Exogenous Ethephon Research Articles

Molecular cloning and expression analysis of the mevalonate diphosphate decarboxylase gene from the latexof Hevea brasiliensis

Mevalonate diphosphate decarboxylase (MVD) catalyzes the conversion of mevalonate diphosphate to isopentenyl diphosphate (IPP), a monomer of a large family of plant isoprenoids and cis-1,4-polyisoprene (natural rubber), which is present in most rubber-producing plants including Hevea brasiliensis (Para rubber tree). Here, we isolated the gene encoding MVD from the latex transcriptome of an elite rubber tree clone, Chinese Academy of Tropical Agriculture Sciences (CATAS) 7-33-97. The full-length cDNA of this gene, designated HbMVD, is 2032 bp long with a 1248-bp open reading frame (ORF) encoding a putative MVD of 415 amino acid residues with a theoretical molecular mass of 45.83 kDa and an isoelectric point (pI) of 6.52. Sequence alignment demonstrated that HbMVD cDNA shares 91 % identity with MVD genes from both Ricinus communis and Jatropha curcas. The genomic sequence of HbMVD is 11,749 bp long, comprising 10 exons and nine introns. The HbMVD promoter contains numerous cis-regulatory elements that are responsive to light, hormones, stress, and so on. Reverse-transcription quantitative PCR (qRT-PCR) revealed that HbMVD was most highly expressed in female flowers, followed by the bark, latex, male flowers, and leaves of untapped, mature rubber trees. The expression level of HbMVD in latex decreased progressively from the first, second, fourth, and third leaf stories of young shoots. Bark tapping (mechanical wounding), as well as exogenous ethephon and methyl jasmonate treatment, significantly upregulated HbMVD expression in the latex. This gene was upregulated in the bark and latex of tapping panel dryness (TPD)-affected trees but downregulated in latex from healthy, renewed bark. Further characterization of HbMVD would provide valuable insights into the involvement of HbMVD in regulating the biosynthesis of natural rubber and other IPP-derived isoprenoids in rubber tree.

Physiological and proteomic mechanisms of waterlogging priming improves tolerance to waterlogging stress in wheat (Triticum aestivum L.)

Both physiological and proteomic analyses were performed to explore the mechanism of waterlogging priming on plant tolerance to waterlogging stress in wheat. Compared with non-primed plants (CW), waterlogging primed plants (WW) showed higher activity of enzymes in the ascorbate–glutathione cycle. In agreement with the physiological results, proteins associated with energy metabolism and stress defense had a significantly higher expression in WW than CW. In particular, the proteins related to ethylene biosynthesis showed a higher expression in WW than CW. Moreover, exogenous ethephon (EW), ethylene precursor 1-aminocyclopropanecarboxylic acid (ACW) and an ethylene inhibitor amino-oxyacetic acid were applied before waterlogging to ascertain the effects of ethylene on waterlogging. Use of ACW resulted in a higher yield as compared with non-pretreatment with waterlogging stress. A greater yield loss in EW was due to the fact that higher ethylene concentration led to a more severe seed abortion. Use of ethylene alleviated the negative effects on leaf photosynthesis by increasing stomatal conductance under waterlogging stress. In short, priming alleviated the negative effects of waterlogging stress in wheat, and use of exogenous ethylene resulted in an increase in leaf photosynthesis by promoting stomata opening under waterlogging stress.

Molecular Cloning and Characterization of Four Genes Encoding Ethylene Receptors Associated with Pineapple (Ananas comosus L.) Flowering.

