Effect of ethylene and 1-methylcyclopropene on chlorophyll catabolism of broccoli florets

Branchlets of broccoli (Brassica oleracea L.) were used to examine ethylene-stimulated chlorophyll catabolism. Branchlets treated with: 1) air (CK); 2) 1 µL·L^–1 1-methylcyclopropene (1-MCP) for 14 hr at 20 °C; 3) 1000 µL·L^–1 ethylene (C₂H₄) for 5 hr at 20 °C; or 4) 1-MCP then C₂H₄, were stored in the dark at 20 °C for up to 3 d. Chlorophyll (Chl) content and branchlet hue angle decreased during the storage period and 1-MCP treatment delayed this change. Chl degradation in broccoli was accelerated by exposure to C₂H₄, especially for Chl a. Prior treatment with 1-MCP prevented degreening stimulated by C₂H₄. Lipoxygenase activity was not altered by any of the treatments, however, 1-MCP with or without ethylene resulted in reduced activity of chlorophyllase (Chlase) and peroxidase (POD). Exposure to C₂H₄ stimulated Chlase activity and extended the duration of high POD activity. Treatment with 1-MCP followed by C₂H₄ resulted in reduced POD activity and delayed the increase in Chlase activity. The results suggest chlorophyll in broccoli can be degraded via the POD – hydrogen peroxide system. Exposure to C₂H₄ enhances activity of Chlase and extends the duration of high POD activity, and these responses may accelerate degreening. Treatment with 1-MCP delays yellowing of broccoli, an effect that may be due to the 1-MCP-induced reduction in POD and Chlase activities.     

Control of ethylene activity in various plant systems by structural analogues of 1-methylcyclopropene

Two structural analogues of 1-methylcyclopropene (1-MCP), 1-ethylcyclopropene (1-ECP) and 1-propylcyclopropene (1-PCP) were found to inhibit ethylene action and thereby the responses to ethylene in various plant systems. When applied prior to exposure to ethylene, the analogues considerably delayed ethylene-induced ripening of avocado and tomato fruits, delayed citrus leaf explants abscission and reversed ethylene-induced swelling and inhibition of elongation in etiolated pea plants. The analogues exerted their effect in a concentration-depended manner, at a range of several parts per million. Of the two analogues, 1-ECP was found in all cases more potent than 1-PCP but less potent then the mother compound 1-MCP. It is proposed that the analogues inhibit ethylene action by competing for the sites of binding on the ethylene receptor, similar to the mode of action suggested for 1-MCP. Findings revealed in this study imply that the competition of ethylene and the analogues for the ethylene site of binding is of a non-competitive nature. The analogues effectively inhibited ethylene action only if applied before the plant material was exposed to ethylene, or in the case of fruits shortly after harvest. Simultaneous application of the analogues and ethylene reduced the inhibitory effect of the analogues. Application of the analogues after exposure to ethylene or after fruit ripening had nullified the inhibitory effect of the analogues. Ripening of fruits, treated with the analogues, was inhibited for a finite period of time after which the fruits ripened normally. This resumption of ripening ability is attributed to presence of free binding sites on the ethylene receptor at the point of recovery from the inhibition. As the analogues are volatile, non-corrosive, non-toxic, odorless compounds and effective at minute concentrations, they can be considered promising candidates for practical use.     

1-MCP对柿贮藏期间几种生理变化的影响

以火柿为试验材料,研究了1-MCP处理对其在常温下贮藏效果及其生理变化的影响。结果表明,1-MCP明显降低了柿采后贮藏前期果实呼吸强度的上升,并延缓了呼吸峰出现的时间及可溶性固形物含量的变化进程,一定程度上降低了膜相对透性,提高了硬果率。但对Vc的分解无明显抑制作用,在贮藏后期处理果有呼吸峰值上升的表现。     

Effect of 1-methylcyclopropene and methylenecyclopropane on ethylene binding and ethylene action on cut carnations

1-Methylcyclopropene (1-MCP), formerly designated as Sis-X, has been shown to be an effective inhibitor of ethylene responses in carnation flowers in either the light or the dark. The binding appears to be to the receptor and to be permanent. A 6 h treatment at 2.5 nl l^–1 is sufficient to protect against ethylene, and 0.5 nl l^–1 is sufficient if exposure is for 24 h. As carnation flowers age, a little higher concentration appears to be needed. Most of the natural increase in ethylene production during senescence is prevented by treatment with 1-MCP. A closely related compound, methylenecyclopropane shows ethylene activity. A tritium labelled 1-MCP (60 mCi mmol^–1) has been prepared. A higher specific activity is needed for more critical studies.     

