Ethylene Accumulation Research Articles

Effects of Efficient Ethylene Remover on the Lignification of Fresh Faba Bean (Vicia faba L.) during Storage.

Postharvest ethylene accumulation and lignification are significant issues affecting the storage quality of fresh faba beans, resulting in rapid quality decline. However, there is still a lack of effective preservation methods to preserve the quality of faba beans during storage. This study aimed to investigate the regulation of lignification in faba beans during storage using a high-efficiency ethylene remover (HEER), examining physiological responses, key enzyme activities, and transcriptomic changes. Results showed that the HEER treatment inhibited the lignification, reducing it by 45% and lowering the respiratory rate of fresh pods by 32.8% during storage. Additionally, the HEER treatment suppressed respiration rates and the activities of lignin synthesis-related enzymes, including phenylalanine ammonia-lyase (from 353.73 to 246.60 U/g), cinnamic acid-4-hydroxylase (from 635.86 to 125.00 U/g), 4-coumarate: coenzyme A ligase (from 1008.57 to 516.52 U/g), and cinnamyl-alcohol dehydrogenase (from 129.42 to 37.12 U/g), thus slowing lignin accumulation. During storage, the hardness of fresh faba bean increased by 9.79% from the initial period, being 1.44 times higher than that of HEER. On days 8 and 16 of storage, the respiratory rate of the treated beans decreased by 24.38% and 4.12%, respectively. Physiological and enzyme activity analyses indicated that HEER treatment-induced increase in hardness was associated with the phenylpropanoid metabolic pathway. Moreover, the HEER significantly down-regulated the expression of several key genes, namely FaPAL, FaC4H, and FaCAD. This study helps to deepen the understanding of the inhibition of lignification by HEER and provide new insights for the development of preservation technology of faba bean.

Mutation of tomato xyloglucan transglucosylase/hydrolase5 increases fruit firmness and contributes to prolonged shelf life

Fruit ripening in tomato is a highly coordinated developmental process accompanied with fruit softening, which is closely associated with cell wall degradation and remodeling. Xyloglucan endotransglucosylase/hydrolases (XTHs) are known to play an essential role in cell wall xyloglucan metabolism. Tomato XTH5 exhibits xyloglucan endotransglucosylase (XET) activity in vitro, but the understanding of its biological role in fruit ripening remains unclear. In this study, we revealed that SlXTH5 is highly expressed in mature fruits. Knockout mutant plants of SlXTH5 were generated by CRISPR/Cas9 gene editing strategy in tomato cultivar Micro-Tom. The mutant fruits showed accelerated transition from unripe to ripe process and earlier ethylene accumulation compared to wild type fruits. Although the mutation of SlXTH5 did not affect the size, weight and number of fruits, it indeed increased fruit firmness and extended shelf life, which is probably attributed to the increased cell layer and cell wall thickness of pericarp tissue. Pathogen infection experiment showed the enhanced resistance of mutant fruits to Botrytis cinerea. These results revealed the role of SlXTH5 in fruit ripening process, and provide new insight into how cell wall metabolism and remodeling regulate fruit softening and shelf life.

Aminoethoxyvinylglicine and 1-Methylcyclopropene: Effects on Preharvest Drop, Fruit Maturity, Quality, and Associated Gene Expression of 'Honeycrisp' Apples in the US Mid-Atlantic.

Preharvest fruit drop is one of the main challenges in apple production as it can lead to extensive crop losses in commercially important cultivars including 'Honeycrisp'. Plant growth regulators, such as aminoethoxyvinylglicine (AVG) and 1-methylcyclopropene (1-MCP), which hinder ethylene biosynthesis and perception, respectively, can control preharvest fruit drop, but an assessment of their effects in 'Honeycrisp' fruit grown under US mid-Atlantic conditions is lacking. In this study, we evaluated the effects of AVG (130 mg a.i. L-1) and 1-MCP (150 mg a.i. L-1) on preharvest fruit drop, ethylene production, fruit physicochemical parameters, skin color, and transcript accumulation of ethylene and anthocyanin-related genes in 'Honeycrisp' apples throughout on-the-tree ripening. We showed that both AVG and 1-MCP significantly minimized preharvest fruit drop with respect to the control fruit. Additionally, AVG was the most effective in decreasing ethylene production, downregulating ethylene biosynthesis and perception-related gene expression, and delaying fruit maturity. Nevertheless, AVG negatively impacted apple red skin color and exhibited the lowest expression of anthocyanin-biosynthesis-related genes, only allowing apples to reach the minimum required 50% blush at the last ripening stage. Conversely, 1-MCP-treated fruit displayed an intermediate behavior between AVG-treated and control fruit, decreasing ethylene production rates and the associated gene expression as well as delaying fruit maturity when compared to the control fruit. Remarkably, 1-MCP treatment did not sacrifice red skin color development or anthocyanin-biosynthesis-related gene expression, thus exhibiting > 50% blush one week earlier than AVG.

