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In indoor vertical farms, energy consumption represents a bottleneck for both a system’s affordability and environmental footprint. Although switching frequency (sf) represents a crucial factor in determining the efficacy of light emitting diodes (LED) lighting systems in converting electricity into light, the impact of sf is still underexplored. The aim of this work was to investigate the effect of LEDs sf on the productive and qualitative responses of lettuce (Lactuca sativa L.), also considering the resource use efficiency. Plants were grown for 14 days under red and blue LEDs (215 μmol m−2 s−1 and 16/8 h light/dark, with a red:blue ratio of 3) characterized by two different sf for the blue diode, namely high sf (850 kHz) and low sf (293 kHz). A fluorescent light (same light intensity and photoperiod) was included. LED sf did not alter plant morphological parameters, including fresh or dry biomass, leaf number, leaf area, or water use efficiency. A low sf increased the energy use efficiency (EUE) by 40% as compared to high sf. The latter enhanced the leaf antioxidant capacity, as a consequence of increased concentrations of caftaric and chicoric acids, isoquercetin, and luteolin, consistent with the upregulation of a few genes related to the biosynthetic pathway of phenolic compounds (4C3H and DFR). The study highlights that different sf may significantly affect the EUE as well as crop nutritional properties.

The involvement of auxin, abscisic acid (ABA), polyamines (PAs), and proline in adaptation to long-term exposure of woody plants to high levels of heavy metals in soil has received scant attention, even in poplar which is a good candidate for phytoremediation of metal-polluted soils and is regarded as a model for basic research in tree species. Three poplar clones (M1, PE19/66, and B229) were comparatively analyzed in a pot experiment for their responses to 300 mg kg -1 Cu(NO 3 ) 2 at morphological, physiological, and biochemical levels. After 4 months, despite the prevalent accumulation of Cu in roots, where the metal reached potentially toxic concentrations, the three clones showed distinct Cu accumulation and translocation capacities, whereas they did not display evi- dent toxicity symptoms or growth inhibition. Several pro- tective mechanisms, namely decreased photosynthetic functionality, enhanced guaiacol peroxidase (GPOD) activity, and accumulation of proline and PAs, were dif- ferentially activated in Cu-treated plants in an organ- and clone-specific manner. Overall, a positive relationship between root Cu concentration with GPOD, proline, and PAs was observed. In M1, higher Cu accumulation in roots and leaves compared with other clones was reflected in stimulation of GPOD activity in both organs and in enhanced proline, and PA levels. In PE19/66, these responses were observed only in roots concomitant with high Cu accumulation. Clone B229 accumulated very low amounts of Cu, therefore, these defense responses were attenuated compared with other clones. Enhanced ABA concentrations in response to Cu were observed in PE19/66 and B229; this was likely responsible for stomatal limita- tion of photosynthesis in PE19/66, whereas in B229 this effect may have been counteracted by increased IAA. Essentially unchanged leaf auxin levels under Cu stress may account for the lack of shoot growth inhibition observed in all three clones; B229 was the only clone that displayed Cu-induced IAA accumulation in roots. Results are discussed in terms of clone-specific adaptive mecha- nisms to Cu stress in tolerant poplars.

Phytoremediation is a cost-effective and environment friendly in situ technique for the reclamation of heavy metal-polluted soils. The efficacy of this technique, which relies on tolerant plant species, can be improved by the use of chelating agents. A pot experiment was carried out to evaluate the phytoextraction and phytostabilisation capacities of a white poplar (Populus alba L.) clone named AL35 previously selected for its marked tolerance to copper (Cu) and zinc (Zn). Cuttings were grown on agricultural soil highly contaminated with Cu and Zn, in the presence or not (controls) of a chelant mixture (EDTA/EDDS) known to enhance metal bioavailability and, hence, uptake by plant roots, or the not yet investigated synthetic, highly biodegradable polyaspartic acid (PASP). Both chelant treatments improved the phytostabilisation of Cu and Zn in AL35 plants, whilst the phytoextraction capacity was enhanced only in the case of Cu. Considering that the effectiveness of PASP as phytostabilizer was comparable or better than that of EDTA/EDDS, the low cost of its large-scale chemical synthesis and its biodegradability makes it a good candidate for chelant-enhanced metal phytoextraction from soil while avoiding the toxic side-effects previously described for both EDTA and EDDS.