Exogenous ethylene, or ethephon, has been widely used to induce pineapple flowering, but the molecular mechanism behind ethephon induction is still unclear. In this study, we cloned four genes encoding ethylene receptors (designated AcERS1a, AcERS1b, AcETR2a, and AcETR2b). The 5′ flanking sequences of these four genes were also cloned by self-formed adaptor PCR and SiteFinding-PCR, and a group of putative cis-acting elements was identified. Phylogenetic tree analysis indicated that AcERS1a, AcERS1b, AcETR2a, and AcETR2b belonged to the plant ERS1s and ETR2/EIN4-like groups. Quantitative real-time PCR showed that AcETR2a and AcETR2b (subfamily 2) were more sensitive to ethylene treatment compared with AcERS1a and AcERS1b (subfamily 1). The relative expression of AcERS1b, AcETR2a, and AcETR2b was significantly increased during the earlier period of pineapple inflorescence formation, especially at 1–9 days after ethylene treatment (DAET), whereas AcERS1a expression changed less than these three genes. In situ hybridization results showed that bract primordia (BP) and flower primordia (FP) appeared at 9 and 21 DAET, respectively, and flowers were formed at 37 DAET. AcERS1a, AcERS1b, AcETR2a, and AcETR2b were mainly expressed in the shoot apex at 1–4 DAET; thereafter, with the appearance of BP and FP, higher expression of these genes was found in these new structures. Finally, at 37 DAET, the expression of these genes was mainly focused in the flower but was also low in other structures. These findings indicate that these four ethylene receptor genes, especially AcERS1b, AcETR2a, and AcETR2b, play important roles during pineapple flowering induced by exogenous ethephon.

The role of wheat jasmonic acid and ethylene pathways in response to Fusarium graminearum infection

To study the roles of jasmonic acid (JA) and ethylene (ET) pathways in mediating defense against wheat Fusarium head blight (FHB), the expression patterns of genes in the Fusarium graminearum-challenged spikes between Wangshuibai and its susceptible mutant NAUH117 at the Fhb1 locus were compared using wheat microarray. The results showed that most of JA-associated genes were induced in Wangshuibai while only a few were induced in NAUH117, and most ET-associated genes were up-regulated in both genotypes. ELISA assay showed that in the F. graminearum-challenged spikes, endogenous JA content was increased in Wangshuibai while not in NAUH117. Pre-treatment with exogenous methyl JA could decrease the wheat disease severity. However, pretreatment by exogenous ethephon had no such effect. A lipid transfer protein gene, which is a representative gene for JA pathway, was selected for function analysis in Arabidopsis system using a T-DNA insertion mutant line for LTP gene. It was found that the mutant showed compromised FHB resistance compared with its wildtype, proving the possible role of LTP in FHB resistance of Arabidopsis. These results demonstrated that JA pathway should play a critical role in FHB resistance.

The effects of light and ethylene and their interaction on the regulation of proanthocyanidin and anthocyanin synthesis in the skins of Vitis vinifera berries

Several environmental stimulants and hormones can affect phenolic accumulation in grape berries, but the effects of ethylene and light and their interaction have not been completely deciphered. We measured the accumulation of anthocyanins (ATs) and proanthocyanidins (PAs) in berries of a red-wine grape, Vitis vinifera cv. Cabernet Sauvignon, in four treatments: light exposure with and without ethephon, a commercial growth regulator that quickly converts to ethylene, and box-shading with and without ethephon. Ethephon did not significantly increase the weight and diameter of the berries but altered maturity parameters at 49 days after treatment. Ethephon and light increased the fresh and dry weights of the berry skins, induced the accumulation of total phenolics, total flavonoids, and PAs and up-regulated the transcription of VvLAR1, VvLAR2, VvANR, and VvMYBPA1. Light promoted the accumulation of ATs and the expression of AT biosynthetic genes more effectively than did ethephon. Ethephon and light had interactive effects on grape ripening and the contents of PAs and ATs by the way that light interfered with the effect of exogenous ethephon on endogenous ethylene biosynthesis and the downstream ethylene regulatory pathway. These findings provide new information about the physiological and molecular function of ethylene during berry development and the impact of the interaction between ethylene and light in Vitis vinifera.

Effect of ethylene treatment on phytochemical and ethylene-related gene expression during ripening in strawberry fruit Fragaria x ananassa cv. Camino Real.

In contrast to climacteric fruits, in which ethylene is known to be pivotal, the regulation of ripening in non-climacteric fruits is not well understood. The strawberry is a typical example of a non-climacteric fruit, which has been used as a model system of these types of fruit. In this study, the effect of exogenous ethephon on the expression of ethylene biosynthesis and signaling genes, FaERF2 and FaACO1, was analyzed in the Fragaria ananassa cultivar Camino Real by quantitative real-time polymerase chain reaction, and the physicochemical and phytochemical characteristics of fruits were evaluated in field trials and postharvest tests. Transcript accumulation was influenced by exogenous treatment with ethephon, which affected the pattern of gene expression during different stages of growth and fruit development, with the highest expression occurring during postharvest tests. In addition, ethephon significantly influenced the phytochemical profile of sugars, anthocyanins, phenolic compounds, and vitamin C contents both in the field- and postharvest-treated fruits at different stages. These results indicate that ethylene regulates the phenylpropanoid maturation pathway in strawberry fruit.

