Ethylene Treatment Research Articles

Settings, Quantification, and Statistical Analyses beyond p‐Values for Arabidopsis Ethylene Responses

AbstractEthylene is a gaseous plant hormone and plays various roles in plant growth and development. Studies on ethylene‐induced responses have advanced the knowledge about ethylene signaling and effects of its interactions with other plant hormones and with biotic and abiotic cues. Degrees of the ethylene response can be quantified on the basis of the “seedling triple‐response assay” that primarily measures the hypocotyl and/or root lengths of etiolated Arabidopsis seedlings. Different laboratories perform the assay differently, possibly with various degrees of arbitrariness, and experimental results across independent studies can hardly be shared and compared. An optimal and standardized protocol for the setting of ethylene treatment may facilitate data sharing, reproducing, and new findings. Data collected from experiments are quantified and analyzed statistically to support scientific inference. On the other hand, erroneous statistical practices are criticized for muddling scientific inference, leading to poor reproducibility and false results. Grasping the basic concepts of statistics may avoid erroneous practices and inference. Different settings for ethylene treatment prevalently adapted in the field are compared in this study, analyzed statistically to explain how the settings may affect the outcome, and a standardized conduct for the seedling triple‐response assay is proposed.

Ethylene Induces a Rapid Degradation of Petal Anthocyanins in Cut Vanda 'Sansai Blue' Orchid Flowers.

Ethylene plays a major role in the regulation of flower senescence, including in the ethylene-sensitive Vanda ‘Sansai Blue’ orchid flowers. This cut flower is popular in Thailand due to its light blue big size florets possessing a beautiful shape pattern. In the present study, we further examined the rapid ethylene-induced process of active anthocyanin degradation in cut Vanda ‘Sansai Blue’ flowers, which occurred much before detection of other typical senescence-related symptoms. For this purpose, the cut inflorescences were exposed to air (control), 1 or 10 μl L−1 ethylene for 24 h, or to 0.2 μl L−1 1-methylcyclopropene (1-MCP) for 6 h followed by 10 μl L−1 ethylene for 24 h at 21°C, and the effects of these treatments on various parameters were assayed. While the fading-induced effect of ethylene was not concentration-dependent in this range, the ethylene treatment significantly reduced the flower vase life in a concentration-dependent manner, further confirming the separation of the bleaching process from senescence. Exposure of the inflorescences to 1-MCP pre-treatment followed by 10 μl L−1 ethylene, recovered both inflorescence color and anthocyanin content to control levels. Quantification of total anthocyanin content, performed by HPLC analysis on the basis of cyanidin-3-glocuside equivalents, showed that ethylene reduced and 1-MCP recovered the anthocyanins profile in non-hydrolyzed anthocyanin samples of Vanda ‘Sansai Blue’ florets, assayed at half bloom and bloom developmental stages. The results showed that the ethylene-induced color fading, observed immediately after treatment, resulted from a significant reduction in the levels of the two main anthocyanidins, cyanidin and delphinidin, as well as of other anthocyanidins present in low abundance, but not from changes in the levels of flavonols, such as kaempferol. This anthocyanin degradation process seems to operate via ethylene-increased peroxidase activity, detected at the bud stage. Taken together, our results suggest that the ethylene-induced rapid color bleaching in petals of cut Vanda ‘Sansai Blue’ flowers is an outcome of in-planta anthocyanin degradation, partially mediated by increased peroxidase activity, and proceeds independently of the flower senescence process.