Poplar is a suitable species for phytoremediation, able to tolerate high concentrations of heavy metals (HMs). Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with the roots of most land plants; they improve nutrient uptake and enhance phytoextraction of HMs while alleviating stress in the host plant. This review summarizes previous results from field and greenhouse studies conducted by us and dealing with this topic. In a field trial on a highly Zn- and Cu-contaminated site, differences in plant survival and growth were observed among 168 clones originating from natural populations of Populus alba L. and Populus nigra L. from northern Italy. After two and a half years from planting, the density, activity and metabolic versatility of the culturable fraction of the soil bacteria in the HM-polluted field was higher in the soil close to where larger poplar plants were growing, in spite of comparable HM concentrations recorded in these soils. One well-performing clone of P. alba (AL35), which accumulated a higher concentration of both metals and had high foliar polyamine (PA) levels, was used for further investigation. In a greenhouse study, AL35 cuttings pre-inoculated with AMF (Glomus mosseae or Glomus intraradices) and then transferred to pots containing soil, collected from the HM-polluted site, displayed growth comparable to that of controls grown on unpolluted soil, in spite of higher Cu and Zn accumulation. Such plants also showed an overall up-regulation of metallothionein (MT) and PA biosynthetic genes, together with increased PA levels. A genome-wide transcriptomic (cDNA-AFLP) analysis allowed the identification of a number of genes, mostly belonging to stress-related functional categories of defense and secondary metabolism, that were differentially regulated in mycorrhizal vs. non mycorrhizal plants. A proteomic analysis revealed that, depending on sampling time, changes in protein profiles were differentially affected by AMF and/or HMs. It is concluded that soil-borne microorganisms affect plant performance on HM-polluted soil. In particular, mycorrhizal plants exhibited increased capacity for phytostabilization of HMs, together with improved growth. Their greater stress tolerance may derive from the protective role of PAs, and from the strong modulation in the expression profiles of stress-related genes and proteins.

International audience; Climate change is rapidly degrading the conditions of crop production. For instance, increasing salinization and aridity is forecasted to increase in most parts of the world. As a consequence, new stress-tolerant species and genotypes must be identified and used for future agriculture. Stress-tolerant species exist but are actually underutilized and neglected. Many stress-tolerant species are indeed traditional crops that are only cultivated by farmers at a local scale. Those species have a high biodiversity value. Besides, the human population will probably reach nine billion within coming decades. To keep pace with population growth, food production must increase dramatically despite the limited availability of cultivable land and water. Here, we review the benefits of quinoa, Chenopodium quinoa Willd., a seed crop that has endured the harsh bioclimatic conditions of the Andes since ancient times. Although the crop is still mainly produced in Bolivia and Peru, agronomic trials and cultivation are spreading to many other countries. Quinoa maintains productivity on rather poor soils and under conditions of water shortage and high salinity. Moreover, quinoa seeds are an exceptionally nutritious food source, owing to their high protein content with all essential amino acids, lack of gluten, and high content of several minerals, e.g., Ca, Mg, Fe, and health-promoting compounds such as flavonoids. Quinoa has a vast genetic diversity resulting from its fragmented and localized production over the centuries in the Andean region, from Ecuador to southern Chile, and from sea level to the altiplano. Quinoa can be adapted to diverse agroecological conditions worldwide. Year 2013 has therefore been declared the International Year of Quinoa by the United Nations Food and Agriculture Organization. Here, we review the main characteristics of quinoa, its origin and genetic diversity, its exceptional tolerance to drought and salinity, its nutritional properties, the reasons why this crop can offer several ecosystem services, and the role of Andean farmers in preserving its agrobiodiversity. Finally, we propose a schematic model integrating the fundamental factors that should determine the future utilization of quinoa, in terms of food security, biodiversity conservation, and cultural identity.

