Ethylene Biosynthesis Inhibitor Research Articles

Ethylene Biosynthesis Inhibitors on the Quality of the Coffee Beverage and Efficiency of the Mechanical Harvest

The aim of the project is to evaluate the efficiency of the product based in Ethephonin® the standartization of the maturation of the fruits, in an answer of the mechanical harvest and the quality of the coffee beverage. The study was conducted at Aruã Farm, in Piumhi, Southwest of Brazil. The plants used in the research are from Coffea arábica L, planted in 2005, in the space of 3.2m x 0.60m. The experimental design adopted had randomized blocks with four treatments: T1 – Ethephon® (130ml/100ml water), T2 – controlling treatment, T3 – Ethephon® plus pH reductor (130ml plus 40ml/100 L water), T4 – Ethephon® plus bioprotector (130 ml plus 285.71 gr/100 L water) and 4 repetitions, totalizing, 16 parcels. To determine the percentual of the leaves fall of the coffee trees, four scores of the leaves: before applying the product, 15 days after applying, before and after the mechanical harvest. The harvest started when, the maturation of the beans got the following levels: T1 – 89.79% of cherry fruits, T2 – 72.98% of fruits, T – 86.02% of cherry fruits, T4 86.63% of cherry fruits. After the harvest the beans were taken to testes, of the region. The product Ethephon influenced in the maturation of the coffee fruits, increasing the efficiency of the mechanical harvest, reducing the volume (percentual) of the pass through. The product didn’t influence the defoliation of the plants. There was no interference among the treatments to taste the beverages and the samples ranking.

Supraoptimal Cytokinin Content Inhibits Rice Seminal Root Growth by Reducing Root Meristem Size and Cell Length via Increased Ethylene Content.

Cytokinins (CKs), a class of phytohormone, regulate root growth in a dose-dependent manner. A certain threshold content of CK is required for rapid root growth, but supraoptimal CK content inhibits root growth, and the mechanism of this inhibition remains unclear in rice. In this study, treatments of lovastatin (an inhibitor of CK biosynthesis) and kinetin (KT; a synthetic CK) were found to inhibit rice seminal root growth in a dose-dependent manner, suggesting that endogenous CK content is optimal for rapid growth of the seminal root in rice. KT treatment strongly increased ethylene level by upregulating the transcription of ethylene biosynthesis genes. Ethylene produced in response to exogenous KT inhibited rice seminal root growth by reducing meristem size via upregulation of OsIAA3 transcription and reduced cell length by downregulating transcription of cell elongation-related genes. Moreover, the effects of KT treatment on rice seminal root growth, root meristem size and cell length were rescued by treatment with aminoethoxyvinylglycine (an inhibitor of ethylene biosynthesis), which restored ethylene level and transcription levels of OsIAA3 and cell elongation-related genes. Supraoptimal CK content increases ethylene level by promoting ethylene biosynthesis, which in turn inhibits rice seminal root growth by reducing root meristem size and cell length.

Ethylene biosynthesis is involved in regulating chilling tolerance and SlCBF1 gene expression in tomato fruit

Ethylene plays positive role in cold response of tomato fruit. CBFs (C-repeat/dehydration-responsive element binding factors) have been proved important in regulating plant chilling tolerance. Till now, the role that ethylene biosynthesis played in chilling response of tomato fruit is still unclear. In this study, we used antisense SlACS2 and wild-type Lichun tomato fruit as inhibited- and normal- ethylene biosynthesis models, in order to investigate whether inhibiting ethylene biosynthesis could affect chilling tolerance and SlCBF1 relative expression in tomato fruit. Results showed that antisense SlACS2 tomato fruit suffered more chilling injury, accompanied by higher malondialdehyde content and ion leakage, less proline and soluble protein content, as well as lower antioxidant enzymes activities, suggesting that inhibiting ethylene biosynthesis reduced tomato fruit chilling tolerance. Furthermore, SlCBF1 expression in transgenic fruit was lower than in WT, the second peak of SlCBF1 expression was coincidence with the peaks of both endogenous ethylene production and ACS activity, and there was significant correlation between ACC content and SlCBF1 relative expression, which implied that endogenous ethylene biosynthesis could contribute to upregulate SlCBF1 expression under cold stress. These results revealed that ethylene biosynthesis played important roles in regulating tomato fruit chilling tolerance and SlCBF1 relative expression in tomato fruit.

