Induction Of Ethylene Production Research Articles

Melatonin enhances salt tolerance by promoting MYB108A-mediated ethylene biosynthesis in grapevines

The signal molecules melatonin and ethylene play key roles in abiotic stress tolerance. The interplay between melatonin and ethylene in regulating salt tolerance and the underlying molecular mechanism of this interplay remain unclear. Here, we found that both melatonin and 1-aminocyclopropane-1-carboxylic acid (ACC, a precursor of ethylene) enhanced the tolerance of grapevine to NaCl; additionally, ethylene participated in melatonin-induced salt tolerance. Further experiments indicated that exogenous treatment and endogenous induction of melatonin increased the ACC content and ethylene production in grapevine and tobacco plants, respectively. The expression of MYB108A and ACS1, which function as a transcription factor and a key gene involved in ethylene production, respectively, was strongly induced by melatonin treatment. Additionally, MYB108A directly bound to the promoter of ACS1 and activated its transcription. MYB108A expression promoted ACC synthesis and ethylene production by activating ACS1 expression in response to melatonin treatment. The suppression of MYB108A expression partially limited the effect of melatonin on the induction of ethylene production and reduced melatonin-induced salt tolerance. Collectively, melatonin promotes ethylene biosynthesis and salt tolerance through the regulation of ACS1 by MYB108A.

Ethylene is all around.

Ethylene is all around.

Nicotiana benthamiana Calreticulin 3a Is Required for the Ethylene-Mediated Production of Phytoalexins and Disease Resistance Against Oomycete Pathogen Phytophthora infestans

Mature Nicotiana benthamiana shows strong resistance to the potato late blight pathogen Phytophthora infestans. By screening using virus-induced random gene silencing, we isolated a gene for plant-specific calreticulin NbCRT3a as a required gene for resistance of N. benthamiana against P. infestans. NbCRT3a encodes an endoplasmic reticulum quality-control (ERQC) chaperone for the maturation of glycoproteins, including glycosylated cell-surface receptors. NbCRT3a-silenced plants showed no detectable growth defects but resistance to P. infestans was significantly compromised. Defense responses induced by the treatment with INF1 (a secretory protein of P. infestans), such as production of reactive oxygen species and accumulation of phytoalexins, were suppressed in NbCRT3a-silenced N. benthamiana. Expression of an ethylene-regulated gene for phytoalexin biosynthesis, NbEAS, was reduced in NbCRT3a-silenced plants, whereas the expression of salicylic acid-regulated NbPR-1a was not affected. Consistently, induction of ethylene production by INF1 was suppressed in NbCRT3a-silenced plants. Resistance reactions induced by a hyphal wall components elicitor prepared from P. infestans were also impaired in NbCRT3a-silenced plants. However, cell death induced by active mitogen-activated protein kinase kinase (NbMEK2(DD)) was not affected by the silencing of NbCRT3a. Thus, NbCRT3a is required for the initiation of resistance reactions of N. benthamiana in response to elicitor molecules derived from P. infestans.

Deciphering cGMP signatures and cGMP-dependent pathways in plant defence

The second messenger, 3’, 5’-cyclic monophosphate (cGMP), is a critical component of many different processes in plants while guanylyl cyclases that catalyse the formation of cGMP from GTP have remained somewhat elusive in higher plants. Consequently, two major aims are the discovery of novel GCs and the identification of cGMP mediated processes. Recently, we have reported temporal signatures of ozone (O3)-induced hydrogen peroxide (H2O2) and nitric oxide (NO) generation, their effect on cGMP generation, and consequent transcriptional changes of genes diagnostic for stress responses in tobacco. We demonstrated that O3 and NO induced early transcriptional activation of the scavenger encoding proteins, alternative oxidase (AOX1a), glutathione peroxidase (GPX) and the induction of ethylene production through aminocyclopropancarboxylic acid synthase (ACS2) are cGMP-independent. By contrast, the early response of the phenylalanine ammonia lyase gene (PALa) and the late response of the gene encoding the pathogenesis-related protein (PR1a) show critical dependence on cGMP. Here we show differential cGMP responses to virulent and avirulent Pseudomonas syringae strains and propose that host-pathogen recognition and/or down-stream processes are transduced by complex cGMP signatures. This is in accordance with the identification of a growing number of multi-domain molecules in Arabidopsis that are reported to contain putative functional GC catalytic centres.

