gene expression in accordance with the chloroplast's needs. Genetic evidence indicates that GUN1, a chloroplast-localized pentatricopeptide repeat (PPR) protein with a C-terminal Small MutS-Related (SMR) domain, is involved in integrating multiple developmental and stress-related signals in both young seedlings and adult leaves. Recently, GUN1 was found to interact physically with factors involved in chloroplast protein homeostasis, and with enzymes of tetrapyrrole biosynthesis in adult leaves that function in various retrograde signalling pathways. Here we show that following perturbation of chloroplast protein homeostasis: (i) by growth in lincomycin-containing medium; or (ii) in mutants defective in either the FtsH protease complex (ftsh), plastid ribosome activity (prps21-1 and prpl11-1) or plastid protein import and folding (cphsc70-1), GUN1 influences NEP-dependent transcript accumulation during cotyledon greening and also intervenes in chloroplast protein import.

Green Technology: Bacteria-Based Approach Could Lead to Unsuspected Microbe⁻Plant⁻Animal Interactions

The recent and massive revival of green strategies to control plant diseases, mainly as a consequence of the Integrated Pest Management (IPM) rules issued in 2009 by the European Community and the increased consumer awareness of organic products, poses new challenges for human health and food security that need to be addressed in the near future. One of the most important green technologies is biocontrol. This approach is based on living organisms and how these biocontrol agents (BCAs) directly or indirectly interact as a community to control plant pathogens and pest. Although most BCAs have been isolated from plant microbiomes, they share some genomic features, virulence factors, and trans-kingdom infection abilities with human pathogenic microorganisms, thus, their potential impact on human health should be addressed. This evidence, in combination with the outbreaks of human infections associated with consumption of raw fruits and vegetables, opens new questions regarding the role of plants in the human pathogen infection cycle. Moreover, whether BCAs could alter the endophytic bacterial community, thereby leading to the development of new potential human pathogens, is still unclear. In this review, all these issues are debated, highlighting that the research on BCAs and their formulation should include these possible long-lasting consequences of their massive spread in the environment.

Effect of sprouting on nutritional quality of pulses

In order to investigate the nutritional quality of industrial-scale sprouted versus unsprouted chickpeas and green peas, before and after cooking, the ultrastructure, chemical composition, antioxidant capacity, starch digestibility, mineral content and accessibility were analysed. Sprouting did not deeply affect raw seed structure, although after cooking starch granules appeared more porous and swelled. Chemical composition of raw sprouted seeds was not strongly affected, excepting an increase in protein (both pulses), and in free sugars (in peas; +10% and +80%, respectively, p < .05). The industrial sprouting favoured phytic acid leaching in cooking water (-35% in seeds, compared to unsprouted cooked ones, p < .05), and promoted antioxidant capacity reductions in raw and cooked seeds (-10% and -37%, respectively, p < .05). In conclusion, sprouting on an industrial-scale induced mild structural modifications in chickpeas and peas, sufficient to reduce antinutritional factors, without strongly influencing their nutritional quality. These products could represent nutritionally interesting ingredients for different dietary patterns as well as for enriched cereal-based foods.

Thermotolerant isolates of Beauveria bassiana as potential control agent of insect pest in subtropical climates

The use of Beauveria bassiana in biological control of agricultural pests is mainly hampered by environmental factors, such as elevated temperatures and low humidity. These limitations, further amplified in a global warming scenario, could nullify biological control strategies based on this fungus. The identification of thermotolerant B. bassiana isolates represents a possible strategy to overcome this problem. In this study, in order to maximize the probability in the isolation of thermotolerant B. bassiana, soil samples and infected insects were collected in warm areas of Syria. The obtained fungal isolates were tested for different biological parameters (i.e., growth rate, sporulation and spore germination) at growing temperatures ranging from 20°C to 35°C. Among these isolates (eight from insects and 11 from soil samples), the five with the highest growth rate, spore production and germination at 30°C were tested for their entomopathogenicity through in vivo assays on Ephestia kuehniella larvae. Insect mortality induced by the five isolates ranged from 31% to 100%. Two isolates, one from Phyllognathus excavatus and one from soil, caused 50% of the larval mortality in less than four days, reaching values exceeding 92% in ten days. These two isolates were molecularly identified as B. bassiana sensu stricto by using three markers (i.e., ITS, Bloc and EF1-α). Considering these promising results, further studies are ongoing, testing their efficiency in field conditions as control agents for agricultural insect pests in Mediterranean and Subtropical regions.

Maize 16-kD γ-zein forms very unusual disulfide-bonded polymers in the endoplasmic reticulum: implications for prolamin evolution

In the lumen of the endoplasmic reticulum (ER), prolamin storage proteins of cereal seeds form very large, ordered heteropolymers termed protein bodies (PBs), which are insoluble unless treated with alcohol or reducing agents. In maize PBs, 16-kD γ-zein locates at the interface between a core of alcohol-soluble α-zeins and the outermost layer mainly composed of the reduced-soluble 27-kD γ-zein. 16-kD γ-zein originates from 27-kD γ-zein upon whole-genome duplication and is mainly characterized by deletions in the N-terminal domain that eliminate most Pro-rich repeats and part of the Cys residues involved in inter-chain bonds. 27-kD γ-zein also forms insoluble PBs when expressed in transgenic vegetative tissues. We show that in Arabidopsis leaves, 16-kD γ-zein assembles into disulfide-linked polymers that fail to efficiently become insoluble. Instead of forming PBs, these polymers accumulate as very unusual threads that markedly enlarge the ER lumen, resembling amyloid-like fibers. Domain-swapping between the two γ-zeins indicates that the N-terminal region of 16-kD γ-zein has a dominant effect in preventing full insolubilization. Therefore, a newly evolved prolamin has lost the ability to form homotypic PBs, and has acquired a new function in the assembly of natural, heteropolymeric PBs.