外源乙烯利、锌协同促进长春花叶片中长春碱的含量

药用植物长春花叶片中含有的长春碱在外源锌胁迫条件下其含量有一定程度上的增加。而在此基础上加入外源乙烯利后的协同作用下，更加促进了长春碱含量的增加，并且随着处理浓度的增加使之呈现出规律性变化。在外源锌和乙烯利的协同作用条件下，长春花叶片的干物质积累以及乙烯气体释放量等参数也有显著提高。 Under Zinc (Zn) stress conditions, the production of vinblastine was increased in the medicinal plant Catharanthus roseus leaves. The combinational treatment with Zn and ethephon further promoted vinblastine accumulation in C. roseus leaves compared with Zn-stressed plants. This elevation of vinblastine induced by ethephon was dependent on the dose of exogenous ethephon. Besides, the dry biomass accumulation of leaves and ethylene release were also increased significantly in Catharanthus roseus seedlings affected by the combined treatment with exogenous Zn and ethephon.

Influence of exogenous ethylene on cambial activity, xylogenesis and ray initiation in young shoots of Leucaena leucocephala (lam.) de Wit

The effect of exogenous ethephon on cambial activity, xylem production and ray population in young shoots of Leucaena leucocephala was investigated anatomically. The application of ethephon showed a diphasic effect on cambial activity and xylogenesis in a dose dependent manner. Lower concentration of ethephon enhanced cambial activity while high concentrations reduced cambial cell divisions and daughter-cell differentiation. High ethephon concentration also resulted in shorter vessel elements, thick walled fibers and phenolic accumulation in ray cells and vessel elements, whereas low concentration allowed elongation of fibers and vessel elements. The density of rays increased significantly with increase in ethylene concentration. The evaluation of longitudinal sections of cambial zone in ethephon treated plants showed high frequency of transformation of fusiform initials into ray initials through divisions and segmentation, resulting in high ray frequency in both xylem and phloem. The present study demonstrates that ethylene plays an important role in regulating secondary vascular tissue composition by reducing the population of fusiform initials in the cambium.

Interactions between polyamines and ethylene during grain filling in wheat grown under water deficit conditions

This study was to test the hypothesis that polyamines (PAs) and ethylene may be involved in mediating the effect of water deficit on grain filling. Two wheat cultivars, drought-tolerant Shannong16 (SN16) and drought-sensitive Jimai22 (JM22), were used and subjected to well-watered and severe water deficit (SD) during grain filling. SD reduced the weight of superior and inferior grains, by 7.38 and 23.54 % in JM22, 13.8 and 2.2 % in SN16, respectively. Higher free-spermidine (Spd) and free-spermine (Spm) concentration and lower free-putrescine (Put) concentration, ethylene evolution rate (EER) and 1-aminocylopropane-1-carboxylic acid (ACC) concentration were found in superior grains than those in inferior ones. Opposite to the variations of Spd and Spm concentration, ACC, Put concentration and EER were significantly increased under SD. The percentage variation of PAs and ACC differed with cultivars and grain types. ACC concentration of superior and inferior grains under SD increased significantly at 21 days post-anthesis, by 90 and 164 % in JM22, 65 and 13.2 % in SN16, respectively. The equivalent value of Put concentration was 1.04 and 7.9 % in JM22, 34.4 and 10.3 % in SN16. Spd concentration of superior grains showed a higher decrease than that of inferior ones in both cultivars, while Spm exhibited an opposite trend between both grain types. These percentage variations were highly consistent with the differed responses of weight of both grain types to SD in JM22 and SN16. Grain filling rate was negatively correlated with EER and ACC concentration, while positively correlated with Spd and Spm concentration as well as the ratio of Spd or Spm to ACC. Exogenous Spd or aminoethoxyvinylglycine (an inhibitor of ethylene synthesis by inhibiting ACC synthesis) obviously reduced ACC concentration and EER and increased Spd and Spm concentration, while exogenous ethephon (an ethylene-releasing agent) or methylglyoxal-bis (an inhibitor of Spd and Spm synthesis) showed the opposite effects. The results suggested that it would be good for wheat to have the physiological traits of higher Spd and Spm, as well as a higher Spd/ACC or Spm/ACC, under SD.