Ethylene insensitive and post-harvest yellowing retardation in mutant ethylene response sensor (boers) gene transformed broccoli (Brassica olercea var. italica)

A mutant broccoli ers (ethylene-response-sensor, boers) gene was obtained through site directed mutagenesis by replacing the isoleucine with phenylanine at the 62th residue. Two plasmids were constructed with this mutant gene regulated by the CaMV 35S promoter together with the nptII (kanamycin resistance gene) coding sequence and hpt (hygromycin resistance gene), respectively, for the pBI-mERSI62F and pSM1H-mERSI62F plasmids. Genetic transformation of the above two constructs via A. tumefaciens has been conducted to evaluate their effects on floret yellowing of harvested broccoli. Over a hundred transformants have been obtained on the selected cotyledon and hypocotyl explants. PCR and Southern analysis demonstrated integration of the transgenes in the transformants. However, through Southern hybridization, we determined that multi-site integration and DNA rearrangements had occurred in most transformants. Morphological and characteristic alternation such as slower plant growth, shorter plant height, easy branching, late bolting, and relative higher mortality in comparison with other transgenes were noted in some transformants. Transgenic lines showing delayed senescence in leaves and floral heads were obtained. The expression of transgene was confirmed by Northern blot analysis. The transformed progenies also showed ethylene insensitivity in seed germination, detached leaves and harvested florets. Nevertheless, in most lines, the yellowing was only delayed 1–2 days.     

Inhibition of ethylene-induced cellular senescence symptoms by 1-methylcyclopropene, a new inhibitor of ethylene action

Ethylene is known to accelerate flower senescence, but the sequence of events that links its interaction with the tissue and the final senescence symptoms is still obscure. Recently, 1-methylcyclopropene (1-MCP) was found to inhibit ethylene-induced wilting in flowers. This work was carried out in order to investigate the effects of 1-MCP on cellular senescence symptoms in petunia flowers following expossure to ethylene. Cut petunia ( Petunia hybrida ) flowers that were exposed to ethylene for 12 h at concentrations of 1–12 ppm wilted sooner than their untreated counterparts. This effect was abolished by a 6-h pre-treatment with 1-MCP. Immediately following the ethylene treatment, decreases in petal fresh weight and total protein content were measured, along with higher electrolyte leakage, and lower membrane lipid fluidity and protein content. When applied alone, 1-MCP had relatively little impact on these parameters. However, when the flowers were treated with 1-MCP prior to the ethylene treatment, ethylene had no effect. These results indicate that while ethylenes effects on wilting were obvious 3 days after the treatment, cellular parameters were affected already at the end of the treatment. Since 1-MCP repressed these early ethylene effects, it was concluded that it interferes with ethylene action in petunia flowers at a rather early stage, long before apparent wilting.     

Effects of 1-MCP and exogenous ethylene on fruit ripening and antioxidants in stored mango

Mango (Mangifera indica L. cv. Tainong) fruits were harvested at the green-mature stage in Hainan and air-freighted to the laboratory at Peking. The fruits were treated with either 1 μl l⁻¹ 1-MCP or 5 μl l⁻¹ ethylene for 24 h and stored at 20°C for up to 16 days. 1-MCP maintained fruit firmness, whereas exogenous ethylene decreased fruit firmness. Exogenous ethylene accelerated the increase in ethylene and 1-aminocyclopropane-1-carboxylate (ACC) oxidase, whereas 1-MCP reduced both. Exogenous ethylene stimulated and 1-MCP inhibited the production of H₂O₂ of mango fruit during storage. Ascorbic acid was maintained at a high concentration in 1-MCP-treated fruit but was low in ethylene-treated fruit. 1-MCP inhibited activities of antioxidant enzymes including catalase, superoxide dismutase and ascorbate peroxidase. These results suggest that 1-MCP could play a positive role in regulating the activated oxygen metabolism balance. Baogang Wang and Jianhui Wang contributed equally to this work.     