Chenopodium quinoa (Willd.) is an Andean plant showing a remarkable tolerance to abiotic stresses. In Chile, quinoa populations display a high degree of genetic distancing, and variable tolerance to salinity. To investigate which tolerance mechanisms might account for these differences, four genotypes from coastal central and southern regions were compared for their growth, physiological, and molecular responses to NaCl at seedling stage. Seeds were sown on agar plates supplemented with 0, 150 or 300mM NaCl. Germination was significantly reduced by NaCl only in accession BO78. Shoot length was reduced by 150mM NaCl in three out of four genotypes, and by over 60% at 300mM (except BO78 which remained more similar to controls). Root length was hardly affected or even enhanced at 150mM in all four genotypes, but inhibited, especially in BO78, by 300mM NaCl. Thus, the root/shoot ratio was differentially affected by salt, with the highest values in PRJ, and the lowest in BO78. Biomass was also less affected in PRJ than in the other accessions, the genotype with the highest increment in proline concentration upon salt treatment. Free putrescine declined dramatically in all genotypes under 300mM NaCl; however (spermidine+spermine)/putrescine ratios were higher in PRJ than BO78. Quantitative RT-PCR analyses of two sodium transporter genes, CqSOS1 and CqNHX, revealed that their expression was differentially induced at the shoot and root level, and between genotypes, by 300mM NaCl. Expression data are discussed in relation to the degree of salt tolerance in the different accessions.

The present investigation recorded significant restoration of seedling growth (root length, shoot length and fresh weight) upon application of 24-epibrassinolide (EBL) and putrescine (Put) to 7-day-old seedlings of Raphanus sativus L. cv. Pusa chetki grown under copper (Cu) ion stress. EBL and Put with/or without Cu ion treated seedlings showed increased titers of ascorbic acid, total phenols and proline when compared with Cu-stressed seedlings. Differential responses in the activities of guaiacol peroxidase (GPOX) and catalase (CAT) were noted for EBL and Put alone or with/or without Cu ion treatment. Decreased activities of glutathione reductase (GR) and superoxide dismutase (SOD) noted for EBL and Put alone were observed to enhance significantly when applied in combination with Cu ion solution. A remarkable decrease in malondialdehyde contents was observed in seedlings treated with EBL and Put alone and with/or without Cu ion stress. Enhanced free radical scavenging activities were also recorded for seedlings given EBL and Put alone or in combination over Cu ion stressed seedlings. Maximum DPPH activity was observed in seedlings treated with Put and EBL 10−9 M + Put. Significant enhancements in deoxyribose and reducing power activities were too recorded for Put, EBL and Put + 10−9 M EBL treatments. Improved seedling growth, antioxidant levels (ascorbic acid, total phenols and proline) and enzymic (GPOX, CAT, SOD and GR) activities and free radical scavenging capacities along with reduced membrane damage in seedlings given EBL and Put with/or without Cu stress suggests significant and positive interactions of EBL and Put in alleviating the Cu ion induced oxidative damage in radish seedlings.