Ethylene-mediated resistance to bacterial canker in kiwifruit is suppressed by cool temperature

Ambient temperature affects the occurrence and prevalence of plant disease. Most bacterial diseases are damaging at high temperatures. However, kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) has been found to be prevalent at relatively cool temperatures, and it is unclear how ambient temperature affects the development of kiwifruit bacterial canker. In this study, basal resistance to Psa was suppressed in kiwifruit at cool growth temperature (16 °C) compared with at normal temperature (24 °C). In addition, RNA sequence analysis and ethylene content assessment indicated that ethylene modulated kiwifruit resistance to Psa at normal growth temperature and that cool temperature inhibited ethylene accumulation and Psa-induced activation of the ethylene signaling pathway in kiwifruit. Virus-mediated silencing of the kiwifruit ethylene signaling gene AcEIN2 suppressed kiwifruit resistance to Psa at normal growth temperature. Exogenous application of ethylene inhibitor 1-methylcyclopropene eliminated the difference in kiwifruit resistance to Psa at 16 and 24 °C. Exogenous application of ethylene analogues ethephon induced resistance to Psa in kiwifruit. In conclusion, cool temperatures impair basal resistance to Psa by reducing the activation of ethylene biosynthesis and signaling in kiwifruit. The results provide clues for new strategies to control plant diseases in a context of global environmental change.

High expression of ethylene response factor BcERF98 delays the flowering time of non-heading Chinese cabbage.

BcERF98 is induced by ethylene signaling and inhibits the expression of BcFT by interacting with BcNF-YA2 and BcEIP9, thereby inhibiting plant flowering. Several stresses trigger the accumulation of ethylene, which then transmits the signal to ethylene response factors (ERFs) to participate in the regulation of plant development to adapt to the environment. This study clarifies the function of BcERF98, a homolog of AtERF98, in the regulation of plant flowering time mediated by high concentrations of ethylene. Results indicate that BcERF98 is a nuclear and the cell membrane-localized transcription factor and highly responsive to ethylene signaling. BcERF98 inhibits the expression of BcFT by interacting with BcEIP9 and BcNF-YA2, which are related to flowering time regulation, thereby participating in ethylene-mediated plant late flowering regulation. The results have enriched the theoretical knowledge of flowering regulation in non-heading Chinese cabbage (NHCC), providing the scientific basis and gene reserves for cultivating new varieties of NHCC with different flowering times.

Cucumber JASMONATE ZIM-DOMAIN 6 interaction with transcription factor MYB6 impairs waterlogging-triggered adventitious rooting.

Waterlogging is a serious abiotic stress that drastically decreases crop productivity by damaging the root system. Jasmonic acid (JA) inhibits waterlogging-induced adventitious root (AR) formation in cucumber (Cucumis sativus L.). However, we still lack a profound mechanistic understanding of how JA governs AR formation under waterlogging stress. JAZ (JASMONATE ZIM-DOMAIN) proteins are responsible for repressing JA signaling in a transcriptional manner. In this study, we showed that overexpressing CsJAZ8 inhibited the formation of ARs triggered by waterlogging. Molecular analyses revealed that CsJAZ8 inhibited the activation of the R2R3-MYB transcription factor CsMYB6 via direct interaction. Additionally, silencing of CsMYB6 negatively impacted AR formation under waterlogging stress, as CsMYB6 could directly bind to the promoters of 1-aminocyclopropane-1-carboxylate oxidase2 gene CsACO2 and gibberellin 20-oxidases gene CsGA20ox2, facilitating the transcription of these genes. The overexpression of CsACO2 and CsGA20ox2 led to increased levels of ethylene and gibberellin, which facilitated AR formation under waterlogging conditions. On the contrary, silencing these genes resulted in contrasting phenotypes of AR formation. These results highlight that the transcriptional cascade of CsJAZ8 and CsMYB6 plays a critical role in regulating hormonal-mediated cucumber waterlogging-triggered AR formation by inhibiting ethylene and gibberellin accumulation. We anticipate that our findings will provide insights into the molecular mechanisms that drive the emergence of AR in cucumber plants under waterlogging stress.

