Tuber Cells Research Articles

Early physiological and cytological events induced by wounding in potato tuber

The response of potato tuber (Solanum tuberosum L. cv. Kennebec) to mechanical wounding was investigated at different times. Changes in the levels of indole-3-acetic acid (IAA), polyunsaturated fatty acids (PUFAs) and lipid hydroperoxides (LOOHs) were monitored up to 120 min after wounding and related to the cytological events occurring up to 24 h. Twenty minutes after injury, an increase in IAA and LOOH levels and a decrease in the levels of PUFAs was observed. Wounding induced mitoses in differentiated (parenchyma) cells starting at 120 min, and promoted an increase of mitotic activity in the meristematic cells (procambium and bud dome), after 360 min. The inhibition of the increase in LOOHs and IAA by lipoxygenase (LOX) inhibitors, as well as the ability of in vitro peroxidated linoleic acid to enhance IAA production, suggest a close relationship among lipoperoxidation, IAA and mitotic activity in the response of potato tuber cells to injury, resulting in a specific growth response, i.e. bud growth and periderm formation.

Nutritive value of GM potato

The tuber-specific and constitutive expression of the seed albumin gene of the AmA1 protein from Amaranthus hypochondriacus has been reported in potato – the protein is found in the cytoplasm and vacuoles of transgenic tuber cells. The AmA1 protein is nonallergenic, rich in all essential amino acids, and the composition corresponds well with the World Health Organization standards for optimal human nutrition. Proc. Natl. Acad. Sci. U. S. A. (2000) 97, 3724–3729.

Cellulose microfibrils from potato tuber cells: Processing and characterization of starch-cellulose microfibril composites

The ultrastructure and morphology of potato (Solanum tuberosum L.) tuber cells were investigated by optical, scanning, and transmission electron microscopies. After removal of starch granules, pectins and hemicelluloses were solubilized under alkaline conditions. The alkaline insoluble residue consisted mainly of primary cell wall cellulose, which can be disintegrated under shearing to produce a homogenized microfibril suspension, as reported in a previous work.40 Composite materials were processed from this potato cellulose microfibril suspension, gelatinized potato starch as a matrix and glycerol as a plasticizer. After blending and casting, films were obtained by water evaporation. The mechanical properties and water absorption behavior of the resulting films were investigated, and differences were observed depending on the glycerol, cellulose microfibrils, and relative humidity content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 2080–2092, 2000

Expression of a Petunia inflata pectin methyl esterase in Solanum tuberosum L. enhances stem elongation and modifies cation distribution.

Transgenic potato (Solanum tuberosum L.) plants were constructed with a Petunia inflata-derived cDNA encoding a pectin methyl esterase (PME; EC 3.1.1.11) in sense orientation under the control of the cauliflower mosaic virus 35S promoter. The PME activity was elevated in leaves and tubers of the transgenic lines but slightly reduced in apical segments of stems from mature plants. Stem segments from the base of juvenile PME-overexpressing plants did not differ in PME activity from the control, whereas in apical parts PME was less active than in the wild-type. During the early stages of development stems of these transgenic plants elongated more rapidly than those of the wild-type. Further evidence that overexpression of a plant-derived PME has an impact on plant development is based on modifications of tuber yield, which was reduced in the transgenic lines. Cell walls from transgenic tubers showed significant differences in their cation-binding properties in comparison with the wild-type. In particular, cell walls displayed increased affinity for sodium and calcium, while potassium binding was constant. Furthermore, the total ion content of transgenic potatoes was modified. Indications of PME-mediated differences in the distribution of ions in transgenic plants were also obtained by monitoring relaxations of the membrane potential of roots subsequent to changes in the ionic composition of the bathing solution. However, no effects on the chemical structure of pectin from tuber cell walls could be detected.

Immunocytochemical Intracellular Localization of the 22-ku Kunitz-type Potato Proteinase Inhibitor in Potato Tubers and Leaves

The twenty-two ku (kDa) Kunitz-type potato proteinase inhibitor (22-ku KPP1) is synthesized as a preprotein with a hydrophobic signal sequence of 40 amino acids. Using 22-ku KPPI specific antibody and GAR-IgG colloidal gold for electron-microscopical immunocytochemistry, the 22-ku KPPI was localized mainly in the cell wall, with some detectable levels of label in or near plasma membrane of cells in both tubers and non-wounded upper leaves from wounded potatoes (Solanum tuberosum L). Neither vacuole nor the intercellular air space contained detectable levels of 22-ku KPPI.

