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.     

Expression of ethylene biosynthetic and receptor genes in rose floral tissues during ethylene-enhanced flower opening

Ethylene production, as well as the expression of ethylene biosynthetic (Rh-ACS1-4 and Rh-ACO1) and receptor (Rh-ETR1-5) genes, was determined in five different floral tissues (sepals, petals, stamens, gynoecia, and receptacles) of cut rose (Rosa hybrida cv. Samantha upon treatment with ethylene or the ethylene inhibitor 1-methylcyclopropene (1-MCP). Ethylene-enhanced ethylene production occurred only in gynoecia, petals, and receptacles, with gynoecia showing the greatest enhancement in the early stage of ethylene treatment. However, 1-MCP did not suppress ethylene production in these three tissues. In sepals, ethylene production was highly decreased by ethylene treatment, and increased dramatically by 1-MCP. Ethylene production in stamens remained unchanged after ethylene or 1-MCP treatment. Induction of certain ethylene biosynthetic genes by ethylene in different floral tissues was positively correlated with the ethylene production, and this induction was also not suppressed by 1-MCP. The expression of Rh-ACS2 and Rh-ACS3 was quickly induced by ethylene in gynoecia, but neither Rh-ACS1 nor Rh-ACS4 was induced by ethylene in any of the five tissues. In addition, Rh-ACO1 was induced by ethylene in all floral tissues except sepals. The induced expression of ethylene receptor genes by ethylene was much faster in gynoecia than in petals, and the expression of Rh-ETR3 was strongly suppressed by 1-MCP in all floral tissues. These results indicate that ethylene biosynthesis in gynoecia is regulated developmentally, rather than autocatalytically. The response of rose flowers to ethylene occurs initially in gynoecia, and ethylene may regulate flower opening mainly through the Rh-ETR3 gene in gynoecia.     

Ethylene biosynthetic genes are differentially expressed during carnation (Dianthus caryophyllus L.) flower senescence

Ethylene production and expression patterns of an 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (CARAO1) and of two ACC synthase (EC 4.4.1.14) genes (CARACC3 and CARAS1) were studied in floral organs of cut carnation flowers (Dianthus caryophyllus L.) cv. White Sim. During the vase life and after treatment of fresh flowers with ethylene, production of ethylene and expression of ethylene biosynthetic genes first started in the ovary followed by the styles and the petals. ACC oxidase was expressed in all the floral organs whereas, during the vase life, tissue-specific expression of the two ACC synthase genes was observed. After treatment with a high ethylene concentration, tissue specificity of the two ACC synthase genes was lost and only a temporal difference in expression remained. In styles, poor correlation between ethylene production and ACC synthase (CARAS1) gene expression was observed suggesting that either activity is regulated at the translational level or that the CARAS1 gene product requires an additional factor for activity.Isolated petals showed no increase in ethylene production and expression of ethylene biosynthetic genes when excised from the flower before the increase in petal ethylene production (before day 7); showed rapid cessation of ethylene production and gene expression when excised during the early phase of petal ethylene production (day 7) and showed a pattern of ethylene production and gene expression similar to the pattern observed in the attached petals when isolated at day 8. The interorgan regulation of gene expression and ethylene as a signal molecule in flower senescence are discussed.     

Pollination-Induced Expression of Ethylene Biosynthetic Genes at Transcription Level in Orchid Flowers

The authors investigated pollination-induced ethylene production and expression patterns of genes encoding 1-aminocyclopropane-l-carboxylate (ACC) synthase and ACC oxidase in orchid flowers (Doritaenopsis hybrida Hort. ). Following pollination both ACC synthase and ACC oxidase mRNAs were detected in the different organs of flowers, and the patterns of both ACC synthase and ACC oxidase mRNA accumulation were similar, mRNA accumulation of ACC synthase mRNA was more organ-specific than that of ACC oxidase mRNA. However, ACC oxidase mRNAs were much more abundant than ACC synthase mRNAs in the flower organs.     

