Inhibited Ethylene Production Research Articles

GLABRA 2 regulates ETHYLENE OVERPRODUCER 1 accumulation during nutrient deficiency-induced root hair growth.

Root hairs (RHs), extensive structures of root epidermal cells, are important for plant nutrient acquisition, soil anchorage, and environmental interactions. Excessive production of the phytohormone ethylene (ET) leads to substantial root hair growth, manifested as tolerance to plant nutrient deficiencies. However, the molecular basis of ET production during root hair growth in response to nutrient starvation remains unknown. Herein, we found that a critical transcription factor, GLABRA 2 (GL2), inhibits ET production during root hair growth in Arabidopsis (Arabidopsis thaliana). GL2 directly binds to the promoter of the gene encoding ET OVERPRODUCER 1 (ETO1), one of the most important ET-production-regulation factors, in vitro and in vivo, and then regulates the accumulation and function of ETO1 in root hair growth. The GL2-regulated-ETO1 module is required for promoting root hair growth under nitrogen, phosphorus, or potassium deficiency. Genome-wide analysis revealed numerous genes, such as ROOT HAIR DEFECTIVE 6-LIKE 4, ETHYLENE-INSENSITIVE 3-LIKE 2, ROOT HAIR SPECIFIC 13, are involved in the GL2-regulated-ETO1 module. Our work reveals a key transcription mechanism in the control of ET production during root hair growth under three major nutrient deficiencies.

One-pot co-crystallized hexanal-loaded ZIF-8/quaternized chitosan film for temperature-responsive ethylene inhibition and climacteric fruit preservation

Controlling ethylene production and microbial infection are key factors to prolong the shelf life of climacteric fruit. Herein, a nanocomposite film, hexanal-loaded ZIF-8/CS (HZCF) with “nano-barrier” structure, was developed by a one-pot co-crystallized of ZIF-8 in situ growth on quaternized chitosan (CS) and encapsulation of hexanal into ZIF-8 via microporous adsorption. The resultant film realized the temperature responsive release of hexanal via the steric hindrance and hierarchical pore structure as “nano-barrier”, which can inhibit ethylene production in climacteric fruit on demand. Based on this, the maximum ethylene inhibition rate of HZCF was up to 52.6 %. Meanwhile, the film exhibits excellent antibacterial, mechanical, UV resistance and water retention properties, by virtue of the functional synergy between ZIF-8 and CS. Contributed to the multifunctional features, HZCF prolonged the shelf life of banana and mango for at least 16 days, which is 8 days longer than that of control fruit. More strikingly, HZCF is washable and biodegradable, which is expected to replace non-degradable plastic film. Thus, this study provides a convenient novel approach to simplify the encapsulation of active molecule on metal-organic frameworks (MOFs), develops a packaging material for high-efficient freshness preservation, and helps to alleviate the survival crisis caused by food waste.

1-MCP microbubbles reduce chlorophyll degradation and maintain the quality of Dendrobium cv. Burana Jade orchid flowers

The effect of 1-methylcycloprepene microbubbles (1-MCP-MBs) on reducing chlorophyll degradation, prolonging vase life and maintaining the quality of Dendrobium cv. ‘Burana Jade’ inflorescences was investigated. The inflorescences were immersed in 50 ppm 1-MCP-MBs or tap water (control) for 5 min and then held at 23 ± 1 °C for 12 days. The 1-MCP-MB-treated inflorescences exhibited increased water uptake and significantly higher fresh weight than the controls. The results also showed that 1-MCP-MBs remarkably delayed bud opening and flower abscission, accompanied by suppression of ethylene production and a lower respiration rate than that of controls. Additionally, the treatment maintained the green color (hue angle value was comparable to initial storage day) of the inflorescences by delaying chlorophyll degradation related to inhibition of chlorophyllase and Mg-dechelatase activities. 1-MCP-MBs prolonged the vase life of Dendrobium cv. ‘Burana Jade’ up to 12 days, which was 2-fold longer than that of the control (approximately 5 days only). The results suggest that 1-MCP-MBs have the potential to be another alternative to conventional methods (fumigation) in prolonging vase life and maintaining the quality of Dendrobium orchids with the advantage of a shorter treatment time.

