Low Levels Of Ethylene Research Articles

ACC (1-aminocyclopropane-1-carboxylic acid) deaminase producing endophytic bacteria improve hydroponically grown lettuce in the greenhouse during summer season

In the summer, cool season crops like lettuce are typically not grown in a greenhouse because evaporative coolers cannot sufficiently lower the temperature to their optimal range (12–18 °C). The objective of this study was to increase yields of two butterhead lettuce cultivars (‘Buttercrunch’ and ‘Rex’) under summer heat stress utilizing bacterial endophytes with high 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. ACC is a precursor of ethylene. ACC deaminase reduces stress in plants by cleaving ACC into α-ketobutyrate and ammonia and lowering ethylene levels. Four bacterial endophytes (IALR387, IALR1385, IALR1794 and IALR1819) having high levels of ACC deaminase activity were selected from the Plant Endophyte Research Center's bacterial endophyte collection. The endophytes were identified as either Paraburkholderia sp. (IALR387 and IALR1385) or Burkholderia contaminans (IALR1794 and IALR1819). These 4 bacterial endophytes were tested in ‘Buttercrunch’ and ‘Rex’ during summer 2022 in two greenhouse experiments. The inoculation of lettuce with these bacterial endophytes enhanced lettuce growth in greenhouse hydroponic production except for IALR1385. In both cultivars, IALR1819 improved lettuce growth the most with shoot fresh and dry weights and the chlorophyll content.

Cell wall modifications lead to cultivar differences in apple (Malus domestica) fruit mealiness

Recently, four quantitative trait loci linked to flesh mealiness in apples were identified, with one associated with the MdPG1 allele. Hence, this study analyzed cell wall changes in two mealy (Orin and Akane) and three non-mealy (Kiou, Kitaro, Fuji) apple cultivars during ripening. The fruits were harvested for each cultivar at optimum maturity and stored at 20°C for 20 days. The flesh firmness of ‘Kitaro’ and ‘Fuji’ fruit did not change strikingly over the 20 days, whereas that of the other three cultivars, especially ‘Akane’ and ‘Orin’, gradually decreased during ripening. Between the two cultivars with a mealy texture, ‘Akane’ fruit produced extremely low levels of ethylene, whereas ‘Orin’ fruit produced high levels. The water-soluble polyuronide (WSP) contents of ‘Kiou’ and ‘Fuji’ fruit did not change clearly. In contrast, the WSP contents of the other three cultivars, especially ‘Akane’ and ‘Orin’, increased during ripening. In ‘Kiou’, ‘Kitaro’, and ‘Fuji’ fruit, the molecular-mass distributions of WSPs did not change during ripening. Conversely, the molecular-mass distribution of WSPs in ‘Akane’ and ‘Orin’ fruit exhibited downshifts during ripening. These results indicate that solubilization and depolymerization of pectic polyuronides occur during ripening in mealy ‘Akane’ and ‘Orin’ fruit, and that ethylene may not be involved in these changes.

Microorganisms in Plant Growth and Development: Roles in Abiotic Stress Tolerance and Secondary Metabolites Secretion.

Crops aimed at feeding an exponentially growing population are often exposed to a variety of harsh environmental factors. Although plants have evolved ways of adjusting their metabolism and some have also been engineered to tolerate stressful environments, there is still a shortage of food supply. An alternative approach is to explore the possibility of using rhizosphere microorganisms in the mitigation of abiotic stress and hopefully improve food production. Several studies have shown that rhizobacteria and mycorrhizae organisms can help improve stress tolerance by enhancing plant growth; stimulating the production of phytohormones, siderophores, and solubilizing phosphates; lowering ethylene levels; and upregulating the expression of dehydration response and antioxidant genes. This article shows the secretion of secondary metabolites as an additional mechanism employed by microorganisms against abiotic stress. The understanding of these mechanisms will help improve the efficacy of plant-growth-promoting microorganisms.

Reduction of ethylene biosynthesis in sugarcane induces growth and investment in the non-enzymatic antioxidant apparatus.