Effect of temperature on the microstructure of fat globules and the immunoglobulin-mediated interactions between fat and bacteria in natural raw milk creaming

Natural creaming of raw milk is the first step in production of Grana Padano and Parmigiano Reggiano Protected Denomination of Origin cheeses. This process decreases the fat content and plays an important role in the removal of clostridia species that may cause late-blowing defects in ripened cheeses. Partial coalescence of fat globules-that may influence fat behavior in cheese making and affect the microstructure of fat in the final cheese product-was observed at creaming temperatures higher than 22°C by confocal laser scanning microscopy. The widespread practice of heating of milk at 37°C before creaming at 8°C resulted in important changes in the size distribution of fat globules in raw milk, potentially altering the ability of fat to entrap clostridia spores. We investigated the role of immunoglobulin classes in both the clustering of fat globules and the agglutination of Clostridium tyrobutyricum to fat globules during creaming. Immunogold labeling and transmission electron microscopy showed that IgA and IgM but not IgG were involved in both clustering and agglutination. Both vegetative cells and spores were clearly shown to agglutinate to fat droplets, a process that was suppressed by thermal denaturation of the immunoglobulins. The debacterization of raw milk through natural creaming was improved by the addition of purified immunoglobulins. Overall, these findings provide not only a better understanding of the phenomena occurring during the natural creaming but also practical insights into how the process of creaming may be optimized in cheese production plants.

Cellular Fractionation and Nanoscopic X-Ray Fluorescence Imaging Analyses Reveal Changes of Zinc Distribution in Leaf Cells of Iron-Deficient Plants

Multilevel interactions among nutrients occur in the soil-plant system. Among them, Fe and Zn homeostasis in plants are of great relevance because of their importance for plant and human nutrition. However, the mechanisms underlying the interplay between Fe and Zn in plants are still poorly understood. In order to elucidate how Zn interacts with Fe homeostasis, it is crucial to assess Zn distribution either in the plant tissues or within the cells. In this study, we investigated the subcellular Zn distribution in Fe-deficient leaf cells of cucumber plants by using two different approaches: cellular fractionation coupled with inductively coupled plasma mass spectrometry (ICP/MS) and nanoscopic synchrotron X-ray fluorescence imaging. Fe-deficient leaves showed a strong accumulation of Zn as well as a strong alteration of the organelles' ultrastructure at the cellular level. The cellular fractionation-ICP/MS approach revealed that Zn accumulates in both chloroplasts and mitochondria of Fe deficient leaves. Nano-XRF imaging revealed Zn accumulation in chloroplast and mitochondrial compartments, with a higher concentration in chloroplasts. Such results show that (i) both approaches are suitable to investigate Zn distribution at the subcellular level and (ii) cellular Fe and Zn interactions take place mainly in the organelles, especially in the chloroplasts.

The ozone-like syndrome in durum wheat (Triticum durum Desf.): Mechanisms underlying the different symptomatic responses of two sensitive cultivars

Colombo and Sculptur are two modern durum wheat cultivars that, in previous studies, proved to be very sensitive to ozone injury in terms of eco-physiological parameters and significant grain yield loss. Nevertheless, their response regarding leaf visible symptoms was very different; Sculptur showed almost no symptoms, even after several weeks of ozone exposure, whereas Colombo showed in a few weeks typical ozone-like symptoms (chlorotic/necrotic spots). The mechanisms underlying this different response has been studied with a biochemical and microscopical approach. Plants were grown in Open-Top Chambers (OTCs) and exposed to charcoal filtered and ozone enriched air. Flag leaves were analyzed at two phenological stages (pre- and post-anthesis). At pre-anthesis the ascorbate pool was significantly lower in Colombo, which also underwent an increase in the oxidized glutathione content and abundant H₂O₂ deposition in mesophyll cells around the substomatal chamber. No or scarce H₂O₂ was found at both phenological stages in ozone exposed leaf tissues of Sculptur, where stomata appeared often closed. In this cultivar, transmission electron microscopy showed that chloroplasts in apparently undamaged mesophyll cells were slightly swollen and presented numerous plastoglobuli, as a result of a mild oxidative stress. These results suggest that Sculptur leaves remains symptomless as a consequence of the higher content of constitutive ascorbate pool and the synergistic effect of stomata closure. Instead, Colombo shows chlorotic/necrotic symptoms because of the lower ROS (Reactive Oxygen Species) scavenging capacity and the less efficient stomata closure that lead to severe damages of groups of the mesophyll cells, however leaving the surrounding photosynthetic tissue functional.