Ozone and nitric oxide induce cGMP‐dependent and ‐independent transcription of defence genes in tobacco

Here, we analyse the temporal signatures of ozone (O3)-induced hydrogen peroxide(H2O2) and nitric oxide (NO) and the role of the second messenger guanosine3′,5′-cyclic monophosphate (cGMP) in transcriptional changes of genes diagnostic for biotic and abiotic stress responses. Within 90 min O3 induced H2O2 and NO peaks and we demonstrate that NO donors cause rapid H2O2 accumulation in tobacco (Nicotiana tabacum) leaf. Ozone also causes highly significant, late (> 2 h) and sustained cGMP increases, suggesting that the second messenger may not be required in all early (< 2 h) responses to O3,but is essential and sufficient for the induction of some O3-dependent pathways.This hypothesis was tested resolving the time course of O3-induced transcript accumulation of alternative oxidase (AOX1a), glutathione peroxidase (GPX),aminocyclopropancarboxylic acid synthase (ACS2) that is critical for the synthesis of ethylene, phenylalanine ammonia lyase (PALa) and the pathogenesis-related protein PR1a.The data show that early O3 and NO caused transcriptional activation of the scavenger encoding proteins AOX1a, GPX and the induction of ethylene production through ACS2 are cGMP independent. By contrast, the early response of PALa and the late response of PR1a show critical dependence on cGMP.

Efficiency of selenium compounds in breaking dormancy of Townsville stylo seeds

Selenium compounds break dormancy of seeds of Townsville stylo (Stylosanthes humilis) through the induction of ethylene production. This was supported by the fact that antiethylenic substances inhibited germination of Se-treated dormant seeds. Under these conditions germination was restored by ethylene-producing compounds. Efficacy of the compounds was monitored through an Efficiency Index (Ief) which takes into account not only the maximal germination but also the optimal concentration responsible for eliciting the process. The most efficient compounds were SeCl4, SeO2 and Na2SeO3 and the least efficient were selenourea, H2SeO4 and selenomethionine. Although ethylene was required for dormancy breakage the compounds triggering the highest ethylene productions were not necessarily the same ones leading to the largest Ief(s). Hence it was concluded that the index is an overall integrating parameter, encompassing uptake of the compound, arrival to target cells and also post-ethylene biosynthesis effects.

An Elicitor from Botrytis cinerea Induces the Hypersensitive Response in Arabidopsis thaliana and Other Plants and Promotes the Gray Mold Disease

ABSTRACT Botrytis cinerea is a necrotrophic fungus that infects over 200 plant species. Previous studies showed that host cells collapse in advance of the hyphae, suggesting secretion of toxins or elicitors. We have partially characterized elicitor activity from intercellular fluid extracted from Arabidopsis thaliana leaves infected with B. cinerea. Treatment of intact leaves or cell cultures with either intercellular fluid from infected leaves or medium from inoculated A. thaliana cell culture induced generation of reactive oxygen species, resulting in reduced photosynthesis, electrolyte leakage, and necrotic lesions that resembled the hypersensitive response (HR). The necrosis was inhibited by diphenyleneiodonium, a specific inhibitor of NADPH oxidase, and by chelating free iron, suggesting the involvement of hydroxyl radicals. The necrosis was also suppressed in dnd1 mutants that are compromised in HR. In contrast, increased cell death was observed in acd2 mutants, indicating the involvement of the host defense signaling pathways. Treatment with the intercellular fluid from infected leaves also induced transcription of pathogenesis-related (PR) genes, such as PR-1, PR-5, HSR203J, and of senescence-associated gene SAG-13. Moreover, rapid transcription of the ethylene-dependent AtEBP gene was detected, indicating induction of ethylene production. The inter-cellular fluid from infected A. thaliana induced cell death in other plants, in line with the lack of B. cinerea specificity. In summary, the intercellular fluid mimicked a range of molecular and physiological host responses that are observed during infection with a live fungus. Moreover, it accelerated the B. cinerea infection, suggesting that the elicitor may act as a pathogenicity factor in the progression of gray mold disease.