The Phytophthora sojae RXLR effector Avh238 destabilizes soybean Type2 GmACSs to suppress ethylene biosynthesis and promote infection.

Phytophthora pathogens secrete many effector proteins to manipulate host innate immunity. PsAvh238 is a Phytophthora sojae N-terminal Arg-X-Leu-Arg (RXLR) effector, which evolved to escape host recognition by mutating one nucleotide while retaining plant immunity-suppressing activity to enhance infection. However, the molecular basis of the PsAvh238 virulence function remains largely enigmatic. By using coimmunoprecipitation and liquid chromatography-tandem mass spectrometry analysis, we identified the 1-aminocyclopropane-1-carboxylate synthase (ACS) isoforms, the key enzymes in ethylene (ET) biosynthesis, as a host target of PsAvh238. We show that PsAvh238 interacts with soybean ACSs (GmACSs) invivo and invitro. By destabilizing Type2 GmACSs, PsAvh238 suppresses Type2 ACS-catalyzed ET biosynthesis and facilitates Phytophthora infection. Silencing of Type2 GmACSs, and inhibition of ET biosynthesis or signaling, increase soybean susceptibility to P.sojae infection, supporting a role for Type2 GmACSs and ET in plant immunity against P.sojae. Moreover, wild-type P.sojae but not the PsAvh238-disrupted mutants, inhibits ET induction and promotes P.sojae infection in soybean. Our results highlight the ET biosynthesis pathway as an essential part in plant immunity against P.sojae and a direct effector target.

Transient induction of a subset of ethylene biosynthesis genes is potentially involved in regulation of grapevine bud dormancy release.

Transient increases in ethylene biosynthesis, achieved by tight regulation of transcription of specific ACC oxidase and ACC synthase genes, play a role in activation of grapevine bud dormancy release. The molecular mechanisms regulating dormancy release in grapevine buds are as yet unclear. It has been hypothesized that its core involves perturbation of respiration which induces an interplay between ethylene and ABA metabolism that removes repression and allows regrowth. Roles for hypoxia and ABA metabolism in this process have been previously supported. The potential involvement of ethylene biosynthesis in regulation of dormancy release, which has received little attention so far, is now explored. Our results indicate that (1) ethylene biosynthesis is induced by hydrogen cyanamide (HC) and azide (AZ), known artificial stimuli of dormancy release, (2) inhibitors of ethylene biosynthesis and signalling antagonize dormancy release by HC/AZ treatments, (3) ethylene application induces dormancy release, (4) there are two sets of bud-expressed ethylene biosynthesis genes which are differentially regulated, (5) only one set is transiently upregulated by HC/AZ and during the natural dormancy cycle, concomitant with changes in ethylene levels, and (6) levels of ACC oxidase transcripts and ethylene sharply decrease during natural dormancy release, whereas ACC accumulates. Given these results, we propose that transient increases in ethylene biosynthesis prior to dormancy release, achieved primarily by regulation of transcription of specific ACC oxidase genes, play a role in activation of dormancy release.

Effects of aminoethoxyvinylglycine treatments on pre-harvest fruit drop and fruit quality of Braeburn apples

This study was conducted to determine the effects of increasing aminoethoxyvinylglycine (AVG) concentrations on pre-harvest drop and fruit quality parameters of ‘Braeburn’ apples. Results revealed that AVG treatments increased the fruit removal force and significantly decreased pre-harvest drops compared to control treatment. AVG was found to be more effective in controlling pre-harvest drops than naphthaleneacetic acid (NAA). There were significant differences among AVG doses with regard to preharvest drop rates. The lowest ratio of pre-harvest drop was observed in 400 mg/l AVG treatment. All AVG doses decreased ethylene biosynthesis. Inhibition of ethylene biosynthesis was higher in 300 and 400 mg/l AVG treatments than the other AVG treatment. AVG retarded fruit ripening of ‘Braeburn’ apples. Measurements, performed at different dates of ripening process, revealed higher flesh firmness values for AVG-treated fruits than the control. Starch degradation was delayed by AVG treatments. Effects of AVG on fruit peel color varied with years. While significant effects of AVG treatments on peel color were not observed in the first year, especially higher AVG doses significantly increased L* values and hue angles in the second year. AVG treatments also significantly increased fruit mass in both years. Significant changes in fruit geometric diameters were not observed with AVG treatments, except for 300 mg/l AVG treatment of second year.

