Ethylene Perception Inhibitor Research Articles

Gravitropic plant growth regulation and ethylene: an unsought cardinal coordinate for a disused model

According to the Cholodny-Went hypothesis, gravitropic differential growth is brought about by the redistribution of auxin (indolyl-3-acetic acid, IAA). We reinvestigated the relevance of different auxins and studied the role of ethylene in hypocotyls of sunflower and shoots and roots of rye and maize seedlings. Incubation of coleoptiles and of sunflower hypocotyls in solutions of IAA and dichlorophenoxyacetic acid as well as naphthylacetic acid resulted in a two- to threefold length increase compared to water controls. In spite of this pronounced general effect on elongation growth, gravi-curvature was similar to water controls. In contrast to this, inhibition of ethylene synthesis by aminoethoxyvinylglycine prevented differential growth of both hypocotyls and coleoptiles and of roots of maize. In horizontally stimulated maize roots growing on surfaces, inhibition of ethylene perception by methylcyclopropene inhibited roots to adapt growth to the surface, resulting in a lasting vertical orientation of the root tips. This effect is accompanied by up- and down-regulation of a number of proteins as detected by two-dimensional matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. Together the data query the regulatory relevance of IAA redistribution for gravitropic differential growth. They corroborate the crucial regulatory role of ethylene for gravitropic differential growth, both in roots and coleoptiles of maize as well as in hypocotyls.

Petal abscission in rose ( Rosa bourboniana var Gruss an Teplitz) is associated with the enhanced expression of an alpha expansin gene, RbEXPA1

Abscission is a process that involves separation of the organ from the parent plant. In this paper we show that the progressive abscission of petals, commonly observed post-pollination is sensitive to treatment with ethylene in the fragrant varieties of Rosa bourboniana (var Gruss an Teplitz). We also provide the first evidence that the expression of the expansin gene is associated with petal abscission not only under ethylene-induced conditions but also under natural conditions. The gene, RbEXPA1, encodes for a putative protein of 253 amino acids with essential features conserved as in other alpha expansins. The expression of RbEXPA1 increases in abscission zones of petals during the course of natural abscission and post-ethylene treatment. Treatment of flowers with 1-methyl cyclopropene (an ethylene perception inhibitor) results in a delay in abscission and is associated with a simultaneous reduction in the expression of RbEXPA1. Flowers require a longer time for petal abscission under field conditions, and this is correlated with a delay in expression of RbEXPA1 as compared to ethylene treated flowers. Transcript accumulation is specific to petals and is enhanced in response to ethylene. The enhancement in expression is more prominent in the petal abscission zones than in whole petals. Expression of RbEXPA1 is not observed during development of the flower and petal expansion indicating that it is not an expansion related gene. It is concluded that transcriptional up regulation of the ethylene sensitive expansin gene may help in wall modification leading to petal abscission in rose.

Role of ethylene signaling in the production of rice volatiles induced by the rice brown planthopper Nilaparvata lugens

Ethylene signaling pathway plays an important role in induced plant direct defense against herbivores and pathogens; however, up to now, only few researches have focused on its role in induced plant indirect defense, i.e. the release of herbivore-induced volatiles, and the results are variable. Using a model system consisting of rice plants, the rice brown planthopper Nilaparvata lugens and its egg parasitoid Anagrus nilaparvatae, we examined the role of ethylene signaling in the production of rice volatiles induced by N. lugens by measuring both the timing of herbivore-induced ethylene levels and the relationships between ethylene, rice volatiles and attraction of the parasitoid. N. lugens infestation significantly enhanced the release of ethylene during 2–24 h after infestation. Plants treated with ethephon, a compound that breaks down to release ethylene at cytoplasmic pH, released volatiles profiles similar to those released by N. lugens-infested plants, and both of them showed an equal attraction of the parasitoid. Moreover, pretreatment with 1-MCP, an inhibitor of ethylene perception, reduced the release of most of rice volatiles whose amount was enhanced by N. lugens infestation and decreased the attractiveness to the parasitoid. These results demonstrate that ethylene signaling is required for the production of rice volatiles induced by N. lugens.