PhERF71 regulates petunia flower senescence by modulating ethylene biosynthesis

Ethylene, an endogenous hormone, commonly promotes flower senescence, but the molecular regulatory mechanisms underlying ethylene-induced flower senescence remain elusive. In this study, we describe an ethylene-responsive element binding factor, PhERF71, which affects flower senescence in petunia (Petunia hybrida). PhERF71 was up-regulated in senescing petunia flowers and after exogenous ethylene treatment, but silver thiosulfate (STS), an ethylene inhibitor, treatment decreased PhERF71 transcripts. Transient silencing of PhERF71 delayed petunia flower senescence, and reduced the transcription of senescence-associated gene 12 (PhSAG12). PhERF71-RNAi transgenic plants showed prolonged flower longevity, and PhERF71-overexpressing plants displayed shortened flower longevity, compared with wild-type (WT) plants. Electrolyte leakage rates and expression levels of PhSAG12 were lower in PhERF71-RNAi plants but higher in PhERF71-overexpressing plants. Silencing or overexpression of PhERF71 influenced the accumulation of ethylene, gibberellin (GA3), and abscisic acid (ABA), and the effect on ethylene accumulation was earlier than that on ABA and GA3. Ethylene treatment restored the delayed flower senescence to WT levels in PhERF71-silenced plants. Silencing of PhERF71 reduced expression levels of several ethylene biosynthetic genes, including 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 4 (PhACS4), PhACS6, and ACC oxidase 4 (PhACO4), while overexpression of PhERF71 imposed the opposite effect on their expression levels. Dual luciferase assay showed that PhERF71 directly bound to the promoters of PhACS4 and PhACO4, and transient silencing of PhACS4 and PhACO4 delayed flower senescence. Our results suggest that PhERF71 is a positive regulator of flower senescence by promoting ethylene biosynthesis.

The responses of ‘Hayward’ kiwifruit to ethylene during regular and controlled atmosphere storage

ABSTRACT Maintaining kiwifruit firmness is key to global supply chain. Controlled atmosphere (CA) technology can maintain kiwifruit quality. However, there is a risk of ethylene (C2H4) accumulation in CA that may accelerate kiwifruit softening. The objectives of this study were to determine the impact of ethylene on kiwifruit quality in CA. ‘Hayward’ kiwifruit were stored in air and CA (5% CO2 + 2% O2) at 0°C, 95% RH for 13 weeks. Ethylene at concentrations of 10, 100, 1000 nL·L−1 was added after 3 weeks of storage. The responses of kiwifruit to ethylene were dose-dependent in both air and CA storage. Ethylene-induced kiwifruit softening was delayed and slowed by CA. However, white-core inclusions (WCI) disorder was observed after 8 weeks of exposure to 100 and 1000 nL·L−1 ethylene in CA. The lowest concentrations of ethylene (≤ 10 nL·L−1) in CA did not influence kiwifruit quality. This work demonstrates that kiwifruit sensitivity to ethylene is lower in CA than that in air, but excessive softening and WCI may negatively impact kiwifruit quality when exposed to a high ethylene concentration in CA for extended periods. Hence, ethylene monitoring and management may be less critical in kiwifruit stored in CA but are required.

The Expression of Key Ethylene and Anthocyanin Biosynthetic Genes of 'Honeycrisp' Apples Subjected to the Combined Use of Reflective Groundcovers and Aminoethoxyvinylglycine in the Mid-Atlantic US.