Temperature Modifications during Storage to Overcome Weak Neck Disorder in Banana (cv. Rasthali) using α- Amino Isobutyric Acid

Climacteric fruits respond well to the environmental temperature, because the respiration rate and ethylene production would vary according to the temperature. Banana fruit possess very short postharvest life, prone to injuries and postharvest disorders like weak neck because of the climacteric and perishable nature of the fruit. Hence an attempt was made with α- Amino isobutyric acid (AIB) to study the weak neck disorder of the banana under cold storage condition to increase the postharvest life. AIB is an ethylene biosynthesis inhibitor which inhibits the ethylene synthesis by inhibiting ACC oxidase enzyme. Banana fruits were treated with different AIB concentrations (50, 100, 150, 200 ppm along with control) and spraying methods (Dipping and Spraying). AIB @ 150 ppm dipped for 5 minutes showed decreased finger dislodge from the hands (50-70 per cent at 11th day after treatment) compared to control fruits (100 per cent at 9th day after treatment). On comparing AIB with ethylene inhibitor (1-MCP) and chemicals (Hexanal and calcium chloride) under cold and ambient storage condition, AIB showed better result with reduced finger drop. At 11th day of cold storage AIB treated fruits exhibited minimum finger drop of 50 per cent followed by 1-MCP vaporization with finger drop percentage of 60 and control fruits reported the maximum number of finger drop (90 per cent). Under ambient condition at 7th day itself the AIB treated fruits showed 60 per cent finger drop. Hence from the present study, the external temperature would alter the storage life of the fruits which may be an important factor and noted for further improvement of postharvest life of fruits by storing under required temperatures and minimizing the postharvest losses. .

Ethylene promotes cadmium-induced root growth inhibition through EIN3 controlled XTH33 and LSU1 expression in Arabidopsis.

Cadmium (Cd) stress is one of the most serious heavy metal stresses limiting plant growth and development. However, the molecular mechanisms underlying Cd-induced root growth inhibition remain unclear. Here, we found that ethylene signalling positively regulates Cd-induced root growth inhibition. Arabidopsis seedlings pretreated with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid exhibited enhanced Cd-induced root growth inhibition, whereas the addition of the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine decreased Cd-induced root growth inhibition. Consistently, ethylene-insensitive mutants, such as ein4-1, ein3-1 eil1-1 double mutant, and EBF1ox, displayed an increased tolerance to Cd. Furthermore, we also observed that Cd inhibited EIN3 protein degradation, a process that was regulated by ethylene signalling. Genetic and biochemical analyses showed that EIN3 enhanced root growth inhibition under Cd stress through direct binding to the promoters and regulating the expression of XTH33 and LSU1, which encode key regulators of cell wall extension and sulfur metabolic process, respectively. Collectively, our study demonstrates that ethylene plays a positive role in Cd-regulated root growth inhibition through EIN3-mediated transcriptional regulation of XTH33 and LSU1 and provides a molecular framework for the integration of environmental signals and intrinsic regulators in modulating plant root growth.

Technical note: Manipulating interactions between plant stress responses and soil methane oxidation rates

Abstract. It has recently been hypothesised that ethylene, released into soil by stressed plants, reduces the oxidation of methane by methanotroph. To test this, a field trial was established in which maize plants were grown with and without soil moisture stress, and the effects of addition aminoethoxyvinylglycine (AVG; an ethylene biosynthesis inhibitor) and biochar (increases soil water holding capacity and reduces plant stress) were determined following the static incubation of soil samples. AVG increased methane oxidation rates by 50 % (P=0.039), but only in the absence of irrigation. No other treatment effects were observed. This result provides evidence for a positive feedback system between plant stress, ethylene production, and impacts on methanotrophic activity.