Comparative performance of three test methods for determining chipping quality in tubers of potato (Solanum tuberosum L.)

The capacity of a colour chart and a reflectance photometer (Agtron) to accurately determine chipping quality of potato tubers was assessed using data sets taken over a 4-yr period for 17–32 cultivars. Both tests gave a high diagnostic accuracy for chipping quality regardless of sampling time from storage or the occurrence of high temperature reconditioning when evaluated by receiver operating characteristic (ROC) curve analysis. Receiver operating characteristic curve analysis showed that both tuber glucose content and chip colour provided good diagnostic performance in correctly separating processing from non-processing tubers over a range of growing and storage conditions. Identification of chipping from non-chipping tuber samples from a 13 °C storage across a range of cultivars and growing conditions occurred with a minimum chipping colour threshold range of 41–47 or a maximum glucose concentration range of 4.3–5.4 mmol L−1 of tuber cell sap. The practical value of a test can depend on such factors as prevalence of chippers in a tuber population as well as the cost of misclassifications, i.e., costs associated with false positive or false negative test results and expressed in relative terms as the unit cost ratio. An examination of Prevalence-Value-Accuracy (PVA) plots for one of the data sets indicated that total misclassification costs could increase rapidly, depending on the prevalence of chipping tubers and the relative amounts of false negative and false positive costs. Maximum costs were consistently associated with a prevalence of 50% chippers and a unit cost ratio of 0.5. In a tuber sample containing a high prevalence of chippers (50–70%) and a low unit cost ratio (<0.2), an acceptable colour threshold determined by PVA-Threshold (PVAT) plots would be approximately 40 to 50 from the Agriculture and Agri-Food Canada colour chart. However, if the colour chart was used for screening tuber samples with a low prevalence (20–40%) of chippers and a unit cost ratio >0.20, a threshold between 60 and 65 would be optimum. The latter range would be conservative and agrees with, and supports, current industry standards, which reside at 60 or better. Since a good diagnostic test should be repeatable and subject to minimal inter-observer variation, the more objective glucose or reflectance photometric tests may be preferable and provide acceptable diagnostic accuracy for processing quality. However, the present study indicates that all three test methods are acceptable for accurately separating chipping from non-chipping tubers regardless of sampling or storage protocols. Key words: Potato, colour chart, reflectance colorimetry, glucose content

Loss of the TSC2 product tuberin in subependymal giant-cell tumors.

We investigated immunocytochemically the expression of tuberin, the TSC2 gene product, in brain resections from children with and without tuberous sclerosis, to characterize the phenotype of balloon and tumor cells, and to elucidate the relationship between tuberin and formation of subependymal giant-cell tumors. In cortical tubers, tuberin was expressed in processes and cell bodies of balloon cells, which also showed consistent vimentin and nestin immunoreactivity, but no glial fibrillary acidic protein, neurofilament, or galactocerebroside positivity by immunofluorescence confocal microscopy. The majority of balloon cells in white matter showed weaker tuberin immunoreactivity than similar cells in cortical tubers. In subependymal giant-cell tumors, there was minimal to no immunoreactivity. Why tuberin is expressed in tubers but not in subependymal giant-cell tumors is not known. If tuberin plays a role in tumor suppression, then lack of tuberin might be a marker for deletion of both alleles, leading to enhanced cellular growth in subependymal giant-cell hamartomas, eventually of sufficient size to cause clinical symptoms.

Antisense inhibition of the GDP-mannose pyrophosphorylase reduces the ascorbate content in transgenic plants leading to developmental changes during senescence.

GDP-mannose pyrophosphorylase (GMPase, EC 2.7.7.22) catalyses the synthesis of GDP-D-mannose and represents the first committed step in the formation of all guanosin-containing sugar nucleotides found in plants which are precursors for cell wall biosynthesis and, probably more important, the synthesis of ascorbate. A full-length cDNA encoding GMPase from S. tuberosum was isolated. Transgenic potato plants were generated in which the GMPase cDNA was introduced in antisense orientation to the 35S promoter. Transformants with reduced GMPase activity were selected. Transgenic plants were indistinguishable from the wild-type when held under tissue culture conditions, however, a major change was seen 10 weeks after transfer into soil. Transgenic plants showed dark spots on leaf veins and stems with this phenotype developing from the bottom to the top of the plant. In case of the line with the strongest reduction, all aerial parts finally dried out after 3 months in soil, in contrast to the wild-type plants which did not start to senesce at this time. This coincides with a reduction of ascorbate contents in the transgenic plants, which is in agreement with the recently proposed pathway of ascorbate biosynthesis. Furthermore, leaf cell walls of the transgenic potato plants had mannose contents that were reduced to 30-50% of the wild-type levels, whereas the composition of tuber cell walls was unchanged. The glycosylation pattern of proteins was unaffected by GMPase inhibition, as studied by affinoblot analysis.