The decreased profitability of important apple cultivars, such as 'Honeycrisp', results from the poor red skin coloration and high fruit drop in the mid-Atlantic US. Apple red skin coloration is determined by the anthocyanin concentration. Reflective groundcovers promote red skin coloration, whereas aminoethoxyvinylglycine (AVG) decreases the ethylene production and fruit drop, thus reducing the coloration. Although our previous study showed that combinations of these practices impact the fruit quality and color, research is lacking regarding their effects at the gene and metabolite levels. In this work, for two years, we compared the differences in the internal ethylene concentration (IEC), red skin coloration, fruit drop, transcript accumulation of key ethylene and anthocyanin biosynthetic pathway-related genes, and total anthocyanin concentration of 'Honeycrisp' apples. The fruit was treated with combinations of reflective groundcover (Extenday) and AVG (130 mg L-1) and was assessed throughout ripening. Extenday-only-treated fruit displayed the highest upregulation of ethylene and anthocyanin biosynthetic-related genes and of total anthocyanins, exceeding 50% blush, while boosting the IEC. In contrast, AVG significantly decreased the expression of key ethylene and anthocyanin biosynthetic-related genes and total anthocyanins, thus preventing apples from reaching 50% blush, while also decreasing the IEC and fruit drop. The combination of Extenday x AVG fine-tuned the transcript accumulation of ethylene and anthocyanin biosynthetic-related genes as well as the total anthocyanins, allowing the 'Honeycrisp' fruit to exceed 50% blush, while increasing the IEC moderately and reducing the fruit drop (as compared to Extenday-only and control), thus enhancing the fruit economic value.

Marine Plant Growth Promoting Bacteria (PGPB) inoculation technology: Testing the effectiveness of different application methods to improve tomato plants tolerance against acute heat wave stress

Regenerative agriculture aims to boost native biodiversity and ensure sustainable production. Plant Growth Promoting Bacteria (PGPB) enhance crop yield through improved nutrient use efficiency or stress tolerance. Utilizing synthetic bacterial communities (SynCom) tailored to specific challenges holds promise for enhancing plant resilience. However, challenges include designing microbial consortia and selecting SynCom application techniques. This study tested four PGPB SynCom application methods on tomato plants to evaluate their effectiveness in promoting plant resistance and recovery from short extreme heat waves. Non-invasive phenotyping techniques were used to assess plant responses to three delivery methods (watering, foliar spray, and alginate spheres immobilization) under heat stress. Plants treated with the marine PGPB SynCom through methods like leaf spraying or encapsulation in alginate spheres exhibited improved resilience in terms of Kautsky curve intensity and shape, indicating better photochemical apparatus function. These techniques also facilitated post-stress recovery. Deep photochemical analysis revealed SynCom-induced improvements in the plant's photochemical apparatus, particularly the PS II donor side. Moreover, it was also possible to observe that upon stress relief these two techniques, alongside the plants inoculated throughout watering were able to recover their photochemical profiles. Analysing the Fv/Fm values, plants inoculated through watering, alginate beads and leaf spray can be considered heat-tolerant, a characteristic conserved throughout the three sampling moments. Heat-wave exposure led to an increase in the energy absorbed by the non-inoculated plants as a counteractive measure to overcome the low energy use efficiency observed (low trapping and transported energy fluxes). The reduction in stress impact was attributed to SynCom's ACC-deaminase production, which lowered ethylene accumulation, promoting growth and photosynthetic efficiency. The study also noted reduced energy dissipation under stress relief, indicating efficient heat dissipation mechanisms due to SynCom application. Statistical models generated with the attained photochemical data allowed depicting specific fluorescence signatures of each thermal and inoculation treatment with a very high degree of accuracy, reinforcing that these different inoculation treatments have in fact different impacts on plant photochemistry but also provide a tool for future phenotyping assessments using the proposed inoculation techniques. Alginate bead based PGPB release emerged as an efficient, scalable technique with continuous benefits for plant growth and stress response.

Differential leaf flooding resilience in Arabidopsis thaliana is controlled by ethylene signaling-activated and age-dependent phosphorylation of ORESARA1

