Effect of aeration efficiency and carbon source on the production of anthracyclines inStreptomyces galilaeus

Biosynthesis of anthracyclines inStreptomyces galilaeus during submerged cultivation is considerably influenced by aeration and by the concentration of glucose in the medium. At higher values of oxygen absorption rate both the production of ε-pyrromycinone glycosides in the wild strain JA 3043 and its production mutant G-167 and accumulation of free ε-pyrromycinone in the blocked mutant G-162 were found to be higher; the production of 7-deoxyaglycones was lower in all strains. The studied strains differed in the rate of glucose consumption and in the ability to utilize starch for the biosynthesis of anthracyclines. A two-fold concentration of glucose in the medium resulted in the G-162 strain in an increase of the yield of ε-pyrromycinone by 120 %. The production of glycosides in strain G-167 increased even after exhaustion of glucose from the medium and the amount of 7-deoxyaglycones simultaneously decreased.     

Biotransformations of anthracyclinones inStreptomyces coeruleorubidus andStreptomyces galilaeus

The ability to transorm biologically exogenous daunomycinone, 13-dihydrodaunomycinone, aklavinone, 7-deoxyaklavinone, epsilon-rhodomycinone, epsilon-isorhodomycinone and epsilon-pyrromycinone was studied in submerged cultures of the following strains: wild Streptomyces coeruleorubidus JA 10092 (W1) and its improved variants 39-146 and 84-17 (type P1) producing glycosides of daunomycinone and of 13-dihydrodaunomycinone, together with epsilon-rhodomycinone, 13-dihydrodaunomycinone and 7-deoxy-13-dihydrodaunomycinone; in five mutant types of S. coeruleorubidus (A, B, C, D, E) blocked in the biosynthesis of glycosides and differing in the production of free anthracyclinones; in the wild Streptomyces galilaeus JA 3043 (W2) and its improved variant G-167 (P2) producing glycosides of epsilon-pyrromycinone and of aklavinone together with 7-deoxy and bisanhydro derivatives of both aglycones; in two mutant types S. galilaeus (F and G) blocked in biosynthesis of glycosides and differing in the occurrence of anthracyclinones. The following bioconversions were observed: daunomycinone leads to 13-dihydrodaunomycinone and 7-deoxy-13-dihydrodaunomycinone (all strains); 13-dihydrodaunomycinone leads to 7-deoxy-13-dihydrodaunomycinone (all strains); daunomycinone or 13-dihydrodaunomycinone leads to glycosides of daunomycinone and of 13-dihydrodaunomycinone, identical with metabolites W1 and P1 (type A), or only a single glycoside of daunomycinone (type E); aklavinone leads to epsilon-rhodomycinone (types A and B); aklaviinone leads to 7-deoxyaklavinone and bisanhydroaklavinone (type C); epsilon-rhodomycinone leads to zeta-rhodomycinone (types C, E); epsilon-rhodomycinone leads to glycosides of epsilon-rhodomycinone (types W2, P2); epsilon-isorhodomycinone leads to glycosides of epsilon-isorhodomycinone (types W2, P2); epsilon-pyrromycinone leads to a glycoside of epsilon-pyrromycinone (types W1, P1). 7-Deoxyaklavinone remained intact in all tests. Exogenous daunomycinone suppressed the biosynthesis of its own glycosides in W1 and P1; it simultaneously increased the production of epsilon-rhodomycinone in P1.     

Intra- and interspecific cosynthetic activity of mutants ofStreptomyces coeruleorubidus andStreptomyces galilaeus impaired in the biosynthesis of anthracyclines

Cosynthesis of anthracycline compounds was followed in five phenotypic groups of mutants of Streptomyces coeruleorubidus (A--E), blocked in the biosynthesis of the daunomycine complex, and in two mutant types of Streptomyces galilaeus (F, G) blocked in the biosynthesis of glycosides of epsilon-pyrromycinone and aklavinone. Glycosides of daunomycinone and 13-dihydrodaunomycinone were produced in combinations A+B, A+C, A+D, A+E and A+F, epsilon-rhodomycinone was synthesized in combinations A+E, A+F, B+E and B+F. During the cultivation of types B--E with type G or F non-anthracycline compounds, typical of S. galilaeus, were cosynthesized. No cosynthesis could be observed in other combinations of the mutant types. Negative results were also obtained with combinations of mutants of the same group and during cultivation of all mutant types with streptomycetes not producing anthracyclines. A scheme illustrating metabolic pathways leading to the biosynthesis of daunomycinone, aklavinone, epsilon-rhodomycinone in S. coeruleorubidus and S. galilaeus was constructed.     