Lower ethylene production in sugarcane results in plants with higher stature, expression of growth-promoting genes, higher photosynthetic rate, and increased antioxidant compounds. The hormone ethylene is involved in critical processes in sugarcane, such as the growth and accumulation of sucrose. The lack of mutants for ethylene biosynthesis or signaling genes makes it difficult to understand the role of this phytohormone throughout sugarcane development. This study aimed to evaluate the physiology and development of sugarcane plants with low ethylene production. To achieve this goal, we used RNA interference to silence three genes, ScACS1, ScACS2, and ScACS3, encoding 1-aminocyclopropane-1-carboxylic acid synthases (ACS), responsible for a limiting step of the ethylene biosynthesis pathway. Sugarcane plants with reduced ethylene levels presented increased growth, faster germination of lateral gems, and activation of non-enzymatic antioxidant mechanisms. We observed an augmentation in the expression of ScACO5, which encodes the final enzyme regulating ethylene biosynthesis, and ScERF1, encoding a transcription factor, linked to the ethylene response. The increase in plant height was correlated with higher expression of ScPIF3, ScPIF4, and ScPIF5, which encode for transcription factors related to growth induction. Interestingly, there was also an increase in the expression of the ScGAI gene, which encodes a DELLA protein, a growth repressor. The final content of sucrose in the stems was not affected by the low levels of ethylene, although the rate of CO2 assimilation was reduced. This study reports for the first time the impacts of low endogenous production of ethylene in sugarcane and provides helpful insights on the molecular mechanisms behind ethylene responses.

Semi-dominant effects of a novel ripening inhibitor (rin) locus allele on tomato fruit ripening.

The tomato (Solanum lycopersicum) ripening inhibitor (rin) mutation completely represses fruit ripening, as rin fruits fail to express ripening-associated genes and remain green and firm. Moreover, heterozygous rin fruits (rin/+) ripen normally but have extended shelf life, an important consideration for this perishable fruit crop; therefore, heterozygous rin has been widely used to breed varieties that produce red tomatoes with improved shelf life. We previously used CRISPR/Cas9 to produce novel alleles at the rin locus. The wild-type allele RIN encodes a MADS-box transcription factor and the novel allele, named as rinG2, generates an early stop codon, resulting in C-terminal truncation of the transcription factor. Like rin fruits, rinG2 fruits exhibit extended shelf life, but unlike rin fruits, which remain yellow-green even after long-term storage, rinG2 fruits turn orange due to ripening-associated carotenoid production. Here, to explore the potential of the rinG2 mutation for breeding, we characterized the effects of rinG2 in the heterozygous state (rinG2/+) compared to the effects of rin/+. The softening of rinG2/+ fruits was delayed compared to the wild type but to a lesser degree than rin/+ fruits. Lycopene and β-carotene levels in rinG2/+ fruits were similar to those of the wild type, whereas rin/+ fruits accumulated half the amount of β-carotene compared to the wild type. The rinG2/+ fruits produced lower levels of ethylene than wild-type and rin/+ fruits. Expression analysis revealed that in rinG2/+ fruits, the rinG2 mutation (like rin) partially inhibited the expression of ripening-associated genes. The small differences in the inhibitory effects of rinG2 vs. rin coincided with small differences in phenotypes, such as ethylene production, softening, and carotenoid accumulation. Therefore, rinG2 represents a promising genetic resource for developing tomato cultivars with extended shelf life.

Unravelling the cold-induced regulation of ethylene and α-farnesene and its involvement with the development of scald-like disorders in different pear cultivars

To better understand the cold-induced regulation of scald-like disorders in pears and the specific roles played by ethylene and α-farnesene, three pear cultivars with different patterns of ethylene production and chilling requirement were used in this study. Fruit were treated with 1-MCP (ethylene inhibitor) and Lovastatin (α-farnesene inhibitor) and stored at -0.5 °C and 90 % RH during 6 months. Changes in targeted metabolites, enzymes and genes were monitored periodically up to 120 d of storage and superficial scald incidence was assessed after this time and after 180 d of cold storage. 1-MCP treatment induced in the three cultivars a down-regulation of PcACS1, PcACO1, PcERF1 and PcAFS1 gene expression, but also a significant up-regulation of PcETR1 and PcEIN2 that led in all cases to the inhibition of the disorder incidence. In contrast, Lovastatin treatment caused diverse molecular or biochemical responses depending on the cultivar. In ‘Blanquilla’ pears, this treatment completely inhibited superficial scald reinforcing the idea that ethylene-α-farnesene interaction plays a decisive role in this specific cultivar. In contrast to 1-MCP, Lovastatin treatment did not control the disorder incidence in ‘Flor d’Hivern’ pears. Inversely, 1-MCP inhibited the development of the disorder, showing then that the inhibition of ethylene biosynthetic and signalling pathway may control superficial scald even in cultivars producing very low or undetectable ethylene levels. Finally, the inefficacy of both treatments to prevent the disorder development in ‘Conference’ pears, suggests the existence of a disorder different from that observed for the other cultivars whose biochemical basis remain unknown. Collectively our results show that the regulatory processes triggered by cold stress in pears are complex and cultivar dependent.