The phytohormone ethylene is a major regulator of plant adaptive responses to flooding. In flooded plant tissues, ethylene quickly increases to high concentrations owing to its low solubility and diffusion rates in water. Ethylene accumulation in submerged plant tissues makes it a reliable cue for triggering flood acclimation responses, including metabolic adjustments to cope with flood-induced hypoxia. However, persistent ethylene accumulation also accelerates leaf senescence. Stress-induced senescence hampers photosynthetic capacity and stress recovery. In submerged Arabidopsis, senescence follows a strict age-dependent pattern starting with the older leaves. Although mechanisms underlying ethylene-mediated senescence have been uncovered, it is unclear how submerged plants avoid indiscriminate breakdown of leaves despite high systemic ethylene accumulation. We demonstrate that although submergence triggers leaf-age-independent activation of ethylene signaling via EIN3 in Arabidopsis, senescence is initiated only in old leaves. EIN3 stabilization also leads to overall transcript and protein accumulation of the senescence-promoting transcription factor ORESARA1 (ORE1) in both old and young leaves during submergence. However, leaf-age-dependent senescence can be explained by ORE1 protein activation via phosphorylation specifically in old leaves, independent of the previously identified age-dependent control of ORE1 via miR164. A systematic analysis of the roles of the major flooding stress cues and signaling pathways shows that only the combination of ethylene and darkness is sufficient to mimic submergence-induced senescence involving ORE1 accumulation and phosphorylation. Hypoxia, most often associated with flooding stress in plants, appears to have no role in these processes. Our results reveal a mechanism by which plants regulate the speed and pattern of senescence during environmental stresses such as flooding. Age-dependent ORE1 activity ensures that older, expendable leaves are dismantled first, thus prolonging the life of younger leaves and meristematic tissues that are vital to whole-plant survival.

Preliminary Analysis, Combined with Omics of Chilling Injury Mechanism of Peach Fruits with Different Cold Sensitivities during Postharvest Cold Storage

The storage of peach fruits at 4–5 °C can easily lead to chilling injury and greatly reduce the quality and commercial value of peach fruits. In this study, two kinds of peach fruits (CX and CM) were selected to analyze the mechanisms of chilling injury in fruits with different chilling sensitivity by means of their lipidomic, transcriptome, and dynamic changes in plant hormones. We found that the ethylene, abscisic acid (ABA), and lipid contents changed differently between CX and CM. The ABA and dilactosyl diacylglycerol (DGDG) contents significantly increased after refrigeration in CM fruit, leading to strong cold resistance. However, low temperatures induced a greater accumulation of ethylene, phospholipids, and ABA-GE in CX fruit than in CM fruit, eventually leading to more severe CI symptoms in CX fruit. Additionally, a transcriptional regulatory network for CM and CX fruits during cold storage was constructed, providing a new theoretical reference for the cultivation of cold-resistant peach cultivars and the development of postharvest preservation technology.

Flood induced adventitious root formation and ethylene accumulation in Solanum species

Flood induced adventitious root formation and ethylene accumulation in Solanum species

A model integrating fruit physiology, perforation, and scavenger for prediction of ethylene accumulation in fruit package

The modelling of headspace atmosphere (O2, CO2), relative humidity, condensation, and shelf life of packaged fresh produce has been extensively reported. However, there has been a lack of effort in modelling ethylene (C2H4) accumulation within the packaging or storage environment. This study aimed to address this significant research gap by developing a model for the prediction of C2H4 accumulation within fruit package. This model integrated fruit physiology, gas transmission through perforation, and C2H4 removal by a scavenger made up of KMnO4. The experimental validation was conducted using packaged avocados, encompassing various storage conditions, package (perforation), scavenger, and fruit parameters. The use of perforation effectively maintained C2H4 accumulation below 2 µL L−1 in the avocado package for 12 days within the temperature range of 5 to 25ºC. Moreover, the scavenger successfully kept C2H4 accumulation below 1 µL L−1 within just 8 h for all experimental conditions. The scavenger demonstrated a higher efficacy in C2H4 removal compared to perforation, achieving a complete removal. The level of accuracy through statistical parameters underscores the acceptability and reliability of the model in predicting C2H4 accumulation in fruit package. The model was used to optimize the perforation size according to the required equilibrium O2 and C2H4 accumulation in the avocado package.