Co-localization of TSC1 and TSC2 gene products in tubers of patients with tuberous sclerosis.

Two genes, mutations in which result in the phenotype of tuberous sclerosis (TSC), have recently been cloned. TSC2 on chromosome 16p13.3 encodes the protein tuberin, which appears to have growth regulating properties. TSC1 on chromosome 9q34 encodes hamartin which, as yet, has no specified cellular functions. Polyclonal antibodies were raised to synthetic peptides representing portions of tuberin and hamartin and used in immunoblots and immunohistochemical studies to localize the proteins in surgically resected neocortical tubers from four TSC patients. On Western blots of autopsy brain specimens, K-562 cell, and NT2 lysates, each antibody labelled a single band at the expected molecular weight. In immunohistochemical protocols on paraffin embedded tissue, antibodies to both tuberin and hamartin prominently labelled atypical and dysmorphic neuroglial cells that are a defining feature of TSC tubers. Some abnormal cells within cortical tuber sections were labelled with both tuberin and hamartin antisera. Our results suggest that tuberin and hamartin are both robustly expressed in similar populations of neuroglial cells of TSC tubers, even in the presence of TSC1 or TSC2 germline mutations. The roles of these gene products in normal and abnormal cortical development, tuber pathogenesis and the generation of seizures remain to be defined.

Stable isotope distribution in the major metabolites of source and sink organs of Solanum tuberosum L.: a powerful tool in the study of metabolic partitioning in intact plants

A method was developed for the purification of main intermediates and storage products of leaves and tubers of potato for analysis of their 13C content. The method was tested for recovery of metabolites and carbon isotope discrimination during the purification process. Leaf metabolite δ13C values showed an enrichment of starch relative to sucrose and citrate. This result is in agreement with previous findings in other higher plants and indicates the existence of isotope discrimination steps during transport and metabolism of triose-phosphates in potato leaf mesophyll cells. Active anaplerotic replenishment of the tricarboxylic acid cycle in the leaves of the plants investigated was also deduced from the significant 13C enrichment of malate relative to citrate and asparagine/aspartate relative to glutamine/glutamate. Analysis of tuber metabolite δ13C values showed no difference between starch and sucrose. However, tuber sucrose appeared significantly enriched compared with leaf sucrose and also relative to tuber citrate and malate. This finding suggests the existence of sites of isotopic discrimination during sucrose processing in developing tubers. It also confirms that metabolic cycles of sucrose synthesis and breakdown and of hexose-phosphate/triose-phosphate interconversion, which have been described in excised tuber tissue, also occur in intact organs. The δ13C values were also used to estimate the metabolic rate of carbon oxidation in developing tubers on the assumption that pyruvate dehydrogenase is the main site of isotopic discrimination in the tuber cells. The result obtained was in agreement with the available literature, suggesting that analyses of natural isotopic distribution in plant products may be a useful tool for the study of metabolic processes and sink-source relationships in intact plants.

Tyrosine and cysteine are substrates for blackspot synthesis in potato

Partially purified blackspot pigments from potato tubers ( Solanum tuberosum L.) of two commercial cultivars were subjected to a microassay for melanin, which consisted of specific chemical degradation and subsequent HPLC analysis. Permanganate oxidation yielded pyrrole-2,3,5-tricarboxylic acid, whereas hydrolysis in hydriodic acid liberated aminohydroxyphenylalanine isomers. These results indicate that the polymeric pigments, which have previously been found to contain a protein matrix, carry crosslinked 5,6-dihydroxyindole-2-carboxylic acid and benzothiazine units. This leads to the conclusion that free tyrosine and free cysteine are incorporated in the proteinaceous pigments via the polyphenol oxidase catalysed pathway of melanogenesis in the process of blackspot formation. The findings are in accordance with the hypothesis that the process of blackspot formation is a non-regulated cascade of reactions in disintegrated tuber cells, rather than a finely tuned biosynthesis.