Evidence for the Involvement of Auxin, Ethylene and ROS Signaling During Primary Root Inhibition of Arabidopsis by the Allelochemical Benzoic Acid.

Allelopathy is mediated by plant-derived secondary metabolites (allelochemicals) which are released by donor plants and affect the growth and development of receptor plants. The plant root is the first organ which senses soil allelochemicals this results in the production of a shorter primary root. However, the mechanisms underlying this process remain elusive. Here, we report that a model allelochemical benzoic acid (BA) inhibited primary root elongation of Arabidopsis seedlings by reducing the sizes of both the meristem and elongation zones, and that auxin signaling affected this process. An increase in auxin level in the root tips was associated with increased expression of auxin biosynthesis genes and auxin polar transporter AUX1 and PIN2 genes under BA stress. Mutant analyses demonstrated that AUX1 and PIN2 rather than PIN1 were required for the inhibition of primary root elongation during BA exposure. Furthermore, BA stimulated ethylene evolution, whereas blocking BA-induced ethylene signaling with an ethylene biosynthesis inhibitor (Co2+), an ethylene perception antagonist (1-methylcyclopropene) or ethylene signaling mutant lines etr1-3 and ein3eil1 compromised BA-mediated inhibition of root elongation and up-regulation of auxin biosynthesis-related genes together with AUX1 and PIN2, indicating that ethylene signal was involved in auxin-mediated inhibition of primary root elongation during BA stress. Further analysis revealed that the BA-induced reactive oxygen species (ROS) burst contributed to BA-mediated root growth inhibition without affecting auxin and ethylene signals. Taken together, our results reveal that the allelochemical BA inhibits root elongation by increasing auxin accumulation via stimulation of auxin biosynthesis and AUX1/PIN2-mediated auxin transport via stimulation of ethylene production and an auxin/ethylene-independent ROS burst.

Vacuolar processing enzymes, AmVPE1 and AmVPE2, as potential executors of ethylene regulated programmed cell death in the lace plant (Aponogeton madagascariensis)

Perforation formation in Aponogeton madagascariensis (Mirb.) H.Bruggen (lace plant) is an excellent model for studying developmentally regulated programmed cell death (PCD). In this study, we isolated and identified two lace plant vacuolar processing enzymes (VPEs) and investigated their involvement in PCD and throughout leaf development. Lace plant VPE transcript levels were determined during seven different stages of leaf development. PCD and non-PCD cells from “window” stage leaves (in which perforations are forming) were separated through laser-capture microscopy and their transcript levels were also determined. VPE activity was also studied between the cell types, through a VPE activity-based probe JOPD1. Additionally, VPE transcript levels were studied in plants treated with an ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG). The two isolated VPEs, AmVPE1 and AmVPE2, are vegetative type VPEs. AmVPE1 had higher transcript levels during a pre-perforation developmental stage, immediately prior to visible signs of PCD. AmVPE2 transcript levels were higher later during window and late window stages. Both VPEs had higher transcript and activity levels in PCD compared with the non-PCD cells. AVG treatment inhibited PCD and associated increases in VPE transcript levels. Our results suggested that VPEs are involved in the execution of the ethylene-related PCD in the lace plant.

Role of ethylene and related gene expression in the interaction between strawberry plants and the plant growth-promoting bacterium Azospirillum brasilense.