Exogenous ethylene alleviates chilling injury of ‘Huangguan’ pear by enhancing the proline content and antioxidant activity

Peel browning spots (PBS) is a chilling injury (CI) symptom in cold-stored ‘Huangguan’ pear. In the present study, the effect of exogenous ethylene on CI and its correlation to proline and reactive oxygen species (ROS) metabolism was investigated. The results showed that ethylene treatment (100 μL L−1 for 24 h) could completely inhibit PBS appearance without significantly affecting fruit firmness, soluble solids content (SSC) and titratable acidity (TA), enhance ethylene production rate at the initiate stage of storage, and promote proline accumulation by increasing activities of pyrroline-5-carboxylate synthetase (P5CS), ornithine-delta-aminotransferase (OAT) and up-regulating expression of P5CS1 and OAT1 genes, decreasing proline dehydrogenase (PDH) activity and the expression of PDH1 gene in peel. Moreover, the ethylene treatment suppressed the accumulation of H2O2, O2- and malondialdehyde (MDA), maintained higher levels of ascorbic acid (AsA) and glutathione (GSH), and meanwhile enhanced activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as expression of the genes such as SOD1, CAT1, and APX1 which could encode these enzymes in peel. These results suggested that ethylene alleviated the CI of ‘Huangguan’ pear by promoting the proline accumulation and antioxidant activity of peel.

Ethylene and 1-MCP treatments affect leaf abscission and associated metabolism of Chinese cabbage

Leaf abscission during storage of Chinese cabbage (Brassica rapa, subspecies pekinensis and chinensis) can result in serious losses. To uncover the effects of the plant hormone ethylene on leaf abscission, harvested cabbages were treated with ethylene and its competitive inhibitor, 1-methylcyclopropene (1-MCP), and with 1-MCP followed by ethylene. Ethylene treatment accelerated leaf abscission, altered cell structure of the abscission zones, and increased activity and gene expression of cell wall-degrading enzymes. Expression of genes related to ethylene receptors and signaling pathways including BcERS1, BcERS2, BcETR2, BcCTR1, BcEIL1, BcEIL2, and BcEIL3 were also up-regulated. In 1-MCP-treated samples, leaf breakstrength was higher, and the increase of cell wall-degrading enzyme activity and the expression of enzyme-related genes were reduced. Notably, ethylene sensitivity recovered upon subsequent ethylene treatment following 1-MCP treatment. These results indicated that ethylene may constitute an important factor in leaf abscission of Chinese cabbage.

Deciphering the involvement of glutathione in phytohormone signaling pathways to mitigate stress in planta

Phytohormone signaling in plant defence is a well-established fact. In this intricate process, glutathione (GSH) is progressively gaining an importance. To unravel further, exogenous treatment of Arabidopsis thaliana plants, viz. wild type Col-0; AtECS1, the transgenic line exhibiting enhanced GSH content, and pad2-1, a GSH-deficient mutant, with various phytohormones like salicylic acid (SA), jasmonic acid (JA), ethylene (ET) and abscisic acid (ABA) followed by quantitative real time (RT) PCR analysis of stress responsive transcripts were performed. Results showed upregulation of PR1, PR2 (pathogenesis related1, 2) and NPR1 (nonexpressor of PR gene1), with greater expressions in AtECS1 and lower in pad2-1, while PR4 (pathogenesis related4) and AOS (allene oxide synthase) remained unchanged, after SA treatment. Whereas, ACO1 (1-aminocyclopropane-1-carboxylate, ACC oxidase1), PR4 and AOS were upregulated with highest expression in AtECS1, lowest in pad2-1 along with unchanged expressions of NPR1 and PR1 after JA treatment. Upon ET treatment, upregulation of ACO1 and PR4, as well as PR1, PR5 and NPR1 were noted, with maximum expressions in AtECS1 and lower in pad2-1. ABA treatment enhanced the expression of LHY (late elongated hypocotyl), ADC2 (arginine decarboxylase2) and PR4 with highest expression in AtECS1, while, expression of NPR1 and PR1 remained unchanged. Collectively, our results demonstrated the upregulation of stress responsive genes in AtECS1 both under control and treated conditions. Thus, GSH seems to play an essential role in modulating the complex crosstalk that exists within phytohormonal signaling pathways, probably in a beneficial way which might suggests its significance to mitigate stress in planta.