Evidence of a bacterial core in the stored products pest Plodia interpunctella: the influence of different diets

The potential influence of insects' feeding behaviour on their associated bacterial communities is currently a matter of debate. Using the major pest of commodities, Plodia interpunctella, as a model and adopting a culture-independent approach, the impact of different diets on the host-associated microbiota was evaluated. An analysis of similarity showed differences among the microbiotas of moths fed with five substrates and provided evidence that diet represents the only tested factor that explains this dissimilarity. Bacteria shared between food and insects provide evidence for a limited conveyance to the host of the bacteria derived from the diet; more likely, the content of carbohydrates and proteins in the diets promotes changes in the insect's microbiota. Moth microbiotas were characterized by two robust entomotypes, respectively, associated with a carbohydrate-rich diet and a protein-rich diet. These results were also confirmed by the predicted metagenome functional potential. A core microbiota, composed of six taxa, was shared between eggs and adults, regardless of the origin of the population. Finally, the identification of possible human and animal pathogens on chili and associated with the moths that feed on it highlights the possibility that these bacteria may be conveyed by moth frass.

Brown Rot Strikes Prunus Fruit: An Ancient Fight Almost Always Lost

Brown rot (BR) caused by Monilinia spp., has been an economic problem for the stone fruit market due to dramatic losses, mainly during the postharvest period. There is much literature about basic aspects of Monilinia spp. infection, which indicates that environment significantly influences its occurrence in the orchard. However, progress is needed to sustainably limit this disease: the pathogen is able to develop resistance to pesticides, and most of BR resistance research programs in plant models perish. Solving this problem becomes important due to the need to decrease chemical treatments and reduce residues on fruit. Thus, research has recently increased, exploring a wide range of disease control strategies (e.g., genetic, chemical, physical). Summarizing this information is difficult, as studies evaluate different Monilinia and Prunus model species, with diverse strategies and protocols. Thus, the purpose of this review is to present the diversity and distribution of agents causing BR, focusing on the biochemical mechanisms of Monilinia spp. infection both of the fungi and of the fruit, and report on the resistance sources in Prunus germplasm. This review comprehensively compiles the information currently available to better understand mechanisms related to BR resistance.

Fusarium graminearum produces different xylanases causing host cell death that is prevented by the xylanase inhibitors XIP-I and TAXI-III in wheat

To shed light on the role of Xylanase Inhibitors (XIs) during Fusarium graminearum infection, we first demonstrated that three out of four F. graminearum xylanases, in addition to their xylan degrading activity, have also the capacity to cause host cell death both in cell suspensions and wheat spike tissue. Subsequently, we demonstrated that TAXI-III and XIP-I prevented both the enzyme and host cell death activities of F. graminearum xylanases. In particular, we showed that the enzymatic inhibition by TAXI-III and XIP-I was competitive and only FGSG_11487 escaped inhibition. The finding that TAXI-III and XIP-I prevented cell death activity of heat inactivated xylanases and that XIP-I precluded the cell death activity of FGSG_11487 - even if XIP-I does not inhibit its enzyme activity - suggests that the catalytic and the cell death activities are separated features of these xylanases. Finally, the efficacy of TAXI-III or XIP-I to prevent host cell death caused by xylanases was confirmed in transgenic plants expressing separately these inhibitors, suggesting that the XIs could limit F. graminearum infection via direct inhibition of xylanase activity and/or by preventing host cell death.

The xylanase inhibitor TAXI-III counteracts the necrotic activity of a Fusarium graminearum xylanase in vitro and in durum wheat transgenic plants

The xylanase inhibitor TAXI-III has been proven to delay Fusarium head blight (FHB) symptoms caused by Fusarium graminearum in transgenic durum wheat plants. To elucidate the molecular mechanism underlying the capacity of the TAXI-III transgenic plants to limit FHB symptoms, we treated wheat tissues with the xylanase FGSG_03624, hitherto shown to induce cell death and hydrogen peroxide accumulation. Experiments performed on lemmas of flowering wheat spikes and wheat cell suspension cultures demonstrated that pre-incubation of xylanase FGSG_03624 with TAXI-III significantly decreased cell death. Most interestingly, a reduced cell death relative to control non-transgenic plants was also obtained by treating, with the same xylanase, lemmas of TAXI-III transgenic plants. Molecular modelling studies predicted an interaction between the TAXI-III residue H395 and residues E122 and E214 belonging to the active site of xylanase FGSG_03624. These results provide, for the first time, clear indications in vitro and in planta that a xylanase inhibitor can prevent the necrotic activity of a xylanase, and suggest that the reduced FHB symptoms on transgenic TAXI-III plants may be a result not only of the direct inhibition of xylanase activity secreted by the pathogen, but also of the capacity of TAXI-III to avoid host cell death.

Is modulating virus virulence by induced systemic resistance realistic?

Induction of plant resistance, either achieved by chemicals (systemic acquired resistance, SAR) or by rhizobacteria (induced systemic resistance, ISR) is a possible and/or complementary alternative to manage virus infections in crops. SAR mechanisms operating against viruses are diverse, depending on the pathosystem, and may inhibit virus replication as well as cell-to-cell and long-distance movement. Inhibition is often mediated by salicylic acid with the involvement of alternative oxidase and reactive oxygen species. However, salicylate may also stimulate a separate downstream pathway, leading to the induction of an additional mechanism, based on RNA-dependent RNA polymerase 1-mediated RNA silencing. Thus, SAR and RNA silencing would closely cooperate in the defence against virus infection. Despite tremendous recent progress in the knowledge of SAR mechanisms, only a few compounds, including benzothiadiazole and chitosan have been shown to reduce the severity of systemic virus disease in controlled environment and, more modestly, in open field. Finally, ISR induction, has proved to be a promising strategy to control virus disease, particularly by seed bacterization with a mixture of plant growth-promoting rhizobacteria. However, the use of any of these treatments should be integrated with cultivation practices that reduce vector pressure by the use of insecticides, or by Bt crops.