Cyclic Storage Chamber Ozonation as a Method to Inhibit Ethylene Generation during Plum Fruit Storage

This study presents a method for inhibiting ethylene production during the room-temperature storage of plum fruits, using gaseous ozone (O3). The proposed storage strategy involves the cyclic ozone treatment of fruits every 24 h with specified O3 doses. Throughout the storage period, cyclic analyses of the atmosphere composition in storage chambers were conducted, measuring ethylene and carbon dioxide levels. Several parameters describing changes in fruit quality and biochemical transformations were systematically monitored until the end of the storage process. The results clearly indicate that fruits subjected to cyclic ozone treatment with the highest O3 doses during storage exhibit the slowest ripening rate. This reduced ripening rate is primarily attributed to the downregulation of S-adenosylmethionine synthetase expression, leading to a lower ethylene concentration in the storage chambers. Other obtained results concerning soluble solid content, titratable acidity, total polyphenols, anthocyanins, and vitamin C content confirm the observations regarding the impact of ozone treatment in slowing down the fruit ripening process. The best outcomes were achieved by applying a cyclic ozone process with a 100 ppm dose for 30 min.

Influence of Different Pulsing Solutions on Postharvest Life of Tuberose (Polianthes tuberosa L.) cv. Prajwal

Tuberose flower (Polianthes tuberosa L.) is a perennial and bulbous flowering plant, related to the Amaryllidaceae family and now it is placed in family Agavaceae. The investigation entitled “Influence of different pulsing solutions on postharvest life of tuberose (Polianthes tuberosa L.) cv. Prajwal” was carried out at the experimental farm and laboratory of Department of Floriculture and Landscape Architecture, College of Horticulture, SVPUAT, Meerut during the year of 2021-22 & 2022-23. Experiment was laid out in Completely Randomized Design with 10 treatments and 3 replications. In the present experiment we aimed at prolonging the vase life and improving the quality of cut spike of tuberose by Pulsing or hydration procedure using different noble treatments in tuberose, as the main challenge was to reduce abscission of buds, initiation of bud opening mechanism and leaf yellowing due to the sensitivity, vascular infections, high rate of respiration and inhibition of ethylene production. These differences in physiological behavior of cut stem dipped in different pulsing solution are very important to consider when developing post harvest physiology of tuberose. In the present finding we have primarily focused and observed under the light of pertinent literature available substantiated with robust evidence thus we derived the overall best treatment for different parameters for improving the vase life of tuberose that were recorded under the treatment T9 (Sucrose 15% + 8-HQC 300 ppm) followed by the treatment T6 (Sucrose 10% + 8-HQC 300 ppm) and T8 (Sucrose 15% + 8-HQC 200 ppm) resulted in most of the postharvest parameters such as amount of pulsing solution consumed (13.16, 15.82 ml), days taken to opening of floret (2.53, 2.54 days), floret diameter (3.38, 3.40 cm), vase life (10.78, 10.80 days), weight change/loss in cut spike (13.29 %, 14.52 %), fungal infection, fragrance score (2.95, 2.96), freshness index (4.97, 4.98) and moisture content (89.89, 85.60, 83.21%).

The impact of growing season on the ethylene biosynthesis and signaling pathways of a heat tolerant tomato during off-vine postharvest ripening

