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.     

Interrelationship between the Different Flower Parts during Emasculation-Induced Senescence in Cymbidium Flowers

In Cymbidium flowers emasculation by removal of the anther capand the pollinia, led to rapid colouration of the lip and advancedwilting of the petals and sepals. The ethylene production ofwhole flowers showed an emasculation-induced early peak in ethyleneevolution followed some days later by a second increase concomitantwith the wilting of the flower. In non-emasculated flowers theethylene production increased later and simultaneously withcolouration of the lip and wilting of the petals and sepals.At all stages of senescence, the contribution of the lip, petals,and sepals to the total amount of ethylene produced was negligible. Parallel to the increase in ethylene production of whole flowers,an increase in 1-aminocyclopropane-l-carboxylic acid (ACC) andmalonyl-ACC (MACC) in the central column and, to a lesser extent,in the ovary was observed. Also an increase in internal ethyleneconcentration was demonstrated and this, in contrast, was apparentin all the different flower parts. The activity of the ethylene-formingenzyme in lips, petals, and sepals showed an increase afteremasculation and such an effect could also be induced by treatmentof isolated lips with low concentrations of ethylene. The data indicate that senescence in Cymbidium flowers is regulatedby the central column and perhaps the ovary and that both ACCand ethylene may play a signalling role in inter-organ communication. Key words: 1-aminocyclopropane-l-carboxylic acid, ethylene, Cymbidium, senescence     

Aroma production from cut sweet pea flowers (Lathyrus odoratus): the role of ethylene

The major components of the scent of cut sweet pea flowers ( Lathyrus odoratus L. cv Royal Wedding) are (E) and (Z)-ocimene, linalool, nerol, geraniol and phenylacetaldehyde. The aroma is almost exclusively produced by the standard and wing petals, with very little emanating from the keel petals and other floral structures. Only traces of these volatiles were detected in the liquid excreted by glandular trichomes on the surface of the scented petals. Once flowers are cut for display they produce increasing amounts of ethylene which induces wilting after 48 h and petal abscission 24 h later. The rate of linalool and ocimene emission declines over the first 48 h to approximately 10% of that directly after harvest. Ethylene production is not saturating during the first 24 h of vase life and exogenous ethylene further accelerates the senescence processes and loss of fragrance. Addition of the ethylene antagonists 1-methylcyclopropene (1-MCP) and silver thiosulphate (STS) delayed wilting and abscission for several days and similarly inhibits the decline in terpenoid emission.     

多胺对月季切花衰老过程中生理生化和瓶插寿命的影响

精胺处理可保持月季切花瓶插前期花瓣还原糖和蛋白质的较高水平、减缓花瓣和叶片细胞膜稼性的增加,减少共 积累以及降低乙烯释放速率,这与精胺处理后月季切花瓶插寿命提高相一致;但亚精胺处理对季切花瓶插寿命和改善观赏品质无明显影响。     

1-aminocyclopropane-l-carboxylic acid (ACC)—The transmitted stimulus in pollinated flowers?

Ethylene production and senescence of petals of pollinated carnation flowers were not prevented by removal of the ethylene produced by the gynoecium, suggesting that these events are a response to movement from the gynoecium of some stimulus other than ethylene gas. Application of 1-aminocyclopropane-1-carboxylic acid (ACC) to the stigmas caused an initial increase in gynoecium and petal ethylene production similar to that reported for pollinated flowers. This response was not seen in flowers whose stigmas were treated with indoleacetic acid (IAA). When [2-¹⁴C]ACC was applied to the stigmas of carnation flowers, radioactive ethylene was produced both by the gynoecia and by the petals. The possibility that ACC, transported from the stigmas to the petals, is responsible for the postpollination changes in carnation flowers is discussed.     

Involvement of ethylene in the disease caused by Botrytis cinerea on rose and carnation flowers and the possibility of control*

Ethylene production by flowers, petals and leaves of rose was correlated with severity of grey mould. However, when the host became completely macerated, ethylene production diminished. Ethylene production by Botrytis cinerea grown on autoclaved flowers which were supplemented with methionine was negligible. Methionine spray, incubation with ethylene, or precooling of flowers at 4°C increased disease incidence considerably. Ethylene also induced susceptibility of carnation flowers to attack by B. cinerea. On the other hand, sprays of silver thiosulphate (STS) aminooxyacetic acid (AOA) and aminoethoxyvinylglycine (AVG) decreased disease severity in rose petals and leaves inoculated with mycelial plugs or conidia. Treatment of cut rose flowers with STS (by dipping) or AOA (by spraying) significantly decreased disease incidence during subsequent incubation at 20 and 10°C. This suggests a treatment for reducing grey mould damage in flowers transported overseas.     

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.     