Characterisation of the yam tuber storage protein dioscorin

Dioscorin ( M r 31,000) is the major soluble protein present in the tubers of the tropical root crop yam ( Dioscorea spp.) and in view of its abundance is considered to act as a storage protein. Because of the importance of the tuber as food for human nutrition the characterisation of dioscorin from Dioscorea caye-nensis was undertaken to evaluate the possibility of crop improvement through genetic modification. Six charge isomers were detected by IEF, with pis in the range 5.68–6.38, and 2-D non-reduced/reduced SDS-PAGE showed two major groups of components differing in the presence or absence of intra-chain disulphide bonds. The partial amino acid sequence determined from the protein N -terminus and a V8 protease cleavage product agreed with the sequences deduced from the nucleotide sequences of cDNAs. Circular dichroism spectroscopy showed a secondary structure rich in α-helix which agreed with secondary structure predictions based on the protein sequence. A significant degree of sequence similarity was found between dioscorins and α-carbonic anhydrase enzymes from animals. However, dioscorin may not be an active enzyme due to the presence of amino acid substitutions in the region corresponding to the carbonic anhydrase active site. Immuno-localisacion experiments showed that dioscorin accumulates specifically in the vacuoles of tuber cells, as reported for the tuber storage proteins of potato and sweet potato.

S.09.02 The metabotropic glutamate receptors: Structural domains and coupling to G proteins

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder associated with cortical malformations (cortical tubers) and the development of glial tumors (subependymal giant-cell tumors, SGCTs). Expression of metabotropic glutamate receptor (mGluR) subtypes is developmentally regulated and several studies suggest an involvement of mGluR-mediated glutamate signaling in the regulation of proliferation and survival of neural stem-progenitor cells, as well as in the control of tumor growth. In the present study, we have investigated the expression and cell-specific distribution of group I (mGluR1, mGluR5), group II (mGluR2/3) and group III (mGluR4 and mGluR8) mGluR subtypes in human TSC specimens of both cortical tubers and SGCTs, using immunocytochemistry.Strong group I mGluR immunoreactivity (IR) was observed in the large majority of TSC specimens in dysplastic neurons and in giant cells within cortical tubers, as well as in tumor cells within SGCTs. In particular mGluR5 appeared to be most frequently expressed, whereas mGluR1α was detected in a subpopulation of neurons and giant cells. Cells expressing mGluR1α and mGluR5, demonstrate IR for phospho-S6 ribosomal protein (PS6), which is a marker of the mammalian target of rapamycin (mTOR) pathway activation. Group II and particularly group III mGluR IR was less frequently observed than group I mGluRs in dysplastic neurons and giant cells of tubers and tumor cells of SGCTs. Reactive astrocytes were mainly stained with mGluR5 and mGluR2/3.These findings expand our knowledge concerning the cellular phenotype in cortical tubers and in SGCTs and highlight the role of group I mGluRs as important mediators of glutamate signaling in TSC brain lesions. Individual mGluR subtypes may represent potential pharmacological targets for the treatment of the neurological manifestations associated with TSC brain lesions.

S.09.01 The use of gene targeting to study the biological roles of metabotropic glutamate receptors

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder associated with cortical malformations (cortical tubers) and the development of glial tumors (subependymal giant-cell tumors, SGCTs). Expression of metabotropic glutamate receptor (mGluR) subtypes is developmentally regulated and several studies suggest an involvement of mGluR-mediated glutamate signaling in the regulation of proliferation and survival of neural stem-progenitor cells, as well as in the control of tumor growth. In the present study, we have investigated the expression and cell-specific distribution of group I (mGluR1, mGluR5), group II (mGluR2/3) and group III (mGluR4 and mGluR8) mGluR subtypes in human TSC specimens of both cortical tubers and SGCTs, using immunocytochemistry.Strong group I mGluR immunoreactivity (IR) was observed in the large majority of TSC specimens in dysplastic neurons and in giant cells within cortical tubers, as well as in tumor cells within SGCTs. In particular mGluR5 appeared to be most frequently expressed, whereas mGluR1α was detected in a subpopulation of neurons and giant cells. Cells expressing mGluR1α and mGluR5, demonstrate IR for phospho-S6 ribosomal protein (PS6), which is a marker of the mammalian target of rapamycin (mTOR) pathway activation. Group II and particularly group III mGluR IR was less frequently observed than group I mGluRs in dysplastic neurons and giant cells of tubers and tumor cells of SGCTs. Reactive astrocytes were mainly stained with mGluR5 and mGluR2/3.These findings expand our knowledge concerning the cellular phenotype in cortical tubers and in SGCTs and highlight the role of group I mGluRs as important mediators of glutamate signaling in TSC brain lesions. Individual mGluR subtypes may represent potential pharmacological targets for the treatment of the neurological manifestations associated with TSC brain lesions.