Harvest time affects quality and storability of kiwifruit (Actinidia spp.): Cultivars during long-term cool storage

In this study, the possibility of prolonging the freshness of kiwifruit cultivars for the purpose of even distribution in time and place has been investigated. Green ‘Hayward’, gold ‘Haegeum’ and red ‘Hongyang’ kiwifruit cultivars were harvested at 160, 170 and 180 days after full bloom (DAFB) and stored at 0 °C until 4 months. Firmness and firmness related parameters, biochemical parameters, physiological parameters, decay percentage and overall sensory evaluation were observed during the study. On the basis of harvesting time, the order of storability of all the three cultivars could be 160 DAFB > 170 DAFB >180 DAFB, respectively. The study revealed that kiwifruit harvested at 160 DAFB were stored up to 4 months without affecting major quality indices during storage. However, overall sensory quality evaluation showed that kiwifruits harvested at 160 DAFB attained good eating quality after 3 months of storage in green and red kiwi cultivars, and after one month storage in gold kiwi cultivar. Hence, in order to ensure good sensory quality and to fulfill consumer's preference during distribution, further ripening studies like exogenous ethylene treatment are necessary immediately after harvest or at any time during the storage period

The Roles of GmERF135 in Improving Salt Tolerance and Decreasing ABA Sensitivity in Soybean.

Abscisic acid (ABA) mediates various abiotic stress responses, and ethylene responsive factors (ERFs) play vital role in resisting stresses, but the interaction of these molecular mechanisms remains elusive. In this study, we identified an ABA-induced soybean ERF gene GmERF135 that was highly up-regulated by ethylene (ET), drought, salt, and low temperature treatments. Subcellular localization assay showed that the GmERF135 protein was targeted to the nucleus. Promoter cis-acting elements analysis suggested that numerous potential stress responsive cis-elements were distributed in the promoter region of GmERF135, including ABA-, light-, ET-, gibberellin (GA)-, and methyl jasmonate (MeJA)-responsive elements. Overexpression of GmERF135 in Arabidopsis enhanced tolerance to drought and salt conditions. In addition, GmERF135 promoted the growth of transgenic hairy roots under salt and exogenous ABA conditions. These results suggest that soybean GmERF135 may participate in both ABA and ET signaling pathways to regulate the responses to multiple stresses.

Ethylene-mediated improvement in sucrose accumulation in ripening sugarcane involves increased sink strength

BackgroundSugarcane is a major crop producing about 80% of sugar globally. Increasing sugar content is a top priority for sugarcane breeding programs worldwide, however, the progress is extremely slow. Owing to its commercial significance, the physiology of sucrose accumulation has been studied extensively but it did not lead to any significant practical outcomes. Recent molecular studies are beginning to recognize genes and gene networks associated with this phenomenon. To further advance our molecular understanding of sucrose accumulation, we altered sucrose content of sugarcane genotypes with inherently large variation for sucrose accumulation using a sugarcane ripener, ethylene, and studied their transcriptomes to identify genes associated with the phenomenon.ResultsSucrose content variation in the experimental genotypes was substantial, with the top-performing clone producing almost 60% more sucrose than the poorest performer. Ethylene treatment increased stem sucrose content but that occurred only in low-sugar genotype. Transcriptomic analyses have identified about 160,000 unigenes of which 86,000 annotated genes were classified into functional groups associated with carbohydrate metabolism, signaling, localization, transport, hydrolysis, growth, catalytic activity, membrane and storage, suggesting the structural and functional specification, including sucrose accumulation, occurring in maturing internodes. About 25,000 genes were differentially expressed between all genotypes and treatments combined. Genotype had a dominant effect on differential gene expression than ethylene treatment. Sucrose and starch metabolism genes were more responsive to ethylene treatment in low-sugar genotype. Ethylene caused differential gene expression of many stress-related transcription factors, carbohydrate metabolism, hormone metabolism and epigenetic modification. Ethylene-induced expression of ethylene-responsive transcription factors, cytosolic acid- and cell wall-bound invertases, and ATPase was more pronounced in low- than in high-sugar genotype, suggesting an ethylene-stimulated sink activity and consequent increased sucrose accumulation in low-sugar genotype.ConclusionEthylene-induced sucrose accumulation is more pronounced in low-sugar sugarcane genotype, and this is possibly achieved by the preferential activation of genes such as invertases that increase sink strength in the stem. The relatively high enrichment of differentially expressed genes associated with hormone metabolism and signaling and stress suggests a strong hormonal regulation of source-sink activity, growth and sucrose accumulation in sugarcane.