Cooperation and functional diversification of two closely related galactolipase genes for jasmonate biosynthesis

Jasmonic acid (JA) plays pivotal roles in diverse plant biological processes, including wound response. Chloroplast lipid hydrolysis is a critical step for JA biosynthesis, but the mechanism of this process remains elusive. We report here that DONGLE (DGL), a homolog of DEFECTIVE IN ANTHER DEHISCENCE1 (DAD1), encodes a chloroplast-targeted lipase with strong galactolipase and weak phospholipase A(1) activity. DGL is expressed in the leaves and has a specific role in maintaining basal JA content under normal conditions, and this expression regulates vegetative growth and is required for a rapid JA burst after wounding. During wounding, DGL and DAD1 have partially redundant functions for JA production, but they show different induction kinetics, indicating temporally separated roles: DGL plays a role in the early phase of JA production, and DAD1 plays a role in the late phase of JA production. Whereas DGL and DAD1 are necessary and sufficient for JA production, phospholipase D appears to modulate wound response by stimulating DGL and DAD1 expression.     

Nitric oxide mediates the fungal elicitor-induced hypericin production of Hypericum perforatum cell suspension cultures through a jasmonic-acid-dependent signal pathway

Fungal elicitor prepared from the cell walls of Aspergillum niger induces multiple responses of Hypericum perforatum cells, including nitric oxide (NO) generation, jasmonic acid (JA) biosynthesis, and hypericin production. To determine the role of NO and JA in elicitor-induced hypericin production, we study the effects of NO scavenger 2- to 4-carboxyphenyl-4,4, 5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPITO), nitric oxide synthase inhibitor S,S'-1,3-phenylene-bis(1,2-ethanediyl)-bis-isothiourea, and inhibitors of the octadecanoid pathway on elicitor-induced NO generation, JA biosynthesis, and hypericin production. Pretreatment of the cells with cPITO and JA biosynthesis inhibitors suppresses not only the elicitor-induced NO generation and JA accumulation but also the elicitor-induced hypericin production, which suggests that both NO and JA are involved in elicitor-induced hypericin biosynthesis. S,S'-1,3-phenylene-bis(1,2-ethanediyl)-bis-isothiourea and cPITO inhibit both elicitor-induced NO generation and JA biosynthesis, while JA biosynthesis inhibitors do not affect the elicitor-induced NO generation, indicating that JA acts downstream of NO generation and that its biosynthesis is regulated by NO. External application of NO via its donor sodium nitroprusside induces hypericin production in the absence of fungal elicitor. Sodium-nitroprusside-induced hypericin production is blocked by JA biosynthesis inhibitors, showing that JA biosynthesis is essential for NO-induced hypericin production. The results demonstrate a causal relationship between elicitor-induced NO generation, JA biosynthesis, and hypericin production in H. perforatum cells and indicate a sequence of signaling events from NO to hypericin production, within which NO mediates the elicitor-induced hypericin biosynthesis at least partially via a JA-dependent signaling pathway.     

Effects of carbohydrate substrate on the vegetative mycelial growth of an ectomycorrhizal mushroom, <Emphasis Type="Italic">Tricholoma matsutake</Emphasis>, isolated from <Emphasis Type="Italic">Quercus</Emphasis>

We studied the characteristics of the utilization of carbohydrate substrates and the production of those hydrolyzing enzymes of the Tricholoma matsutake J-1 strain isolated from hardwood (Quercus sp.). In the culture medium, 5% glucose inhibited mycelial growth. The growth inhibition rate was remarkable in the Z-1 strain from softwood (Pinus densiflora) compared with that of the J-1 strain from hardwood. α-Amylase production varied with starches from different origins in contrast to mycelial growth. The range of the effect of 0.5%–15% soluble starch on vegetative mycelial growth was also investigated. The optimal concentration for mycelial growth was 15% for the J-1 strain but 10% for the Z-1 strain. Mycelial growth of the J-1 strain was strongly inhibited in PMML medium containing Sunpeal-CP prepared from sulfite pulp softwood waste, but that of the Z-1 strain was not inhibited by Sunpeal-CP. Moreover, mycelial growth of the J-1 strain from Quercus sp. dramatically decreased with the addition of CNF-HWSF (hot water-soluble fractions from corn fiber) to the PMML and PDL medium. However, inhibition by CNF-HWSF was not shown in the Z-1 strain from P. densiflora.     