Inhibition of the ethylene response by 1-MCP in tomato suggests that polyamines are not involved in delaying ripening, but may moderate the rate of ripening or over-ripening

Ethylene initiates the ripening and senescence of climacteric fruit, whereas polyamines have been considered as senescence inhibitors. Ethylene and polyamine biosynthetic pathways share S-adenosylmethionine as a common intermediate. The effects of 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception, on ethylene and polyamine metabolism and associated gene expression was investigated during ripening of the model climacteric fruit, tomato (Solanum lycopersicum L.), to determine whether its effect could be via polyamines as well as through a direct effect on ethylene. 1-MCP delayed ripening for 8 d compared with control fruit, similarly delaying ethylene production and the expression of 1-aminocyclopropane-1-carboxylic acid (ACC)-synthase and some ethylene receptor genes, but not that of ACC oxidase. The expression of ethylene receptor genes returned as ripening was reinitiated. Free putrescine contents remained low while ripening was inhibited by 1-MCP, but increased when the fruit started to ripen; bound putrescine contents were lower. The activity of the putrescine biosynthetic enzyme, arginine decarboxylase, was higher in 1-MCP-treated fruit. Activity of S-adenosylmethionine-decarboxylase peaked at the same time as putrescine levels in control and treated fruit. Gene expression for arginine decarboxylase peaked early in non-treated fruit and coincident with the delayed peak in putrescine in treated fruit. A coincident peak in the gene expression for arginase, S-adenosylmethionine-decarboxylase, and spermidine and spermine synthases was also seen in treated fruit. No effect of treatment on ornithine decarboxylase activity was detected. Polyamines are thus not directly associated with a delay in tomato fruit ripening, but may prolong the fully-ripe stage before the fruit tissues undergo senescence.

Involvement of Negative Feedback Regulation in Wound-Induced Ethylene Synthesis in ‘Saijo' Persimmon

Wounding is one of the most effective stress signals to induce ethylene synthesis in persimmon (Diospyros kaki Thunb.). We found that wound-induced ethylene biosynthesis is subjected to negative feedback regulation in mature 'Saijo' persimmon fruit since ethylene production was enhanced by 1-methylcyclopropene (1-MCP) (an inhibitor of ethylene perception) pretreatment, which was approximately 1.8 fold of that in control tissues (without 1-MCP pretreatment). Wound-induced 1-aminocyclopropane-1-carboxylate (ACC) synthase activity and DK-ACS2 gene expression were substantially increased by 1-MCP pretreatment after 12 h, which resulted in much higher ACC content in 1-MCP pretreated tissues than that in a control after 24 h. These results indicated that wound-induced DK-ACS2 gene expression was negatively regulated by ethylene in mature persimmon fruit. However, 1-MCP pretreatment had no effect on DK-ACO1 gene expression, suggesting the independence of wound-induced DK-ACO1 on ethylene. Out of accord with DK-ACO1 gene expression, ACC oxidase activity was enhanced 48 h after wounding in 1-MCP pretreated tissues, reaching a peak 1.5-fold higher than that in control tissues at 60 h.

EFFECT OF 1-MCP ON PHYSIOLOGICAL CHANGES IN BANANA ´KHAI´

Bananas are classified as climacteric fruit due to their ethylene response. The rate of respiration and the production of ethylene increase during banana ripening and accelerate senescence of plant. 1-Methylcyclopropene, ethylene perception inhibitor, effectively inhibits ethylene responses. Study of 1-MCP fumigation at 50 100 and 250 ppb for 24 hours on storage life and quality of 'Khai' Banana stored at 20°C was determined. The delay of firmness was found in bananas treated with 1-MCP by higher concentration showed more effective. In addition, bananas treated with 250 ppb 1-MCP showed the lowest respiration rate and ethylene production. However, there is no significant difference among treatments for color changes. 1-MCP treatments also prolonged the shelf life of banana to 20 days of storage at 20°C.