授粉诱导兰花花部乙烯生物合成基因在转录水平上的表达

朵丽蝶兰（Ｄｏｒｉｔａｅｎｏｐｓｉｓｈｙｂｒｉｄａ Ｈｏｒｔ．）的花授粉后,测定乙烯的产生,并分析授粉后花部各器官乙烯生物合成的ＡＣＣ合成酶和ＡＣＣ氧化酶两个基因转录水平上的表达。授粉后在花部均可探测到ＡＣＣ合成酶和ＡＣＣ氧化酶的ｍ ＲＮＡ。在花部不同器官之间,此两种酶的ｍ ＲＮＡ的积累水平均表现出一些差异。ＡＣＣ合成酶的ｍ ＲＮＡ 积累与ＡＣＣ氧化酶相比,具有更明显的特异性。而ＡＣＣ氧化酶ｍ ＲＮＡ 的积累水平远比ＡＣＣ合成酶高     

Recovery of ethylene biosynthesis in diazocyclopentadiene (DACP)-treated tomato fruit

Diazocyclopentadiene (DACP), a competitive ethylene action inhibitor binds irreversibly to the ethylene receptor to reduce tissue responses to ethylene. Tomato fruit (Lycopersicon esculentum Mill cv lsquo;Rondellorsquo;) were treated with DACP at the mature green stage. Ethylene biosynthesis and respiration rate were depressed. Color changes from green to red were delayed. Compared to the control, ACC content increased and ACC oxidase activity in vivo decreased in DACP-treated fruit. Thus, decrease of ethylene production caused by DACP treatment was due to the reduction of ACC oxidase activity. The decline in ripening subsequently recovered after DACP treatment. Results from the Northern analysis for gene expression of ACC synthase and ACC oxidase, showed that expression of both genes declined in DACP-treated fruit, and then recovered. Therefore the recovery of ethylene production was due to the recovery in gene expression and activity of ACC oxidase. We conclude that the effects of DACP on ethylene biosynthesis are on expression of ACC synthase and ACC oxidase genes, and/or regulation of ACC oxidase activity.     

Ethylene and fruit ripening

The latest advances in our understanding of the relationship between ethylene and fruit ripening are reviewed. Considerable progress has been made in the characterisation of genes encoding the key ethylene biosynthetic enzymes, ACC synthase (ACS) and ACC oxidase (ACO) and in the isolation of genes involved in the ethylene signal transduction pathway, particularly those encoding ethylene receptors ( ETR ). These have allowed the generation of transgenic fruit with reduced ethylene production and the identification of the Nr tomato ripening mutant as an ethylene receptor mutant. Through these tools, a clearer picture of the role of ethylene in fruit ripening is now emerging. In climacteric fruit, the transition to autocatalytic ethylene production appears to result from a series of events where developmentally regulated ACO and ACS gene expression initiates a rise in ethylene production, setting in motion the activation of autocatalytic ethylene production. Differential expression of ACS and ACO gene family members is probably involved in such a transition. Finally, we discuss evidence suggesting that the NR ethylene perception and transduction pathway is specific to a defined set of genes expressed in ripening climacteric fruit and that a distinct ETR pathway regulates other ethylene-regulated genes in both immature and ripening climacteric fruit as well as in non-climacteric fruit. The emerging picture is one where both ethylene-dependent and -independent pathways coexist in both climacteric and non-climacteric fruits. Further work is needed in order to dissect the molecular events involved in individual ripening processes and to understand the regulation of the expression of both ethylene-dependent and -independent genes.     

Effects of methyl jasmonate (MeJA) on the dark-induced senescence in oat (Avena sativa L.) leaf segments

To investigate the relationship between methyl jasmonate (MeJA) and ethylene in leaf senescence, we studied the effects of MeJA on ethylene production and ethylene biosynthetic enzyme activities in oat(Avena sativa L.) leaf segments incubated in darkness. MeJA promoted dark-induced senescence judged from the contents of chlorophyll and protein, and increased ethylene production 6 times of the control. MeJA also increased the activities of ethylene biosynthetic enzymes, 1-aminocyclopropane carboxylic acid (ACC) synthase and ACC oxidase as compared to control. In MeJA-treated leaf segments, ACC synthase activity reached its maximum level at 24 h of incubation and ACC oxidase activity peaked at 6 h of incubation. Aminoethoxyvinylglycine (AVG) and Co²⁺, inhibitors of ACC synthase and ACC oxidase respectively, reduced MeJA-induced ethylene production. They also delayed leaf senescence that was promoted by the treatment of MeJA. From these results, we can suggest that MeJA increased the activities of ACC synthase and ACC oxidase, these increased activities lead to increase in ethylene production and this increased ethylene production might promote dark-induced leaf senescence.     