Ectopic Expression of Cold Responsive LlaCIPK Gene Enhances Cold Stress Tolerance in Nicotiana tabacum.

Low-temperature stress severely affects the growth, development, and geographical distribution of various crop plants, resulting in significant economic loss to producers. In a quest to identify cold-regulated genes, we constructed a cDNA suppression subtractive library from a high altitude adapted ecotype of Lepidium. We cloned a cold-induced gene LlaCIPK from the subtracted cDNA library which gave homology to Arabidopsis CIPK15 gene. The predicted 3D structure of LlaCIPK protein also showed homology with Arabidopsis CIPK protein. Quantitative real-time PCR analysis in Lepidium seedlings exposed to 6 h of cold stress shows a 3-fold increase in the expression of LlaCIPK transcript. The expression of LlaCIPK was also differentially regulated by ethylene, CaCl2, ABA, and SA treatments. Ethylene and CaCl2 treatments up regulated LlaCIPK expression, whereas ABA and SA treatments down regulated the LlaCIPK expression. Transgenic plants overexpressing LlaCIPK gene under constitutive promoter show an increased level of proline and cell membrane stability. Taken together, our results suggest that the LlaCIPK contributes to the cold-response pathway in Lepidium plants.

Involvement of cytokinin response regulator RhRR1 in the control of flowering

Flowering at a suitable time is critical for ensuring reproductive success in the plant life cycle. The transition from vegetative growth to reproduction development is finely tuned by environmental and endogenous signals. To date, control of flowering involves five genetically defined pathways. However, the role of type-A response regulator genes in regulation of this process remains largely unclear. In the present study, we cloned and characterized a type-A response regulator gene (RhRR1) in rose. The expression of RhRR1 significantly increased in axillary bud during the transition from the vegetative growth to the start of floral differentiation, and in rose flowers in response to exogenous cytokinin or 1-methylcyclopropene (1-MCP) treatments, while that expression was markedly repressed by ethylene treatment. RhRR1 has the highest degree of sequence homology to AtARR8 and AtARR9, and is localized in the nucleus. Ectopic expression RhRR1 in Arabidopsis promoted early flowering, accompanied with the less rosette leaf number at bolting, and shorter bolting time after transferring the plants into pots. In addition, the expression of flowering regulatory genes in RhRR1 transgenic Arabidopsis, including FLOWERING LOCUS D, GA REQUIRING 1, LUMINIDEPENDENS, LEAFY, and TWIN SISTER OF FT clearly increased. These results allow us to infer that RhRR1 plays a key role in the control of flowering.

Transcriptome analysis of atemoya pericarp elucidates the role of polysaccharide metabolism in fruit ripening and cracking after harvest

