Expression Of Ethylene Receptor Genes Research Articles

The Role of 1-Methylcyclopropene in the regulation of ethylene biosynthesis and ethylene receptor gene expression in Mangifera indica L. (Mango Fruit).

Mango (Mangifera indica L.) is respiratory climacteric fruit that ripens and decomposes quickly following their harvest. 1‐methylcyclopropene (1‐MCP) is known to affect the ripening of fruit, delaying the decay of mango stored under ambient conditions. The objective of this study was to clarify the role of 1‐MCP in the regulation of ethylene biosynthesis and ethylene receptor gene expression in mango. 1‐MCP significantly inhibited the 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content. The activity of ACC oxidase (ACO) increased on days 6, 8, and 10 of storage, whereas delayed ACC synthase (ACS) activity increased after day 4. The two homologous ethylene receptor genes, ETR1 and ERS1 (i.e., MiETR1 and MiERS1), were obtained and deposited in GenBank® (National Center for Biotechnology Information‐National Institutes of Health [NCBI‐NIH]) (KY002681 and KY002682). The MiETR1 coding sequence was 2,220 bp and encoded 739 amino acids (aa). The MiERS1 coding sequence was 1,890 bp and encoded 629 aa, similar to ERS1 in other fruit. The tertiary structures of MiETR1 and MiERS1 were also predicted. MiERS1 lacks a receiver domain and shares a low homology with MiETR1 (44%). The expression of MiETR1 and MiERS1 mRNA was upregulated as the storage duration extended and reached the peak expression on day 6. Treatment with 1‐MCP significantly reduced the expression of MiETR1 on days 4, 6, and 10 and inhibited the expression of MiETR1 on days 2, 4, 6, and 10. These results indicated that MiETR1 and MiERS1 had important functions in ethylene signal transduction. Treatment with 1‐MCP might effectively prevent the biosynthesis of ethylene, as well as ethylene‐induced ripening and senescence. This study presents an innovative method for prolonging the storage life of mango after their harvest through the regulation of MiETR1 and MiERS1 expression.

Involvement of ethylene biosynthesis and perception during germination of dormant Avena fatua L. caryopses induced by KAR1 or GA3

Main conclusionGermination of primary dormant wild oat caused by KAR1 or GA3 is associated with ACC accumulation and increased ethylene production shortly before radicle protrusion as a result of the non-transcriptional and transcriptional activation of ACS and ACO enzymes, respectively. Response to both compounds involves the modulation of ethylene sensitivity through ethylene receptor genes.Harvested Avena fatua caryopses are primary dormant and, therefore, germinated poorly at 20 °C. Karrikin 1 (KAR1), which action probably requires endogenous gibberellins (GAs), and gibberellin A3 (GA3) was found to induce dormant caryopses to germinate. The stimulatory effects were accompanied by the activation of the ethylene biosynthesis pathway and depended on undisturbed ethylene perception. KAR1 and GA3 promoted 1-aminocyclopropane-1-carboxylic acid (ACC) accumulation during coleorhizae emergence and ethylene production shortly prior to the radicle protrusion, which resulted from the enhanced activity of two ethylene biosynthesis enzymes, ACC synthase (ACS) and ACC oxidase (ACO). The inhibitor of ACS adversely affected beneficial impacts of both KAR1 and GA3 on A. fatua caryopses germination, while the inhibitor of ACO more efficiently impeded the GA3 effect. The inhibitors of ethylene action markedly lowered germination in response to KAR1 and GA3. Gene expression studies preceded by the identification of several genes related to ethylene biosynthesis (AfACS6, AfACO1, and AfACO5) and perception (AfERS1b, AfERS1c, AfERS2, AfETR2, AfETR3, and AfETR4) provided further evidence for the engagement of ethylene in KAR1 and GA3 induced germination of A. fatua caryopses. Both AfACO1 and AfACO5 were upregulated, whereas AfACS6 remained unaffected by the treatment. This suggests the existence of different regulatory mechanisms of enzymatic activity, transcriptional for ACO and non-transcriptional for ACS. During imbibition in water, AfERS1b was stronger expressed than other receptor genes. In the presence of KAR1 or GA3, the expression of AfETR3 was substantially induced. Differential expression of ethylene receptor genes implies the modulation of caryopses sensitivity adjusted to ethylene availability and suggests the functional diversification of individual receptors.