Ethylene biosynthesis and ripening behaviour of ‘Hayward’ kiwifruit subjected to some controlled atmospheres

The effects of storage in air (AS), controlled atmosphere (CA) or ultra low oxygen (ULO) on ethylene biosynthesis and ripening of ‘Hayward’ kiwifruit during storage at 0 °C and post-storage at 20 °C, were investigated. Fruit were stored for 60, 120 and 180 days at 0 °C in AS, CA (2%O 2 +5%CO 2 ) and ULO (0.7%O 2 +0.7%CO 2 and 1%O 2 +1%CO 2 ). Freshly harvested fruit and fruit removed from storage were treated with 130 μl/l propylene or propylene-free air for 9 days at 20 °C. Fruit treated with propylene at 20 °C at harvest produced ethylene with a lag period of 3 days, had concomitant 1-aminocyclopropane-1-carboxylic acid (ACC) production, 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) activities, and were ripe after 3–5 days while fruit not treated with propylene were not able to produce ethylene and ripen during the 9 days experiment. AS fruit softened faster during the first 60 days of storage. This effect was reduced in CA and ULO treatments. The soluble solids content (SSC) increased markedly during the first 60 days of storage and remained almost constant thereafter in all treatments. After 9 days shelf life, only AS and CA stored fruit were ripe. Fruit from ULO storage required propylene treatment to ripen fully. When kiwifruit were placed at 20 °C, after 60, 120 or 180 days storage at 0 °C, there was an induction of ethylene production with no lag period in fruit from AS or CA, with or without propylene. There was some ACC content and ACC synthase activity after 60 days storage for all treatments, while ACC oxidase activity increased only upon rewarming of the fruit in AS or CA. Kiwifruit removed from ULO-storage showed drastically reduced capacity to produce ethylene mainly due to low ACC oxidase activity rather than reduced ACC production or ACC synthase activity. Respiration increased upon rewarming of the fruit in all treatments. With storage time, there was a decrease in the capacity of the warmed fruit to produce ethylene and CO 2 as well as in the activities of ACC synthase and ACC oxidase, mostly after 60 days storage.

Effect of 1‐methylcyclopropene on ethylene‐induced abscission in citrus

Pre‐treatment of citrus leaves and leaf explants (Citrus sinensis [L.] Osbeck cv. Shamouti), with 1‐methylcyclopropene (1‐MCP), induced endogenous ethylene production when leaves were further incubated in air. The induction of ethylene production was 1‐MCP concentration‐dependent. Abscission was concomitantly delayed. In leaves pre‐treated with 1‐MCP followed by exposure to ethylene, abscission was significantly delayed in comparison with those without 1‐MCP pre‐treatment. When leaf explants were co‐treated for 24 h with ethylene and 1‐MCP, abscission was delayed quite efficiently. The Lineweaver‐Burke plot yielded a half‐maximal value of 0.234 μl l−1 for the effect of ethylene on abscission. 1‐MCP−1 competed kinetically with ethylene with a Ki value of approximately 1.4−5.5 nl l−1 1‐MCP. Under these experimental conditions there was some competition between 1‐MCP and ethylene. However, ethylene was not able to completely counteract the inhibitory effect of 1‐MCP. Pre‐treatment with 1‐MCP, followed by exogenous ethylene treatment, suppressed the induction of endo‐β‐glucanase (EG) activity at the laminar abscission zone. The ethylene‐dependent accumulation of the hydrolyse gene was demonstrated by blocking the accumulation of CsCel a1 mRNA by 1‐MCP. Six hours of exposure of leaves to 1‐MCP at various times during a total of 24 h ethylene treatment efficiently reversed ethylene induction of CsCel a1 gene at mRNA level up to 18 h. The results demonstrate that the induction of abscission by ethylene is controlled at mRNA level at the abscission zone.

Induction by ozone of ethylene production and an ACC oxidase cDNA in rice (Oryza sativa L.) leaves

Exposure to ozone at 1 µl l−1 for 6 h induced ethylene production in rice (Oryza sativa L. cv. Hitomebore) leaves. The stimulation of ethylene production was detectable 2 h after the start of the exposure to ozone, and lasted for 6 h after the exposure. A 429-bp cDNA fragment encoding ACC oxidase was obtained by RT-PCR from ozone-treated rice leaves. Its nucleotide sequence and deduced amino-acid sequence had 97.2% and 94.4% identity, respectively, to those of OS1A1COX, which was previously obtained from deepwater rice. The abundance of the cDNA increased in accordance with the induction of ethylene production by the exposure to ozone.