Role of ethylene action in ethylene production and poststorage leaf senescence and survival of pelargonium cuttings

This study investigated the role of ethylene action in ethylene production and in poststorage performance of pelargonium cuttings. Cuttings of zonal pelargonium (Pelargonium x hortorum L.H. Bailey) of the cultivars Isabell and Mitzou were treated with ethylene and with the ethylene action inhibitors 1-methylcyclopropene (MCP), silver-thiosulfate (STS) and silver nitrate (SN) and were stored in the dark at different temperatures (5, 12, and 20 °C) for 48 h. Ethylene concentrations in the storage boxes were monitored and poststorage leaf senescence, survival and root formation of cuttings were determined. Applications of MCP resulted in a significant increase of ethylene evolution by cuttings of both cultivars which was more pronounced with increasing storage temperature. After 48 h of storage at 20 °C, ethylene concentrations were more than 20-fold higher for the MCP-treated cuttings as compared to those of the untreated controls. Also preharvest applications of STS and SN increased ethylene evolution by cuttings, even though these effects were less pronounced. However, application of these inhibitors caused severe poststorage leaf injury. Application of ethylene during storage had no effect on subsequent leaf damage. Leaf senescence during rooting and decay of cuttings, which raised with increasing storage temperature, could only partially been reduced by MCP. The results strongly support the conclusion, that in zonal pelargonium cuttings, ethylene production is controlled by autoinhibition, and clearly indicate, that temperature dependent processes other than ethylene action are substantially involved in storage-induced leaf senescence and decay.     

1-甲基环丙烯处理对采后杨桃果实软化和细胞壁代谢的影响

为探讨1-甲基环丙烯(1-methylcyclopropene, 1-MCP)延缓采后杨桃果实软化的作用机理,本文研究了0.6 μL/L 1-MCP处理对在(15±1)℃、相对湿度90%下贮藏的‘香蜜’甜杨桃(Averrhoa carambola Linn. cv. Xiangmi)果实软化和细胞壁代谢的影响。结果表明：与对照果实相比,1-MCP处理可保持较高的杨桃果实硬度,有效降低果胶酯酶(pectinesterase, PE)、多聚半乳糖醛酸酶(polygalacturonase, PG)、纤维素酶等细胞壁降解酶活性,延缓原果胶、纤维素、半纤维素含量的下降和水溶性果胶含量的增加。因此认为,0.6 μL/L 1-MCP处理能有效控制采后‘香蜜’甜杨桃果实的软化进程,延长果实保鲜期。     

Effects of ethylene and 1-MCP (1-methylcyclopropene) on bud and flower drop in mini <Emphasis Type="Italic">Phalaenopsis</Emphasis> cultivars

Phalaenopsis frequently exhibits bud drop during production and in response to adverse postharvest conditions. The effect of exogenous ethylene on bud drop of mini Phalaenopsis was studied and ethylene sensitivity of four cultivars was compared. Water content, membrane permeability and ABA (abscisic acid) content in floral buds and flowers were determined after ethylene treatment. Exogenous ethylene induced flower bud drop in all tested Phalaenopsis cultivars and the different cultivars showed distinct differences in ethylene sensitivity. The cultivar Sogo ‘Vivien’ exhibited the highest bud drop, water loss and change in membrane permeability in floral petals, while Sogo ‘Berry’ showed the lowest sensitivity. The ethylene inhibitor 1-MCP (1-methylcyclopropene) reduced ethylene-induced floral bud drop in the cultivar Sogo ‘Yenlin’. ABA content in floral buds was increased in response to ethylene and 1-MCP pretreatment inhibited the ethylene-induced increase in ABA levels efficiently. This finding suggests that the observed increase in ABA content during bud drop was mediated by ethylene. The interaction between ABA and ethylene is discussed.     

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 -(p-chlorophenoxy)isobutyric acid (PCIB) and -naphthaleneacetic acid (-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.Prof. Rudich passed away in May 1986.     