Characterization and differential expression of ethylene receptor genes during fruit development and dehiscence of durian (Durio zibethinus)

Abstract Durian (Durio zibethinus) is a climacteric fruit. Biochemical changes take place in the durian pulp while the husk is dehiscent during fruit ripening. Fruit development of durian cv. Monthong showed a sigmoid curve and reached a maturity stage week 16 after anthesis, while fruit dehiscence started a week after harvest, was hastened by ethephon treatment, and delayed by 1-methylcyclopropene (1-MCP). 1-MCP treatment delayed dehiscence for 5 days from day 7 to day 12 compared with control fruit at 25 °C. Two ethylene receptors (DzETR1 and DzETR2), a CTR1-like protein (DzCTR1) and two ethylene insensitive-like proteins (DzEIL1 and DzEIL2) in the pulp and husk shared high homology to Theobroma cacao. The transcript levels of DzETR2, DzCTR1 and DzEIL2 slightly decreased during fruit development (week 2 to week 10), while DzETR2 transcript level showed the highest expression. The gene expression of DzETR2 in the dehiscence zone, increased at day 12 after harvest, while gene expression of DzETR1, DzCTR1 and DzEIL2 slightly increased after harvest. All genes were reduced in expression with 1-MCP treatment. After that, an increase in expression was found at day 9, followed by a gradual decrease until day 12. These results suggest that DzETR2 plays a role in fruit development and dehiscence of ripening durian.

The effect of 1-methylcyclopropene (1-MCP) on expression of ethylene receptor genes in durian pulp during ripening

Rapid fruit ripening is a significant problem that limits the shelf life of durian, with ethylene having a major impact on the regulation of this event. Durian treated with ethephon ripened 3 d after treatment with increased pulp total soluble solids, ethylene production of the whole fruit and decreased pulp firmness compared to the control fruit. 1-MCP treatment delayed ripening by up to 9 d with inhibited accumulation of total soluble solids, color change, softening and ethylene production. Genes related to ethylene perception (DzETR1 and DzETR2) and the signaling pathway (DzCTR1, DzEIL1 and DzEIL2) in the pulp were investigated during this process, using qPCR to quantify changes in gene transcription. All candidate genes were significantly up-regulated in ripening durian pulp. Ethephon treatment increased the expression of DzETR1 and DzETR2 genes, while expression of DzCTR1, DzEIL1 and DzEIL2 were slightly affected. 1-MCP treatment significantly inhibited the expression of the DzETR2 and DzEIL1 genes. The promoters of DzETR2 genes were isolated and their activation by fruit transcription factors studied using transient expression in tobacco leaves. It was found that members of the kiwifruit and apple EIL1, EIL2 and EIL3 genes strongly activated the DzETR2 promoter. These results suggest that ethylene-induced ripening of durian is via the regulation of DzETR2 by EIL transcription factors.