Induced systemic resistance (ISR) is one of the indirect mechanisms of growth promotion exerted by plant growth-promoting bacteria, and can be mediated by ethylene (ET). We assessed ET production and the expression of related genes in the Azospirillum-strawberry plant interaction. Ethylene production was evaluated by gas chromatography in plants inoculated or not with A.brasilense REC3. Also, plants were treated with AgNO3 , an inhibitor of ET biosynthesis; with 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ET biosynthesis; and with indole acetic acid (IAA). Plant dry biomass and the growth index were determined to assess the growth-promoting effect of A.brasilense REC3 in strawberry plants. Quantitative real time PCR (qRT-PCR) was performed to analyse relative expression of the genes Faetr1, Faers1 and Faein4, which encode ET receptors; Factr1 and Faein2, involved in the ET signalling pathway; Faacs1 encoding ACC synthase; Faaco1 encoding ACC oxidase; and Faaux1 and Faami1 for IAA synthesis enzymes. Results showed that ET acts as a rapid and transient signal in the first 12h post-treatment. A.brasilense REC3-inoculated plants had a significantly higher growth index compared to control plants. Modulation of the genes Faetr1, Faers1, Faein4, Factr1, Faein2 and Faaco1 indicated activation of ET synthesis and signalling pathways. The up-regulation of Faaux1 and Faami1 involved in IAA synthesis suggested that inoculation with A.brasilense REC3 induces production of this auxin, modulating ET signalling. Ethylene production and up-regulation of genes associated with ET signalling in strawberry plants inoculated with A.brasilense REC3 support the priming activation characteristic of ISR. This type of resistance and the activation of systemic acquired resistance previously observed in this interaction indicate that both are present in strawberry plants, could act synergistically and increase protection against pathogens.

Phytoglobins regulate nitric oxide-dependent abscisic acid synthesis and ethylene-induced program cell death in developing maize somatic embryos.

During maize somatic embryogenesis, suppression of phytoglobins (Pgbs) reduced ABA levels leading to ethylene-induced programmed cell death in the developing embryos. These effects modulate embryonic yield depending on the cellular localization of specific phytoglobin gene expression. Suppression of Zea mays phytoglobins (ZmPgb1.1 or ZmPgb1.2) during somatic embryogenesis induces programmed cell death (PCD) by elevating nitric oxide (NO). While ZmPgb1.1 is expressed in many embryonic domains and its suppression results in embryo abortion, ZmPgb1.2 is expressed in the basal cells anchoring the embryos to the embryogenic tissue. Down-regulation of ZmPgb1.2 is required to induce PCD in these anchor cells allowing the embryos to develop further. Exogenous applications of ABA could reverse the effects caused by the suppression of either of the two ZmPgbs. A depletion of ABA, ascribed to a down-regulation of biosynthetic genes, was observed in those embryonic domains where the respective ZmPgbs were repressed. These effects were mediated by NO. Depletion in ABA content increased the transcription of genes participating in the synthesis and response of ethylene, as well as the accumulation of ethylene, which influenced embryogenesis. Somatic embryo number was reduced by high ethylene levels and increased with pharmacological treatments suppressing ethylene synthesis. The ethylene inhibition of embryogenesis was linked to the production of reactive oxygen species (ROS) and the execution of PCD. Integration of ABA and ethylene in the ZmPgb regulation of embryogenesis is proposed in a model where NO accumulates in ZmPgb-suppressing cells, decreasing the level of ABA. Abscisic acid inhibits ethylene biosynthesis and the NO-mediated depletion of ABA relieves this inhibition causing ethylene to accumulate. Elevated ethylene levels trigger production of ROS and induce PCD. Ethylene-induced PCD in the ZmPgb1.1-suppressing line [ZmPgb1.1 (A)] leads to embryo abortion, while PCD in the ZmPgb1.2-suppressing line [ZmPgb1.2 (A)] results in the elimination of the anchor cells and the successful development of the embryos.

Quinclorac resistance induced by the suppression of the expression of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase genes in Echinochloa crus-galli var. zelayensis

We previously reported that the mechanism of quinclorac resistance in Echinochloa crus-galli var. zelayensis may be closely related to ethylene biosynthesis and the detoxification of cyanide. Differences in EcCAS gene sequences and expression levels may result in higher capacity to detoxify cyanide in resistant biotypes, which may avoid cyanide accumulation and avoid more ethylene and cyanide production and then avoid damage. In the present study, we focused on the mechanism of resistance related to ethylene biosynthesis in E. crus-galli var. zelayensis. The fresh weight of susceptible and moderately resistant biotypes were significantly reduced after treatment with quinclorac. However, AOA, an ethylene biosynthesis inhibitor, reduced the impact of quinclorac. On pretreatment with AOA, ethylene production was significantly reduced in the three biotypes. The highly resistant biotype produced less ethylene compared to the other two biotypes. Three ACS and seven ACO genes, which are the key genes in ethylene biosynthesis, were obtained. The expression levels of EcACS-like, EcACS7, and EcACO1 varied in the three biotypes upon treatment with quinclorac, which could be manipulated by AOA. In summary, it is inferred that the expression of EcACS-like, EcACS7, and EcACO1 can be stimulated to varying extent after quinclorac treatment in three E. crus-galli var. zelayensis biotypes, which consequently results in varying levels of ethylene production. Lower expression of these three genes results in more resistance to quinclorac, which may also be related to quinclorac resistance in E. crus-galli var. zelayensis.