Construction of a synthetic infectious cDNA clone of Grapevine Algerian latent virus (GALV-Nf) and its biological activity in Nicotiana benthamiana and grapevine plants

BACKGROUND

Grapevine Algerian latent virus (GALV) is a tombusvirus first isolated in 1989 from an Algerian grapevine (Vitis spp.) plant and more recently from water samples and commercial nipplefruit and statice plants. No further reports of natural GALV infections in grapevine have been published in the last two decades, and artificial inoculations of grapevine plants have not been reported. We developed and tested a synthetic GALV construct for the inoculation of Nicotiana benthamiana plants and different grapevine genotypes to investigate the ability of this virus to infect and spread systemically in different hosts.

METHODS

We carried out a phylogenetic analysis of all known GALV sequences and an epidemiological survey of grapevine samples to detect the virus. A GALV-Nf clone under the control of the T7 promoter was chemically synthesized based on the full-length sequence of the nipplefruit isolate GALV-Nf, the only available sequence at the time the project was conceived, and the infectious transcripts were tested in N. benthamiana plants. A GALV-Nf-based binary vector was then developed for the agroinoculation of N. benthamiana and grapevine plants. Infections were confirmed by serological and molecular analysis and the resulting ultrastructural changes were investigated in both species.

RESULTS

Sequence analysis showed that the GALV coat protein is highly conserved among diverse isolates. The first epidemiological survey of cDNAs collected from 152 grapevine plants with virus-like symptoms did not reveal the presence of GALV in any of the samples. The agroinoculation of N. benthamiana and grapevine plants with the GALV-Nf binary vector promoted efficient infections, as revealed by serological and molecular analysis. The GALV-Nf infection of grapevine plants was characterized in more detail by inoculating different cultivars, revealing distinct patterns of symptom development. Ultrastructural changes induced by GALV-Nf in N. benthamiana were similar to those induced by tombusviruses in other hosts, but the cytopathological alterations in grapevine plants were less severe.

CONCLUSIONS

This is the first report describing the development of a synthetic GALV-Nf cDNA clone, its artificial transmission to grapevine plants and the resulting symptoms and cytopathological alterations.

Contrasting effects of water salinity and ozone concentration on two cultivars of durum wheat (Triticum durum Desf.) in Mediterranean conditions

This paper reports the results of an Open-Top Chambers experiment on the responses of two durum wheat cultivars (Neodur and Virgilio) exposed to two different levels of ozone (charcoal-filtered air and ozone-enriched air) and irrigation water salinity (tap water as control and a 75 mM NaCl solution once a week). The stomatal conductance of the flag leaves was measured on four dates during May. Flag leaf samples were collected to detect ozone visible leaf injuries. At the end of the growing season, the yield/biomass and grain quality parameters were assessed. Saline irrigation caused significant reductions in gs, yield and grain quality in Neodur, while Virgilio was more tolerant. The yield response to ozone was almost negligible, with Virgilio, despite the higher susceptibility to visible leaf injuries, being more productive than Neodur. The responses to the combined stress were not consistent, with the main tendencies undoubtedly driven by the saline irrigation factor.

Systemic acquired resistance (50 years after discovery): moving from the lab to the field

Induction of plant defense(s) against pathogen challenge(s) has been the object of progressively more intense research in the past two decades. Insights on mechanisms of systemic acquired resistance (SAR) and similar, alternative processes, as well as on problems encountered on moving to their practical application in open field, have been carefully pursued and, as far as possible, defined. In reviewing the number of research works published in metabolomic, genetic, biochemical, and crop protection correlated disciplines, the following outline has been adopted: 1, introduction to the processes currently considered as models of the innate immunity; 2, primary signals, such as salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA), involved with different roles in the above-mentioned processes; 3, long-distance signals, identified from petiole exudates as mobile signaling metabolites during expressed resistance; 4, exogenous inducers, including the most significant chemicals known to stimulate the plant resistance induction and originated from both synthetic and natural sources; 5, fungicides shown to act as stimulators of SAR in addition to their biocidal action; 6, elusive mechanism of priming, reporting on the most recent working hypotheses on the pretranscriptional ways through which treated plants may express resistance upon pathogen attack and how this resistance can be transmitted to the next generation; 7, fitness costs and benefits of SAR so far reported from field application of induced resistance; 8, factors affecting efficacy of induced resistance in the open field, indicating that forces, unrevealed under controlled conditions, may be operative in the field; 9, concluding remarks address the efforts required to apply the strategy of crop resistance induction according to the rules of integrated pest management.