Establishing the structure of anthracyclinones produced by Streptomyces griseoruber

Streptomyces grisoruber strain 1618-306 produces three types of anthracycline antibiotics, derivatives of epsilon-pyrromycinone (methyl (7S, 9R, 10R)-9-ethyl-5,7,8,9,10,12-hexahydro-1,4,6,7,9-pentahydroxy-5,12-di oxo-10- naphthacenecarboxylate), epsilon-1-hydroxyauramycinone and epsilon-1-hydroxysulfurmycinone, differing in C-9 substituent in D ring of anthracyclines (Et, Met or CH2COCH3, respectively). Besides 7-O-glycosides of these aglycones, complex of antibiotics contains corresponding 7-deoxy- and 7,8,9,10-bisanhydroanthracyclinones.     

Jasmonic Acid is Induced in a Biphasic Manner in Response of Pea Seedlings to Wounding

The role of jasmonic acid (JA) in plant wounding response has been demonstrated. However, the source of JA in wound signaling remains unclear. In the present study, pea seedlings were used as material to investigate the systemic induction of JA and the activation of lipoxygenase (LOX)-dependent octadecanoid pathway upon wounding. The results showed that endogenous JA could induce two peaks in the wounded leaves and the stalks, while only one peak in the systemic leaves.LOX activity and its protein amount were also induced and the stimulation mainly occurred in the late phase, while one peak of induction was present after pretreatment with JA. Applied nordihydroguaiaretic acid (NDGA), an inhibitor of LOX activity, only inhibited the induction of JA in the late phase, and the resistance of pea was impaired. Furthermore, 13(S)-hydroperoxy-9(Z), 11 (E)-octadecadienoic acid (13(S)-H(P)ODE) was confirmed to be the main product of LOX throughout the experimental time. In addition, immunocytochemical analysis also revealed the occurrence of JA biosynthesis and transport upon wounding. These results demonstrated that wound-induced JA in wounded leaves resulted from Its biosynthesis and conversion from its conjugates, while in systemic leaves resulted from its transport and biosynthesis; and proved that the LOX pathway was vital to the wound-induced defense response involved in JA biosynthesis.     

Role of beta-oxidation in jasmonate biosynthesis and systemic wound signaling in tomato

Jasmonic acid (JA) is a lipid-derived signal that regulates plant defense responses to biotic stress. Here, we report the characterization of a JA-deficient mutant of tomato (Lycopersicon esculentum) that lacks local and systemic expression of defensive proteinase inhibitors (PIs) in response to wounding. Map-based cloning studies demonstrated that this phenotype results from loss of function of an acyl-CoA oxidase (ACX1A) that catalyzes the first step in the peroxisomal beta-oxidation stage of JA biosynthesis. Recombinant ACX1A exhibited a preference for C12 and C14 straight-chain acyl-CoAs and also was active in the metabolism of C18 cyclopentanoid-CoA precursors of JA. The overall growth, development, and reproduction of acx1 plants were similar to wild-type plants. However, the mutant was compromised in its defense against tobacco hornworm (Manduca sexta) attack. Grafting experiments showed that loss of ACX1A function disrupts the production of the transmissible signal for wound-induced PI expression but does not affect the recognition of this signal in undamaged responding leaves. We conclude that ACX1A is essential for the beta-oxidation stage of JA biosynthesis and that JA or its derivatives is required both for antiherbivore resistance and the production of the systemic wound signal. These findings support a role for peroxisomes in the production of lipid-based signaling molecules that promote systemic defense responses.     

Nitric oxide mediates the fungal elicitor-induced puerarin biosynthesis in Pueraria thomsonii Benth. suspension cells through a salicylic acid (SA)-dependent and a jasmonic acid (JA)-dependent signal pathway

Higher plants constitute one of our most important natural resources, which provide not only foodstuffs, fibers, and woods, but also many chemicals, such as flavorings, dyes, and pharmaceuticals. Although plants are renewable resources, some species are b…     

Nitric oxide mediates the fungal elicitor-induced puerarin biosynthesis in Pueraria thomsonii Benth. suspension cells through a salicylic acid (SA)-dependent and a jasmonic acid (JA)-dependent signal pathway