Characterization and transcriptional regulation of chlorophyll b reductase gene NON-YELLOW COLORING 1 associated with leaf senescence in perennial ryegrass (Lolium perenne L.)

Chlorophyll (Chl) degradation leads to leaf senescence and adversely affects biomass production of forage grasses and aesthetic appearance of turfgrasses. The objectives of this study were to characterize the function of a Chl catabolic gene, NON-YELLOW COLORING 1 (LpNYC1), and to understand its transcriptional regulatory pattern involved in leaf senescence in perennial ryegrass (Lolium perenne L.). The LpNYC1 was initially cloned using the RACE-PCR method. Its encoded protein was localized in chloroplasts and its expression pattern was correlated with the progression of leaf senescence. LpNYC1 shared the same biological function with Arabidopsis NYC1, as overexpression of its encoding gene accelerated chlorophyll degradation in Nicotiana benthamiana and rescued the stay-green phenotype of the Arabidopsis nyc1 null mutant. A yeast one-hybrid cDNA library was prepared from senescent leaves of perennial ryegrass. Using the LpNYC1 promoter as bait, five putative transcription factors upstream of LpNYC1 were pooled out using this method, among which three (LpABI5, LpABF3, and LpEIN3) were orthologous to Arabidopsis transcription factors involved in the ABA and ethylene signaling pathways. The expression of LpNYC1 was highly inducible by ABA and ethephon (ethylene releasing reagent) but was suppressed by treatment with AVG (ethylene biosynthesis inhibitor). Furthermore, LpABI5, LpABF3, LpEIN3 directly activated the expression of LpNYC1 by binding to its promoter. The current result laid the groundwork for future in-depth analysis of the molecular regulation of LpNYC1 and Chl metabolism during leaf senescence in perennial grass species.

Ethylene coordinates seed germination behavior in response to low soil pH in Stylosanthes humilis

Stylosanthes humilis is known to exhibit high persistence in acid soils, however, how low soil pH controls seed germination as well as root and hypocotyl growth remains unknown. This study was carried out to evaluate the hormonal and metabolic alterations induced by low soil pH on seed germination behavior of S. humilis. Seeds of S. humilis were sown in acid soil samples or sand soaked in buffer solution with pH ranging from 4.0 to 7.0. Concentrations of indole-3-acetic acid, ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), primary metabolite profile and final seed germination were evaluated after four days. Low soil pH led to increased final seed germination, concomitantly with higher root penetration into the soil as well as higher ACC and ethylene production by seedlings. Treatment with the ethylene biosynthesis inhibitor L-α-(2-aminoethoxyvinyl)-glycine (AVG) greatly reduced final seed germination under acidic conditions. Final seed germination of seeds treated with AVG was increased by exogenous ethylene application in a dose-dependent manner. Furthermore, low soil pH promoted distinct changes in IAA concentrations, and in carbon and nitrogen metabolism in hypocotyl and roots. Low soil pH increases the final germination of S. humilis seeds through alterations in ethylene metabolism, allowing root penetration into the soil.