Differential timing of defense-related responses induced by cerato-platanin and cerato-populin, two non-catalytic fungal elicitors

The cerato-platanin (CP) family consists of fungal-secreted proteins involved in various stages of the host-fungus interaction and acting as phytotoxins and elicitors of defense responses. The founder member of this family is CP, a non-catalytic protein with a six-stranded double-ψβ-barrel fold. Cerato-populin (Pop1) is an ortholog showing low sequence identity with CP. CP is secreted by Ceratocystis platani, the causal agent of the canker stain of plane. Pop1 is secreted by Ceratocystis populicola, a pathogen of poplar. CP and Pop1 have been suggested to act as PAMPs (pathogen-associated molecular patterns) because they induce phytoalexin synthesis, transcription of defense-related genes, restriction of conidia growth and cell death in various plants. Here, we treated plane leaves with CP or Pop1, and monitored defense responses to define the role of these elicitors in the plant interactions. Both CP and Pop1 were able to induce mitogen-activated protein kinases (MAPKs) phosphorylation, production of reactive oxygen species and nitric oxide, and overexpression of defense related genes. The characteristic DNA fragmentation and the cytological features indicate that CP and Pop1 induce cell death by a mechanism of programmed cell death. Therefore, CP and Pop1 can be considered as two novel, non-catalytic fungal PAMPs able to enhance primary defense. Of particular interest is the observation that CP showed faster activity compared to Pop1. The different timing in defense activation could potentially be due to the structural differences between CP and Pop1 (i.e. different hydrophobic index and different helix content) therefore constituting a starting point in unraveling their structure-function relationships.

A Fusarium graminearum xylanase expressed during wheat infection is a necrotizing factor but is not essential for virulence

Fusarium graminearum is the fungal pathogen mainly responsible for Fusarium head blight (FHB) of cereal crops, which attacks wheat spikes, reducing crop production and quality of grain by producing trichothecene mycotoxins. Several cytohistological studies showed that spike infection is associated with the production of cell wall degrading enzymes. Wheat tissue, as in other commelinoid monocot plants, is particularly rich in xylan which can be hydrolyzed by fungal endo-1,4-β-xylanase. The FG_03624 is one of the most expressed xylanase genes in wheat spikes 3 days after inoculation and was heterologously expressed in the yeast Pichia pastoris. The recombinant protein (22.7 kDa) possessed xylanase activity and induced cell death and hydrogen peroxide accumulation in wheat leaves infiltrated with 10 ng/μl or in wheat lemma surface treated with 20 ng/μl. This effect reflects that observed with other described fungal xylanases (from Trichoderma reesei, Trichoderma viride and Botrytis cinerea) with which the FG_03624 protein shares a stretch of amino acids reported as essential for elicitation of necrotic responses. Several F. graminearum mutants with the FG_03624 gene disrupted were obtained, and showed about 40% reduction of xylanase activity in comparison to the wild type when grown in culture with xylan as carbon source. However, they were fully virulent when assayed by single floret inoculation on wheat cvs. Bobwhite and Nandu. This is the first report of a xylanase able to induce hypersensitive-like symptoms on a monocot plant.

Potato virus X movement in Nicotiana benthamiana: new details revealed by chimeric coat protein variants

Potato virus X coat protein is necessary for both cell-to-cell and phloem transfer, but it has not been clarified definitively whether it is needed in both movement phases solely as a component of the assembled particles or also of differently structured ribonucleoprotein complexes. To clarify this issue, we studied the infection progression of a mutant carrying an N-terminal deletion of the coat protein, which was used to construct chimeric virus particles displaying peptides selectively affecting phloem transfer or cell-to-cell movement. Nicotiana benthamiana plants inoculated with expression vectors encoding the wild-type, mutant and chimeric viral genomes were examined by microscopy techniques. These experiments showed that coat protein-peptide fusions promoting cell-to-cell transfer only were not competent for virion assembly, whereas long-distance movement was possible only for coat proteins compatible with virus particle formation. Moreover, the ability of the assembled PVX to enter and persist into developing xylem elements was revealed here for the first time.

Benzothiadiazole (BTH) activates sterol pathway and affects vitamin D3 metabolism in Solanum malacoxylon cell cultures

Benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a particularly efficient inducer of systemic acquired resistance (SAR), was developed as an immunizing agent to sensitize various crop species against pathogen infections. Recent works highlighted its activating effect on different metabolic pathways, concerning both primary and secondary metabolites. In this study, we investigated the effect of BTH treatment on sterol levels and vitamin D(3) metabolism in Solanum malacoxylon cultures. Calli of S. malacoxylon were incubated in Gamborg B5 liquid medium alone or added with 50 μM BTH for different times (one, two or three cycles of light). Histocytochemical investigations performed on our experimental system using 3,3'-diaminobenzidine (DAB) for hydrogen peroxide (H(2)O(2)) detection and phloroglucinol for lignin staining showed that BTH causes H(2)O(2) accumulation and lignin deposition in treated calli. Gas chromatographic analysis of principal cell membrane sterols (β-sitosterol, campesterol, stigmasterol) showed that BTH transiently increases their cellular levels. Callus cultures were found to contain also cholesterol, 7-dehydrocholesterol, the putative precursor of vitamin D(3), and the hydroxylated metabolites 25-hydroxyvitamin D(3) [25(OH)D(3)] and 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)]. BTH treatment enhanced 7-dehydrocholesterol while reduced cholesterol. HPLC analysis of sample extracts showed that BTH does not affect the cell content of vitamin D(3), though results of ELISA tests highlighted that this elicitor moderately enhances the levels of 25(OH)D(3) and 1α,25(OH)(2)D(3) metabolites. In conclusion, BTH treatment not only causes cell wall strengthening, a typical plant defence response, as just described in other experimental models, but in the same time increases the cellular level of the main sterols and 7-dehydrocholesterol.