Nitric oxide (NO) has emerged as a key signaling molecule in plant secondary metabolite biosynthesis recently. In order to investigate the molecular basis of NO signaling in elicitor-induced secondary metabolite biosynthesis of plant cells, we determined the contents of NO, salicylic acid (SA), jasmonic acid (JA), and puerarin in Pueraria thomsonii Benth. suspension cells treated with the elicitors prepared from cell walls of Penicillium citrinum. The results showed that the fungal elicitor induced NO burst, SA accumulation and puerarin production of P. thomsonii Benth. cells. The elicitor-induced SA accumulation and puerarin production was suppressed by nitric oxide specific scavenger cPITO, indicating that NO was essential for elicitor-induced SA and puerarin biosynthesis in P. thomsonii Benth. cells. In transgenic NahG P. thomsonii Benth. cells, the fungal elicitor also induced puerarin biosynthesis, NO burst, and JA accumulation, though the SA biosynthesis was impaired. The elicitor-induced JA accumulation in transgenic cells was blocked by cPITO, which suggested that JA acted downstream of NO and its biosynthesis was controlled by NO. External application of NO via its donor sodium nitroprusside (SNP) enhanced puerarin biosynthesis in transgenic NahG P. thomsonii Benth. cells, and the NO-triggered puerarin biosynthesis was suppressed by JA inhibitors IBU and NDGA, which indicated that NO induced puerarin production through a JA-dependent signal pathway in the transgenic cells. Exogenous application of SA suppressed the elicitor-induced JA biosynthesis and reversed the inhibition of IBU and NDGA on elicitor-induced puerarin accumulation in transgenic cells, which indicated that SA inhibited JA biosynthesis in the cells and that SA might be used as a substitute for JA to mediate the elicitor-and NO-induced puerarin biosynthesis. It was, therefore, concluded that NO might mediate the elicitor-induced puerarin biosynthesis through SA-and JA-dependent signal pathways in wildtype P. thomsonii Benth. cells and transgenic NahG cells respectively.     

The level of jasmonic acid in Arabidopsis thaliana and Phaseolus coccineus plants under heavy metal stress

The effect of heavy metal stress as a potent abiotic elicitor for triggering an accumulation of jasmonic acid (JA) was investigated. Copper and cadmium in in vivo conditions induced accumulation of jasmonates in mature leaves of Arabidopsis thaliana and in young and oldest Phaseolus coccineus plants. The dynamics of jasmonate accumulation showed a biphasic character in both plants. In the first phase, after 7 (A. thaliana) or 14 h (P. coccineus) of exposure to Cu or Cd, a rapid increase of JA level occurred, followed by a rapid decrease observed during 7 successive hours. In the next phase, a repeated but slow increase of JA content occurred. The heavy metal stress induced in particular a more stable (3R,7R) form of jasmonates. These results indicate that JA is connected with the mechanism of toxic action of both heavy metals in plants, differentially reacting to exogenous JA and possessing variable dynamics depending on the plants studied as well as their growth stage.     

Nitric oxide mediates the fungal elicitor-induced puerarin biosynthesis in Pueraria thomsonii Benth. suspension cells through a salicylic acid (SA)-dependent and a jasmonic acid (JA)-dependent signal pathway

Nitric oxide (NO) has emerged as a key signaling molecule in plant secondary metabolite biosynthesis recently. In order to investigate the molecular basis of NO signaling in elicitor-induced secondary metabolite biosynthesis of plant cells, we determined the contents of NO, salicylic acid (SA), jasmonic acid (JA), and puerarin in Pueraria thomsonii Benth. suspension cells treated with the elicitors prepared from cell walls of Penicillium citrinum. The results showed that the fungal elicitor induced NO burst, SA accumulation and puerarin production of P. thomsonii Benth. cells. The elicitor-induced SA accumulation and puerarin production was suppressed by nitric oxide specific scavenger cPITO, indicating that NO was essential for elicitor-induced SA and puerarin biosynthesis in P. thomsonii Benth. cells. In transgenic NahG P. thomsonii Benth. cells, the fungal elicitor also induced puerarin biosynthesis, NO burst, and JA accumulation, though the SA biosynthesis was impaired. The elicitor-induced JA accumulation in transgenic cells was blocked by cPITO, which suggested that JA acted downstream of NO and its biosynthesis was controlled by NO. External application of NO via its donor sodium nitroprusside (SNP) enhanced puerarin biosynthesis in transgenic NahG P. thomsonii Benth. cells, and the NO-triggered puerarin biosynthesis was suppressed by JA inhibitors IBU and NDGA, which indicated that NO induced puerarin production through a JA-dependent signal pathway in the transgenic cells. Exogenous application of SA suppressed the elicitor-induced JA biosynthesis and reversed the inhibition of IBU and NDGA on elicitor-induced puerarin accumulation in transgenic cells, which indicated that SA inhibited JA biosynthesis in the cells and that SA might be used as a substitute for JA to mediate the elicitor-and NO-induced puerarin biosynthesis. It was, therefore, concluded that NO might mediate the elicitor-induced puerarin biosynthesis through SA-and JA-dependent signal pathways in wildtype P. thomsonii Benth. cells and transgenic NahG cells respectively.     