Construction of photocatalytic coating for alleviating the shriveling of postharvest fruit cucumber after simulated transportation

The shriveling of fruit cucumber was commonly occurred during supply chain, photocatalyst exposed to UV light can endow the coatings with ethylene removal capacity to reduce the respiration of fruit and water loss. The study developed a novel photodynamic technology responsive photocatalytic coating with exceptional ultraviolet (UV) photocatalytic degradation of ethylene ability to decay the shriveling of postharvest fruit cucumber during supply chain. This coating involved the integration of Carbon dots (CDs)-loaded nano ZnO and the skillful selection of pullulan (Pul) and apple pectin (AP) matrix. The CDs/ZnO coatings boasted an impressive array of photocatalytic degradation of ethylene and adhesion properties, including high ethylene removal rates of 32.04 % in 60 min UV light stimulation. The decrease of cell-wall strength, degradation of the cell wall polysaccharides and water loss resulted in cucumber shriveling. Compared with CK sample, after UV-CDs/ZnO coating treatment, the higher firmness and cell wall polysaccharides were found in cucumbers with lower cell wall degrading enzymes activities, weight loss and water movement, which was associated with the decrease of respiration and ethylene accumulation. The UV-CDs/ZnO coatings possessed promising potential for alleviating the shriveling of postharvest fruit cucumber and applications in fruits preservation in the future.

Effects of thidiazuron on the quality and storage properties of mango fruit during postharvest

Abstract Thidiazuron (TDZ) is used for the expansion of fruits, but excessive levels of TDZ lead to a decline in fruit quality. The appropriate concentration of TDZ for mango expansion without a decline in quality is not clear. In the present study, four different concentrations (5, 10, 15, and 20 mg/L) of TDZ were applied via spraying on mango plants, and several physiological and biochemical indicators were measured. The results showed that TDZ treatment significantly increased mango fruit size and single-fruit weight. In mango fruit, TDZ treatment decreased the disease index, delayed the increase in the malondialdehyde and H2O2 content, and maintained firmness and antioxidant capacities at a relatively high level during postharvest storage. At the same time, TDZ treatment delayed the decrease in the giberellin, indoleacetic acid and jasmonic acid content in mango, and reduced the accumulation of abscisic acid and ethylene. These trends are consistent with TDZ treatment leading to extension of the shelf life of mango. Furthermore, ethylene biosynthesis, signal transduction, and cell wall dismantling-related genes were investigated. The results indicated that the expression of the MiACS, MiETR2, MiERF113, MiERF010, MiERF054, MiEXP, MiPG14, MiPG21, MiCEL, and MiPEL genes in mango was inhibited under TDZ treatment compared with the control. In summary, TDZ treatment can significantly increase the size and weight of mango fruit and can extend its shelf life. The most suitable concentration is 10–15 mg/L TDZ, which will not affect the quality of mango fruit.

Inhibitor AN3661 reveals biological functions of Arabidopsis CLEAVAGE and POLYADENYLATION SPECIFICITY FACTOR 73.

Cleavage and polyadenylation specificity factor (CPSF) is a protein complex that plays an essential biochemical role in mRNA 3'-end formation, including poly(A) signal recognition and cleavage at the poly(A) site. However, its biological functions at the organismal level are mostly unknown in multicellular eukaryotes. The study of plant CPSF73 has been hampered by the lethality of Arabidopsis (Arabidopsis thaliana) homozygous mutants of AtCPSF73-I and AtCPSF73-II. Here, we used poly(A) tag sequencing to investigate the roles of AtCPSF73-I and AtCPSF73-II in Arabidopsis treated with AN3661, an antimalarial drug with specificity for parasite CPSF73 that is homologous to plant CPSF73. Direct seed germination on an AN3661-containing medium was lethal; however, 7-d-old seedlings treated with AN3661 survived. AN3661 targeted AtCPSF73-I and AtCPSF73-II, inhibiting growth through coordinating gene expression and poly(A) site choice. Functional enrichment analysis revealed that the accumulation of ethylene and auxin jointly inhibited primary root growth. AN3661 affected poly(A) signal recognition, resulted in lower U-rich signal usage, caused transcriptional readthrough, and increased the distal poly(A) site usage. Many microRNA targets were found in the 3' untranslated region lengthened transcripts; these miRNAs may indirectly regulate the expression of these targets. Overall, this work demonstrates that AtCPSF73 plays important part in co-transcriptional regulation, affecting growth, and development in Arabidopsis.

The local and systemic accumulation of ethylene determines the rapid defence responses induced by flg22 in tomato (Solanum lycopersicum L.)