The presence of melatonin in grapevine (Vitis vinifera L.) berry tissues

Melatonin has been reported in a variety of food plants and, consequently, in a number of plant-derived foodstuffs. In grapevine (Vitis vinifera L.) products, it was found in berry exocarp (skin) of different cultivars and monovarietal wines. Herein, we assessed, by means of mass spectrometry, the occurrence of melatonin in all berry tissues (skin, flesh, and seed) at two different phenological stages, pre-véraison and véraison. We detected the highest melatonin content in skin, at pre-véraison, whereas, at véraison, the highest levels were reported in the seed. Furthermore, during ripening, melatonin decreased in skin, while increasing in both seed and flesh. The relative concentrations of melatonin in diverse berry tissues were somewhat different from those of total polyphenols (TP), the latter measured by the Folin-Ciocalteau assay, and more abundant in seed at pre-véraison and in exocarp at véraison. The highest antiradical activity, determined by both DPPH (2,2-diphenyl-1-pycryl hydrazyl) and ABTS [(2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] radical-scavenging assay, was reported at pre-veráison in seed. To the best of our knowledge, we reported, for the first time, the occurrence of melatonin in grape seeds.

From vineyard to glass: agrochemicals enhance the melatonin and total polyphenol contents and antiradical activity of red wines

Resistance inducers are a class of agrochemicals, including benzothiadiazole and chitosan, which activate the plant own defence mechanisms. In this work, open-field treatments with plant activators were performed on two red grape (Vitis vinifera L.) varieties cultivated in different localities, Groppello (Brescia, Lombardia, Italy) and Merlot (Treviso, Veneto, Italy). Treatments were carried out every 10 days until the véraison and, after harvesting, experimental wines (microvinificates) were prepared. In general, both melatonin and total polyphenol content, determined by mass spectrometry and Folin-Ciocalteu assay, respectively, were higher in wines produced from grapes treated with resistance inducers than in those obtained from untreated control and conventional fungicide-treated grapes. Accordingly, antiradical power of wines derived from plant activator-treated grapes, measured by both DPPH (2,2-diphenyl-1-picrylhydrazyl) and the ABTS [(2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] radical-scavenging assay, was higher than in their counterparts. To the best of our knowledge, this is the first report on the effects of agrochemicals on the melatonin content of red wine.

Neuroprotective herbs and foods from different traditional medicines and diets

Plant secondary metabolites include an array of bioactive constituents form both medicinal and food plants able to improve human health. The exposure to these phytochemicals, including phenylpropanoids, isoprenoids and alkaloids, through correct dietary habits, may promote health benefits, protecting against the chronic degenerative disorders mainly seen in Western industrialized countries, such as cancer, cardiovascular and neurodegenerative diseases. In this review, we briefly deal with some plant foods and herbs of traditional medicines and diets, focusing on their neuroprotective active components. Because oxidative stress and neuroinflammation resulting from neuroglial activation, at the level of neurons, microglial cells and astrocytes, are key factors in the etiopathogenesis of both neurodegenerative and neurological diseases, emphasis will be placed on the antioxidant and anti-inflammatory activity exerted by specific molecules present in food plants or in remedies prescribed by herbal medicines.

Early events in Populus hybrid and Fagus sylvatica leaves exposed to ozone

This paper aims to investigate early responses to ozone in leaves of Fagus sylvatica (beech) and Populus maximowiczii x Populus berolinensis (poplar). The experimental setup consisted of four open-air (OA) plots, four charcoal-filtered (CF) open-top chambers (OTCs), and four nonfiltered (NF) OTCs. Qualitative and quantitative analyses were carried out on nonsymptomatic (CF) and symptomatic (NF and OA) leaves of both species. Qualitative analyses were performed applying microscopic techniques: Evans blue staining for detection of cell viability, CeCl₃ staining of transmission electron microscope (TEM) samples to detect the accumulation of H₂O₂, and multispectral fluorescence microimaging and microspectrofluorometry to investigate the accumulation of fluorescent phenolic compounds in the walls of the damaged cells. Quantitative analyses consisted of the analysis of the chlorophyll a fluorescence transients (fast kinetics). The early responses to ozone were demonstrated by the Evans blue and CeCl₃ staining techniques that provided evidence of plant responses in both species 1 month before foliar symptoms became visible. The fluorescence transients analysis, too, demonstrated the breakdown of the oxygen evolving system and the inactivation of the end receptors of electrons at a very early stage, both in poplar and in beech. The accumulation of phenolic compounds in the cell walls, on the other hand, was a species-specific response detected in poplar, but not in beech. Evans blue and CeCl₃ staining, as well as the multispectral fluorescence microimaging and microspectrofluorometry, can be used to support the field diagnosis of ozone injury, whereas the fast kinetics of chlorophyll fluorescence provides evidence of early physiological responses.

Chemical diversity and defence metabolism: how plants cope with pathogens and ozone pollution

Chemical defences represent a main trait of the plant innate immune system. Besides regulating the relationship between plants and their ecosystems, phytochemicals are involved both in resistance against pathogens and in tolerance towards abiotic stresses, such as atmospheric pollution. Plant defence metabolites arise from the main secondary metabolic routes, the phenylpropanoid, the isoprenoid and the alkaloid pathways. In plants, antibiotic compounds can be both preformed (phytoanticipins) and inducible (phytoalexins), the former including saponins, cyanogenic glycosides and glucosinolates. Chronic exposure to tropospheric ozone (O(3)) stimulates the carbon fluxes from the primary to the secondary metabolic pathways to a great extent, inducing a shift of the available resources in favour of the synthesis of secondary products. In some cases, the plant defence responses against pathogens and environmental pollutants may overlap, leading to the unspecific synthesis of similar molecules, such as phenylpropanoids. Exposure to ozone can also modify the pattern of biogenic volatile organic compounds (BVOC), emitted from plant in response to herbivore feeding, thus altering the tritrophic interaction among plant, phytophagy and their natural enemies. Finally, the synthesis of ethylene and polyamines can be regulated by ozone at level of S-adenosylmethionine (SAM), the biosynthetic precursor of both classes of hormones, which can, therefore, mutually inhibit their own biosynthesis with consequence on plant phenotype.