BackgroundMature fruit cracking during the normal season in African Pride (AP) atemoya is a major problem in postharvest storage. Our current understanding of the molecular mechanism underlying fruit cracking is limited. The aim of this study was to unravel the role starch degradation and cell wall polysaccharide metabolism in fruit ripening and cracking after harvest through transcriptome analysis.ResultsTranscriptome analysis of AP atemoya pericarp from cracking fruits of ethylene treatments and controls was performed. KEGG pathway analysis revealed that the starch and sucrose metabolism pathway was significantly enriched, and approximately 39 DEGs could be functionally annotated, which included starch, cellulose, pectin, and other sugar metabolism-related genes. Starch, protopectin, and soluble pectin contents among the different cracking stages after ethylene treatment and the controls were monitored. The results revealed that ethylene accelerated starch degradation, inhibited protopectin synthesis, and enhanced the soluble pectin content, compared to the control, which coincides with the phenotype of ethylene-induced fruit cracking. Key genes implicated in the starch, pectin, and cellulose degradation were further investigated using RT-qPCR analysis. The results revealed that alpha-amylase 1 (AMY1), alpha-amylase 3 (AMY3), beta-amylase 1 (BAM1), beta-amylase 3 (BAM3), beta-amylase 9 (BAM9), pullulanase (PUL), and glycogen debranching enzyme (glgX), were the major genes involved in starch degradation. AMY1, BAM3, BAM9, PUL, and glgX all were upregulated and had higher expression levels with ethylene treatment compared to the controls, suggesting that ethylene treatment may be responsible for accelerating starch degradation. The expression profile of alpha-1,4-galacturonosyltransferase (GAUT) and granule-bound starch synthase (GBSS) coincided with protopectin content changes and could involve protopectin synthesis. Pectinesterase (PE), polygalacturonase (PG), and pectate lyase (PEL) all involved in pectin degradation; PE was significantly upregulated by ethylene and was the key enzyme implicated pectin degradation.ConclusionBoth KEGG pathway enrichment analysis of DEGs and material content analysis confirmed that starch decomposition into soluble sugars and cell wall polysaccharides metabolism are closely related to the ripening and cracking of AP atemoya. A link between gene up- or downregulation during different cracking stages of atemoya fruits and how their expression affects starch and pectin contents were established by RT-qPCR analysis.

Increased firmness and modified cell wall composition by ethylene were reversed by the ethylene inhibitor 1-methylcyclopropene (1-MCP) in the non-climacteric olives harvested at dark green stage – Possible implementation of ethylene for olive quality

This study aimed to investigate the firmness retention by ethylene treatment in olive fruit, as observed earlier. Ethylene concentrations up to 1000 μL L−1 were applied to dark green ‘Konservolia’ olives harvested shortly before the green maturation and exposed to 20 °C for up to 9 d. Surprisingly, the results indicated a tendency to fruit firmness increases in concentration-dependent manner in a non-climacteric fruit. The highest concentration increased the firmness within 12 h by approximately 1.35-fold, but transiently for approximately up to 5 d; all ethylene inhibitors tested, either of synthesis (ethoxyvinyl glycine or AVG), or perception (1 -methyl-cyclopropene or 1-MCP, and silver nitrate) prevented the firmness increase. Texture was evaluated by firmness and changes in lignin, cellulose (CL), total pectins (TPC), water soluble pectins (WSP) and total non-cellulosic sugars (total sugars) concentrations, and in pectin esterification degree (DE) in the alcohol insoluble residue (AIR) of ‘Konservolia’ fruit pericarp during 1.5-d, 5-d and 10-d treatments with 1000 μL L-1 ethylene at 20 °C. Pectins in AIR were also extracted sequentially with cyclohexane-trans-1,2-diaminetetra-acetate (CDTA), Na2CO3, 1 M and 4 M KOH. The results showed that on day 1.5, the increased firmness was consistent with increased CL (crystalline formation, as observed by microscopy), total sugars and DE levels, but reduced WSP, whereas softening reversed the changes and lowered TPC and CDTA-soluble pectins in all fruit on day 10. However, on day 5 ethylene-treated olives exhibited a transitional phase during softening, characterized by retention of high TPC concentration and energy demand, as indicated by elevated respiration rates. The inhibitor 1-MCP, applied before ethylene, did inhibit the responses to ethylene treatment. Ethylene firming effect and the respective cell wall changes in olives are demonstrated for first time. The experiments could be used for research on perception and transcription responses to ethylene in olive, a non-climacteric fruit. In practice, high ethylene concentrations could also be beneficial for firmness increase and/or short storage of dark green olives.