GhXB38D represses cotton fibre elongation through ubiquitination of ethylene biosynthesis enzymes GhACS4 and GhACO1

Ethylene plays an essential role in the development of cotton fibres. Ethylene biosynthesis in plants is elaborately regulated by the activities of key enzymes, 1-aminocyclopropane-1-carboxylate oxidase (ACO) and 1-aminocyclopropane-1-carboxylate synthase (ACS); however, the potential mechanism of post-translational modification of ACO and ACS to control ethylene synthesis in cotton fibres remains unclear. Here, we identify an E3 ubiquitin ligase, GhXB38D, that regulates ethylene biosynthesis during fibre elongation in cotton. GhXB38D gene is highly expressed in cotton fibres during the rapid elongation stage. Suppressing GhXB38D expression in cotton significantly enhanced fibre elongation and length, accompanied by the up-regulation of genes associated with ethylene signalling and fibre elongation. We demonstrated that GhXB38D interacts with the ethylene biosynthesis enzymes GhACS4 and GhACO1 in elongating fibres and specifically mediates their ubiquitination and degradation. The inhibition of GhXB38D gene expression increased the stability of GhACS4 and GhACO1 proteins in cotton fibres and ovules, resulting in an elevated concentration of ethylene. Our findings highlight the role of GhXB38D as a regulator of ethylene synthesis by ubiquitinating ACS4 and ACO1 proteins and modulating their stability. GhXB38D acts as a negative regulator of fibre elongation and serves as a potential target for enhancing cotton fibre yield and quality through gene editing strategy.     

Exogenous Eethylene influences flower opening of cut roses (Rosa hybrida) by regulating the genes encoding ethylene biosynthesis enzymes

1 Introduction The simple gaseous phytohormone ethylene as apotent modulator has various roles in plant growth,development and in response to biotic and abioticstress, such as germination, fruit ripening, flower andleaf senescence, and responsiveness to pathogen attack and mechanical damage[1]. The opening and senes-cence of many kinds of flowers are correlated tightly to ethylene, including carnation, petunia, orchid and rose[2]. Generally, roses are classified as ethylene-sen-sitive, however…     

Ethylene-promoted malonylation of 1-aminocyclopropane-1-carboxylic acid participates in autoinhibition of ethylene synthesis in grapefruit flavedo discs

The increase in ethylene formation and in 1-aminocyclopropane-1-carboxylic acid (ACC) content in flavedo tissue of grapefruit (Citrus paradisi Macfad. cv. Ruby Red) in response to excision was markedly inhibited by exogenous ethylene. Ethylene treatment inhibited the synthesis of ACC, but increased the tissue's capability to malonylate ACC to N-malonyl-ACC, resulting in further reduction in the endogenous ACC content. The development of extractable ACC-malonyl-transferase activity in the tissue was markedly promoted by treatment with exogenous ethylene. These results indicate that the autoinhibition of ethylene production in this tissue results not only from suppression of ACC synthesis, but also from promotion of ACC malonylation; both processes reduce the availability of ACC for ethylene synthesis.Abbreviations ACC 1-Aminocyclopropane-1-carboxylic acid - AVG aminoethyoxyvinylglycine (2-amino-4-(2-aminoexthoxy)-trans-3-butenoic acid) - MACC 1-(malonylamino)-cyclopropane-1-carboxylic acid     

Phytochrome-controlled ethylene biosynthesis of intact etiolated bean seedlings

Intact etiolated bean (Phaseolus vulgaris L. cv. Limburgse vroege) seedlings were illuminated with red light (10.5 W·m^-2) for 10 min. After different time intervals ethylene production, and contents of 1-aminocyclopropane-1-carboxylic acid (ACC) and 1-(malonylamino)cyclopropane-1-carboxylic acid were measured. The red-light-induced decrease of ethylene production in 8-d-old intact etiolated bean seedlings was fast, strong and long-lasting ad was mediated through the phytochrome system. This effect appeared to be strictly age-dependent, as it could not be detected in plants younger than 6 d or older than 11 d.The capacity for the conversion of ACC to ethylene was not affected by red light. The inhibitory effect of the light treatment on ethylene production could be related to a reduced free-ACC content. This reduction was a consequence of a temporary non-reversible increase of ACC malonylation and a long-lasting, for a certain time reversible, inhibition of ACC synthesis. The effect of a brief irradiation with red light on the decrease of ethylene production and free-ACC content was completed after about 2 h. Reversibility by far-red, however, persisted for at least 3 h, and was lost between 3 and 6 h.Abbrevation ACC 1-aminocyclopropane-1-carboxylic acid - M-ACC 1-(malonylamino)cyclopropane-1-carboxylic acid     