Direct organogenesis and ethylene regulators in the cloning of Epidendrum denticulatum (Orchidaceae)

The popularization of trade and the high risk of extinction of species of the Orchidaceae family have increased the need for effective cloning techniques, such as direct organogenesis. The present study aims to analyze the influence of ethylene during the micropropagation of Epidendrum denticulatum, as well as verifying the action of ethylene regulators. The explants were inoculated in MS medium, with or without the addition of AgNO3, CoCl2 and CEPA. Ethylene quantification was performed at 1, 5, 10, 15, 20, 30, 45 and 60 days after inoculation under a 12 h/12 h (light/dark) and 0/24 h (light/dark) photoperiods. Treatments with lower levels of ethylene showed higher survival percentages and better developed plants. These results provide a better understanding of the influence of ethylene during tissue regeneration of E. denticulatum and will be helpful in the propagation of other native Brazilian orchids.

Tolerance to cadmium toxicity and phytoremediation potential of three Brassica rapa CAX1a TILLING mutants

Cadmium (Cd) is one of the most toxic heavy metals that reduces crop productivity and is a threat to all the food chain including human health. Phytoremediation is an environmentally friendly strategy to clean up soil contaminated with heavy metals. Researchers are selecting new varieties with an enhanced capacity for phytoremediation purposes. Three Brassica rapa mutants for CAX1 transporter were obtained through TILLING. The objective of this work is to evaluate the tolerance of these mutants to Cd toxicity and its potential for Cd phytoremediation. For this, the mutants and the parental R-o-18 were grown under control and Cd toxicity conditions (100μM CdCl2) and growth, Cd accumulation and physiological parameters were analyzed. The results show that BraA.cax1a mutation provides greater Cd uptake capacity although only BraA.cax1a-12 would be useful for phytoremediation because it registered more than three-fold the Cd content of R-o-18 and presented greater Cd tolerance. This tolerance could be due to the higher Ca and Mg accumulations, the maintaining of photosynthesis performance, the enhanced ROS detoxification and AsA/GSH and TCA cycles, the higher malate, and GA4 concentrations and the lower ethylene levels. Briefly, this study identifies BraA.cax1a-12 as a potential mutant for phytoremediation of Cd contaminated soil and identifies possible physiological elements that contribute to this capacity.

New technology of protecting apple fruits from bitter pit and other physiological diseases during storage