Ethylene initiates and mediates fruit ripening throughout a cascade of signal transductions from ethylene receptors (ETRs) to ethylene response factors (ERFs). High temperatures impair fruit ripening by suppressing ethylene biosynthesis and parts of physiological and biochemical processes. This study made use of the ethylene inhibitor (1-MCP) and exogenous ethylene to investigate the ethylene biosynthesis and signaling pathways of a heat tolerant tomato cultivar, cv. ‘Savior’, during off-vine postharvest ripening during two distinct growing seasons. Mature green ’Savior‘ tomatoes grown in winter (mild temperature) and summer (high temperature) were harvested at and treated with 1-MCP or exogenous ethylene. During off-vine ripening, summer fruit showed a different ethylene biosynthesis profile compared to winter fruit. The application of exogenous ethylene did not accelerate fruit ripening of the heat tolerant cultivar. 1-MCP suppressed ethylene production for a long time, and delayed fruit ripening of winter tomato, while for summer fruit, a limited effect of 1-MCP on inhibiting ethylene biosynthesis and delaying ripening was observed despite the strong suppression of ACC oxidase (ACO) activity. Our work also showed that a 1-MCP treatment reduced gene expression of several ethylene receptors (ETR) but did not have a strong effect on constitutive triple response (CTR), except CTR1, and ethylene-insensitive protein 2 (EIN2). Overall, our results indicate that i) ethylene biosynthesis is differentially regulated in winter as compared to summer fruit by ethylene signaling, ii) a high cultivation temperature impacts ethylene biosynthesis and ethylene sensitivity during fruit ripening despite the fact that this is a heat tolerant cultivar, iii) the expression of most ETRs and CTRs, and especially EIN2 did not respond to the 1-MCP or ethylene treatment.

Synthesis and application of Ag-doped TiO2 nanoparticles with antifungal activity and ethylene inhibition in postharvest of avocado cv. Hass

Avocado is highly susceptible to postharvest diseases and rapid ripening, making it challenging to maintain its quality and shelf life. One potential solution is the use of nanoparticles that can act as both antimicrobial agents and ethylene inhibitors. In this study, we synthesized Ag-doped TiO2 nanoparticles through a solution combustion method and subjected them to various characterization techniques, including X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. These nanoparticles were then tested for their effectiveness in combating common avocado pathogens and their ability to inhibit ethylene production. To apply our findings practically, we treated Hass avocado fruits in the postharvest stage with a suspension of Ag-doped TiO2 nanoparticles and stored them under controlled conditions to simulate the ripening process. The Ag-doped TiO2 nanoparticles formed agglomerates within the nanometric range and exhibited oxidation-reduction characteristics, effectively inhibiting ethylene production and degrading Rhodamine-B dye. Moreover, these nanoparticles displayed robust antimicrobial activity, significantly suppressing the growth of Colletotrichum gloeosporioides sensu lato pathogens. Treated fruits in the postharvest phase showed reduced microbial growth, decreased incidence of anthracnose, stem and root diseases, and an extended shelf life compared to the control group, due to ethylene inhibition. Ag-doped TiO2 nanoparticles, with their dual capabilities of antimicrobial activity and ethylene inhibition, show promise in improving postharvest management of Hass avocados. They have the potential to enhance fruit quality, reduce postharvest losses, and improve marketability. Further research and field trials are essential to fully explore the practical applications of these nanoparticles in commercial avocado production and distribution.

Effects of postharvest edible coating applications on storage life and quality of some apple cultivars

In this study, the effects of postharvest calcium chloride dihydrate (CaCl2.2H2O), rosehip essential oil (REO) (cold pressed), and CaCl2.2H2O+REO combination edible coating applications on some fruit quality parameters and storage life of ‘Starkrimson Delicious’ (‘S. Delicious’), ‘Golden Delicious’ (‘G. Delicious’) and ‘Granny Smith’ (‘G. Smith’) apple cultivars were investigated. For this purpose, the fruit was divided into four groups after harvest: 1st group: Fruit was dipped in distilled water (control), 2nd group: Fruit was dipped in 1.5% CaCl2.2H2O, 3rd group: Fruit was dipped in 2% REO, 4th group: Fruit was dipped in 1.5% CaCl2.2H2O+REO (%2) to form an edible coating on fruit. Before and during storage at periodical intervals weight loss, fruit color, fruit flesh color, fruit flesh firmness, soluble solids content, titratable acidity, pH, respiration rate, ethylene production, sensory evaluations (overall quality, taste and aroma, odor, decay) superficial scald, and superficial scald severity analyzes were performed. In the ‘S. Delicious’, the lowest weight loss was in CaCl2.2H2O+REO during and at the end of storage, REO had the lowest in the ‘G. Delicious’. ‘G. Smith’ had lower weight loss in CaCl2.2H2O and the control group than the others. The REO preserved the fruit flesh firmness better than others with the least loss. REO was the most effective treatment in suppressing ethylene production in all cultivars, followed by CaCl2.2H2O+REO. In ‘S. Delicious’ and ‘G. Smith’, fruit color and vividness of fruit color were best preserved by REO. As a result, postharvest edible coating applications of CaCl2.2H2O, REO, and CaCl2.2H2O+REO in ‘S. Delicious’, ‘G. Delicious’ and ‘G. Smith’ had positive contributions in maintaining fruit quality attributes during storage.