Inhibition of auxin-induced ethylene production in cucumber fruit discs by carbon dioxide

The induction of ethylene biosynthesis by indole-3-acetic acid (IAA) and its regulation by CO 2 was examined in cucumber ( Cucumis sativus L., var. Sharp-1) fruit discs. Treatment of discs with IAA significantly stimulated ethylene production and the extent depended on IAA concentration upto 1 mM. The increase in IAA-induced ethylene production was accompanied by increase in the activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase (also known as ethylene-forming enzyme) and a massive accumulation of ACC and 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC). The induction of ethylene production by IAA was inhibited by treatment with CO 2 . The extent of inhibition was dependent upon the concentration of CO 2 . Carbon dioxide inhibited IAA-induced ethylene biosynthesis by suppressing ACC synthase and ACC oxidase activities. Additionally, CO 2 inhibited ACC conjugation into MACC. The results indicate that inhibition of ethylene production by CO 2 in cucumber fruit discs following IAA treatment is due to inhibition of both ACC synthesis and ACC oxidation.

Ethylene as a Possible Mediator of Light- and Nitrate-Induced Inhibition of Nodulation of Pisum sativum L. cv Sparkle

Exposure of pea (Pisum sativum L. cv Sparkle) roots to light suppressed nodulation and induced an increase in ethylene production by roots. Dim light did not affect the number of infections per centimeter of root on the primary root, but most infections were blocked when the infection thread was in the epidermis or in the outer cortex. This is the same stage of infection on lateral roots that is blocked by exogenous ethylene. Silver, an inhibitor of ethylene action, increased nodule number on roots exposed to dim light. Exposure of pea roots to nitrate also suppressed nodulation and induced increased ethylene production by roots. However, induction of ethylene production from roots by nitrate was less than that induced by dim light. Nitrate decreased the number of infections per centimeter of lateral root. With 25 mm nitrate, about half of the infections that occurred were blocked in the epidermis or in the outer cortex. Silver did not reverse the inhibitory effects of nitrate on nodulation. Our data indicate that the inhibitory effect of light may occur via increased ethylene production, but they do not support the hypothesis that ethylene mediates nitrate control of nodule number. The possible role of ethylene in regulating nodule number should be studied in experiments in which light is excluded from the roots.

Regulation of ethylene biosynthesis in citrus leaves infected with Xanthomonas campestris pv. citri

Inoculation of Poncirus trifoliata (L.) Raf. x Citrus Paradisi Macf. (Swingle citrumelo) leaves with Xanthomonas campestris pv. citri (Hasse) Dye (Xc). a nursery strain of bacteria causing citrus canker, induced significant ethylene production. No ethylene biosynthesis was induced by Xanthomonas campestris pv. dieffenbachiae (McCulloh and Pirrone) Dye (Xd), a non pathogen to citrus. Leaves inoculated with Xc had a higher endogenous 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content than the leaves treated with aminoethoxyvinylglycine (AVG) or streptomycin before inoculation. All the inhibitors of ethylene biosynthesis tested were effective in suppression of ethylene production from Xc inoculated leaves. The inhibitors also suppressed the rate of disease progression. Major points of regulation of pathogen induced ethylene appear to reside at the transcriptional and/or translational levels, as indicated by the inhibitor studies. It appears that the pathogen‐induced ethylene biosynthesis in this case is closely associated with disease progression and that denovo induction and activation of ACC synthase is the key step in the induction of ethylene production. The induction of ethylene production as a result of pathogen invasion may be a plant defense response as it leads to the abscission of leaves which helps retard the spread of the pathogen into the plant‐system.

Shoot inversion-induced ethylene production: a general phenomenon?

Shoot inversion induction of ethylene production was found in inverted shoots of corn, peas, soybean, sunflower, tomato, andPharbitis nil. The increases in ethylene production were found to range from two- to threefold in soybean to eightfold in corn and sunflower. The occurrence of peaks of ethylene production ranged from 16 h following shoot inversion in corn to 72 h inPharbitis. That the enhanced ethylene production was due to activation of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase is supported by the finding of increased ACC content in inverted shoots of all species tested. Shoot inversion inhibition of elongation was found in inverted shoots of pea, soybean, sunflower, tomato, andPharbitis nil. This inhibition is thought to be mediated via increased ethylene production in the inverted shoots. That shoot inversion induction of ethylene is not a persistent effect is supported by the finding that ethylene synthesis could be terminated by reorientation of shoots to the upright position and could be reinitiated by the subsequent inversion of the shoots. The effects of shoot inversion on the enhancement of ethylene production and on the inhibition of elongation of the inverted shoot appear to be general phenomena.