The work was performed in the I. V. Michurin Federal Scientifi c Center (Tambov region, Russia) in 2015-2018. The fruits of Sinap Orlovsky variety with high susceptibility to bitter pit, medium – to superfi cial scald and CO2 -skin injuries were used. The main post-harvest strategy of protecting fruits from bitter pit (BP) is storage in a controlled atmosphere (CA), short-term low oxygen storage (10 days, O2<1 %) reduces losses from scald and BP, but does not provide protection from diseases of varieties with high susceptibility; post-harvest treatment with ethylene biosynthesis inhibitor (1-MCP) provides protection from scald, but has an ambiguous effect on the development of BP, and may increase the degree of disease appearance. The purpose of the research is the development of innovative technology of managing of bitter pit and other post-harvest pathological diseases. In the experiment, the control and 1-MCP-treated fruits were stored at 0 + 1 °C under regular (RA) and controlled atmosphere (CA) conditions: CA-1 (CO2 – 1.2-1.5 %, O2 – 1.2-1.5 %), CA-2 (СО2<0.1 %, О2 – 1.2-1.5 %), under conditions of short (10 days) post-harvest impact of controlled factors: temperature 18-20 °С, О2 – 1.2-1.5 %, CO2<0.1 % and further storage in regular atmosphere (LO2 ). Ethylene, α-farnesen and its oxidation products (CТ281), phenolic compounds were determined in fruits, losses from bitter pit, scald, CO2 -skin injuries, quality (fi rmness) were estimated. 1-MCP-treatment ensured a low level of ethylene and CT281 accumulation in fruits, protection from scald, preservation of fi rmness in all variants of fruit storage, with maximum effi ciency of variants CA-2, CA-1 and LO2 . Fruit protection from bitter pit was provided by CA-2 technology, a signifi cant reduction of losses – LO2 . When using the technology of CA-2, losses from CO2 -skin injuries, noted in the conditions of CA-1, were excluded. The maximum efficiency of protection of fruits from BP, scald, CO2 -injuries is provided by the developed technology CA-2 (CO2<0.1 %, O2 — 1.2-1.5 %).

Cyanobacteria Respond to Low Levels of Ethylene.

Ethylene is a gas that has long been known to act as a plant hormone. We recently showed that a cyanobacterium, Synechocystis sp. PCC 6803 (Synechocystis) contains an ethylene receptor (SynEtr1) that regulates cell surface and extracellular components leading to altered phototaxis and biofilm formation. To determine whether other cyanobacteria respond to ethylene, we examined the effects of exogenous ethylene on phototaxis of the filamentous cyanobacterium, Geitlerinema sp. PCC 7105 (Geitlerinema). A search of the Geitlerinema genome suggests that two genes encode proteins that contain an ethylene binding domain and Geitlerinema cells have previously been shown to bind ethylene. We call these genes GeiEtr1 and GeiEtr2 and show that in air both are expressed. Treatment with ethylene decreases the abundance of GeiEtr1 transcripts. Treatment of Geitlerinema with 1000 nL L–1 ethylene affected the phototaxis response to white light as well as monochromatic red light, but not blue or green light. This is in contrast to Synechocystis where we previously found ethylene affected phototaxis to all three colors. We also demonstrate that application of ethylene down to 8 nL L–1 stimulates phototaxis of both cyanobacteria as well as biofilm formation of Synechocystis. We formerly demonstrated that the transcript levels of slr1214 and CsiR1 in Synechocystis are reduced by treatment with 1000 nL L–1 ethylene. Here we show that application of ethylene down to 1 nL L–1 causes a reduction in CsiR1 abundance. This is below the threshold for most ethylene responses documented in plants. By contrast, slr1214 is unaffected by this low level of ethylene and only shows a reduction in transcript abundance at the highest ethylene level used. Thus, cyanobacteria are very sensitive to ethylene. However, the dose-binding characteristics of ethylene binding to Geitlerinema and Synechocystis cells as well as to the ethylene binding domain of SynEtr1 heterologously expressed in yeast, are similar to what has been reported for plants and exogenously expressed ethylene receptors from plants. These data are consistent with a model where signal amplification is occurring at the level of the receptors.

Hormone balance in a climacteric plum fruit and its non-climacteric bud mutant during ripening

Hormone balance plays a crucial role in the control of fruit ripening. We characterized and compared hormone balance in two Japanese plum cultivars (Prunus salicina Lindl.), namely Santa Rosa, a climacteric type, and Sweet Miriam, its non-climacteric bud-sport mutant. We assessed hormonal changes in gene expression associated with hormone biosynthesis, perception and signaling during ripening on-the tree and throughout postharvest storage and in response to ethylene treatments. Non-climacteric fruit displayed lower ethylene levels than climacteric fruit at all stages and lower auxin levels during the initiation of ripening on-the-tree and during most of post-harvest storage. Moreover, 1-MCP-induced ethylene decrease also resulted in low auxin contents in Santa Rosa, supporting the role of auxin in climacteric fruit ripening. The differences in auxin contents between Santa Rosa and Sweet Miriam fruit could be the consequence of different routed auxin biosynthesis pathways as indicated by the significant negative correlations between clusters of auxin metabolism-associated genes. Ethylene induced increased ABA levels throughout postharvest storage in both ripening types. Overall, ripening of Santa Rosa and Sweet Miriam fruit are characterized by distinct hormone accumulation pathways and interactions.