Overexpression of acdS in petunia improved tolerance to copper stress by reducing ethylene production and metal accumulation

We overexpressed the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene (acdS), which encodes the enzyme responsible for the degradation of an ethylene precursor (ACC), in Petunia hybrida cv. Mirage Rose. We investigated whether acdS overexpression rendered the petunia more tolerant to copper (Cu) stress. The transgenic plants exhibited greater tolerance to Cu stress than wild type (WT) plants, as evidenced by better plant growth and physiological performances. Additionally, the transgenic plants displayed significantly suppressed ethylene production and related genes, elevated expression of antioxidant and proline activity-related genes, reduced accumulation of reactive oxygen species and Cu, and increased expression of genes regulating heavy metal when compared to the WT plants. These findings elucidate the mechanism by which acdS imparts Cu stress tolerance, suggesting that overexpressing acdS in plants can facilitate their resilience to Cu stress.

Aminoethoxyvinylglycine and low oxygen controlled atmosphere storage shift functional microbiomes of ‘Gala’ apples

The complexity and interconnected dynamics of postharvest microbial communities require whole-microbiome characterization to fully understand relationships among pathogens, biocontrol, and fruit quality. This study investigated the effects of the preharvest plant growth regulator aminoethoxyvinylglycine (AVG, 0.25 g L−1), which inhibits ethylene production, and low O2 (0.5 % and 2 %) controlled atmosphere (CA) storage compared with air storage, on the surface microbiome of ‘Gala’ apples stored at 0.5 °C. AVG and low O2 concentrations affected bacterial but not fungal communities. Bacterial but not fungal diversity decreased after 9 months of CA storage. Microbial genera with potential biocontrol functions such as Pseudomonas and Aureobasidium were found across all time points and treatments. The microbiomes detected in CA stored fruit were the most different from those in air stored fruit late in storage. At this time, metagenome prediction methods found that low O2 fruit may harbor bacteria with fewer gene pathways using O2 as a reactant compared to fruit in air storage. The results indicate that storage conditions influence the composition, diversity, and function of microbiomes inhabiting fruit surfaces, which provide a greater basis for understanding biocontrol and pathogen population dynamics in a more holistic manner.

Rhizobacteria-enhanced drought tolerance and post-drought recovery of creeping bentgrass involving differential modulation of leaf and root metabolism.

Rhizobacteria that produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCd) that inhibits ethylene production may mitigate stress damages. The objectives of this study were to examine whether a novel strain of ACCd-producing bacteria, Paraburkholderia aspalathi "WSF23," promotes plant tolerance to drought stress and post-stress recovery and determine changes in metabolic profiles in leaves and roots associated with the positive ACCd-bacteria effects in cool-season perennial grass species. Creeping bentgrass (Agrostis Stolonifera L. cv. "Penncross") plants were inoculated with P. aspalathi "WSF23" and exposed to drought by withholding irrigation for 35 days, followed by re-watering for 15 days in growth chambers. Inoculated plants demonstrated increased turf quality, canopy density, and root growth during drought stress and more rapid re-growth upon re-watering. Metabolomic analysis demonstrated that inoculation with P. aspalathi "WSF 23" increased the content of metabolites in the metabolic pathways related to stress defense, including osmoregulation, cell wall stability, and antioxidant protection in both leaves and roots, as well as nitrogen metabolism in roots of creeping bentgrass exposed to drought stress. The promotion of post-stress recovery by P. aspalathi "WSF 23" was mainly associated with enhanced carbohydrate and pyrimidine metabolism and zeatin biosynthesis pathways in leaves and increased carbohydrates, biosynthesis of DNA and proteins, cellular metabolism, and TCA cycle activity in roots. These results provide insights into the metabolic pathways regulated by "WSF23," with the PGPR conferring improvements in drought stress tolerance and post-drought recovery in a perennial grass species.