Ethylene Signaling Mediates a Maize Defense Response to Insect Herbivory

The signaling pathways that enable plants to mount defenses against insect herbivores are known to be complex. It was previously demonstrated that the insect-resistant maize (Zea mays L.) genotype Mp708 accumulates a unique defense cysteine proteinase, Mirl-CP, in response to caterpillar feeding. In this study, the role of ethylene in insect defense in Mp708 and an insect-susceptible line Tx601 was explored. Ethylene synthesis was blocked with either cobalt chloride or aminoethoxyvinylglycine. Alternatively, ethylene perception was inhibited with 1-methylcyclopropene. Blocking ethylene synthesis and perception resulted in Mp708 plants that were more susceptible to caterpillar feeding. In addition, fall armyworm (Spodoptera frugiperda) larvae that fed on inhibitor-treated Mp708 plants had signifycantly higher growth rates than those reared on untreated plants. In contrast, these responses were not significantly altered in Tx601. The ethylene synthesis and perception inhibitors also reduced the accumulation of Mirl-CP and its transcript mir1 in response to herbivory. These results indicate that ethylene is a component of the signal transduction pathway leading to defense against insect herbivory in the resistant genotype Mp708.

1-Methylcyclopropene (1-MCP) based technologies for storage and shelf life extension

1-MCP is an inhibitor of ethylene perception that can markedly affect ripening and/or senescence processes of many horticultural products. In general, 1-MCP delays ripening and senescence and reduces ethylene production, respiration, colour change and softening. Information about these effects is increasing rapidly and is available on a regularly updated website (http://www.hort.cornell.edu/mcp/). 1-MCP is registered for use on a number of horticultural products in several countries, although commercial information remains limited except for apple fruit and ornamental products. The commercial potential for 1-MCP will be affected by many factors including the product response (especially in relation to quality as perceived by the consumer), how successfully 1-MCP use can be incorporated into handling, storage and transport systems, the scale of the industry involved, competition in the marketplace, and whether it provides access to markets that are otherwise unavailable using current technologies.

Actions and uses of 1-methylcyclopropene (1-MCP).

Abstract A new strategy for controlling ethylene production and thus ethylene-mediated responses during ripening and senescence of fruit, and senescence of ornamental products and vegetative tissues, has emerged with the discovery and commercialization of the inhibitor of ethylene perception, 1-methylcyclopropene (1-MCP). 1-MCP competes with ethylene for binding sites, preventing ethylene perception and subsequent effects of ethylene on metabolism. 1-MCP is available commercially, and registration for use on various horticultural products has occurred worldwide. 1-MCP has been investigated widely as a tool to maintain quality of horticultural products, as well as to investigate the role of ethylene in the physiological and biochemical responses of these products during ripening and senescence. The effects of 1-MCP on ethylene-mediated responses depend on its concentration and the exposure period, product type and post-treatment manipulations such as storage regime and storage period. Research has led to the identification of strengths and limitations in applying 1-MCP-based technology at the commercial level.

Fusarium confers protection against several mycelial pathogens of pepper plants

Inoculation of nonhost pepper (Capsicum annuum) plants with the tomato wilt pathogen, Fusarium oxysporum f.sp. lycopersici (FOL), caused no symptoms and the fungus was not recovered from any part of the plant. FOL, however, partially protected pepper plants from subsequent infection with Phytophthora capsici, Verticillium dahliae or Botrytis cinerea by significantly reducing the percentage of diseased plants and the appearance and intensity of symptoms. FOL did not inhibit the mycelial growth of these pathogens in vitro. The protection induced by FOL against Botrytis was inhibited by 1‐methylcyclopropene (MCP), an inhibitor of ethylene perception, suggesting the involvement of this hormone in the signalling of FOL‐induced resistance. The activities of β‐1,3‐glucanase and peroxidase 48 h after FOL induction were similar to those in control plants. Chitinase activity, however, was higher in the stems of plants inoculated with FOL. A study of the levels of phenolic compounds revealed that cell‐wall‐bound phenolics were more abundant in plants treated with FOL, especially in stems, while soluble phenolic contents did not differ.

Efficacy of New Inhibitors of Ethylene Perception in Improvement of Display Quality of Miniature Potted Roses (Rosa hybrida L.)

1-Octylcyclopropene (1-OCP) and 1-Decylcyclopropene (1-DCP), ethylene receptor inhibitors, analogues to 1-MCP, substituted with longer carbon chain in the 1-position were investigated in miniature potted roses cultivar ’Lavender‘. All levels of both chemicals protected as compared to untreated plants. 1-OCP and 1-DCP were the most effective at concentrations 1000 and 1500 nl l−1, which was five times higher than the concentration of 1-methylcyclopropene (1-MCP) (200 nl l−1) used as a standard. The effectiveness of 1-OCP and 1-DCP was a function of time and temperature. At short (2 h) exposure times, the plants were highly sensitive to ethylene. Exposure time of 4 h for both 1-OCP and 1-DCP was sufficient to improve display life of miniature roses and longer exposures did not have any additional beneficial effect. Apparently, exposing miniature potted roses to various temperatures did not have an influence on the performance of both 1-OCP and 1-DCP while low temperature at 5 °C reduced their performance. The reasons for differences in the effects of these compounds are discussed.

