Control Of Ethylene Production Research Articles

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.

Circadian Ethylene Synthesis in Sorghum bicolor: Expression and Control of the System at the Whole Plant Level

Ethylene production by sorghum is rhythmic and the amplitude of the rhythm is increased both by dim, far-red enriched light and in mutant plants deficient in phytochrome B. The mechanisms involved in controlling ethylene production were examined in detail by measuring the rate of ethylene production among organs and tissues, examining the organ-specific levels of ACC (1-aminocyclopropane-1-carboxylic acid, the ethylene precursor) and investigating the contribution of the roots to shoot ethylene production. The results demonstrate that the expanding leaves were the major source of ethylene under dim, far-red enriched light and in the phytochrome B mutant. Enhanced ethylene production by the expanding leaf appeared to be the result of targeted delivery of ACC to this tissue. Root ACC levels were much higher than those in the shoot but roots converted much less of this endogenous ACC to ethylene. Applying ACC to the roots had only a marginal effect on their ethylene production, but greatly increased that of the shoots. Decapitated shoots continued to produce ethylene in a rhythmic pattern but the amplitude decreased with time compared to intact plants. The results collectively suggest that some, but not all, of the shoot ethylene rhythm depends on the transport of ACC from the roots to the shoots.

Asymmetric expression of a poplar ACC oxidase controls ethylene production during gravitational induction of tension wood.

Ethylene is produced in wood-forming tissues, and when applied exogenously, it has been shown to cause profound effects on the pattern and rate of wood development. However, the molecular regulation of ethylene biosynthesis during wood formation is poorly understood. We have characterised an abundant 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene (PttACO1) in the wood-forming tissues of Populus tremula (L.) x P. tremuloides (Michx). PttACO1 is primarily expressed in developing secondary xylem, and is specifically upregulated during secondary wall formation. Nevertheless, according to GC-MS analysis combined with tangential cryosectioning, the distribution of ACC was found to be fairly uniform across the cambial-region tissues. Gravitational stimulation, which causes tension wood to form on the upper side of the stem, resulted in a strong induction of PttACO1 expression and ACC oxidase activity in the tension wood-forming tissues. The ACC levels increased in parallel to the PttACO1 expression. However, the increase on the upper (tension wood) side was only minor, whereas large amounts of both ACC and its hydrolysable conjugates accumulated on the lower (opposite) side of the stem. This suggests that the relatively low level of ACC on the tension wood side is a result of its conversion to ethylene by the highly upregulated PttACO1, and the concurrent accumulation of ACC on the opposite side of the wood is because of the low PttACO1 levels. We conclude that PttACO1 and ACC oxidase activity, but not ACC availability, are important in the control of the asymmetric ethylene production within the poplar stem when tension wood is induced by gravitational stimulation.

Ethylene inhibitors enhance elicitor-induced paclitaxel production in suspension cultures of Taxus spp. cells

The effects of ethylene biosynthesis inhibitors including α-amino isobutyric acid, CoCl 2 and NiCl 2, and an inhibitor of ethylene action, Ag +, on fungal elicitor-induced paclitaxel production were assessed in cell suspension cultures of Taxus chinensis, T. chinensis var. mairei and T. yunnanensis to elucidate the role of ethylene in paclitaxel synthesis. All these ethylene inhibitors enhanced the paclitaxel yield, and most significantly (up to three-fold) by the combination of CoCl 2 (20 μM) and Ag + (30 μM). On the contrary, ethrel, an ethylene-releasing reagent, and acetylsalicylic acid (ASA), an inhibitor of both jasmonic acid (JA) and ethylene biosynthesis, depressed the elicitor-induced paclitaxel production. Importantly, the positive or negative effects of these ethylene inhibitors or generator on paclitaxel production were mainly observed when they were added to the culture before or simultaneously with the fungal elicitor, but became less significant or negligible when they were added 24 h after the elicitor. These findings suggest that the control of ethylene production is important for the elicitation of paclitaxel biosynthesis of the cultured Taxus spp. cells. Therefore, the application of ethylene inhibitors to Taxus cell cultures before elicitor treatment is an effective measure to enhance elicitor-induced paclitaxel production.

Structure, catalytic activity and evolutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, the key enzyme of ethylene synthesis in higher plants.