Plant water stress: Associations between ethylene and abscisic acid response

Agriculture is severely impacted by water stress due either to excess (hypoxia/anoxia) or deficit of water availability. Hypoxia/anoxia is associated with oxygen (O2) deficiency or depletion, inducing several anatomical, morphological, physiological, and molecular changes. The majority of these alterations are adaptive mechanisms to cope with low O2 availability; among them, alterations in shoot length, aerenchyma formation and adventitious roots have been described in several studies. The aim of this review was to address the association between abscisic acid (ABA) and ethylene in function of water availability in plants. The major physiological responses to low O2 are associated with changes in root respiration, stomatal conductance, photosynthesis, and fermentation pathways in roots. In addition, several changes in gene expression have been associated with pathways that are not present under normal O2 supply. The expression of ethylene receptor genes is up-regulated by low O2, and ethylene seems to have a crucial role in anatomical and physiological effects during hypoxia/anoxia. During O2 depletion, ethylene accumulation down-regulates ABA by inhibiting rate-limiting enzymes in ABA biosynthesis and by activating ABA breakdown to phaseic acid. With regard to water deficit, drought is primarily sensed by the roots, inducing a signal cascade to the shoots via xylem causing physiological and morphological changes. Several genes are regulated up or down with osmotic stress; the majority of these responsive genes can be driven by either an ABA-dependent or ABA-independent pathway. Some studies suggest that ethylene shuts down leaf growth very fast after the plant senses limited water availability. Ethylene accumulation can antagonize the control of gas exchange and leaf growth upon drought and ABA accumulation.

Roles of Ethylene Production and Ethylene Receptor Expression in Regulating Apple Fruitlet Abscission.

Apple (Malus × domestica) is increasingly being considered an interesting model species for studying early fruit development, during which an extremely relevant phenomenon, fruitlet abscission, may occur as a response to both endogenous and/or exogenous cues. Several studies were carried out shedding light on the main physiological and molecular events leading to the selective release of lateral fruitlets within a corymb, either occurring naturally or as a result of a thinning treatment. Several studies pointed out a clear association between a rise of ethylene biosynthetic levels in the fruitlet and its tendency to abscise. A direct mechanistic link, however, has not yet been established between this gaseous hormone and the generation of the abscission signal within the fruit. In this work, the role of ethylene during the very early stages of abscission induction was investigated in fruitlet populations with different abscission potentials due either to the natural correlative inhibitions determining the so-called physiological fruit drop or to a well-tested thinning treatment performed with the cytokinin benzyladenine. A crucial role was ascribed to the ratio between the ethylene produced by the cortex and the expression of ethylene receptor genes in the seed. This ratio would determine the final probability to abscise. A working model has been proposed consistent with the differential distribution of four receptor transcripts within the seed, which resembles a spatially progressive cell-specific immune-like mechanism evolved by apple to protect the embryo from harmful ethylene.

A STAY‐GREEN protein SlSGR1 regulates lycopene and β‐carotene accumulation by interacting directly with SlPSY1 during ripening processes in tomato

As a primary source of lycopene in the human diet, fleshy fruits synthesize this compound both de novo and via chlorophyll metabolism during ripening. SlSGR1 encodes a STAY-GREEN protein that plays a critical role in the regulation of chlorophyll degradation in tomato leaves and fruits. We report that SlSGR1 can regulate tomato (Solanum lycopersicum) lycopene accumulation through direct interaction with a key carotenoid synthetic enzyme SlPSY1, and can inhibit its activity. This interaction with SlSGR1 mediates lycopene accumulation during tomato fruit maturation. We confirmed this inhibitory activity in bacteria engineered to produce lycopene, where the introduction of SlSGR1 reduced dramatically lycopene biosynthesis. The repression of SlSGR1 in transgenic tomato fruits resulted in altered accumulation patterns of phytoene and lycopene, whilst simultaneously elevating SlPSY1 mRNA accumulation and plastid conversion at the early stages of fruit ripening, resulting in increased lycopene and β-carotene (four- and nine-fold, respectively) in red ripe fruits. SlSGR1 influences ethylene signal transduction via the altered expression of ethylene receptor genes and ethylene-induced genes. Fruit shelf-life is extended significantly in SlSGR1-repressed tomatoes. Our results indicate that SlSGR1 plays a pivotal regulatory role in color formation and fruit ripening regulation in tomato, and further suggest that SlSGR1 activity is mediated through direct interaction with PSY1.