Ethylene regulation of fruit ripening: Molecular aspects

Progress in ethylene regulating fruit ripening concerning itsperception and signal transduction and expression of ACC synthaseand ACC oxidase genes is reviewed. ACC synthase and ACC oxidasehave been characterized and their genes cloned from various fruittissues. Both ACC synthase and ACC oxidase are encoded bymultigene families, and their activities are associated withfruit ripening. In climacteric fruit, the transition toautocatalytic ethylene production appears to be due to a seriesof events in which ACC sythase and ACC oxidase genes have beenexpressed developmentally. Differential expression of ACCsynthase and ACC oxidase gene family members is probably involvedin such a transition that ultimately controls the onset of fruitripening.In comparison to ACC synthase and ACC oxidase, less is knownabout ethylene perception and signal transduction because of thedifficulties in isolating and purifying ethylene receptors orethylene-binding proteins using biochemical methods. However, theidentification of the Nr tomato ripening mutant as anethylene receptor, the applications of new potent anti-ethylenecompounds and the generation of transgenic fruits with reducedethylene production have provided evidence that ethylenereceptors regulate a defined set of genes which are expressedduring fruit ripening. The properties and functions of ethylenereceptors, such as ETR1, are being elucidated.Application of molecular genetics, in combination withbiochemical approaches, will enable us to better understand theindividual steps leading from ethylene perception and signaltransduction and expression of ACC synthase and ACC oxidase genefamily member to the physiological responses.     

Manipulation of ethylene biosynthesis

The plant hormone ethylene is involved in many plant processes ranging from seed germination to leaf and flower senescence and fruit ripening. Ethylene is synthesized from methionine, via S-adenosyl-L-methionine (SAM) and 1-amino-cyclopropane-1-carboxylic acid (ACC). The key ethylene biosynthetic enzymes are ACC synthase (ACS) and ACC oxidase (ACO). Manipulation of ethylene biosynthesis by chemicals and gene technology is discussed. Biotechnological modification of ethylene synthesis is a promising method to prevent spoilage of agricultural and horticultural products.     

嫁接对网纹甜瓜果实乙烯生物合成及CmACO1基因表达的影响

以“新汉城翠蜜”网纹甜瓜为接穗,以“圣砧一号”南瓜为砧木进行嫁接,研究嫁接对目光温室网纹甜瓜果实乙烯生物合成及CmACO1基因转录水平表达的影响。结果表明：嫁接明显降低了网纹甜瓜果实ACC含量及乙烯释放量,在乙烯释放高峰时,嫁接的网纹甜瓜果实乙烯释放量比自根的降低了12．6％;嫁接降低了果实中ACC合成酶和ACC氧化酶活性,其最大值分别比自根网纹甜瓜降低了9．0％和6．8％;嫁接抑制了CmACO1的表达,其相对表达量最大值比自根网纹甜瓜降低了39．0％;嫁接网纹甜瓜果实中乙烯释放高峰、ACC合成酶和ACC氧化酶活性峰值及CmACO1相对表达量峰值出现的时间均比自根的延迟了3d。     

1,1-Dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS) does not inhibit the in vitro activities of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and ACC synthase obtained from senescing carnation Dianthus caryophyllus L.) petals

The effects of 1,1-dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS) on the in vitro activities of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and ACC synthase isolated from senescing carnation petals were investigated. In contrast to a previous proposal, DPSS at 1 mM did not inhibit the in vitro activity of ACC oxidase. It was confirmed that DPSS does not inhibit ACC synthase activity. DPSS probably does not exert its inhibitory action on ethylene production by a direct action on ACC oxidase and ACC synthase, but by some unknown action.