1-METHYLCYCLOPROPENE (1-MCP) BASED TECHNOLOGIES FOR STORAGE AND SHELF-LIFE EXTENSION

1-MCP is an inhibitor of ethylene perception that can affect ripening and/or senescence processes in fruit, vegetables and ornamental products. Responses to 1-MCP vary widely, including within a product type, perhaps because of cultivar and/or storage regime differences. In general, however, 1-MCP delays ripening and senescence and reduces ethylene production, respiration, color change and softening. Information about these effects is increasing rapidly and is available on a regularly updated web site (http://www.hort.cornell.edu/mcp/). 1-MCP is registered for use on a number of horticultural products in several countries, although commercial information remains limited except for apple fruit and ornamental products. The commercial potential for 1-MCP will be affected by many factors including the product response (especially in relation to quality as perceived by the consumer), how successfully 1-MCP use can be incorporated into handling, storage and transport systems, the scale of the industry involved, competition in the marketplace, and whether it provides access to markets that are otherwise unavailable using current technologies.

A GH3-like gene, CcGH3, isolated from Capsicum chinense L. fruit is regulated by auxin and ethylene*

Auxin, which has been implicated in multiple biochemical and physiological processes, elicits three classes of genes (Aux/IAAs, SAURs and GH3s) that have been characterized by their early or primary responses to the hormone. A new GH3-like gene was identified from a suppressive subtraction hybridization (SSH) library of pungent pepper (Capsicum chinense L.) cDNAs. This gene, CcGH3, possessed several auxin- and ethylene-inducible elements in the putative promoter region. Upon further investigation, CcGH3 was shown to be auxin-inducible in shoots, flower buds, sepals, petals and most notably ripening and mature pericarp and placenta. Paradoxically, this gene was expressed in fruit when auxin levels were decreasing, consistent with ethylene-inducibility. Further experiments demonstrated that CcGH3 was induced by endogenous ethylene, and that transcript accumulation was inhibited by 1-methylcyclopropene, an inhibitor of ethylene perception. When over-expressed in tomato, CcGH3 hastened ripening of ethylene-treated fruit. These results implicate CcGH3 as a factor in auxin and ethylene regulation of fruit ripening and suggest that it may be a point of intersection in the signaling by these two hormones.

POST-HEAT STRESS RESPIRATION PATTERN OF TULIP BULBS IN STORAGE

Dutch-grown tulip bulbs are shipped around the world via ocean freight. Normal transport temperatures are 17 to 20°C, but bulbs can be improperly subjected to high temperature stress due to equipment failure or mishandling. To understand effects of heat stress on internal metabolism of tulip bulbs, we determined the responses to heat treatment of a heat sensitive cultivar (‘Apeldoorn’) and a heat-resistant cultivar (‘Sevilla’). In addition, we tested the hypothesis that heat-induced injuries are related to endogenous ethylene production by treating bulbs with an inhibitor of ethylene perception, 1-methylcyclopropene (1-MCP), prior to heat treatment. Bulbs, either untreated or treated with 1-MCP, were exposed to 35°C for 1 to 7d, and then respirations rates at 17°C were assessed daily. For non-heated bulbs, respiration rates of the heat-resistant cultivar ‘Sevilla’ were much higher than ‘Apeldoorn’. For heated bulbs, respiration rates generally increased as the length of heat stress increased, and patterns of change were similar for both cultivars. Highest rates of respiration over time were found at 2 or 3 days after removal from heat. Effects of 1-MCP were significant, but depended on the stress level.