Enhancement of alfalfa yield and quality by plant growth-promoting rhizobacteria under saline-alkali conditions.

Bacteria with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity could decrease the ethylene level, confer resistance of plant, and stimulate plant growth under biotic and abiotic stress conditions. Plant growth-promoting rhizobacteria (PGPR) strains Enterobacter aerogenes (LJL-5) and Pseudomonas aeruginosa (LJL-13) were obtained from the rhizosphere of alfalfa grown under saline-alkali conditions. The ACC deaminase activity of E. aerogenes (LJL-5) and Ps. aeruginosa (LJL-13) was approximately 2-5 µmol mg-1 h-1 . indole acetic acid synthesis was increased with the increasing concentration of l-tryptophan. Siderophore production and phosphate solubilization in Ps. aeruginosa (LJL-13) were higher than those in E. aerogenes (LJL-5). Compared to the non-inoculated seedlings (1.31 ng mL-1 h-1 ), inoculated alfalfa seedlings with E. aerogenes (LJL-5) (0.90 ng mL-1 h-1 ) and Ps. aeruginosa (LJL-13) (0.78 ng mL-1 h-1 ) emitted lower levels of ethylene. Under saline-alkali conditions in the greenhouse, inoculation with E. aerogenes (LJL-5) and Ps. aeruginosa (LJL-13) increased the biomass, soil and plant analyzer development (SPAD), and P content of alfalfa plants, and also induced the activity of antioxidant enzymes (superoxide dismutase, peroxidase and catalase), promoted the accumulation of antioxidant substances and removed various harmful substances. Under saline-alkali conditions in the field (2012, 2013, and 2014), inoculation of alfalfa with E. aerogenes (LJL-5) and Ps. aeruginosa (LJL-13) significantly increased the shoot height, fresh and dry weights, yield and crude protein content of alfalfa plants, but decreased the fiber content. Two PGPR strains were isolated from the rhizosphere of alfalfa in saline-alkali conditions. Both strains could promote alfalfa growth in saline-alkali soil, and could be used as biofertilizer to promote plant growth under stress and reduce environmental pollution caused by fertilizers simultaneously. © 2018 Society of Chemical Industry.

Effect of Continuous Exposure to Low Levels of Ethylene on Mycelial Growth of Postharvest Fruit Fungal Pathogens

Ethylene enhances the ripening and senescence of fruit with increased susceptibility to fungal decay a common feature of such changes. Most studies on the effect of ethylene have been in vivo where it is not possible to determine whether any effect due to ethylene arises from changes in metabolism of produce or from a direct effect on the pathogen. The few in vitro studies, that have been carried out, have been with very high ethylene levels, and did not identify the source of pathogens tested. This study examined the effect of air and ethylene, at 0.1 and 1 μL L−1, on the growth of fungi isolated from five climacteric fruits (persimmon, pear, tomato, mango and papaya), and three non-climacteric fruits (orange, grape and blueberry). All fungi isolated from climacteric fruits had reduced mycelial growth when held in 0.1 and 1 μL L−1 ethylene but those from non-climacteric fruits showed no effect of ethylene. The finding was unexpected and suggests that fungi that colonise climacteric fruits are advantaged by delaying growth when fruits start to ripen. Since non-climacteric fruits do not exhibit any marked increase in ethylene, colonising pathogens would not need such an adaptive response.

Chlorophytum comosum–bacteria interactions for airborne benzene remediation: Effect of native endophytic Enterobacter sp. EN2 inoculation and blue-red LED light