Role of short-chain saturated fatty acids in the control of ethylene sensitivity in senescing carnation flowers

In cut carnations ( Dianthus caryophyllus L. cv. Cally). petal senescence was associated with a climacteric pattern in ethylene production and an increase in ethylene sensitivity during the preclimacteric stage. The increase in ethylene sensitivity was caused by short-chain saturated fatty acids (C₇ to C₁₀) produced in the petals during the early stages of senescence. Pollination or application of octanoic acid to the styles of unpollinated flowers resulted in a sudden increase in ethylene sensitivity and a marked acceleration of senescence. Treatment with silver thiosulfate (STS) resulted in a suppression of ethylene sensitivity and a marked reduction in the levels of these fatty acids. However, even in STS-treated flowers pollination or treatment with octanoic acid gave rise to a drastic increase in ethylene sensitivity. Exposure of carnation flowers to 2. 5-norbornadicne (NBD) vapours resulted in a dramatic suppression of ethylene sensitivity which was also overridden by stylar application of octanoic acid. Exposure to NBD suppressed the increase in ethylene sensitivity caused by treatment with octanoic acid. It appears that short-chain saturated fatty acids increased ethylene sensitivity by increasing the ability of the tissue to bind ethylene.     

Altered membrane lipase expression delays leaf senescence

A cDNA clone encoding a lipase that is up-regulated in senescing leaves and flower petals has been isolated by screening an expression library. The abundance of the lipase mRNA increases as flowers and leaves begin to senesce, and expression of the gene is also induced by treatment with ethylene. Transgenic Arabidopsis plants in which levels of the senescence-induced lipase protein have been reduced show delayed leaf senescence.     

Comparison of mRNA levels of three ethylene receptors in senescing flowers of carnation (Dianthus caryophyllus L.)

Three ethylene receptor genes, DC-ERS1, DC-ERS2 and DC-ETR1, were previously identified in carnation (Dianthus caryophyllus L.). Here, the presence of mRNAs for respective genes in flower tissues and their changes during flower senescence are investigated by Northern blot analysis. DC-ERS2 and DC-ETR1 mRNAs were present in considerable amounts in petals, ovaries and styles of the flower at the full-opening stage. In the petals the level of DC-ERS2 mRNA showed a decreasing trend toward the late stage of flower senescence, whereas it increased slightly in ovaries and was unchanged in styles throughout the senescence period. However, DC-ETR1 mRNA showed no or little changes in any of the tissues during senescence. Exogenously applied ethylene did not affect the levels of DC-ERS2 and DC-ETR1 mRNAs in petals. Ethylene production in the flowers was blocked by treatment with 1,1-dimethyl-4-(phenylsulphonyl)semicarbazide (DPSS), but the mRNA levels for DC-ERS2 and DC-ETR1 decreased in the petals. DC-ERS1 mRNA was not detected in any cases. These results indicate that DC-ERS2 and DC-ETR1 are ethylene receptor genes responsible for ethylene perception and that their expression is regulated in a tissue-specific manner and independently of ethylene in carnation flowers during senescence.     

Sites of ethylene production in the pollinated and unpollinated senescing carnation (Dianthus caryophyllus) inflorescence

Production of endogenous ethylene from the styles, ovary and petals of pollinated and unpollinated flowers of Dianthus caryophyllus L. was measured. The rate of ethylene production of cut, unpollinated flowers aged in water at 18°C was low until the onset of petal wilting, when a rapid surge of ethylene occurred in all tissues. The flower ethylene production was evolved mostly from the styles and petals. The bases of petals from unpollinated, senescing flowers evolved ethylene faster and sometimes earlier than the upper parts. Treatment of cut flowers with propylene, an ethylene analogue, accelerated wilting of flower petals and promoted endogenous ethylene production in all flower tissues. Pollination of intact flowers also promoted endogenous ethylene production and caused accelerated petal wilting within 2–3 days from pollination. Although the data are consistent with the hypothesis that ethylene forms a link between pollination of the style and petal wilting, in the unpollinated flower the style and petals can evolve a surge of ethylene independently of each other, about the time when the petals irreversibly wilt. The results are discussed in relation to the role of ethylene in flower senescence.     

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.     

Calcium-calmodulin is required for abscisic acid-induced antioxidant defense and functions both upstream and downstream of H2O2 production in leaves of maize (Zea mays) plants

* Using pharmacological and biochemical approaches, the role of calmodulin (CaM) and the relationship between CaM and hydrogen peroxide (H(2)O(2)) in abscisic acid (ABA)-induced antioxidant defense in leaves of maize (Zea mays) plants were investigated. * Treatment with ABA or H(2)O(2) led to significant increases in the concentration of cytosolic Ca(2+) in the protoplasts of mesophyll cells and in the expression of the calmodulin 1 (CaM1) gene and the content of CaM in leaves of maize plants, and enhanced the expression of the antioxidant genes superoxide dismutase 4 (SOD4), cytosolic ascorbate peroxidase (cAPX), and glutathione reductase 1 (GR1) and the activities of the chloroplastic and cytosolic antioxidant enzymes. The up-regulation of the antioxidant enzymes was almost completely blocked by pretreatments with two CaM antagonists. * Pretreatments with CaM antagonists almost completely inhibited ABA-induced H(2)O(2) production throughout ABA treatment, but pretreatment with an inhibitor or scavenger of reactive oxygen species (ROS) did not affect the initial increase in the contents of CaM induced by ABA. * Our results suggest that Ca(2+)-CaM is involved in ABA-induced antioxidant defense, and that cross-talk between Ca(2+)-CaM and H(2)O(2) plays a pivotal role in ABA signaling.