Ethylene modulates the susceptibility of the root for nodulation in actinorhizal Discaria trinervis

Ethylene is produced by plants in response to a wide variety of environmental signals and mediates several developmental processes in higher plants. We investigated whether ethylene has a regulatory function in nodulation in the actinorhizal symbiosis between Discaria trinervis and Frankia BCU110501. Roots of axenic D. trinervis seedlings showed aberrant growth and reduced elongation rate in the presence of ethylene donors [i.e. 2‐aminocyclopropane carboxylic acid (ACC) and 2‐chloroethylphosphonic acid (CEPA)] in growth pouches. By contrast, inhibitors of ethylene synthesis (aminoethoxyvinylglycine, AVG) or perception (Ag+) did not modify root growth. This indicates that the development of D. trinervis roots is sensitive to elevated ethylene levels in the absence of symbiotic Frankia. The drastic response to higher ethylene levels did not result in a systemic impairment of root nodule development. Nodulation occurred in seedlings inoculated with Frankia BCU110501 in the presence of ethylene donors or inhibitors. Overall, the ability of the seedlings to shut down nodule formation in the younger portions of the root (i.e. to autoregulate nodulation) was not significantly impaired by a modification of endogenous ethylene levels. In contrast, we detected subtle changes in the nodulation pattern of the taproots. As a result of exposing the roots to CEPA, less nodules developed in older portions of the taproot. In line with this observation, AVG or Ag+ caused the opposite effect, i.e. a slight increase in nodulation of the mature regions of the taproot. These results suggest that ethylene is involved in modulating the susceptibility for nodulation of the basal portion of D. trinervis seedling roots.

The role of auxin and ethylene for gravitropic differential growth of coleoptiles and roots of rye- and maize seedlings

The relevance of auxin and ethylene for differential gravitropic growth has been analyzed both in shoots and roots of etiolated rye- and maize seedlings. As previously demonstrated for indolyl-3-acetic acid (IAA), incubation of coleoptiles in dichlorophenoxy acetic acid (2,4-D) resulted in a two- to threefold length increase compared to water controls. In spite of this immense effect on elongation growth, gravi-curvature was similar to water controls. In contrast, inhibition of ethylene synthesis prevented differential growth of abraded coleoptiles as well as of roots without a significant inhibiting effect on elongation. Inhibition of ethylene perception in horizontally stimulated maize roots growing on surfaces eliminated the capacity of the roots to adapt growth to the surface and a vertical orientation of the root tip. This effect is accompanied by up- and down-regulation of a number of proteins as detected with the 2D-MALDI-TOF (matrix-assisted laser desorption ionization- time of flight) method. Exogenous ethylene inhibited growth but enhanced gravitropic curvature in roots that were “freely” gravistimulated in a horizontal position, exhibiting a pronounced “waving” behavior. Together the data challenge the regulatory relevance of IAA-redistribution for gravitropic differential growth. They corroborate the crucial regulatory relevance of ethylene for gravitropic growth, in both roots and coleoptiles.

Downstream divergence of the ethylene signaling pathway for harpin-stimulated Arabidopsis growth and insect defense.

Ethylene (ET) signal transduction may regulate plant growth and defense, depending on which components are recruited into the pathway in response to different stimuli. We report here that the ET pathway controls both insect resistance (IR) and plant growth enhancement (PGE) in Arabidopsis (Arabidopsis thaliana) plants responding to harpin, a protein produced by a plant pathogenic bacterium. PGE may result from spraying plant tops with harpin or by soaking seeds in harpin solution; the latter especially enhances root growth. Plants treated similarly develop resistance to the green peach aphid (Myzus persicae). The salicylic acid pathway, although activated by harpin, does not lead to PGE and IR. By contrast, PGE and IR are induced in both wild-type plants and genotypes that have defects in salicylic acid signaling. In response to harpin, levels of jasmonic acid (JA) decrease, and the COI1 gene, which is indispensable for JA signal transduction, is not expressed in wild-type plants. However, PGE and IR are stimulated in the JA-resistant mutant jar1-1. In the wild type, PGE and IR develop coincidently with increases in ET levels and the expression of several genes essential for ET signaling. The ET receptor gene ETR1 is required because both phenotypes are arrested in the etr1-1 mutant. Consistently, inhibition of ET perception nullifies the induction of both PGE and IR. The signal transducer EIN2 is required for IR, and EIN5 is required for PGE because IR and PGE are impaired correspondingly in the ein2-1 and ein5-1 mutants. Therefore, harpin activates ET signaling while conscribing EIN2 and EIN5 to confer IR and PGE, respectively.