Transcriptomic analysis in tomato fruit reveals divergences in genes involved in cold stress response and fruit ripening.

Cold storage is widely used to extend the postharvest life of most horticultural crops, including tomatoes, but this practice triggers cold stress and leads to the development of undesirable chilling injury (CI) symptoms. The underlying mechanisms of cold stress response and CI development in fruits remain unclear as they are often intermingled with fruit ripening changes. To gain insight into cold responses in fruits, we examined the effect of the potent ethylene signaling inhibitor 1-methylcyclopropene (1-MCP) on fruit ripening, CI occurrence and gene expression in mature green tomatoes during storage at 20°C and 5°C. 1-MCP treatments effectively inhibited ethylene production and peel color changes during storage at 20°C. Storage at 5°C also inhibited both ethylene production and peel color change; during rewarming at 20°C, 1-MCP treatments inhibited peel color change but failed to inhibit ethylene production. Furthermore, fruits stored at 5°C for 14 d developed CI symptoms (surface pitting and decay) during the rewarming period at 20°C regardless of 1-MCP treatment. Subsequent RNA-Seq analysis revealed that cold stress triggers a large-scale transcriptomic adjustment, as noticeably more genes were differentially expressed at 5°C (8,406) than at 20°C (4,814). More importantly, we have found some important divergences among genes involved in fruit ripening (up- or down-regulated at 20°C; inhibited by 1-MCP treatment) and those involved in cold stress (up- or down-regulated at 5°C; unaffected by 1-MCP treatment). Transcriptomic adjustments unique to cold stress response were associated with ribosome biogenesis, NcRNA metabolism, DNA methylation, chromatin formation/remodeling, and alternative splicing events. These data should foster further research into cold stress response mechanisms in fruits with the ultimate aim of improving tolerance to low temperature and reduction of CI symptoms during cold storage.

A single MYB transcription factor with multiple functions during flower development.

Members of the R2R3-MYB transcription factor subgroup 19 (SG19) have been extensively studied in multiple plant species using different silenced or mutated lines. Some studies have proposed a function in flower opening, others in floral organ development/maturation, or specialized metabolism production. While SG19 members are clearly key players during flower development and maturation, the resulting picture is complex, confusing our understanding in how SG19 genes function. To clarify the function of the SG19 transcription factors, we used a single system, Petunia axillaris, and targeted its two SG19 members (EOB1 and EOB2) by CRISPR-Cas9. Although EOB1 and EOB2 are highly similar, they display radically different mutant phenotypes. EOB1 has a specific role in scent emission while EOB2 has pleiotropic functions during flower development. The eob2 knockout mutants reveal that EOB2 is a repressor of flower bud senescence by inhibiting ethylene production. Moreover, partial loss-of-function mutants (transcriptional activation domain missing) show that EOB2 is also involved in both petal and pistil maturation through regulation of primary and secondary metabolism. Here, we provide new insights into the genetic regulation of flower maturation and senescence. It also emphasizes the function of EOB2 in the adaptation of plants to specific guilds of pollinators.

1 H-cyclopropa[b]naphthalene: a novel ethylene antagonist for extending storage life and maintaining quality of climacteric and suppressed climacteric plums