Expression of ACO1, ERS1 and ERF1 genes in harvested bananas in relation to heat-induced defense against Colletotrichum musae

The aim of this study was to investigate the connection between heat-induced ethylene signal changes and enhanced disease resistance. Heat enhanced ripening and elevated MaACO1 expression in naturally ripened bananas (NRB), while it delayed ripening and reduced MaACO1expression in the ethephon-treated bananas (ETB). However, in both cases, heat reduced lesion sizes infected by Colletotrichum musae. This indicates that heat-induced disease resistance in bananas was independent of ripening rate. The expression of MaERS1 gene was inhibited by heat treatment in both NRB and ETB, implying that heat as a physical signal could be sensed by banana fruits through the inhibition of ethylene receptor gene expression. The intensity of MaERF1 transcript signals was elevated in heated bananas, suggesting that the enhanced accumulation of MaERF1 transcript following heat treatment could play an important role in activation of the defense system. In ETB, inhibition of JA biosynthesis by application of IBU down-regulated the expression of MaERF and significantly weakened disease resistance, suggesting involvement of endogenous JA in induction of the gene expression, which was reconfirmed by the fact that exposure to exogenous MeJA following the combination of heat plus IBU treatment restored part of the gene expression. On the other hand, in NRB, application of IBU elevated level of MaERF1 expression at 24 h and enhanced disease resistance, suggesting that, when banana was not exposed to ethephon, the expression of MaERF1 gene was not JA dependent, which was verified by the fact that MeJA application did not enhance MaERF1 gene expression. In conclusion, heat-induced disease resistance in harvested bananas could involve down-regulation of MaERS1 expression and up-regulation of MaERF1 expression and JA pathway could be involved in heat activation of the defense system in bananas exposed to ethephon.

Relationship between Rh-RTH1 and ethylene receptor gene expression in response to ethylene in cut rose

A cDNA clone encoding a putative RTE1-like protein (Rh-RTH1) was obtained from total RNA isolated from senescing rose (Rosa hybrida cv. Tineke) petals using RT-PCR and RACE techniques. The cDNA (1,061 bp) contained an open reading frame of 684 bp corresponding to 227 amino acids. The amino acid sequence had 60.0, 49.6, 61.2, 42.5 and 39.8% identity with that of Arabidopsis RTH, RTE1, tomato GRL2, GRL1 and GR, respectively. Northern hybridization indicated that Rh-RTH1 expression is enhanced by endogenous and exogenous ethylene and inhibited by 1-MCP in petals and gynoecia. Rh-RTH1 expression partly correlated with sites of the ethylene receptor gene Rh-ETR1 and Rh-ETR3 expression, such as the petals, gynoecia, roots, and buds. The induction of Rh-RTH1 and Rh-ETR3 expression was substantially suppressed by 1-MCP treatment, while Rh-ETR1 expression was not reduced by 1-MCP treatment. Following treatment of flowers with sucrose, the level of Rh-RTH1 and Rh-ETR3 mRNA was only slightly decreased in petals and gynoecia. Upon wounding treatment, Rh-RTH1, Rh-ETR1 and Rh-ETR3 showed a quick increase in mRNA accumulation which was positively correlated with the increase in ethylene production. The expression of Rh-RTH1 showed partial correlation with that of Rh-ETR1 and Rh-ETR3.