Both ethylene and the enzymes of ethylene synthesis are subjects of intensive scientific investigation. The present review discusses structure, catalytic activity and evolutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, identified for the first time in ripening tomato in 1979. This enzyme is responsible for the conversion of S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylic acid, which is the key step of ethylene synthesis in higher plants. The role of this enzyme (especially in the fruit ripening) was demonstrated in 1991 in transgenic tomato plants, expressing 1-aminocyclopropane-1-carboxylate synthase antisense RNA. On the basis of mutagenesis and crystallization of the enzyme, new data were provided on the three-dimensional structure and amino-acid residues which are critical for catalysis. The control of ethylene production is of great interest for plant biotechnology because it can delay senescence and overmaturation. These processes are responsible for large loss of vegetables and fruit on storage. Detailed structural and biochemical data are necessary to help design 1-aminocyclopropane-1-carboxylate synthase inhibitors, whose application is expected to have immense agricultural effects.

Structure, catalytic activity and evolutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, the key enzyme of ethylene synthesis in higher plants.

Both ethylene and the enzymes of ethylene synthesis are subjects of intensive scientific investigation. The present review discusses structure, catalytic activity and evolutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, identified for the first time in ripening tomato in 1979. This enzyme is responsible for the conversion of S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylic acid, which is the key step of ethylene synthesis in higher plants. The role of this enzyme (especially in the fruit ripening) was demonstrated in 1991 in transgenic tomato plants, expressing 1-aminocyclopropane-1-carboxylate synthase antisense RNA. On the basis of mutagenesis and crystallization of the enzyme, new data were provided on the three-dimensional structure and amino-acid residues which are critical for catalysis. The control of ethylene production is of great interest for plant biotechnology because it can delay senescence and overmaturation. These processes are responsible for large loss of vegetables and fruit on storage. Detailed structural and biochemical data are necessary to help design 1-aminocyclopropane-1-carboxylate synthase inhibitors, whose application is expected to have immense agricultural effects.

Expression of ACC oxidase genes differs among sex genotypes and sex phases in cucumber.

Ethylene has been implicated as a sex-determining hormone in cucumber: its exogenous application increases femaleness, and gynoecious genotypes were reported to produce more ethylene. In this study, three full-length ACC oxidase cDNAs were isolated from cucumber floral buds. RFLP analysis of a population that segregates for the F(femaleness) locus indicated that CS-ACO2 is linked to F at a distance of 8.7 cM. Expression of two of the genes, CS-ACO2 and CS-ACO3, was monitored in flowers, shoot tips and leaves of different sex genotypes. In situ mRNA hybridization indicated different patternsof tissue- and stage-specific expression of CS-ACO2 and CS-ACO3 in developing flowers. CS-ACO3 expression in mid-stage female flowers was localized to the nectaries, pistil and in the arrested staminoids, whereas CS-ACO2 transcript levels accumulated later and were found in placental tissue, ovary and staminoids. In male flowers, petals and nectaries expressed both genes, whereas ACO2 expression was strong in pollen of mature flowers. In young buds, strong expression was observed along developing vascular bundles. Four sex genotypes were compared for CS-ACO2 and CS-ACO3 expression in the shoot apex and young leaf. FF genotypes had higher transcript levels in leaves but lower levels in the shoot apex and in young buds, as compared to ff genotypes; the shoot-tip pattern is, therefore, inversely correlated with femaleness, and the possibility of a feedback inhibition mechanism underlying such correlation is discussed. The two CS-ACO genes studied displayed a differential response to ethrel treatment in different organs and sex genotypes, further demonstrating the complexity of the mechanisms controlling ethylene production during cucumber floral development.

The effect of polyamines on ethylene synthesis during normal and pollination-induced senescence of Petunia hybrida L. flowers

Senescence of Petunia hybrida L. flowers is accompanied by a climacteric pattern in ethylene production and a rapid decline in the levels of putrescine and spermidine during the preclimacteric phase. The decrease in spermidine is caused by the decline in the availability of putrescine which is initially synthesized from L-arginine via agmatine and N-carbamoylputrescine. Inhibition of putrescine and polyamine synthesis resulted in a rapid drop in the levels of putrescine and spermidine without resulting in a concomitant increase in ethylene production. These results indicate that polyamine synthesis is not involved in the control of ethylene synthesis through its effect on the availability of S-adenosylmethionine, and is confirmed by the results obtained with pollinated flowers. Treatment with polyamines may stimulate or suppress ethylene production in the corolla, depending on the concentrations applied. In unpollinated flowers the onset of the climacteric rise in ethylene production was accelerated after treatment with polyamines. However, in pollinated flowers this process was delayed as a result of treatment with low concentrations of polyamines. The effects of exogenous polyamines on ethylene production in both pollinated and unpollinated flowers indicate that ethylene synthesis in these flowers is not regulated by a feedback control mechanism. Although polyamines do not play a key role in the control of ethylene production during the early stages of senescence through their effect on the availability of S-adenosylmethionine, it appears that they play an important role in some of the other processes involved in senescence.