Three ex situ collections of poplar clones from natural populations of Populus alba and P. nigra growing in northern Italy were assessed for their genetic dissimilarity (GD) by means of amplified fragment length polymorphism (AFLP). The high GD evidenced within populations was exploited for screening 168 clones in a field trial on heavy metal-polluted soil. After one growth season, clonal differences in plant survival and growth were observed. On the basis of performance, six clones were singled out, and used to evaluate copper and zinc accumulation in different organs. Clonal differences in metal concentrations were most evident for leaves and stems; one clone of P. alba (AL35) had a distinctly higher concentration of both metals in the roots. Leaf polyamine (putrescine, spermidine, spermine) profiles correlated with tissue metal concentrations, depending on the clone, plant organ and metal. In particular, the high metal-accumulating clone AL35 exhibited a dramatically higher concentration of free and conjugated putrescine. Overall, the results indicate that, given the high GD of Populus even within populations, it is possible to identify genotypes best suited for soil clean-up, and useful also for investigating physiological markers associated with high metal accumulation/tolerance.

Long-sized oligogalacturonides (OGs) are plant cell wall fragments involved in defence responses and developmental processes. A hormone/OG interaction in the control of different organogenic processes is known. However, hormones also modulate polyamine (PA) effects on organogenesis. Furthermore, OGs are known to affect mitotic activity leading to specific morphogenic events, and PAs are known to affect mitotic activity leading to xylogenesis. Thus, it may be reasonable to assume that OGs and PAs affect mitotic activity in the same cell types, and in the same hormone-induced morphogenic processes, e.g., xylogenesis. To gain further insight into this aspect, the effects of OGs, and of putrescine (Put) and spermidine (Spd), on auxin (indoleacetic acid, IAA) plus benzyladenine (BA)-induced morphogenesis in tobacco leaf explants were investigated histologically. The effect of PA biosynthetic inhibitors in the culture medium was also monitored, as well as the combined application of the inhibitor with ...

Long-sized oligogalacturonides (OGs) are cell wall fragments that induce defence and developmental responses. The Ca(2+)-dependent "egg-box" conformation is required for their activity, and polyamines may prevent them from adopting this conformation. Although OGs are known to inhibit auxin-induced growth processes, their effect on cytokinin-induced ones requires investigation. In the present work OGs were shown to promote cytokinin (benzyladenine, BA)-induced vegetative shoot formation from tobacco leaf explants, independent of the presence of CaCl(2) in the medium and of auxin (indoleacetic acid, IAA) supply. The effect of polyamines, putrescine (PU) and spermidine (SD) supplied with/without their biosynthetic inhibitors (DFMO, CHA) was also investigated, and showed that spermidine enhanced adventitious vegetative shoot formation, but only on medium containing Ca(2+) and IAA. Treatments with inhibitors blocked this promotive effect. OGs did not alter free polyamine concentrations, but caused a moderate increase of conjugated ones, and exhibited an early inhibitory effect on polyamine biosynthetic gene expression. OGs, but not SD, caused long-term changes in calcium-associated epifluorescent signals in the cell walls, and, later, inside the cells of specific tissues. Electron microscopy analysis (ESI system) demonstrated that calcium accumulated in the cell walls and vacuoles of OG-cultured explants. The relationship between OGs, cytokinin, calcium, and polyamines in adventitious vegetative shoot formation is discussed.

Callus cultures from several species of Passiflora were initiated in vitro, and their capacity to produce four glycosyl flavonoids (orientin, isoorientin, vitexin, isovitexin) was analysed. The aim of the present work was to examine the possible role of UV-B irradiation and elicitation with methyljasmonate (MJ) on the production of these compounds in callus cultures. All the species tested (P incarnata, P. quadrangularis, P edulis) formed friable callus from leaf explants after 4 weeks on medium supplemented with kinetin and 2,4-dichlorophenoxyacefic acid. Among them, R quadrangularis turned out to have a faster growth rate and a more friable texture, and was therefore chosen for experiments with elicitors. In callus cultures only small amounts of isoorientin were found, while the concentration of the other flavonoids was below the detection limit. UV-B irradiation of calluses was able to increase the production of all four glycosyl flavonoids. After a 7-day exposure of cultures to UV-B light, the production of isoorientin reached concentrations similar to those found in fresh leaves from glasshouse-grown plants. Elicitation with methyl jasmonate also enhanced orientin, vitexin and isovitexin concentrations, even though the stimulation was about 6-fold weaker for orientin and vitexin and about 40-fold for isovitexin, than that exerted by UV-B treatment. Callus cultures treated with the UV-B dose which most enhanced flavonoid production showed a higher antioxidant activity compared to untreated calluses, with an increase ranging from 28% to 76%. Results show that the secondary metabolite biosynthetic capacity of Passiflora tissue cultures can be enhanced by appropriate forms of elicitation. (c) 2007 Elsevier B.V All rights reserved.