Increased expression of ethylene receptor genes during low pH-induced root hair formation in lettuce (Lactuca sativa L.) seedlings: direct and indirect induction by ethylene and auxin, respectively

The plant hormones ethylene and auxin mediate the formation of root hairs on lettuce seedlings that are transferred from pH 6.0 to pH 4.0 medium. To investigate the regulatory mechanism of ethylene, we isolated ethylene receptor genes from lettuce. Three putative transmembrane domains were found in Ls-ERS1 and Ls-ETR1 and four in Ls-ETR2 and Ls-ETR3. Five bacterial histidine kinase motifs were highly conserved in Ls-ERS1 and Ls-ETR1, but not Ls-ETR2 or Ls-ETR3. Phylogenetic analysis supported these similarities among family members. Genomic Southern hybridization revealed that each gene existed as a single copy in the genome. mRNAs of these genes were detected in seedling roots after pre-culture at pH 6.0. After transfer to pH 4.0 medium, Ls-ERS1 and Ls-ETR2 expression and ethylene produc- tion increased and were maintained at higher levels than those found at pH 6.0. The addition of 1-aminocyclopropane-1-carboxylic acid (ACC) to the pH 6.0 medium noticeably induced both ethylene production and Ls-ERS1 and Ls-ETR2 expression. A marked increase in the mRNA level of Ls-ERS1, with a slight increase in Ls-ETR2 mRNA level, was noted with the addition of indole-3-acetic acid (IAA); however, ethylene production was also induced. Simulta- neous treatment with an ethylene biosynthesis inhibitor and IAA markedly inhibited ethylene production and ethylene receptor gene expres- sion. These results suggest that ethylene receptor gene expression is differentially regu- lated among the family members during low pH-induced root hair formation in lettuce seedl- ings, and that the increased expression of Ls-ERS1 and Ls-ETR2 during this process is induced by ethylene rather than by auxin.

Induction of ethylene in avocado fruit in response to chilling stress on tree

Chilling of avocado fruit (Persea americana cv. Arad) in the orchard caused a dramatic induction of fruit ripening and a parallel increase in ethylene biosynthesis and receptor genes' expression during shelf life. In-orchard chilling stress stimulated ethylene and CO(2) production already in fruit attached to the tree, and these reduced thereafter during 20 degrees C storage. In non-chilled control fruit, ethylene and CO(2) production started after 3d at 20 degrees C and exhibited a climacteric peak. In-orchard chilling stress also led to membrane destruction expressed as higher electrical conductivity (EC) in chilling stressed (CS) fruit and accelerated softening compared with control fruit. The increase in ethylene production on the day of harvest in CS fruit was accompanied by high expression of two 1-aminocyclopropane-1-carboxylic aCSd (ACC) synthase genes: PaACS1 and PaACS2, and ACC oxidase PaACO. The initial gene expressions of PaACS1, PaACS2, and PaACO in the CS fruit at the day of harvest was similar to the levels reached by the control fruit after 4d at 20 degrees C. The expression levels of both PaETR and PaERS1 in CS fruit on tree were 25 times higher than the control. In control fruit, expression of ethylene receptor genes was very low at harvest and increased in parallel to the onset of the climacteric ethylene peak. PaCTR1 transcript levels were less affected by chilling stress, and small changes (less than 3-fold) were observed in CS fruit on the day of harvest. Together, our results suggest that ethylene biosynthesis and ethylene response-pathway genes are involved in regulation of ethylene responsiveness in response to in-orchard chilling stress and during ripening.

Ethylene insensitivity conferred by a mutated Arabidopsis ethylene receptor gene alters nodulation in transgenic Lotus japonicus.

Transgenics are used to demonstrate a causal relationship between ethylene insensitivity of a seedling legume plant, the level of ethylene receptor gene expression, lateral root growth and Mesorhizobium loti-induced nodule initiation. Lotus japonicus plants expressing the dominant etr1-1 allele of the Arabidopsis thaliana gene encoding a well-characterized mutated ethylene receptor were created by stable Agrobacterium tumefaciens transformation. Single insertion, homozygous lines were characterized for symbiotic properties. Transgenic plants were ethylene insensitive as judged by the lack of the 'Triple Response', and their continued ability to grow and nodulate in the presence of inhibitory concentrations of ACC (1-aminocyclopropane-1-carboxylic acid; an ethylene precursor). Transgenic plants with high insensitivity to ACC had significantly fewer lateral roots and exhibited increased nodulation while showing no altered nitrate sensitivity or lack of systemic autoregulation. Whereas ACC-insensitive shoot growth and nodulation were observed in transformants, root growth was inhibited similarly to the wild type. Increased nodulation was caused by increased infection and a seven-fold increase in nodules developing between xylem poles. Bacteroid numbers per symbiosome increased about 1.7-fold in ethylene-insensitive plants. The study further demonstrates multiple roles for ethylene in nodule initiation by influencing root cell infections and radial positioning, independent of autoregulation and nitrate inhibition of nodulation.