Effects of different harvest maturities and exogenous ABA, fluridone, and ethephon treatments on fruit ripening of ‘Zhonghuashoutao’ peach

Influence of different maturity stages and treatments of ethephon, exogenous ABA, and fluridone on the ripening and hormone level of ‘Zhonghuashoutao’ peach during development and post-harvest storage were investigated. The accumulation of endogenous ABA appeared at the onset of ripening and peaked at two weeks before harvest. Fruit firmness decreased, while ethylene release and SSC/TA increased sharply after a maximum peak of ABA, which have triggered the initiation of the fruit ripening. The fruits, harvested at 170 d when fruits have ripened and stored at 20 °C, showed an ethylene climacteric peak, and the pulp started softening normally, and the SSC/TA value increased. Compared with them, the immature green fruits harvested at other dates, could not mature normally due to the lack of normal reciprocity between ABA and ethylene. The ethylene release was promoted by the treatment of exogenous ABA and ethephon during ripening until the endogenous ABA reached a maximum value. However, fluridone treatment showed an inhibitory effect. The above-mentioned changes occurred again in the peach fruits after harvest. The results indicated that both ABA and ethylene play important roles in peach ripening, and their action depended on the ripening stage of peach.

Ethylene and its interaction with other hormones in tension wood formation in Leucaena leucocephala (Lam.) de Wit

The effect of exogenous ethephon and its combination with gibberellic acid (GA3), indole-3-acetic acid (IAA) and benzyl amino purine (BAP) on tension wood formation in the vertically growing shoots of Leucaena leucocephala has been studied using light and scanning electron microscopy (SEM). The application of exogenous ethephon induced tension wood formation. The percentage of tension wood severity in the shoots was directly proportional to the concentration of ethephon applied. SEM studies revealed the replacement of S2 and S3 fibre wall layers with the gelatinous layer (G-layer) in response to high concentration of ethephon. Ethephon exhibited synergistic interaction with GA3 and BAP in tension wood formation. Fibres and vessel elements in tension wood, induced by ethylene and its combination with other hormones showed increase or decrease in their dimensions irrespective of their concentration and combination. The density of rays increased in all the treatments except in the combination of ethephon and IAA. The anatomical data indicate that ethylene plays a major role in tension wood formation and it interacts synergistically with gibberellins and cytokinin. On the other hand, such synergistic interaction was not found between ethephon and IAA in tension wood formation.

Hormonal regulation of Freesia cutflowers and FhACS1

The differential transcriptional responses of a freesia 1-aminocyclopropane-l-carboxylate synthase gene (FhACS1) to exogenous ethephon, abscisic acid (ABA), salicylic acid (SA), indole-3-acetic acid (IAA), 6-benzylaminopurine (6-BA), silver thiosulfate (STS) and sugar were studied using real-time quantitative PCR. Pretreatments for periods of 24h were evaluated in bud 3 and bud 6 on the inflorescence during freesia flower development and senescence. The results showed that individual exogenous pretreatment with ethephon, IAA, ABA and SA all resulted in the accelerated senescence of freesia flowers compared to those of control buds. Ethephon enhanced FhACS1 expression and extended this high expression; IAA induced an earlier and higher accumulation of FhACS1 transcripts in bud 3, held-up FhACS1 transcript accumulation in later development in bud 6; ABA evidently stimulated a stronger and earlier response of FhACS1 and SA led a higher and longer FhACS1 transcript accumulation. Conversely, 6-BA, STS and sugar pretreatments had a positive effect on the flower development and downregulated FhACS1 expression. Among these treatments, 6-BA significantly restrained the accumulation of the FhACS1 transcript, especially in bud 6; STS also lowered the FhACS1 transcription level overall; while sugar postponed the arrival of the FhACS1 expression peak and significantly decreased the amount of FhACS1 transcript. These results show that these phytohormones and chemical substances signals lead to transcriptional regulation of FhACS1, conjecturing that FhACS1 may participate in the complex hormonal and developmental net works in freesia flower senescence.