Biosynthesis of phenazine pigments in mutant and wild-type cultures of Pseudomonas aeruginosa.

Pigmentation mutants of Pseudomonas aeruginosa, selected by observed visual differences in coloration from the wild-type strain, were examined for altered patterns of phenazine synthesis. Three classes of mutants that were incapable of pyocyanine production were identified. Pigmentation patterns that were found to characterize the various mutant classes implicated precursor-product relationships, and a biochemical scheme covering the terminal reactions of pyocyanine biosynthesis is proposed. Among compounds tested as inhibitors of pigmentation, two effectively inhibited pyocyanine production production while allowing cell growth. p-Aminobenzoate inhibited total pigmentation; i.e., no other phenazine accumulated. m-Aminobenzoate inhibited a presumptive methylation step in pyocyanine biosynthesis, abolishing the formation of pyocyanine and aeruginosin pigments but increasing the yields of phenazine 1-carboxylic acid and oxychlororaphin. D-[2,3,4,5(n)-14C]shikimate was most efficiently incorporated into phenazines in the middle to late exponential phase of growth. Label was incorporated predominantly into pyocyanine in the absence of inhibitors and into phenazine 1-carboxylic acid when the organism was grown in the presence of m-aminobenzoate.     

Precursor formation and biosynthesis of the macrolide antibiotic a 6599 (turimycin) by streptomyces hygroscopicus JA 6599]

The possible role of some metabolic systems producing acetyl-CoA, and methylmalonyl-CoA as initial precursors in the biosynthesis of the macrolide antibiotic A 6599 by Streptomyces hygroscopicus JA 6599 was studied. The activities of pyruvate decarboxylase exceeded in two higher producing strains about twofold those found in the mycelium of a lower producing one suggesting that in this organism an enhanced production of acetyl-CoA should be one of the prerequisites necessary for an improved antibiotic biosynthesis. No clear interrelationship was established, however, between the biosynthesis of the secondary metabolite A 6599 on the one hand and the acetate and propionate kinase content on the other hand. In S. hygroscopicus JA 6599 the carboxylation of acetyl-CoA or propionyl-CoA seems to be the major pathway giving malonyl-CoA or methylmalonyl-CoA, respectively. Thus, the activities of acetyl-CoA and propionyl-CoA carboxylases corresponded with both the levels of antibiotic production in several strains and with variations observed in the specific antibiotic production rate during the cultivation. Some other pathways synthesizing these precursors, e.g. via oxaloacetate, are assumed to be negligible since even in the mycelium of the lower producing strain increased activities of phosphoenolpyruvate carboxylase were present.     

Synergistic action between jasmonic acid and nitric oxide in inducing matrine accumulation of Sophora flavescens suspension cells

Secondary metabolites not only play important ecological roles in plants but also are important pharmaceutical and source compounds for derivative synthesis. Production of plant secondary metabolites is believed to be controlled by the endogenous signal network of plants. However, the molecular basis is still largely unknown. Here we show that matrine production of Sophora flavescens Ait. cells treated with low levels of jasmonic acid （JA） and nitric oxide （NO） is significantly increased although treatment with low concentrations of JA or NO alone has no effects on matrine production, showing that JA and NO may act synergistically in triggering matrine production. Moreover, treatment with NO triggers lipoxygenase （LOX） activity and enhances JA levels of the cells, showing that NO may activate the endogenous JA biosynthesis of S. flavescens cells. External application of JA induces nitric oxide synthase-like activities and stimulates NO generation of S. flavescens cells, which suggests that JA may trigger NO generation of the cells. Thus, the results reveal a mutually amplifying reaction between JA and NO in S. flavescens cells. Furthermore, JA and NO inhibitors suppress not only the mutually amplifying reaction between JA and NO but also the synergistic effects of NO and JA on matrine production. Therefore, the data demonstrate that the synergistic action of JA and NO in inducing matrine production might be due to the mutually amplifying reaction between JA and NO in the cells.     