Characterization of ethylene-induced organ abscission in F1 breeding lines of miniature roses ( Rosa hybrida L.)

Miniature potted roses are sensitive to ethylene and respond to it by bud and leaf abscission, leaf yellowing and/or flower senescence. The goal of this study was to develop a selection strategy for characterization of ethylene sensitivity in rose breeding lines. Two hundred and thirty-three F1 genotypes were obtained from a reciprocal crossing of ‘Lavender’ and ‘Vanilla’ cultivars, and evaluated in response to ethylene treatment. Based on ethylene-induced organ abscission, low- and high-sensitive genotypes were selected for physiological and molecular studies compared with the parent plants. After 1 week of ethylene treatment, leaf chroma values and chlorophyll degradation were increased in high-sensitive genotypes, much more than in low-sensitive genotypes. However, after 2 weeks of ethylene treatment, low-sensitive genotypes showed no difference in chroma values, but chlorophyll contents decreased in two out of three genotypes. Expression of ethylene receptor genes ( RhETR1/ 3) and signal transduction genes ( RhCTR1/ 2) was not correlated with ethylene sensitivity of the investigated genotypes. The relative expression of laccase ( RhLAC) was evaluated with respect to the relationships of lignin deposition and abscission. Ethylene-induced expression of RhLAC in high-sensitive genotypes increased more strongly than in low-sensitive genotypes. The lowest level of RhLAC transcript was accumulated in pedicels of genotypes that showed the lowest bud abscission. Enhanced expression of the laccase gene by ethylene may be related to the abscission process.

NAA and Ethylene Regulate Expression of Genes Related to Ethylene Biosynthesis, Perception, and Cell Wall Degradation During Fruit Abscission and Ripening in ‘Delicious’ Apples

Expression of genes for ethylene biosynthesis, ethylene perception, and cell wall degradation in the fruit cortex and abscission zone was examined during fruit abscission and ripening in ‘Delicious’ apples (Malus × domestica). An autocatalytic burst of fruit ethylene production and accelerated fruit softening were associated with increased expression of genes related to ethylene biosynthesis (MdACS and MdACO), whereas reduced expression of ethylene receptor genes (MdETR and MdERS), increased expression of an ethylene signal transduction gene (MdCTR1), and increased expression of genes related to cell wall degradation (MdPG and MdEG) in the fruit cortex occurred during fruit ripening. Aminoethoxyvinylglycine (AVG) or 1−methylcyclopropene (1-MCP) inhibited fruit ethylene production, suppressed expression of MdACS1, MdACO1, MdERS1, and MdPG1 in the fruit cortex, and delayed fruit softening, whereas naphthaleneacetic acid (NAA) increased fruit ethylene production, increased expression of MdACS1, MdACO1, MdERS1 and MdPG1 in the fruit cortex, and accelerated fruit softening. Fruit abscission and expression of MdACS5A, MdACS5B, MdACO1, MdPG2, and MdEG1 in the fruit abscission zone were reduced by AVG and 1-MCP. NAA also reduced fruit abscission while reducing expression of MdPG2 and MdEG1 only in the fruit abscission zone. The levels of MdETR1, MdETR2, MdERS1, and MdERS2 transcripts in the fruit abscission zone decreased during fruit abscission and fruit ripening regardless of treatment. The combination of NAA and AVG was more effective in inhibiting expression of MdPG2 and MdEG1 in the fruit abscission zone and reducing fruit abscission than was either NAA or AVG used alone.