Plant cell death and cellular alterations induced by ozone: key studies in Mediterranean conditions

An account of histo-cytological and ultrastructural studies on ozone effect on crop and forest species in Italy is given, with emphasis on induced cell death and the underlying mechanisms. Cell death phenomena possibly due to ambient O(3) were recorded in crop and forest species. In contrast, visible O(3) effects on Mediterranean vegetation are often unclear. Microscopy is thus suggested as an effective tool to validate and evaluate O(3) injury to Mediterranean vegetation. A DAB-Evans blue staining was proposed to validate O(3) symptoms at the microscopic level and for a pre-visual diagnosis of O(3) injury. The method has been positively tested in some of the most important crop species, such as wheat, tomato, bean and onion and, with some restriction, in forest species, and it also allows one to gain some very useful insights into the mechanisms at the base of O(3) sensitivity or tolerance.

Bioactivity of Grape Chemicals for Human Health

Grapevine ( Vitis vinifera) products, grape and grape juice, represent a valuable source of bioactive phytochemicals, synthesized by three secondary metabolic pathways (phenylpropanoid, isoprenoid and alkaloid biosynthetic routes) and stored in different plant tissues. In the last decades, compelling evidence suggested that regular consumption of these products may contribute to reducing the incidence of chronic illnesses, such as cancer, cardiovascular diseases, ischemic stroke, neurodegenerative disorders and aging, in a context of the Mediterranean dietary tradition. The health benefits arising from grape product intake can be ascribed to the potpourri of biologically active chemicals occurring in grapes. Among them, the recently discovered presence of melatonin adds a new element to the already complex grape chemistry. Melatonin, and its possible synergistic action with the great variety of polyphenols, contributes to further explaining the observed health benefits associated with regular grape product consumption.

Bioactivity of grape chemicals for human health

Grapevine (Vitis vinifera) products, grape and grape juice, represent a valuable source of bioactive phytochemicals, synthesized by three secondary metabolic pathways (phenylpropanoid, isoprenoid and alkaloid biosynthetic routes) and stored in different plant tissues. In the last decades, compelling evidence suggested that regular consumption of these products may contribute to reducing the incidence of chronic illnesses, such as cancer, cardiovascular diseases, ischemic stroke, neurodegenerative disorders and aging, in a context of the Mediterranean dietary tradition. The health benefits arising from grape product intake can be ascribed to the potpourri of biologically active chemicals occurring in grapes. Among them, the recently discovered presence of melatonin adds a new element to the already complex grape chemistry. Melatonin, and its possible synergistic action with the great variety of polyphenols, contributes to further explaining the observed health benefits associated with regular grape product consumption.

A flux-based assessment of the effects of ozone on foliar injury, photosynthesis, and yield of bean (Phaseolus vulgaris L. cv. Borlotto Nano Lingua di Fuoco) in open-top chambers

Stomatal ozone uptake, determined with the Jarvis' approach, was related to photosynthetic efficiency assessed by chlorophyll fluorescence and reflectance measurements in open-top chamber experiments on Phaseolus vulgaris. The effects of O(3) exposure were also evaluated in terms of visible and microscopical leaf injury and plant productivity. Results showed that microscopical leaf symptoms, assessed as cell death and H(2)O(2) accumulation, preceded by 3-4 days the appearance of visible symptoms. An effective dose of ozone stomatal flux for visible leaf damages was found around 1.33 mmol O(3) m(-2). Significant linear dose-response relationships were obtained between accumulated fluxes and optical indices (PRI, NDI, DeltaF/F'(m)). The negative effects on photosynthesis reduced plant productivity, affecting the number of pods and seeds, but not seed weight. These results, besides contributing to the development of a flux-based ozone risk assessment for crops in Europe, highlight the potentiality of reflectance measurements for the early detection of ozone stress.

Acute exposure of the aquatic macrophyte Callitriche obtusangula to the herbicide oxadiazon: the protective role of N-acetylcysteine