Plant defence responses induced by the bacterial elicitor flg22 are highly dependent on phytohormones, including gaseous ethylene (ET). While the regulatory role of ET in local defence responses to flg22 exposure has been demonstrated, its contribution to the induction of systemic responses is not clearly understood. For this consideration, we examined the effects of different ET modulators on the flg22-induced local and systemic defence progression. In our experiments, ET biosynthesis inhibitor aminoethoxyvinyl glycine (AVG) or ET receptor blocker silver thiosulphate (STS) were applied 1 h before flg22 treatments and 1 h later the rapid local and systemic responses were detected in the leaves of intact tomato plants (Solanum lycopersicum L.). Based on our results, AVG not only diminished the flg22-induced ET accumulation locally, but also in the younger leaves confirming the role of ET in the whole-plant expanding defence progression. This increase in ET emission was accompanied by increased local expression of SlACO1, which was reduced by AVG and STS. Local ET biosynthesis upon flg22 treatment was shown to positively regulate local and systemic superoxide (O2.-) and hydrogen peroxide (H2O2) production, which in turn could contribute to ET accumulation in younger leaves. Confirming the role of ET in flg22-induced rapid defence responses, application of AVG reduced local and systemic ET, O2.- and H2O2 production, whereas STS reduced it primarily in the younger leaves. Interestingly, in addition to flg22, AVG and STS induced stomatal closure alone at whole-plant level, however in the case of combined treatments together with flg22 both ET modulators reduced the rate of stomatal closure in the older- and younger leaves as well. These results demonstrate that both local and systemic ET production in sufficient amounts and active ET signalling are essential for the development of flg22-induced rapid local and systemic defence responses.

Promotive effects of endophytic rhizobacteria on tiller and root growth in creeping bentgrass during drought stress and post‐stress recovery involving regulation of hormone and sugar metabolism

AbstractStress‐induced accumulation of ethylene exacerbates drought damages in plants and suppressing stress induction of ethylene may promote plant tolerance to drought stress. The objective of this study was to investigate the effects of endophytic bacteria (Paraburkholderia aspalathi) with 1‐aminocyclopropane‐1‐carboxylic acid (ACC) deaminase enzymes in suppressing ethylene production on plant tolerance to drought stress and post‐stress recovery and the underlying physiological mechanisms of P. aspalathi‐regulation in creeping bentgrass (Agrostis stolonifera L.). A novel strain of P. aspalathi, "WSF23," with ACC deaminase activity was used to inoculate the roots of creeping bentgrass plants (cv. "Penncross") subjected to drought stress for 35 days and rewatered for 15 days (post‐stress recovery) in controlled‐environment growth chambers. Inoculation with WSF23 bacteria resulted in an increased number of tillers, tillering production rate, root viability, and root growth (quantified in length, surface area, volume, and dry weight) during drought stress or rewatering. Inoculation of plants with WSF23 bacteria increased cytokinin (CK) (c‐Zeatin and tZ‐riboside) and jasmonate (JA‐Ile) content and reduced ACC and abscisic acid (ABA) content in roots during drought or rewatering. Sugar accumulation in crowns was promoted by inoculation during drought stress. The differential changes in ACC, CK, ABA, and JA‐Ile and sugar accumulation due to the bacterial inoculation could contribute to ACC deamination bacteria‐improved drought tolerance and post‐stress recovery in terms of tiller production and root proliferation and elongation in creeping bentgrass.

Ethylene modelling in package headspace of fresh produce: A review

AbstractEthylene accumulation is one of the main causes of rapid deterioration of climacteric fruit and vegetables in a package as ethylene accelerates the ripening process. Modelling the ethylene gas in a package headspace is a promising way to control the ripening process as it provides and optimises the methods to remove ethylene. In this review, the transmission of ethylene through a package, ethylene removal by a scavenger and ethylene accumulation inside the package are discussed with their models. The permeability of packaging material allows ethylene to escape from the package to a little extent. The perforation in packaging material also helps ethylene to depart rapidly from the fruit package which is explained and modelled using Fick's first law of diffusion. The pseudo‐first‐ and second‐order kinetics based on the adsorption phenomena have been used to model the removal of ethylene by a scavenger. The mass balance between the ethylene transmission rate through the package, ethylene production rate by fruit and ethylene removal by scavenger provides the ethylene accumulation which can be helpful for predicting the quality of the fruit inside a package. This study could lead to the development of an active fruit packaging system with the inclusion of ethylene along with oxygen and carbon dioxide for extending the shelf life of fresh commodities in postharvest storage.