Inhibition of the ethylene response by 1-MCP in tomato suggests that polyamines are not involved in delaying ripening, but may moderate the rate of ripening or over-ripening

Ethylene initiates the ripening and senescence of climacteric fruit, whereas polyamines have been considered as senescence inhibitors. Ethylene and polyamine biosynthetic pathways share S-adenosylmethionine as a common intermediate. The effects of 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception, on ethylene and polyamine metabolism and associated gene expression was investigated during ripening of the model climacteric fruit, tomato (Solanum lycopersicum L.), to determine whether its effect could be via polyamines as well as through a direct effect on ethylene. 1-MCP delayed ripening for 8 d compared with control fruit, similarly delaying ethylene production and the expression of 1-aminocyclopropane-1-carboxylic acid (ACC)-synthase and some ethylene receptor genes, but not that of ACC oxidase. The expression of ethylene receptor genes returned as ripening was reinitiated. Free putrescine contents remained low while ripening was inhibited by 1-MCP, but increased when the fruit started to ripen; bound putrescine contents were lower. The activity of the putrescine biosynthetic enzyme, arginine decarboxylase, was higher in 1-MCP-treated fruit. Activity of S-adenosylmethionine-decarboxylase peaked at the same time as putrescine levels in control and treated fruit. Gene expression for arginine decarboxylase peaked early in non-treated fruit and coincident with the delayed peak in putrescine in treated fruit. A coincident peak in the gene expression for arginase, S-adenosylmethionine-decarboxylase, and spermidine and spermine synthases was also seen in treated fruit. No effect of treatment on ornithine decarboxylase activity was detected. Polyamines are thus not directly associated with a delay in tomato fruit ripening, but may prolong the fully-ripe stage before the fruit tissues undergo senescence.

Ethylene-influenced flower opening and expression of genes encoding Etrs, Ctrs, and Ein3 s in two cut rose cultivars

Exogenous ethylene inhibits floral opening in cut rose ( Rosa hybrida) cv. Kardinal and slightly promotes opening in cv. Samantha. We investigated ethylene production following short exposure to exogenous ethylene, and the expression of ethylene receptor genes ( ETR) and genes in the ethylene signal transduction pathway ( CTR and EIN3). In cv. Kardinal the ethylene production rate was much higher than in cv. Samantha, following ethylene treatment. The expression of ETR fragments was not much affected by ethylene in cv. Kardinal but was up-regulated in cv. Samantha. Data from the literature suggest that ETR is a negative regulator. The up-regulation of ETR, after ethylene treatment, indicates that the sensitivity to ethylene is down-regulated in Samantha but not in Kardinal. No clear effect of ethylene was found on the expression of fragments of CTR and EIN3 genes. It is concluded that the inhibition of floral opening in cv. Kardinal, and its absence in cv. Samantha, can apparently be explained by a differential effect of ethylene on the expression of genes for the ethylene receptor.

Expression of ethylene receptors Dl-ERS1-3 and Dl-ERS2, and ethylene response during flower senescence in Delphinium

To clarify the relationships of flower senescence, especially sepal abscission, and ethylene receptor gene expression in different flower parts, we isolated two cDNAs encoding ethylene receptors Dl-ERS1-3 and Dl-ERS2 from Delphinium flowers. Deduced polypeptides possessed no response regulator domain, indicating that they belong to a family of ethylene response sensor (ERS) ethylene receptors. Dl-ERS1-3 and Dl-ERS2 exhibited constitutive levels during flower senescence. Exogenous ethylene increased transcript levels in sepals, which are influenced by ethylene but not in gynoecia and receptacles, which produce ethylene. It was suggested that expression of ethylene receptor genes under ethylene exposure was differentially regulated in each organ of the flower.