In this study we investigated the acute exposure of the aquatic macrophyte Callitriche obtusangula to the herbicide oxadiazon (Ronstar). The toxic effects on C. obtusangula were evaluated, 24h after exposure, by assessing visible necrotic leaf lesions and, 12 h after exposure, via analyses of dead cells and hydrogen peroxide (H2O2) deposits localized by histocytochemical analysis with Trypan blue and 3,3'-diaminobenzidine (DAB), respectively. As a result, we found that 0.1275 microg L(-1) a.i. (active ingredient) oxadiazon was the maximum concentration that produced no observable adverse effects (NOAEC) both at leaf and tissue levels, at any considered exposure time. Additionally, we assayed the protective effect of pre-treatment with 0.25 mM N-acetylcysteine (NAC), a cysteine donor, on the damage caused by the toxic herbicidal dose of 6.37 microg L(-1) a.i to C. obtusangula, correlating the NAC observed protection to the direct H2O2-scavenging and to the enhancement of glutathione parameters. NAC-treated plants showed a fourfold increase in the GSH (reduced glutathione)+GSSG (oxidised glutathione) content (149.2 nmol g(-1) FW) compared to controls (36.1 nmol g(-1) FW); in the NAC+oxadiazon treatments, the GSH+GSSG content was more than fivefold higher (202.1 nmol g(-1) FW). GSH showed a similar trend in NAC and NAC+oxadiazon treatments, being six- (130.0 nmol g(-1) FW) and eightfold (185.0 nmol g(-1) FW) higher, respectively, compared to controls (20.7 nmol g(-1) FW). Accordingly, the GSH/GSSG ratio in NAC- and NAC+oxadiazon-treated plants was significantly increased compared to controls, indicating alleviation of oxidative stress.

Nutritional traits of bean ( Phaseolus vulgaris ) seeds from plants chronically exposed to ozone pollution

The effect of chronic exposure to ozone pollution on nutritional traits of bean ( Phaseolus vulgaris L. cv. Borlotto Nano Lingua di Fuoco) seeds from plants grown in filtered and nonfiltered open-top chambers (OTCs) has been investigated. Results showed that, among seed macronutrients, ozone significantly raised total lipids, crude proteins, and dietary fiber and slightly decreased total free amino acid content, although with a significant reduction of asparagine, lysine, valine, methionine, and glycine, compensated by a conspicuous augmentation of ornithine and tryptophan. Phytosterol analysis showed a marked increase of beta-sitosterol, stigmasterol, and campesterol in seeds collected from nonfiltered OTCs. With regard to secondary metabolites, ozone exposure induced a slight increase of total polyphenol content, although causing a significant reduction of some flavonols (aglycone kaempferol and its 3-glucoside derivative) and hydroxycinnamates (caffeic, p-coumaric, and sinapic acids). Total anthocyanins decreased significantly, too. Nevertheless, ozone-exposed seeds showed higher antioxidant activity, with higher Trolox equivalent antioxidant capacity (TEAC) values than those measured in seeds collected from filtered air.

Chitosan as a MAMP, searching for a PRR

Chitosan, a deacetylated chitin derivative, behaves like a general elicitor, inducing a non-host resistance and priming a systemic acquired immunity. The defence responses elicited by chitosan include rising of cytosolic H(+) and Ca(2+), activation of MAP-kinases, callose apposition, oxidative burst, hypersensitive response (HR), synthesis of abscissic acid (ABA), jasmonate, phytoalexins and pathogenesis related (PR) proteins. Putative receptors for chitosan are a chitosan-binding protein, recently isolated, and possibly the chitin elicitor-binding protein (CEBiP). Nevertheless, it must be pointed out that biological activity of chitosan, besides the plant model, strictly depends on its physicochemical properties (deacetylation degree, molecular weight and viscosity), and that there is a threshold for chitosan concentration able to switch the induction of a cell death programme into necrotic cell death (cytotoxicity).

Abscisic acid is involved in chitosan-induced resistance to tobacco necrosis virus (TNV)

Chitosan (CHT) antiviral activity has been further investigated in the pathosystem Phaseolus vulgaris - tobacco necrosis virus (TNV). CHT application elicited both callose apposition and ABA accumulation in leaf tissues, at 12 and 24h after treatment, respectively, and induced a high level of resistance against TNV. Besides, treatment with the ABA inhibitor nordihydroguaiaretic acid (NDGA), before CHT application, reduced both callose deposition and plant resistance to the virus, thus indicating the involvement of ABA in these processes. Exogenous application of ABA also induced a significant resistance to TNV, though this resistance was abolished by NDGA pre-treatment. These results, overall, indicate that the rise of ABA synthesis induced by chitosan plays an important role in enhancing callose deposition but the latter has only a partial effect on virus spreading, which must be constraint by other resistance mechanisms.

Type 1 ribosome-inactivating proteins from Phytolacca dioica L. leaves: differential seasonal and age expression, and cellular localization

The expression of type 1 ribosome-inactivating proteins (RIPs) in Phytolacca dioica L. leaves was investigated. Fully expanded leaves of young P. dioica plants (up to 3 years old) expressed two novel RIPs, dioicin 1 and dioicin 2. The former was also found in developing leaves from adult P. dioica within about two and a half weeks after leaf development, and the latter continuously synthesized, with no seasonal or ontogenetic constraint. Fully expanded leaves from adult P. dioica expressed four RIPs (PD-Ls1-4) exhibiting seasonal variation. RIPs were localized in the extracellular space, in the vacuole and in the Golgi apparatus of mesophyll cells. Dioicin 1 and dioicin 2 showed rRNA N-beta-glycosidase activity and displayed the following properties, respectively: (1) Mr values of 30,047.00 and 29,910.00, (2) pIs of 8.74 and 9.37, and (3) IC(50) values of 19.74 (0.658 nM) and 6.85 ng/mL (0.229 nM). Furthermore, they showed adenine polynucleotide glycosylase activity and nicked pBR322 dsDNA. The amino acid sequence of dioicin 2 had 266 amino acid residues, and the highest percentage identity (81.6%) and similarity (84.6%) with PAP-II from Phytolacca americana, while its identity with other RIPs from Phytolaccaceae was around 40%.