Jasmonates (JAs), which derive from α -linolenic acid through allene oxide synthase (AOS), are signal molecules which elicit stress responses through JA-induced proteins (JIPs). They are also involved in growth processes such as cell division, tuber formation and fruit development. JAs induce various biological responses mostly correlated with defense responses; however, their reciprocal relationships with ethylene are not well established. In apple and cherries endogenous JAs peak during the early phase of fruit growth; but only in apple they rise again at climacteric. A JA derivative, methyl jasmonate (MJ), stimulates ethylene production in pre-climacteric apples but inhibits it in climacteric ones. However, MJ-induced apple degreening is partly independent of ethylene. A better established relation is be that between JAs and PAs. PAs are ubiquitous growth regulators involved in fruit set and development; when applied to developing fruit they inhibit ethylene production and delay ripening in peach and other climacteric fruit. To better understand the relationships JA-ethylene in a climacteric fruit, in the present study, MJ and its synthetic analogous propyl jasmonate (PJ) were applied to peach (Prunus persica L. Batsch, cv Stark Red Gold) branches during S2 phase (rapid growth). In treated fruit ethylene production and the evolution of the main fruit quality parameters were inhibited and transcript levels of PpACO1, PpERS1 and PpETR1 were altered in comparison to respective controls. Increases in polyamine titres were associated to JA-induced ripening delay probably contributing to the observed antisenescent effect. A fragment of PpAOS cDNA was isolated and its expression monitored during fruit ripening showing that the corresponding transcript was enhanced in JA-treated fruit. Finally, a microarray comparative trascriptome profiling of treated versus control fruit indicated that MJ down-regulate genes positively involved in ripening thus confirming that JAs slow down such process in peach fruit.

Poplar is a good candidate for phytoremediation purposes because of its rapid growth, extensive root system, and ease of propagation and transformation; however its tolerance to heavy metals has not been fully investigated yet. In the present work, an in vitro model system with shoot cultures was used to investigate the tolerance to high concentrations of zinc (Zn) of a commercial clone (Villafranca) of Populus alba. Based on chlorophyll content (leaf chlorosis) and the rate of adventitious root formation from shoot cuttings as parameters of damage, 0.5-4mM zinc concentrations were all toxic albeit to different extents. Northern blot and reverse transcriptase (RT)-PCR analyses were used to examine the expression profiles of types 1, 2 and 3 PaMT genes in stems, leaves and roots of plants exposed to Zn treatments. In leaves, MT1 and MT3 mRNA levels were enhanced by Zn, while MT2 transcripts were not affected. The PaMT expression profiles were differentially affected by Zn in an organ-specific manner, and the relationship with Zn concentration and exposure time was rarely linear. The developmental and molecular data reveal that the in vitro model is a sensitive and reliable system to study heavy metal stress responses.