Characterization of HbEREBP1, a wound-responsive transcription factor gene in laticifers of Hevea brasiliensis Muell. Arg.

AP2/ERF transcription factors play an important role in regulation of the cross-talk between ethylene and jasmonate signaling pathways mediating defense responses of plants to biotic and abiotic stresses. In this study, an AP2/ERF transcription factor gene was isolated and characterized from laticifers of rubber tree by using RACE and real time PCR. The full length cDNA, referred to as HbEREBP1, was 1,095bp in length and contained a 732bp open reading frame encoding a putative protein of 243 amino acid residues. The molecular mass of the putative protein is 26.4kDa with a pI of 9.46. The deduced amino acid sequence had a specific domain of AP2 superfamily and an ethylene-responsive element binding factor-associated amphiphilic repression motif, sharing 42.4, 39.1, and 38.0% identity with that of AtERF11, AtERF4, and AtERF8 in Arabidopsis, respectively. HbEREBP1 expression was down-regulated by tapping and mechanical wounding in the laticifers of adult trees. It was also down-regulated at early stage while up-regulated at late stage upon treatment with exogenous ethephon or methyl jasmonate, which was reverse to the case of defense genes in laticifers of epicormic shoots of rubber tree. Our results suggest that HbEREBP1 may be a negative regulator of defense genes in laticifers.

Effects of increased endogenous ethylene on plant salt tolerance in Arabidopsis seedlings under saline condition.

The effects of endogenous ethylene on plant salt tolerance in Arabidopsis seedlings in exposure to salinity were investigated in the present work.The results showed that 100 mmol·L-1 NaCl significantly decreased seedling root elongation and root fresh weight.Application of exogenous ethephon obviously alleviated salt-induced inhibition of root length and biomass accumulation.Comparatively,exogenous ACC had a positive effect merely on alleviating root weight inhibition caused by salt stress.The root ROS level in salt-stressed seedlings was also increased drastically,and both ethephon and ACC could keep the root ROS level at a low level as control under NaCl stress conditions.It was proposed that improvement of Arabidopsis salt tolerance induced by ethylene is tightly related to root redox state.

Abscisic acid-induced resistance against the brown spot pathogen Cochliobolus miyabeanus in rice involves MAP kinase-mediated repression of ethylene signaling.

The plant hormone abscisic acid (ABA) is involved in an array of plant processes, including the regulation of gene expression during adaptive responses to various environmental cues. Apart from its well-established role in abiotic stress adaptation, emerging evidence indicates that ABA is also prominently involved in the regulation and integration of pathogen defense responses. Here, we demonstrate that exogenously administered ABA enhances basal resistance of rice (Oryza sativa) against the brown spot-causing ascomycete Cochliobolus miyabeanus. Microscopic analysis of early infection events in control and ABA-treated plants revealed that this ABA-inducible resistance (ABA-IR) is based on restriction of fungal progression in the mesophyll. We also show that ABA-IR does not rely on boosted expression of salicylic acid-, jasmonic acid -, or callose-dependent resistance mechanisms but, instead, requires a functional Galpha-protein. In addition, several lines of evidence are presented suggesting that ABA steers its positive effect on brown spot resistance through antagonistic cross talk with the ethylene (ET) response pathway. Exogenous ethephon application enhances susceptibility, whereas genetic disruption of ET signaling renders plants less vulnerable to C. miyabeanus attack, thereby inducing a level of resistance similar to that observed on ABA-treated wild-type plants. Moreover, ABA treatment alleviates C. miyabeanus-induced activation of the ET reporter gene EBP89, while derepression of pathogen-triggered EBP89 transcription via RNA interference-mediated knockdown of OsMPK5, an ABA-primed mitogen-activated protein kinase gene, compromises ABA-IR. Collectively, these data favor a model whereby exogenous ABA enhances resistance against C. miyabeanus at least in part by suppressing pathogen-induced ET action in an OsMPK5-dependent manner.