Ethylene is a key trigger that governs the rate of fruit ripening, storability, and postharvest quality of fresh fruit. Efficient inhibition of ethylene action is essential to slow down the postharvest ripening processes, extend storage life and maintain optimum fruit quality during storage. Ethylene antagonist compounds with the likelihood of application as liquid formulation would facilitate managing ethylene broadly as both preharvest and/or postharvest treatments. This study examined the effects of different aqueous formulations of 1 H-cyclopropa[b]naphthalene (NC) as an ethylene antagonist in the cold stored (1 °C) Japanese plums ‘Angeleno’ (suppressed-climacteric) and ‘Tegan Blue’, which exhibit climacteric peaks, respectively. NC was applied as a 2 µM spray solution prepared using only distilled water (NCA), 5% ethanol (NCE), 0.02% Tween® 20 (NCT), 5% β-cyclodextrin (NCD) or a 1 µM fumigant for 18 h at ambient conditions (20 ± 1 °C). Regardless of formulation, NC retarded ethylene production in both the suppressed-climacteric and climactic cultivars. The capacity of NC to suppress ethylene production was relatively higher in ‘Angeleno’ than in ‘Tegan Blue’. Levels of bioactive compounds such as total phenols, total anthocyanins and total antioxidant capacity in fruit treated with NC were at par with the control. NC fumigation was the most effective treatment in suppressing ethylene production and maintaining fruit quality followed by NCE, NCT, NCD and NCA in both plum cultivars. Amongst the NC spray solutions, the ones with ethanol or Tween® 20 as adjuvants outperformed other solutions. Ethylene production positively correlated with weight loss, SSC, SSC: TA and concentrations of individual sugars, but was negatively correlated with firmness, titratable acidity (TA) and individual organic acids in both cultivars. The results also support the notion that ethylene has a role in the synthesis of phenolic compounds and anthocyanin depending on the sugar substrates present in the phenylpropanoid and flavonoid pathways.

MaBEL1 regulates banana fruit ripening by activating cell wall and starch degradation-related genes.

Banana is a typical subtropical fruit, sensitive to chilling injuries and prone to softening disorder. However, the underlying regulatory mechanisms of the softening disorder caused by cold stress remain obscure. Herein, we found that BEL1-LIKE HOMEODOMAIN transcription factor 1 (MaBEL1) and its associated proteins regulate the fruit softening and ripening process. The transcript and protein levels of MaBEL1 were up-regulated with fruit ripening but severely repressed by the chilling stress. Moreover, the MaBEL1 protein interacted directly with the promoters of the cell wall and starch degradation-related genes, such as MaAMY3, MaXYL32, and MaEXP-A8. The transient overexpression of MaBEL1 alleviated fruit chilling injury and ripening disorder caused by cold stress and promoted fruit softening and ripening of "Fenjiao" banana by inducing ethylene production and starch and cell wall degradation. The accelerated ripening was also validated by the ectopic overexpression in tomatoes. Conversely, MaBEL1-silencing aggravated the chilling injury and ripening disorder and repressed fruit softening and ripening by inhibiting ethylene production and starch and cell wall degradation. MaABI5-like and MaEBF1, the two positive regulators of the fruit softening process, interacted with MaBEL1 to enhance the promoter activity of the starch and cell wall degradation-related genes. Moreover, the F-box protein MaEBF1 does not modulate the degradation of MaBEL1, which regulates the transcription of MaABI5-like protein. Overall, we report a novel MaBEL1-MaEBF1-MaABI5-like complex system that mediates the fruit softening and ripening disorder in "Fenjiao" bananas caused by cold stress.

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.

Harvest Maturity and Preharvest Aminoethoxyvinylglycine Treatment Effects on Cold-induced Ethylene Production of ‘Gala’ Apples

Cold storage is a commonly adopted technology to maintain quality and extend shelf life; however, depending on the cultivar, ethylene production can be enhanced by short-term cold treatments. In this study, index of absorbance difference (IAD) values, which reflect skin chlorophyll concentrations of cold-influenced ripening patterns, of ‘Gala’ apples were investigated. Fruit that were untreated or treated with aminoethoxyvinylglycine (AVG), which is a plant growth regulator that inhibits ethylene production of fruit, were harvested from a commercial orchard. Two IAD value categories 0.6 to 0.8 and 0.2 to 0.4 were chosen from a single harvest in 2019, whereas in 2020, the fruit in categories 0.6 to 0.8 and 0.2 to 0.4 were chosen for two harvests separated by 1 week, respectively. In 2019, only ethylene production was measured. In 2020, ethylene production, respiration, internal ethylene concentration (IEC), flesh firmness, 1-aminocyclopropane-1-carboxylate (ACC), and malonyl 1-aminocyclopropane-1-carboxylate (MACC) concentrations of fruit kept in air at 20 °C or stored at 0.5 °C for 21 days and then transferred to 20 °C were measured. The results were different from those described in the literature for cold-enhanced ethylene production of ‘Gala’ apples. Although ethylene production occurred without cold exposure of untreated fruit, exposure of fruit to 0.5 °C for 21 days resulted in more rapid and higher ethylene production rates and IEC than for fruit kept at only 20 °C. Ethylene production was suppressed by the preharvest AVG treatment, especially in 2020. The rates of respiration and softening of non-AVG treated fruit were enhanced by cold treatment. The effects of cold treatment were more significant for less mature fruit as indicated by higher IAD values.