Advances in application of small molecule compounds for extending the shelf life of perishable horticultural products: A review

Abstract Most of the horticultural products are highly perishable and reducing their postharvest losses is extremely important. There is a worldwide trend to explore new alternatives to increase shelf life and postharvest quality of horticultural products. This review discusses the use of gaseous and some other low molecular mass compounds as a feasible way to maintain quality and prolong shelf life of rapidly deteriorating horticultural products during postharvest stage. These compounds including nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S), hydrogen peroxide (H2O2), hydrogen gas (H2), carbon dioxide (CO2) and chlorine dioxide (ClO2) could delay horticultural products senescence through different mechanisms such as suppressing respiration rate, inhibiting ethylene biosynthesis, delaying browning and regulating activity of antioxidant enzymes. The review also summarizes the interaction between these molecules and ethylene during horticultural products senescence process. Additionally, NO may cross talk with H2O2 or H2S to promote the quality and prolong the postharvest life of perishable fruits and vegetables. Those compounds regulate the expression of genes during senescence, including ethylene biosynthesis related genes, lipoxygenase gene, cysteine protease gene and chlorophyll degradation related genes. Because of the obvious benefits of these compounds to postharvest freshness of fresh-cut flowers, fruits and vegetables, this area has been and will continue to be one of the priorities of horticultural research in the future.

Mechanisms regulating bitter pit development in ‘Greensleeves’ apples with suppression of ethylene biosynthesis

Mechanisms regulating bitter pit development in ‘Greensleeves’ apples with suppression of ethylene biosynthesis

The Biphasic Root Growth Response to Abscisic Acid in Arabidopsis Involves Interaction with Ethylene and Auxin Signalling Pathways.

Exogenous abscisic acid (ABA) is known to either stimulate or inhibit root growth, depending on its concentration. In this study, the roles of ethylene and auxin in this biphasic effect of ABA on root elongation were investigated using chemical inhibitors and mutants. Inhibitors of ethylene perception and biosynthesis and an auxin influx inhibitor were all found to block the inhibitory effect of high ABA concentrations, but not the stimulatory effect of low ABA concentrations. In addition, three ethylene-insensitive mutants (etr1-1, ein2-1, and ein3-1), two auxin influx mutants (aux1-7, aux1-T) and an auxin-insensitive mutant (iaa7/axr2-1) were all insensitive to the inhibitory effect of high ABA concentrations. In the case of the stimulatory effect of low ABA concentrations, it was blocked by two different auxin efflux inhibitors and was less pronounced in an auxin efflux mutant (pin2/eir1-1) and in the iaa7/axr2-1 auxin-insensitive mutant. Thus it appears that the stimulatory effect seen at low ABA concentrations is via an ethylene-independent pathway requiring auxin signalling and auxin efflux through PIN2/EIR1, while the inhibitory effect at high ABA concentrations is via an ethylene-dependent pathway requiring auxin signalling and auxin influx through AUX1.

Cell wall degrading enzymes activity is altered by high carbon dioxide treatment in postharvest ‘Mihong’ peach fruit

Peach fruits are ripen rapidly after harvest, especially at room temperature. It is difficult to handle because they are scars easily and easy to decay. It is generally acknowledged that modified atmospheres with elevated CO2 inhibits fruit ripening by reduces ethylene biosynthesis. This study was to investigate the affect of high concentration CO2 treatment on ethylene biosynthesis, ACO and softening-related enzymatic activity. Peaches were treated with high CO2 (90 pKa) at the time of sealing in the plastic chambers and then the chambers were ventilated after 3 and 12h. Fruits treated with 90kPa CO2 for 3 or 12h exhibited a significant delay in firmness when compared to control fruits. In addition to fruit softening inhibition, the decay rate was also inhibited by CO2 treatment. Four days after storage at room temperature, CO2 untreated peaches had decay rate of 14%, whereas the decay rate was 6% and 3.5% in fruits treated with 90kPa CO2 for 3 and 12h. The ACO was inhibited by CO2 and the inhibition was enhanced with higher CO2 exposure time. Also High CO2 treatment inhibited the activities of softening-related enzyme such as PG, β-Galactosidase, PEL promoted by ethylene biosynthesis in peaches. These results indicate that increasing levels of CO2 inhibit ethylene biosynthesis by reducing the ACO activity of peach fruits. Results suggest that the effect of CO2 on ethylene production in ‘Mihong’ peach fruit depended on exposure time and CO2 level. Also a short-term treatment with a high concentration of CO2 may be used to reduce ethylene biosynthesis, which may be induced after postharvest of fruit.