Possible involvement of jasmonates in various morphogenic events

Jasmonates (jasmonic acid and related compounds) seem to be involved in various morphogenic events of plants, such as tuberization (potato, yam and Jerusalem artichoke), tuberous root formation (sweet potato), bulb formation (onion and garlic), determination of plant structure (soybean) and thigmomorphogenesis (coiling of tendrils of Bryonia dioica). The involvement of jasmonates in tuberization in these plants was inferred from their ability to induce tubers in vitro, and from changes in the levels of endogenous jasmonates during the growth of the plants, which can account for the initiation of tuberization. As to potato tuberization, jasmonic acid (JA) and its methyl ester (JA‐Me) have strong tuber‐inducing activity. These compounds seem to exert their tuber‐inducing effects by elicting the expansion of cells, because JA and JA‐Me are capable of causing the expansion of cells in potato tubers. The JA‐induced expansion of cells is attributable to both an increase in osmotic pressure due to the accumulation of sucrose and changes in cell wall architecture that appear to affect the extensibility of the wall. And, moreover, the synthesis of cellulose might be indispensable for the JA‐induced expansion. The tuberization and the expansion of cells induced by JA always involve the reorientation of cortical microtubules (MTs), suggesting that JA controls the direction of cell expansion by changing the arrangement of MTs. However, the reorientation of MTs itself seems to be insufficient for the induction of expansion of cells.Involvement of jasmonates in bulb formation and tuberous root formation is presumed from the fact that JA is able to induce these in vitro. The exact nature of the control that the jasmonates exert on morphogenesis remains to be elucidated.

O-acetylated oligosaccharides from pectins of potato tuber cell walls.

Acetylated trigalacturonides and rhamnogalacturonan I (RG-I)-derived oligosaccharides were isolated from a Driselase digest of potato tuber cell walls by ion-exchange and size-exclusion chromatography. The oligosaccharides were structurally characterized by fast atom bombardment-mass spectroscopy, nuclear magnetic resonance spectroscopy, and glycosyl-linkage composition analysis. One trigalacturonide contained a single acetyl group at O-3 of the reducing galacturonic acid residue. A second trigalacturonide contained two acetyl substituents, which were located on O-3 or O-4 of the nonreducing galacturonic acid residue and O-3 of the reducing galacturonic acid residue. RG-I backbone-derived oligomers had acetyl groups at O-2 of the galacturonic acid residues. Some of these galacturonic acid residues were O-acetylated at both O-2 and O-3 positions. Rhamnosyl residues of RG-I oligomers were not acetylated.

Giant cells in cortical tubers in tuberous sclerosis showing synaptophysin-immunoreactive halos

We describe a characteristic pattern of immunoreactivity for synaptophysin in tuberous sclerosis. We analyzed cortical tubers from surgical specimens taken from six patients with tuberous sclerosis, which were obtained by surgical resections for the treatment of intractable seizures. The cortical tubers were characterized by blurred lamination of the cerebral cortex, hypercellularity, and gliotic changes. Neuropil in the cortex of cortical tubers showed reduced immunoreactivity for synaptophysin in all patients. ‘Giant cells’ were investigated in the cortex and white matter regions of cortical tubers. Some ‘giant cells’ had neuronal characteristics such as Nissl substance, a centrally placed. chromatin-marginated nucleus, prominent nucleolus, positive immunoreactivity for microtubule-associated protein 2, and negative immunoreactivity for glial fibrillary acidic protein. Other ‘giant cells’ were indeterminate in cell type because they lacked Nissl bodies, distinct nucleolus, consistent immunoreactivity for microtubule-associated protein 2 and glial fibrillary acidic protein. Almost all ‘neuronal giant cells’ and some of the ‘indeterminate giant cells’ in the white matter showed intense immunoreactivity for synaptophysin: cell borders were surrounded by an intense immunoreactive halo. In conclusion, these immunohistochemical patterns for synaptophysin assist in characterizing these abnormal cells in the cortical tubers of patients with tuberous sclerosis.