Changes of phytochemicals and antioxidant capacity of banana peel during the ripening process; with and without ethylene treatment

Banana peel is a by-product from the food industry, which is rich in dietary fiber and phenolic compounds. It is hypothesised that physicochemical and antioxidant properties of banana peel are significantly changed through different ripening stages. Ethylene treatment for fastening ripening is presumed to influence the changes in physicochemical and antioxidant properties of the peel. As such, this study investigated the impact of ripening stages with and without ethylene treatments on the changes of phytochemicals and antioxidant properties of banana peel. Green bananas were ripened with ethylene (1 ppm and 16 ppm) and without ethylene. The peel was then evaluated for the colour changes, chlorophylls, carotenoids, flavonoids, proanthocyanidins, total phenolic contents, and antioxidants capacity. As the fruit colour changed from green to yellow, chlorophyll was degraded by approximately 90%, while carotenoids and flavonoids increased by approximately 50% and 27%, respectively. In addition, levels of phenolics, proanthocyanidins, and antioxidant capacity also increased as the fruit continued to ripen. However, the overripe fruit peel lost up to 21% of its antioxidant capacity and up to 44% of its phytochemicals. Though statistically not significant, the peel without ethylene treatment had a relatively higher phenolic content and antioxidant power than those of the peel treated by ethylene at stages 5–7. Overall, the banana peel at ripening stages 5–7 ha s the highest levels of physicochemical and antioxidant properties and thus the peel at these stages is recommended for recovery of phenolic compounds for further applications. Additionally, the PCA biplot shows that the ripening stages could be characterised by the clustering behaviour of certain phytochemicals. Therefore, it is suggested to consider phytochemical changes when evaluating the ripening stages of banana.

TaCML36, a wheat calmodulin-like protein, positively participates in an immune response to Rhizoctonia cerealis

Sharp eyespot, mainly caused by the soil-borne fungus Rhizoctonia cerealis, affects wheat (Triticum aestivum L.) production worldwide. In this study, we isolated TaCML36 gene encoding a wheat calmodulin-like protein, and studied its defense role in protection against R. cerealis. Transcription of TaCML36 was significantly elevated by both R. cerealis infection and exogenous ethylene treatment. Transcription was higher in resistant wheat lines than in susceptible ones. There were copies of TaCML36 on chromosomes 5A, 5B, and 5D. The TaCML36 protein is composed of 183 amino acids and contains two calcium-binding EF-hand domains. Subcellular localization assays in wheat indicated that TaCML36 localizes in both the cytoplasm and nucleus. Virus-induced gene silencing and disease assessment indicated that compared to the controls, TaCML36-silenced wheat plants displayed significantly reduced resistance to R. cerealis and had greater fungal biomass, suggesting that knockdown of TaCML36 impaired host resistance. Knockdown of TaCML36 also significantly repressed expression of pathogenesis-related genes such as Chitinase 1, PDF35, and PR17C, the ethylene response factor-encoding gene TaPIE1, and ethylene biosynthesis gene ACO2. Collectively, our results suggest that TaCML36 positively participates in the innate immune response to R. cerealis infection by modulating expression of defense-associated genes possibly in the ethylene signaling pathway.