S‐nitrosylation of ACO homolog 4 improves ethylene synthesis and salt tolerance in tomato

Crop loss due to soil salinization is a global threat to agriculture. Nitric oxide (NO) and ethylene involve in multiple plant tolerance. However, their interaction in salt resistance remains largely elusive. We tested the mutual induction between NO and ethylene, and then identified an 1-aminocyclopropane-1-carboxylate oxidase homolog 4 (ACOh4) that influences ethylene synthesis and salt tolerance through NO-mediated S-nitrosylation. Both NO and ethylene positively responded to salt stress. Furthermore, NO participated in salt-induced ethylene production. Salt tolerance evaluation showed that function of NO was abolished by inhibiting ethylene production. Conversely, function of ethylene was little influenced by blocking NO generation. ACO was identified as the target of NO to control ethylene synthesis. In vitro and invivo results suggested that ACOh4 was S-nitrosylated at Cys172, resulting in its enzymatic activation. Moreover, ACOh4 was induced by NO through transcriptional manner. Knockdown of ACOh4 abolished NO-induced ethylene production and salt tolerance. At physiological status, ACOh4 positively regulates the Na+ and H+ efflux, and keeps K+ /Na+ homeostasis by promoting salt-resistive genes' transcripts. Our findings validate a role of NO-ethylene module in salt tolerance and uncover a novel mechanism of how NO promoting ethylene synthesis against adversity.

Extending the Shelf Life of Bananas with Cinnamaldehyde-Impregnated Halloysite/Polypropylene Nanocomposite Films

Ethylene, the ripening hormone produced by climacteric plants, is an important parameter that determines the shelf life of fresh fruits. Cinnamaldehyde (CA) encapsulated in halloysite nanotube (HNT) nanocarriers was studied as an ethylene production inhibition agent. The slow release of CA from HNT-CA nanohybrids was demonstrated to last for over 180 d and cause inhibition of ethylene production in bananas. The HNT-CA nanohybrids were incorporated into polypropylene (PP) via melt extrusion, resulting in PP/HNT-CA nanocomposite films with suitable mechanical properties for use as flexible packaging. Bananas stored in PP/HNT-CA nanocomposite film bags for 7 d presented significantly lower weight loss, higher firmness, and higher color scores, indicating freshness, than bananas stored in neat PP film bags. The nanocomposite films presented in this study were shown to slow down the ripening by inhibiting ethylene production, and they have strong potential as active food packaging materials that can prevent spoilage of ethylene-sensitive fresh fruits.

The HY5 transcription factor negatively regulates ethylene production by inhibiting ACS1 expression under blue light conditions in pear

Ethylene is the main factor controlling fruit ripening of pear (Pyrus ussuriensis). Ethylene production rate is negatively correlated with fruit shelf life; therefore, it is important to decrease the ethylene levels for optimal fruit storage. Here, we observed that blue light treatment could inhibit ethylene production and promote the expression of ELONGATED HYPOCOTYL 5 (PuHY5), a basic leucine zipper domain (bZIP) transcription factor. The following studies showed that PuHY5 could bind to the promoter of ACC synthase 1 (PuACS1), a rate-limiting enzyme in ethylene biosynthesis, and inhibit its expression. For pears in which PuHY5 was silenced, the ethylene production and PuACS1 expression were much higher than those in the control fruit. These results demonstrated that blue light inhibited ethylene production through the induction of PuHY5 in pear. Our finding provides a new method for prolonging fruit shelf life.