An in vitro model system of micropropagated shoots of the commercial clone ‘Villafranca’ of Populus alba (L.) was used to investigate polyamine (PA) biosynthesis and accumulation in response to high concentrations of zinc (Zn) and copper (Cu). Based on leaf symptoms, rate of adventitious root formation and ethylene production, 0.5–1 mM Zn was transiently toxic while 2–4 mM Zn concentrations were increasingly toxic. Free and conjugated putrescine and spermidine accumulated in a dose–response manner and proportionally to toxicity. The expression profiles of the PA biosynthetic genes were analysed by reverse transcriptase polymerase chain reaction in plants exposed to Zn. In both leaves and stems, PaADC and PaODC transcript levels were early enhanced by all Zn concentrations, while those of PaSAMDC were not. In adventitious roots, free and conjugated PA levels also rose, although their composition and reciprocal ratios were different from those of leaves and no changes in transcript levels of PA biosynthetic genes were detected. Several Cu concentrations (5–500 mM) were tested in shoots showing severe leaf toxicity, strongly impaired adventitious root formation and high ethylene production. No changes in PA levels were detected until end of culture. The different timing of the PA response to Zn and Cu, despite their rapid uptake and translocation already at 24 h, is discussed in relation to the extent of leaf toxicity.

The time course of ethylene biosynthesis and perception was investigated in ripening peach fruit (Prunus persica) following treatments with the polyamines putrescine (Pu) and spermidine (Sd), and with aminoethoxyvinylglycine (AVG). Fruit treatments were performed in planta. Ethylene production was measured by gas chromatography, and polyamine content by high-performance liquid chromatography; expression analyses were performed by Northern blot or real-time polymerase chain reaction. Differential increases in the endogenous polyamine pool in the epicarp and mesocarp were induced by treatments; in both cases, ethylene production, fruit softening and abscission were greatly inhibited. The rise in 1-aminocyclopropane-1-carboxylate oxidase (PpACO1) mRNA was counteracted and delayed in polyamine-treated fruit, whereas transcript abundance of ethylene receptors PpETR1 (ethylene receptor 1) and PpERS1 (ethylene sensor 1) was enhanced at harvest. Transcript abundance of arginine decarboxylase (ADC) and S-adenosylmethionine decarboxylase (SAMDC) was transiently reduced in both the epicarp and mesocarp. AVG, here taken as a positive control, exerted highly comparable effects to those of Pu and Sd. Thus, in peach fruit, increasing the endogenous polyamine pool in the epicarp or in the mesocarp strongly interfered, both at a biochemical and at a biomolecular level, with the temporal evolution of the ripening syndrome.

1-Methylcyclopropene (1-MCP) inhibits ethylene action and fruit quality achievement by binding to ethylene receptors. Developmental stage, timing, concentration and storage temperature may modulate 1-MCP effects. Ethylene and the antisenescent growth regulators polyamines (PAs) share a common precursor and may exert opposite effects. Nectarines (Prunus persica L. Batsch ‘Stark Red Gold’) were harvested and treated with 1-MCP for 12 h at 25°C, and then stored for 3 days at 25 or 4°C. At 25°C, 1-MCP strongly inhibited ethylene production and Pp-ACO gene expression, and development of quality parameters (softening, SSC, loss of acidity). At 4°C, ethylene production was not inhibited, but enhanced on the third day. A transient increase in endogenous PAs is associated with 1-MCP treatment, which at 4°C is accentuated, suggesting a combined negative effect of 1-MCP and cold stress. In fact, the 1-MCP-induced increase in PA levels seems to be more correlated with the cold stress than with preventing post-harvest ripening. Thus, in nectarines a single dose of 1-MCP is sufficient to improve post-harvest storage at 25°C, but has a less beneficial effect at 4°C.