Influence of Ethylene on Morphology and Pigment Changes in Harvested Broccoli

Ethylene and ethylene absorber treatments were used to study the effects of ethylene content on the morphology and pigmentation of broccoli. Results showed that untreated broccoli began to turn yellow 8 days after being harvested at 10 °C. Ethylene treatment caused yellowing to occur 2 days earlier, and ethylene absorber treatment delayed and significantly reduced the degree of yellowing. Yellowing first occurred in the base of the bud; at that time, the shape of the bud had not changed significantly and there was no blooming of the florets. Scanning electron microscopy revealed that the increase in ethylene content caused the calyx cells of broccoli to shrink and that the cell arrangement had become disordered. Ethylene treatment caused increases in the content of chlorophyllide b (Chlide b), pheophorbide b (Pheide b), β-cryptoxanthin, lutein, and β-carotene. The increased degree of yellowing resulted in carotenoids rather than chlorophyll becoming the key pigment (β-cryptoxanthin, β-carotene, and lutein were very significantly correlated with h°). During this change, the expression levels of the BoChl2, BoPaO, BoRCCR, BoPSY, and BoLCYB genes were affected to a greater extent by ethylene. Ethylene absorber treatment did not reduce gene expression, but delayed it. These results indicate that the ethylene absorber only absorbed the ethylene produced and did not directly act on the degradation of chlorophyll. Ethylene also stimulated the expression of BoCCD1 and BoCCD7, resulting in the production of an unknown yellow substance that increased the yellow color of broccoli. In comparison, BoCCD7 expression was more sensitive than BoCCD1.

Isolation and expression patterns of two novel senescence-associated genes RhAA and RhCG in rose (Rosa hybrida)

The functional life and marketability of flowers is restricted by senescence and /or abscission. Many senescence-associated genes have been identified in the Arabidopsis plant. In this research, we isolated two full length clones of RhAA and RhCG in rose (Rosa hybrida) and compared the expression patterns of these genes in cultivars with short (‘Cool Water’) and long (‘Marroussia’) shelf lives. The RhAA gene is more similar to unknown proteins Cucurbita maxima, Gossypium arboretum and senescence-associated protein Medicago truncatula, while the RhCG is closer to the unknown proteins Pisum sativum and Dendrobium catenattum. The results of quantitative real-time polymerase chain reaction (qRT-PCR) analysis showed that the RhAA was expressed at higher levels in at the bud and open stages in most tissues of ‘Cool water’ compared with ‘Marroussia’ in response to the ethylene treatment. In gynoecia, the RhCG gene showed the highest level of expression in both cultivars at the second and seventh stages. It seems that the RhAA and RhCG were encoding a plant-specific protein of unknown function, which may relate to in the degradative and remobilization processes of senescence.

Evaluation of the ethylene effect on display quality and expression of some senescence related enzymes in potted miniature rose

To investigate the effects of exogenous application of ethylene postharvest quality and expression of enzyme involved in leaf abscission, this research was conducted in a completely randomized experimental design with three replications and three levels of ethylene treatment. Whole plants of potted miniature rose cultivar. ‘Sanaz-e-Zard’ were exposed to 0, 5 and 10 μL L(-1) of concentration of ethylene for 12 h in sealed glass aquarium containers. Results showed that treatment of ethylene had significant effects on the physiological and biochemical characteristics of ‘Sanaz-e-Zard’. The higher leaf abscission and activity of laccase was observed in 10 μL L(-1) of ethylene, which was significantly (P<0.01) higher than the control, while the lowest activity of peroxidase was found in plants which received 10 μL L(-1) ethylene. It seems that when the plant is exposed to oxidative stress, antioxidant enzymes have the potential ability to induce the immune system, encountering adversity condition. But when the response of the plant cells to a stressful situation is not sufficient, the plants will die.

Long Term Exposure to Low Ethylene and Storage Temperatures Delays Calyx Senescence and Maintains ‘Afourer’ Mandarins and Navel Oranges Quality