Expression of the carotenoid biosynthesis genes in Xanthophyllomyces dendrorhous

In the yeast Xanthophyllomyces dendrorhous the genes idi, crtE, crtYB, crtl and ast are involved in the biosynthesis of astaxanthin from isopentenyl pyrophosphate. The carotenoid production and the kinetics of mRNA expression of structural genes controlling the carotenogenesis in a wild-type ATCC 24230 and in carotenoid overproducer deregulated atxS2 strains were studied. The biosynthesis of carotenoid was induced at the late exponential growth phase in both strains. However, the cellular carotenoid concentration was four times higher in atxS2 than in the wild-type strain in the exponential growth phase, suggesting that carotenogenesis was deregulated in atxS2 at the beginning of growth. In addition, the maximum expression of the carotenogenesis genes at the mRNA level was observed during the induction period of carotenoid biosynthesis in the wild-type strain. The mRNA level of the crtYB, crtl, ast genes and to a lesser extent the idi gene, decayed at the end of the exponential growth phase. The mRNA levels of the crtE gene remained high along the whole growth curve of the yeast. In the atxS2 strain the mRNA levels of crtE gene were about two times higher than the wild-type strain in the early phase of the growth cycle.     

Oxidative burst, jasmonic acid biosynthesis, and taxol production induced by low-energy ultrasound in Taxus chinensis cell suspension cultures

This work aims to detect the two signal events in the elicitation of plant defense responses and secondary metabolism in plant cell cultures by low-energy ultrasound (US), transient production of reactive oxygen species (ROS) or the oxidative burst and jasmonic acid (JA) biosynthesis, and examine their influence on secondary metabolism. Experiments were carried out in Taxus chinensis cell suspension culture which produces the anticancer diterpenoid Taxol (paclitaxel). The culture was exposed to low-frequency US for a short period of time (2 min). At sufficiently high US power levels the US exposure significantly enhanced the Taxol production and slightly depressed cell growth and viability. The US exposure induced transient production of O(2)*- and H(2)O(2) and an increase in the intracellular JA level as well as the activities of enzymes for JA synthesis, lipoxygenase (LOX), and allene oxide synthase (AOS). Inhibition of the ROS production by putative ROS scavengers or the JA accumulation by LOX inhibitors effectively suppressed the US-stimulated Taxol production. Inhibition of the ROS production also suppressed the US-induced JA accumulation. These results suggest that oxidative burst is an upstream event to JA accumulation, and both ROS from the oxidative burst and JA from the LOX pathway are key signal elements in the elicitation of Taxol production of T. chinensis cells by low-energy US.     

Dual positional specificity and expression of non-traditional lipoxygenase induced by wounding and methyl jasmonate in maize seedlings

Lipoxygenases (LOXs) catalyze the formation of fatty acid hydroperoxides involved in responses to stresses. This study examines the expression of a non-traditional dual positional specific maize LOX in response to wounding or methyl jasmonate (MeJA). Full-length maize LOX cDNA was expressed in Escherichia coli, and recombinant LOX was purified and characterized enzymatically. RP-HPLC and GC-MS analysis showed that the purified LOX converts alpha-linolenic acid into 13-hydroperoxylinolenic acid and 9-hydroperoxylinolenic acid in a 6:4 ratio. LOX mRNA accumulated rapidly and transiently in response to wounding reaching a peak of expression about 3 h after wounding. This increase followed an initial increase in endogenous jasmonic acid (JA) 1 h after wounding (JA burst). However, the expression of LOX induced by MeJA lasted longer than the expression induced by wounding, and the MeJA-induced expression seemed to be biphasic pattern composed of early and late phases. The expression of LOX in the presence of inhibitors of JA biosynthesis was not completely inhibited, but delayed in wound response and the expression period was shortened in MeJA response. These results suggest that wound-responsive JA burst may trigger the early phase of LOX expression which facilitates biosynthesis of endogenous JA through its 13-LOX activity, and subsequently leads to the activation of the late phase LOX expression in MeJA-treated maize seedlings. Implications of dual positional specificity of maize LOX in the observed expression kinetics are discussed.