“Stark Red Gold” nectarines were harvested at 30 N of flesh firmness (FF) and 1 nl g −1 h −1 of ethylene production, and treated in sealed plastic containers with 1 μl l −1 (1 ppm) 1-methylcyclopropene (1-MCP) for 12 h at 25 °C. Treated and control fruit were then transferred either to a growth chamber at 25 °C or to a cold room at 4 °C for 3 days. At the end of treatment with 1-MCP; ethylene production in control fruit had increased relative to production at harvest, and this rise was abolished by the presence of the chemical. Moreover, treated fruit showed lower soluble solids content (SSC) and higher FF and titratable acidity (TA) compared to control ones, and putrescine and spermine levels were moderately enhanced in the mesocarp at the end of treatment. In contrast with the inhibition of ethylene production, 1-aminocyclopropane-1-carboxylate synthase (ACS) and especially 1-aminocyclopropane-1-carboxylate oxidase (ACO1 and ACO2) transcript levels were enhanced relative to controls. During storage, 1-MCP affected ethylene production and biosynthetic gene expression, fruit softening and other quality parameters in a temperature-dependent manner: in fruit held at 25 °C a strong decrease in ethylene production, a delay in ripening and lower ACS and ACO1/ACO2 levels were recorded, while in fruit held at 4 °C an opposite trend was observed. Results suggest that 1-MCP application followed by storage at 25 °C appears effective in controlling postharvest ripening. The lack of efficacy of the chemical in cold-stored fruit is discussed in relation to changes in SAMDC gene expression and putrescine accumulation in treated fruit relative to controls, which may be part of a stress response.

In several in vitro systems, treatment with methyl jasmonate (MJ) stimulates polyamine biosynthesis as well as accumulation of acid-soluble and -insoluble conjugated polyamines. This effect is attributed to changes in gene expression and enzyme activity of arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and S -adenosylmethionine decarboxylase (SAMDC). In the present study, we used tobacco ( Nicotiana tabacum L. cv. Samsun) leaf discs to investigate the interaction between this MJ-induced response and those triggered by indole-3-acetic acid (IAA), N 6 -benzyladenine (BA) and ethylene. Our results indicate that MJ-induced accumulation of conjugated polyamines is further stimulated by auxin and counteracted by BA. The MJ-induced stimulation of ODC and SAMDC, but not ADC, mRNA levels was diminished by IAA±BA, whereas the corresponding enzyme activities were further enhanced in the presence of hormones. MJ enhanced ethylene production only when combined with hormones, and this trend was reflected in 1-aminocyclopropane-1-carboxylate oxidase transcript levels. Results suggest that the induction by MJ of conjugated polyamine levels, and of the polyamine biosynthetic genes and activities are differentially modulated by hormones, and that ethylene does not seem to be directly involved in this response.

Despite the tremendous importance of secondary metabolites for humans as for the plant itself, plant secondary metabolism remains poorly characterized. Here, we present an experimental approach, based on functional genomics, to facilitate gene discovery in plant secondary metabolism. Targeted metabolite analysis was combined with cDNA-amplified fragment length polymorphism-based transcript profiling of jasmonate-elicited tobacco Bright yellow 2 cells. Transcriptome analysis suggested an extensive jasmonate-mediated genetic reprogramming of metabolism, which correlated well with the observed shifts in the biosynthesis of the metabolites investigated. This method, which in addition to transcriptome data also generates gene tags, in the future might lead to the creation of novel tools for metabolic engineering of medicinal plant systems in general.

Production of acid-soluble conjugated di- and polyamines, like that of other secondary metabolites, is enhanced by exposure to methyl jasmonate (MJ). We investigated this metabolic response, and activities of enzymes involved in putrescine (Put) and tropane alkaloid biosynthesis, in root cultures of Hyoscyamus muticus and compared it with that of callus cultures. In root cultures, free Put and N-methylputrescine (mPut) increased upon treatment with MJ, whereas in callus cultures mPut levels were not affected. Differently from roots, conjugated amines were scarce or absent in callus cultures, and accumulated only transiently upon treatment with MJ. Arginine decarboxylase, ornithine decarboxylase and diamine oxidase activities in root cultures were strongly stimulated by treatment with MJ, but were inhibited in callus cultures. Exposure to MJ also enhanced putrescine N-methyltransferase activity in root cultures more than in callus cultures. These results are discussed in relation to the different capacity for tropane alkaloid production in the two culture systems.