Alleviation of Nitric Oxide-induced Flower Abscission and Leaf Toxicity in Phlox by Sucrose and 1-MCP

Low concentration fumigation with nitric oxide (NO*) has been shown to extend the postharvest life of a range of flowers, fruits and vegetables by down-regulating ethylene production. Since ethylene is involved in flower abscission and leaf senescence of `John Fanick' phlox cut flower heads, a superior selection of perennial phlox (Phlox paniculata L.) bearing attractive long-lasting flowers, we have evaluated the effect of NO* delivered in vivo using sodium nitroprusside (SNP) as the source of NO* donor, on postharvest performance of `John Fanick' phlox flower heads. Although the presence of SNP (10-200 μmol·L-1) in the vase solution promoted the abscission of the open flowers, the young flower buds continued to open even in the presence of high SNP concentrations. On the other hand, at high SNP concentrations, the leaves became either yellow, or more frequently turned progressively black and senesced. Inclusion of sucrose in the vase solution, or pretreatment of flower heads with either 1-MCP or STS, significantly delayed the abscission of flowers and blackening of leaves. The pretreatment of flower heads with either 1-MCP or STS, or the presence of sucrose in the vase, together with SNP, greatly reduced the toxicity of the latter chemical resulting in improved postharvest display life. These results indicate that in `John Fanick' the leaves are relatively more susceptible to NO*-induced toxicity than the flowers. However, both sucrose and ethylene perception inhibitors are able to minimize the toxicity of high concentrations of NO* delivered in vivo via SNP.

Sucrose and Ethylene Biosynthesis/Perception Inhibitors Additively Enhance Postharvest Display Life of Cut Racemes of Lupinus havardii Wats.

Over the years, by recurrent phenotypic selection, breeding and evaluation, we have developed blue, white, and pink flowered lines of Big Bend bluebonnet (L. havardii Wats.). The racemes, which differ in their sensitivity to ethylene, hold promise as a new specialty cut flower crop. The key determinants of postharvest longevity and performance of cut racemes are flower abscission and senescence. Our studies indicated that the addition of sucrose in the holding solution greatly enhanced the vase life, although the optimum sucrose concentration varied considerably in different lines. In blue flowered lines (e.g., `Texas Sapphire', Blue Select) sucrose concentration greater than 2% induced `osmotic wilting' followed by senescence of the standard petal (banner spot petal), while the petals in white flowered lines (e.g., `Texas Ice', White Select) did not show any wilting even in 4% to 6% sucrose. Ethylene perception inhibitors such as 1-MCP or STS completely suppressed the induction of flower abscission in racemes of all the bluebonnet lines. Ethylene biosynthesis inhibitors (e.g., ReTain, CO++), on the other hand, were relatively less effective than 1-MCP/STS. Both ethylene perception as well as biosynthesis inhibitors, in combination with sucrose, acted additively and further enhanced the postharvest performance by delaying flower abscission/senescence.

Comparison of ethylene- and wound-induced responses in fruit of wild-type, rin and nor tomatoes

Abstract Responses of wild-type, rin , and no r tomato ( Lycopersicon esculentum Mill.) fruit to exogenous ethylene and wounding were compared to identify the events directly controlled by each mutation. When rin and nor fruit were exposed to exogenous ethylene, respiration and accumulation of E4 , E8 , and LE - ACO1 mRNAs increased to levels similar to those observed in the wild-type fruit, indicating that expression of these genes is independent of either mutations. In contrast, accumulation of LE - ACS4 and PG mRNAs was not restored by exogenous ethylene treatment in both mutants, indicating that the expression of both genes requires both RIN and NOR . Interestingly accumulation of LE - ACS2 mRNA was stimulated by ethylene treatment in rin fruit but not in nor fruit. This suggests that the signaling pathways of RIN and NOR affect the regulation of ripening-associated genes in distinct ways, at least with respect to the expression of LE - ACS2 . Wounding induced ethylene biosynthesis and increased accumulation of LE - ACS2 , LE - ACS6 , LE - ACO1 , and E4 mRNAs in both wild-type and the mutants to the same extent. Treatment with 1-methylcyclopropene (1-MCP), a potent inhibitor of ethylene perception, preceding wounding, inhibited the increase of E4 mRNA but did not affect the expression profile of other genes in all the lines tested. These results show that the wounding signal that controls LE - ACS2 , LE - ACS6 , and LE - ACO1 is independent of rin and nor mutations and ethylene signaling.