Cell suspension cultures of Solanum tuberosum L. as a model system for N and salinity response effect of salinity on NO 3− uptake and PM-ATPase activity

Tuber cell suspension cultures of Solanum tuberosum L. (cv. Alpha and Désirée) were established on a suitable medium in order to relate the interaction of N and salinity stress physiology at the cellular and whole plant level. Preliminary experiments showed that there was no difference in the growth response, viability and NO3− uptake under saline conditions between the Alpha (salt sensitive in the field) and the Désirée cultivar (less salt sensitive in the field). The cell suspension cultures were thus considered unsuitable as screening tools for whole plant responses and were further used as models for N uptake at the cellular level. The suspension cultures were grown on media where the sole N source was from free amino acids so as to ensure that the cells had no exposure to NO3− prior to uptake experiments. It was found that both salinity stressed (75 mmol/L NaCl) and control cells took NO3− up without the often reported «lag phase» and it is suggested that this «lag phase» is due, at least in part, to membrane depolarization incurred by plants/cells during manipulation. Nitrate uptake is postulated to occur via a constitutive NO3− transporter requiring an induction time in the order of minutes. Salinity reduced the Vmax of NO3− uptake from 280 ± 23 nmol g−1 fm in control cells to 220 ± 14 nmol g−1 fm in the stressed cells. Over a period of 300 min it was observed that 75 mmol/L reduced NO3− uptake by approximately 60%. Supplemental Ca2+ up to 8 mmol/L had no effect on the NO3− uptake capacity of either the control or stressed cells in contrast to what has been observed in whole plants. However, an amelioration of growth reduction and cell viability reduction in stressed cells of both cultivars was observed. It is suggested that reduced PM-ATPase activity in stressed cells is partly responsible for the NaCl-induced reduction in NO3− uptake as 75 mmol/L NaCl reduced PM-ATPase activity by approximately 30% over a 300 min time period.

Embryonic neuronal markers in tuberous sclerosis: single-cell molecular pathology.

One hallmark of tuberous sclerosis (TSC) is the presence of highly epileptogenic dysplastic cerebral cortex (tubers) composed of abnormally shaped neurons and giant cells. Mutation of the TSC gene (TSC2) may disrupt differentiation and maturation of neuronal precursors, since the TSC2 gene product tuberin is believed to regulate cellular proliferation. To test the hypothesis that cells in tubers may retain the molecular phenotype of embryonic or immature neurons, tubers from five TSC patients were probed with antibodies to proteins expressed in neuronal precursors (nestin, Ki-67, and proliferating cell nuclear antigen). Many dysmorphic neurons and giant cells in tubers were stained by these antibodies, while neurons in adjacent normal and control cortex were not labeled. To further characterize the molecular phenotype of cells in tubers, we developed a methodology in which poly(A)+ mRNA was amplified from immunohistochemically labeled single cells in paraffin-embedded brain specimens. This approach enabled us to detect mRNAs encoding nestin, and other cytoskeletal elements, cell cycle markers, and synthetic enzymes present in individual nestin-stained cells by means of reverse Northern blotting. We conclude that the presence of immature phenotypic markers (mRNAs and proteins) within tubers suggests disruption of cell cycle regulation and neuronal maturation in TSC during cortical development. Characterization of multiple mRNAs within fixed, immunohistochemically labeled cells provides a powerful tool for studying gene expression and the molecular pathophysiology of many neurologic diseases.

Similarities of the biological activities of coronatine and coronafacic acid to those of jasmonic acid

Coronatine, a phytotoxin produced by Pseudomonas syringae pv. atropurpurea and an amide of coronafacic acid and coronamic acid, is known to induce the expansion of cells in potato tubers just as jasmonic acid (JA) does. Furthermore, the chemical structure of coronafacic acid resembles that of JA to some extent. These observations led us to postulate that coronatine and related compounds might have biological activities similar to those of JA. We compared the biological activities of coronatine and coronafacic acid to those of JA in four jasmonate-responsive assay systems, namely, in assays for tuber-inducing activity (with single-node segments of potato stems), for cell expansion-inducing activity (with cells of potato tubers), for cell division-inhibiting activity (with soybean callus) and for senescence-promoting activity (with oat leaves). Coronatine had a positive effect in all these assays and its activity was 100 to 10 000 times higher than that of JA in terms of the threshold concentration for activity. Coronafacic acid also gave a positive result in all the assays, but its activity was slightly weaker than that of JA in two assay systems. These results suggest that the special configuration of side chains with respect to the plane of the cyclopentanone ring, namely, the 1 R, 2 S configuration in JA and the 3a S, 7a R configuration in coronatine and coronafacic acid, is necessary for these various biological activities.