Eggplant (Solanum melongena L. cv. Violetta lunga 2) cotyledon expiants grown on hormone-free medium (controls) or on medium containing either naphthaleneacetic acid alone (root forming) or in combination with zeatin riboside (shoot forming) showed minor differences in free polyamine titres during culture. In contrast, conjugated polyamines (particularly those in the trichloroacetic acid-soluble fraction) accumulated only in hormonetreated explants, but not in controls. The extent and the temporal changes in soluble-conjugate levels differed between root-forming and shoot-forming expiants; in the former, accumulation began earlier (within 1 day of culture) and reached the highest levels. In both organogenic programmes, maximum conjugate accumulation occurred just before and during organ emergence. Adventitious roots and shoots were formed along the cut surfaces. The regions closest to these (“borders”) displayed a significantly higher ratio of conjugated to free spermidine and/or putrescine than the nonorganogenic regions (“centres”) of the explant. Ornithine decarboxylase activity was higher than arginine decarboxylase activity both in control and hormone-treated explants. However, both activities increased markedly on day 2 of culture in the presence of hormones. Thereafter ornithine decarboxylase activity remained high in shoot-forming explants, but not in root-forming ones. Putrescine oxidising activity was also enhanced by exogenously supplied hormones starting from day 4 of culture. This activity remained high up to day 12 in the presence of auxin plus cytokinin, whereas it peaked on day 6 in auxin-treated explants. Spermidine oxidising activity was the only enzyme activity which was consistently higher in controls than in hormone-treated tissue. Differences between the two organogenic programmes with respect to temporal changes in polyamine content, and putrescine biosynthetic and oxidative activities are discussed in relation to the timing of organ formation. The latter was monitored both histologically and macroscopically.

The effects of two inhibitors of polyamine (spermidine and spermine) biosynthesis, cyclohexylamine (CHA; 5 and 10 mM) and methylglyoxal(bis-guanylhydrazone) (MGBG; 0.1, 0.5 and 1 mM), on the organogenic response in vegetative bud-forming tobacco (Nicotiana tabacum L. cv. Samsun) thin layer explants were evaluated micro- and macroscopically at different times during culture. The final number of buds formed and the percentage of organogenic explants was significantly reduced by both inhibitors, but much more so by MGBG than CHA. This inhibitory effect was already evident in MGBG-treated explants on day 5, in terms of the number of meristemoids per explant. On the contrary, in the presence of CHA, the number of meristemoids on day 5 was higher than that in the controls. Between days 9 and 13, meristemoid formation slowed down considerably in inhibitor-treated explants compared with controls. On day 13, the number of bud primordia was similar in control and CHA-treated explants, but significantly lower in MGBG-treated explants. This inhibitor also induced peculiar cytohistological events, such as a reduced formation of oval-shaped cell aggregates on the explant surface and more frequent cases of nucleolar extrusion, while CHA led to the appearance of hypertrophic epidermal cells; callus formation at the basal end of the explant and xylogenesis were also affected by the inhibitors. Ethylene biosynthesis, measured as [ C]methionine incorporation, was stimulated 2- (day 2) to 3-fold (15 h) by 0.5 mM MGBG, whereas CHA (10 mM) had little effect and aminoethoxyvinylglycine (AVG; 0.1 μM), an ethylene synthesis inhibitor, was strongly inhibitory. In control explants, the incorporation of labelled methionine into ethylene and spermidine followed an inverse trend up to day 8. In these explants, free putrescine increased 32-fold and spermidine increased about 10-fold between days 0 and 8. Trichloroacetic acid (TCA)-soluble conjugated putrescine also accumulated dramatically during culture. While CHA provoked a decline in spermidine levels, MGBG caused an unexpected increase in free spermidine and spermine titres; however, its most conspicuous effect was on the further enhancement of putrescine conjugate accumulation, while CHA and AVG had the opposite effect. Results are discussed in view of establishing a putative link between MGBG-enhanced ethylene synthesis, increased conjugate titres and inhibition of meristemoid formation.