This study was performed to determine the effect of plant–endophytic Enterobacter sp. EN2 interactions and blue-red LED light conditions on gaseous benzene removal by plants. It was found that under consecutive benzene fumigation for three cycles (18 days), inoculation of the strain EN2 into sterilized and non-sterilized native C. comosum resulted in significantly increased gaseous benzene removal compared to that in non-inoculated groups under the same light conditions (P < 0.05). Remarkably, EN2 colonization in inoculated plants under LED conditions was higher than under fluorescence conditions as the EN2 could grow better under LED conditions. Strain EN2 possesses NADPH that is used to facilitate benzene degradation and modulate plant growth under benzene stress by bacterial IAA production and ACC deaminase activity; higher IAA and lower ethylene levels were found in inoculated plants compared to non-inoculated ones. These contributed to better benzene removal efficiency. Interestingly, under fumigation for 16 cycles (67 days), there was no difference in gaseous benzene removal between inoculated plants and non-inoculated plants under the same light conditions at initial benzene concentrations of 5 ppm. This is probably due to EN2 reaching maximum growth under all treatments. However, C. comosum exhibited better benzene removal under LED conditions than under fluorescence conditions during 16 cycles, possibly due to better photosynthetic performance and plant growth, leading to more NADPH, and eventually enhanced benzene removal efficiency. Hence, the most efficient acceleration of benzene removal was provided by inoculation of strain EN2 onto C. comosum under blue-red LED light conditions.

Combined postharvest UV-C and 1-methylcyclopropene (1-MCP) treatment, followed by storage continuously in low level of ethylene atmosphere improves the quality of Tahitian limes.

The green Tahitian limes (Citrus latifolia) were exposed to 7.2kJm-2 UV-C and 0.5μLL-1 1-methylcyclopropene (1-MCP) treatments both separately and in combination. After treatment, fruit were stored in ethylene free (i.e. air containing < 0.005μLL-1) or 0.1μLL-1 ethylene at 20°C and 100% RH. The results showed that UV-C treatment delayed skin degreening and reduced endogenous ethylene production compared to untreated control fruit, however these effects reduced over the storage time. As expected, 1-MCP inhibited ethylene production, reduced calyx abscission and retained peel greenness during the storage. Both of the combination treatments, 1-MCP + UV-C and UV-C + 1-MCP reduced endogenous ethylene production and delayed skin yellowing. In all treatments, UV-C and 1-MCP resulted in lower fruit respiration rates than untreated control fruit, however this effect diminished during 7 and 14days storage for fruits stored in air and 0.1μLL-1 ethylene atmosphere, respectively. There was no difference in weight loss, SSC, TA and SSC/TA ratio between the treatments and storage conditions. The results suggest that a pre-storage UV-C treatment, followed by storage at low level of ethylene improves the quality of limes, with the additional improvement when combined with 1-MCP treatment prior or after UV-C irradiation.

De-hulling facilitates seed germination and ethylene production in dormant and non-dormant rice genotypes

SUMMARYThe hull or husk of rice, comprising the lemma and palea, provides a fitting enclosure for the caryopsis. The physiological significance of the hull in seed dormancy has been examined by comparing the effects of its removal on germination, seed vigour, assimilate mobilization and ethylene production in germinating seeds of six rice genotypes; two each belonging to dormant, semi-dormant and non-dormant groups. Hull removal promoted the above parameters in all three categories of seeds, but the effect was relatively higher in dormant seeds compared with less dormant categories. Ethylene production in non-dormant seeds was initiated after imbibition of water, normally before visible emergence of the radicle. It peaked when the radicle began to protrude and declined thereafter. In comparison, dormant seeds produced very low levels of ethylene during germination; however, hull removal resulted in a dramatic rise in its production. Overall, ethylene evolution at the radicle protrusion stage correlated negatively with germination time. It was concluded that ethylene production starts with breaking of the caryopsis coat and peaks when the radicle ruptures it completely, at the stage of radicle visible emergence. Removal of the hull facilitates germination and ethylene production can be a good indicator for the progress of germination.

Diageotropica and Lateral Rooting, the Rest of the Story

Diageotropica and Lateral Rooting, the Rest of the Story

Genetic Transformation of Dendrobium 'Sonia Earsakul' with Antisense Carica papaya ACO1 Gene