Auxin, biosynthesis of ethylene and sex expression in cucumber (Cucumis sativus)

Ethylene production, level of 1-aminocyclopropane-1-carboxylic acid (ACC) and activity of the ethylene forming enzyme (EFE) were higher in apices of gynoecious cucumber (Cucumis sativus cv. Alma) as compared to monoecious cucumber (C. sativus cv. Elem). Application of indole-3-acetic acid (IAA) enhanced ethylene and ACC production in both cultivars. The stimulatory effect of IAA was more pronounced in gynoecious apices. Induction of ethylene production and accumulation of ACC resulting from treatment with IAA were effectively blocked by aminoethoxyvinylglycine (AVG). Content of endogenous IAA, measured by an enzyme immunoassay, was lower in gynoecious cucumber as compared to monoecious one. Treatment of gynoecious plants with the antiauxins α-(p-chlorophenoxy)isobutyric acid (PCIB) and β-naphthaleneacetic acid (β-NAA) did not inhibit female sex expression. It appears that although exogenous IAA enhances ACC and ethylene production, endogenous IAA might not have a major role in the control of sex expression in cucumber of the Beit-Alfa type.

The Induction of Ethylene Production from Pear Cell Culture by Cell Wall Fragments

Macerase, a pectinase-containing enzyme mixture, was used to digest cell walls isolated from cultured pear cells. Following digestion, the reaction mixture was boiled to inactivate enzymes. Addition of soluble aliquots of the mixture to suspension cultures of pear cells led to a rapid and transient production of ethylene by the cells.

Induction of ethylene biosynthesis in tobacco leaf discs by cell wall digesting enzymes

Cellulysin induces ethylene production in tobacco leaf discs by initiating the formation of 1-aminocyclopropane-1-carboxylic acid. Induction occurred within 30 to 60 min of incubation and was inhibited by aminoethoxyvinylglycine, and the antiproteases, PMSF and soybean trypsin inhibitor. Cycloheximide (CHI) at 2.8 μg/ml and chloramphenicol (CAP) at 100 μg/ml did not inhibit this induction although incorporation of the label from (3,4- 14C)methionine into the acid-insoluble fraction was inhibited by 57%. At 14 μg/ml CHI, and CAP, ethylene production was inhibited by 25% while protein synthesis was inhibited by 75%. We suggest that either the low amounts of protein synthesis that appear to be insensitive to CHI is sufficient to induce ethylene biosynthesis or that Cellulysin activates a preexisting but inactive form of ACC synthase to promote ethylene biosynthesis. Also, induction of ethylene production by microbial enzymes that digests plant cell walls may be an initial protective response of plants that serves to combat microbial infection.

Induction of Ethylene Production in ‘Bosc’ Pears by Postharvest Cold Stress1

Abstract Preclimacteric ‘Bosc’ pears held continuously at 20°C produced ethylene at a very low rate and resisted ripening for 12 days. However, if held at 5 or 10° for the first 7 days, ethylene production at 20° began to increase almost immediately. Rapid and uniform ripening resulted. Storage at 0° was considerably less effective in this regard. Further, the longer pears were held at 5, up to 6 days, the greater was their ethylene production capacity at 23°. Softening lagged behind the onset of autocatalytic ethylene production. Thus, cold stress induces a metabolic change leading to accelerated ethylene production which in turn initiates other ripening reactions in ‘Bosc’ pears.

Interaction of ethylene, oxygen and carbon dioxide in the control of fruit ripening

Ethylene production during the climacteric in many fruits, in vegetative tissue treated with IAA, and in flowers which have been emasculated, pollinated or treated with IAA applied to their stigma, increases rapidly and then returns to a low rate. In root sections exposed to IAA this timing apparently is due to the fact that the rate of ethylene production reflects the internal IAA content; the latter increases initially after auxin is applied but rapidly decreases again due to induction or activation of the enzyme systems conjugating and destroying IAA. A similar mechanism may be involved in the induction of ethylene production in fruits.In vivo ethylene is derived from methionine, possibly after the amino acid is activated to form S-adenosyl methionine, by decarboxylation of C1, transfer of C2 possibly as a folic acid derivative, formation of ethylene from C3–C4, and transfer of the S-methyl to a suitable receptor molecule.