The Role of Ethylene in the Shedding of Red Raspberry Fruit

In the following experimental programme, the changes in ethylene production and accumulation within raspberry fruit at different stages of development have been related to the loss of abscission zone integrity. The control of ethylene production was investigated by the addition of the inhibitor of ethylene biosynthesis AVG or of the immediate precursor of ethylene ACC

Role of Aminocyclopropane-1-carboxylic Acid (ACC) in Control of Ethylene Production in Fresh and Cold-stored Rose Flowers

Faragher, J. D., Mor, Y. and Johnson, F. 1987. Role of aminocyclopropane-l-carboxylic acid (ACC) in control of ethylene production in fresh and cold-stored rose flowers.—J. exp. Bot. 38: 1839-1847. The relationships between ethylene production, aminocyclopropane-l-carboxylic acid (ACC) content and ethylene-forming-enzyme (EFE) activity during ageing and cold storage of rose flower petals (Rose hybrida L. cv. Gabriella) were investigated. During flower ageing at 20 °C there was a climacteric rise in petal ethylene production, a parallel increase in ACC content, but a continuous decrease in EFE activity. Applied ACC increased petal ethylene production c. 200-fold. During cold storage of flowers at 1 °C there were parallel increases in petal ethylene production and ACC content, to levels greater than those reached in fresh flowers held at 20 °C. EFE activity decreased during storage. Immediately after cold-stored flowers were transferred to 20 °C ethylene production and ACC levels were c. four times greater than in freshly cut flowers. These levels increased to maximum values of two to four times the maximum values reached during ageing of fresh, unstored, flowers. It was concluded that in rose petals ethylene synthesis is probably regulated by ACC levels and that cold storage stimulates ethylene synthesis because it increases the levels of ACC in the petals.

Auxin and the Control of Ethylene Production during the Development and Senescence of Leaves and Fruits

The levels of endogenous IAA and the production of ethylene have been followed during maturation and senescence in herbaceous (Phaseolus vulgaris, Ecballium elaterium) and deciduous (Prunus serrulata) leaves. Comparisons have been made with similar estimations during ripening of a herbaceous fruit. Ecballium elaterium. Whereas a correlation can be made between auxin content and ethylene production in immature tissues, no such relationship exists in senescing or ripening tissues where ethylene production appears to be independent of the total endogenous auxin content. Both IAA and fusicoccin enhance ethylene production in developing leaves but fail to do so in senescent tissues. A mechanism for the regulation of the rate of ethylene biosynthesis is described. This involves modifications in the release from a membrane-bound or membrane-enclosed compartment of cofactor(s) essential to one or more steps in the pathway. The mechanism accommodates observed normal and senescence-related rates of ethylene production.

Inhibition of ethylene production by osmotic shock. Further evidence for membrane control of ethylene production

Inhibition of ethylene production by osmotic shock. Further evidence for membrane control of ethylene production

Methionine Metabolism and Ethylene Biosynthesis in Senescent Flower Tissue of Morning-Glory

In immature rib segments prepared from morning-glory (Ipomoea tricolor) flower buds, the major soluble metabolite formed from tracer amounts of l-methionine-U-(14)C was S-methylmethionine (SMM). In segments of senescing ribs, (14)C was progressively lost from SMM and appeared in free methionine. Immature segments contained about 4 nmoles of free methionine and about 16 nmoles of SMM per 30 segments. As the segments senesced, the methionine content increased about 10-fold while the SMM content remained unchanged; during this time about 0.8 nmole of ethylene was produced per 30 segments. Tracer experiments with l-methionine-U-(14)C, l-methionine-methyl-(3)H, and l-homocysteine thiolactone-(35)S indicated that SMM was capable of acting as a methyl donor, and that in senescent segments the methyl group was utilized for methionine production with homocysteine serving as methyl acceptor. Of the 2 molecules of methionine produced in this reaction, 1 was re-methylated to SMM, and the other contributed to the observed rise in the content of free methionine.Internal pools of methionine and SMM were prelabeled (but not significantly expanded) by overnight incubation on 10 mum l-methionine-U-(14)C. The specific radioactivity of the ethylene subsequently evolved during the senescence of the segments closely paralleled the specific radioactivity of carbon atoms 3 plus 4 of free methionine extracted from the tissue, demonstrating that methionine was the major precursor of ethylene in this system. The specific radioactivity of carbon atoms 3 plus 4 of extracted SMM was about twice that of the free methionine.Based on these results, a scheme for methionine biosynthesis in senescent rib tissue is presented. The operation of this pathway in the control of ethylene production is discussed.