&lt;p&gt;&lt;em&gt;Dendrobium&lt;/em&gt; orchid is one of the major export cut flowers not only in Thailand but also for several tropical countries. However, the production of ethylene by their flowers causes a shorter vase life. Flowers that contained lower levels of ethylene usually exhibited delayed senescence and consequently prolonged vase life. The transfer of antisense &lt;em&gt;ACC oxidase (ACO)&lt;/em&gt; gene into orchid, in theory, may leads to decreased ethylene production because this gene can down regulates the ethylene biosynthesis pathway. This study focuses on the transformation and the existence and expression of the antisense &lt;em&gt;ACO&lt;/em&gt;1 gene from papaya, namely (&lt;em&gt;CP-ACO&lt;/em&gt;1), which was transferred in to &lt;em&gt;Dendrobium&lt;/em&gt; 'Sonia Earsakul'. The successful stable transformation event obtained and the existence of the transferred gene was determined using PCR, dot blot hybridization and Southern blot hybridization techniques. The results revealed that antisense &lt;em&gt;CP-ACO&lt;/em&gt;1 and &lt;em&gt;hygromycin phosphotransferase (hpt)&lt;/em&gt; gene existed in all transgenic lines confirmed by PCR technique. The genomic dot blot confirmed the incorporation of the transgene in transgenic plant genome. Southern blot hybridization revealed the existed of one to four sets of the gene in transgenic lines. The expression of antisense &lt;em&gt;CP-ACO&lt;/em&gt;1 gene was analyzed through the level of ACO enzyme activity and ethylene production in transgenic orchid. All of the transgenic lines had lower ACO enzyme activity and lower ethylene production than that of the non-transgenic orchid plants.&lt;strong&gt; &lt;/strong&gt;&lt;/p&gt; &lt;p&gt; &lt;/p&gt;

EFFECTS OF 1-MCP ON DIFFERENT POSTHARVEST QUALITY PARAMETERS IN ZUCCHINI

Ethylene can accelerate ripening and other postharvest physiological processes such as softening and development of chilling injury (CI) in both climacteric and non-climacteric fruit. Zucchini is an immature non-climacteric fruit that produces low levels of ethylene during its postharvest storage at different temperatures. However, when fruit is stored at 4°C and then transferred to 20°C, ethylene production is rapidly induced. We have recently found that this cold-induced ethylene is associated to chilling sensitivity. To analyse the potential benefit of inhibiting ethylene perception of zucchini on quality, fruit of five commercial hybrids were treated with 2.4 µl L-1 1-MCP for 48 h, and then stored for up to 14 days at 4°C. Firmness, weight loss, color, chilling injury incidence and ethylene production of the fruit were evaluated during the storage period. The treatment with 1-MCP was not equally effective in the fruit of all cultivars, it improved chilling tolerance in zucchini, reducing weight loss and delaying the onset of chilling injury in cold stored fruit, These improvements were associated with a delay in the production of cold-induced ethylene. Fruit color and firmness were not affected by 1-MCP.

Expression levels of ethylene biosynthetic genes and senescence-related genes in carnation (Dianthus caryophyllus L.) with ultra-long-life flowers

Carnation (Dianthus caryophyllus L.) line 532-6 has ultra-long flower life (29 days without chemical treatment). We investigated ethylene production and expression of ethylene biosynthetic genes and senescence-related genes in the flowers of 532-6 in comparison with those of a control cultivar, ‘Francesco’ and a cultivar with long flower life, ‘Miracle Rouge’ (MR). ‘Francesco’ flowers, but not those of MR and 532-6, showed typical symptoms of ethylene-dependent senescence. The flowers of MR and 532-6 produced very low levels of ethylene as a result of very low expression levels of two ethylene biosynthetic genes, DcACS1 and DcACO1. The expression of some senescence-related genes (DcbGal, DcGST1 and DcLip) increased in ‘Francesco’ petals by day 6, but remained low in the petals of MR and 532-6 throughout the experiment, whereas there was a small difference between the levels of the DcCP1 transcript in MR and 532-6. The expression of DcCPIn was regulated differently in all three cultivars. In ‘Francesco’ petals, the DcCPIn expression level sharply decreased on day 6 and 7; in MR, the DcCPIn level increased on day 7 and decreased by day 16, whereas in 532-6 it increased on day 3 and then gradually decreased until day 25. The results suggest that the extended flower life of MR and 532-6 in comparison with ‘Francesco’ depends on reduced levels of ethylene production, low levels of ethylene biosynthetic gene expression, and senescence-related gene expression; the difference between MR and 532-6 may be due, in particular, to DcCPIn and DcCP1.