Calyx browning and internal quality loss are major physiological causes for the loss of quality in citrus fruit during storage. While the symptoms of calyx senescence are only superficial, it can affect the appearance and consumer acceptability of citrus fruit. In this study, continuous ethylene exposure at different storage temperatures was investigated to assess their effect on calyx senescence and internal qualities in ‘Afourer’ mandarin and Navel orange fruit during storage. ‘Afourer’ mandarin fruit were stored at ≤0.001 (equivalent to ethylene-free air), 0.01, 0.1 and 1 µL L−1 of ethylene at either 5, 10 or 20 °C, whilst in a parallel experiment, Navel oranges were exposed to ≤0.001, 0.1 and 1 µL L−1 ethylene at either 1 or 10 °C. Changes in external and internal postharvest quality parameters were assessed for up to 8 weeks for ‘Afourer’ mandarins and 10 weeks for Navel oranges. At all storage temperatures, high levels of ethylene were found to increase the level of calyx senescence, weight loss, loss of fruit firmness and respiration rates. Also, there were significant effects of ethylene and storage temperatures on total soluble solids (TSS) content, titratable acidity (TA), and ethanol accumulation in both citrus species. Continuous exposure to high ethylene also significantly reduced vitamin C and ferric reducing antioxidant power (FRAP) in ‘Afourer’ mandarins after 8 weeks of storage. Overall, ethylene treatments had a significant effect on both the external and internal qualities of the fruit during storage. The relationship between ethylene concentrations and storage temperatures demonstrate that lowering atmospheric ethylene levels at reduced storage temperatures maintain fruit quality during long term storage.

Transcriptome analysis of astringent ‘Cheongdo-Bansi’ persimmon fruit treated with ethylene for removal of astringency

This research was conducted to study the gene expression related to the removal of astringency and ripening in astringent ‘Cheongdo-Bansi’ persimmon. Fruit treated with ethylene were used to compare the differentially expressed genes against fruit ripened naturally without ethylene treatment (control). We sequenced total mRNAs using Illumina high-throughput sequencing platform and constructed the transcriptome gene set by de novo assembly. We identified 93,601 unigenes with an average length of 643.2 bp in transcriptome contigs. Differential gene expression analysis was performed and a total of 12,374 unigenes were differentially expressed in the ethylene vs. control. Of these 12,374 unigenes, 6072 were up-regulated and 6302 were down-regulated in the treated fruit. Compared with the control, the number of genes that induced more than 2 fold expression were 2647 and the number of genes whose expression was inhibited more than 2 fold were 2804. We also identified 38 genes showing significantly different expression, 26 of which were up-regulated and the rest 12 genes were down-regulated. The identified genes were categorized as genes related to astringency removal, softening and other ripening-related changes. The present study will add the information on the effect of ethylene treatment for astringency removal, softening and other ripening-related changes of persimmon fruit at genomic level. This study will also contribute important resources for further study of the genes related to astringent substance for persimmon breeding and improvement.

Differential and reciprocal regulation of ethylene pathway genes regulates petal abscission in fragrant and non-fragrant roses

The fragrant rose, Rosa bourboniana, is highly sensitive to ethylene and shows rapid petal abscission (within 16–18 h) while the non-fragrant hybrid rose, R. hybrida, shows delayed abscission (50–52 h) due to reduced ethylene sensitivity. To understand the molecular basis governing these differences, all components of the ethylene pathway (biosynthesis/ receptor/signalling) were studied for expression during abscission. Transcript accumulation of most ethylene biosynthesis genes (ACS/ACO families) increased rapidly in petal abscission zones of R. bourboniana within 4–8 h of ethylene treatment. The expression of most receptor and signalling genes encoding CTRs, EIN2 and EIN3/EIL homologues also followed similar kinetics. Under natural field conditions where abscission takes longer, there was a temporal delay in transcript accumulation of most ethylene pathway genes while some biosynthesis genes (showing reduced ethylene sensitivity) were more strongly up-regulated by abscission cues. In contrast, in R. hybrida where even ethylene-induced abscission is considerably delayed, transcript accumulation of most ethylene biosynthesis and signalling genes was, surprisingly, reduced by ethylene and showed an opposite regulation compared to R. bourboniana. The results suggest that differential and reciprocal regulation of ethylene pathway is one of the major reasons for differences in petal abscission and vase-life between Rosa bourboniana and R. hybrida.