1-Methylcyclopropene and ethylene as regulators of in vitro organogenesis in kiwi explants

In this paper, we study the influence of ACC, AVG and 1-MCP on in vitro organogenesis of kiwi (Actinidia deliciosa) explants and on ethylene metabolism. Results indicated that increasing ethylene production and accumulation in the head space of the culture vessel by adding ACC to the culture medium inhibited organogenesis, except for rooting, which increased and stimulated ACC oxidase activity threefold, whereas AVG increased the length and number of shoots and leaves and inhibited about 80% ACC synthase activity compared with the reference explants. 1-MCP exerts a stimulatory effect analogous to AVG, increasing ACC synthase activity and organogenesis of kiwi explants. This effect is not reverted by the addition of ACC to the culture medium. Therefore, ethylene production and its accumulation in the headspace of the culture vessels seems to be responsible for the inhibition of shoot development as well as increasing rooting in in vitro cultured kiwi explants.     

Exogenous ethylene influences flower opening of cut roses (<Emphasis Type="Italic">Rosa hybrida</Emphasis>) by regulating the genes encoding ethylene biosynthesis enzymes

The purpose of this paper is to investigate the differential responses of flower opening to ethylene in two cut rose cultivars, ‘Samantha’, whose opening process is promoted, and ‘Kardinal’, whose opening process is inhibited by ethylene. Ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) synthase and oxidase activities were determined first. After ethylene treatment, ethylene production, ACC synthase (ACS) and ACC oxidase (ACO) activities in petals increased and peaked at the earlier stage (stage 3) in ‘Samantha’, and they were much more dramatically enhanced and peaked at the later stage (stage 4) in ‘Kardinal’ than control during vasing. cDNA fragments of three Rh-ACSs and one Rh-ACO genes were cloned and designated as Rh-ACS1, Rh-ACS2, Rh-ACS3 and Rh-ACO1 respectively. Northern blotting analysis revealed that, among three genes of ACS, ethylene-induced expression patterns of Rh-ACS3 gene corresponded to ACS activity and ethylene production in both cultivars. A more dramatic accumulation of Rh-ACS3 mRNA was induced by ethylene in ‘Kardinal’ than that of ‘Samantha’. As an ethylene action inhibitor, STS at concentration of 0.2 mmol/L generally inhibited the expression of Rh-ACSs and Rh-ACO in both cultivars, although it induced the expression of Rh-ACS3 transiently in ‘Kardinal’. Our results suggests that ‘Kardinal’ is more sensitive to ethylene than ‘Samantha’; and the changes of Rh-ACS3 expression caused by ethylene might be related to the acceleration of flower opening in ‘Samantha’ and the inhibition in ‘Kardinal’. Additional results indicated that three Rh-ACSs genes were differentially associated with flower opening and senescence as well as wounding.     

1-甲基环丙烯采后处理对樱桃番茄果实成熟过程的影响

研究了不同浓度(0、0.035、0.07和0.11μL/L)的乙烯受体竞争性抑制剂1-甲基环丙烯(1-MCP)采后处理对绿熟期樱桃番茄的乙烯合成、果实软化、果实色素(叶绿素、茄红素、β-胡萝卜素)含量消长的影响.0.07 μL/L及其以上浓度的1-MCP降低了前期乙烯合成,同时推迟了乙烯释放高峰,但0.035 μL/L浓度的1-MCP处理并不能抑制内源乙烯合成.1-MCP显著延迟了果实软化和叶绿素降解,但并不影响这两个过程的启动.茄红素合成的启动和积累均受到了1-MCP抑制,而1-MCP并不推迟β-胡萝卜素合成的启动,只抑制其积累.这些结果提示了乙烯调节成熟生理过程的不同机制.对于绿熟期的樱桃番茄,0.07～0.11μL/L的1-MCP是实用的有效处理浓度.1-MCP有效浓度可能用于了解果实的乙烯受体水平和乙烯敏感性.