Duration and dosage effect of chemical defense in maize (<I>Zea mays</I>) mediated by exogenous ethephon

为探明外源乙烯利对玉米化学防御作用诱导的浓度和时间效应，本文采用化学和分子生物学相结合的方法，研究了不同浓度乙烯利处理玉米后，叶片乙烯释放量及其合成调控关键基因<i>ACS</i>和<i>ACO</i>表达的变化，典型化感物质丁布的含量及其关键调控基因<i>BX</i>₁和<i>BX</i>₉表达的变化，以及其他调控次生代谢物的关键基因表达的时间动态。结果表明，外源乙烯利处理玉米12 h时，玉米叶片中丁布含量明显增加；24 h后，丁布含量反而大量降低，48 h后对丁布含量影响不大。外源乙烯利对合成丁布的调控基因<i>BX</i>₁没有诱导作用，但处理12 h和24 h对BX₉有明显诱导作用。外源乙烯利处理12 h能够使<i>ACS</i>和<i>ACO</i>表达量上升，浓度为40 μL·L^-1和60 μL·L^-1乙烯利处理使玉米叶片丁布含量大量降低，<i>BX</i>₁和<i>BX</i>₉的表达量有所下调。外源乙烯利能够使蛋白酶抑制剂<i>MPI</i>表达量升高，且乙烯利浓度越高，诱导作用越明显，但对调控挥发物的<i>FPS</i>和<i>TPS</i>基因表达没有影响。说明外源乙烯利能够启动玉米体内的乙烯途径，诱导玉米启动化学防御过程，但这种作用很可能是负反馈型的。

Effects of Ethylene on the Production of Female Flowers by “Burpless Hybrid” Cucumber (Cucumis Sativus L.) In Vitro

ABSTRACTTo investigate the role of ethylene in sex expression by cucumber (Cucumis sativus L.) in vitro, whole seeds of ‘Burpless Hybrid’ were explanted onto modified Murashige and Skoog (MS, 1962) medium supplemented with various concentrations of Ethephon (2-Chloroethyl phosphonic acid, Ethrel®), an ethylene releasing compound (0.0, 1.0, 2.0, 5.0, and 10.0 mg/l). Exogenous Ethephon significantly increased the incidence of female flowers and reduced the number of male flowers, especially at 10.0 mg/l (8.5 female flowers/tube vs.0.0 female flowers/tube for control). Control expiants (0.0 mg/l Ethephon) produced only male flowers (2.8 male flowers/tube). This information will be useful for researchers interested in studying flower induction, development, and sex regulation in vitro.

The susceptibility of pepper (Capsicum annuum) to heat induced flower abscission: Possible involvement of ethylene

SUMMARYHeat stress causes abscission of flowers in pepper plants and thus reduces yield. In the present study, we investigated the involvement of ethylene in heat-stress related flower abscission, by comparing the response of flowers of bell pepper, cv. Maor, known to be sensitive to flower abscission, and flowers of paprika, cv. Lehava, a resistant cultivar of Capsicum annuum. Their differing susceptibilities to high temperatures depend on light. Under high-temperature, high-light conditions, bell pepper was less susceptible than paprika, but, under high-temperature low-light, bell pepper was more susceptible. At high temperatures, flower explant abscission was much higher with bell pepper than paprika. Ethylene production (EP) by bell pepper explants reached a maximum at 34°C and decreased at higher temperatures (42 and 48 C), while in paprika EP rates were lower and reached the maximum at 42°C. Explants of bell pepper flowers were more susceptible to exogenous ethephon than paprika flowers. The sensiti...

Effect of 2‐chloroethylphosphonic acid on capsule formation and alkaloid content in Papaver somniferum

Application of different concentrations of ethephon (2‐chloroethylphosphonic acid) to Papaver somniferum L. at the times of stem elongation, bud, and capsule formation produced different effects. Ethephon (10‐2M) retarded growth of the plant and inhibited capsule formation during stem elongation, significantly reduced capsule size during the flowering period, but did not alter capsule development during capsule formation. When applied during the period of stem elongation, ethephon (10‐3M and 10‐4M) reduced capsule size; alkaloid accumulation was reduced by ethephon at a concentration of 10‐3M, but slightly increased by 10‐4M. Ethephon (10‐3M and 10‐4M) did not alter capsule development or alkaloid content significantly when applied during bud formation, but stimulated capsule size and alkaloid content when applied during capsule formation. Pretreating the plants with Ag+ (silver nitrate) did not reverse the ethephon effect. The results suggest that capsule maturation and alkaloid accumulation in P. somniferum are modified by ethylene, which is produced as a result of exogenous ethephon treatment.