Ethylene Synthesis Research Articles

Endophytic yeast protect plants against metal toxicity by inhibiting plant metal uptake through an ethylene-dependent mechanism.

Toxic metal pollution requires significant adjustments in plant metabolism. Here, we show that the plant microbiota plays an important role in this process. The endophytic Sporobolomyces ruberrimus isolated from a serpentine population of Arabidopsis arenosa protected plants against excess metals. Coculture with its native host and Arabidopsis thaliana inhibited Fe and Ni uptake. It had no effect on host Zn and Cd uptake. Fe uptake inhibition was confirmed in wheat and rape. Our investigations show that, for the metal inhibitory effect, the interference of microorganisms in plant ethylene homeostasis is necessary. Application of an ethylene synthesis inhibitor, as well as loss-of-function mutations in canonical ethylene signalling genes, prevented metal uptake inhibition by the fungus. Coculture with S. ruberrimus significantly changed the expression of Fe homeostasis genes: IRT1, OPT3, OPT6, bHLH38 and bHLH39 in wild-type (WT) A. thaliana. The expression pattern of these genes in WT plants and in the ethylene signalling defective mutants significantly differed and coincided with the plant accumulation phenotype. Most notably, down-regulation of the expression of IRT1 solely in WT was necessary for the inhibition of metal uptake in plants. This study shows that microorganisms optimize plant Fe and Ni uptake by fine-tuning plant metal homeostasis.

Variation in Cell Wall Metabolism and Flesh Firmness of Four Apple Cultivars during Fruit Development.

Fruit ripening and softening are highly complex processes, and there is an interplay and coordination between the metabolic pathways that are involved in the biological processes. In this study, we aimed to elucidate the variation in the characters and possible causes of cell wall materials and morphological structure during apple fruits development. We studied the cell wall material (CWM), structure, cellular morphology, hydrolase activity, and the transcriptional levels of the related genes in four apple varieties 'Ruixue' and 'Ruixianghong' and their parents ('Pink Lady' and 'Fuji') during fruit development. The decrease in the contents of CWMs, sodium carbonate soluble pectin, hemicellulose, and cellulose were positively correlated with the decline in the hardness during the fruit development. In general, the activities of polygalacturonase, β-galactosidase, and cellulase enzymes increased during the late developmental period. As the fruit grew, the fruit cells of all of the cultivars gradually became larger, and the cell arrangement became more relaxed, the fruit cell walls became thinner, and the intercellular space became larger. In conclusion, the correlation analysis indicated that the up-regulation of the relative expression levels of ethylene synthesis and cell wall hydrolase genes enhanced the activity of the cell wall hydrolase, resulting in the degradation of the CWMs and the depolymerization of the cell wall structure, which affected the final firmness of the apple cultivars in the mature period.

Involvement of ethylene in melatonin-modified photosynthetic-N use efficiency and antioxidant activity to improve photosynthesis of salt grown wheat.

The involvement of melatonin in the regulation of salt stress acclimation has been shown in plants in this present work. We found that the GOAL cultivar of wheat (Triticum aestivum L.) was the most salt-tolerant among the investigated cultivars, GOAL, HD-2967, PBW-17, PBW-343, PBW-550, and WH-1105 when screened for tolerance to 100 mM NaCl. The application of 100 μM melatonin maximally reduced oxidative stress and improved photosynthesis in the cv. GOAL. Melatonin supplementation reduced salt stress-induced oxidative stress by upregulating the activity of antioxidant enzymes, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR), and reduced the glutathione (GSH) production. This resulted in increased membrane stability, photosynthetic-N use efficiency and photosynthesis in plants. The application of 50 μM of the ethylene biosynthesis inhibitor aminoethoxyvinylglycine (AVG) in the presence of melatonin and salt stress increased H2 O2 content but reduced GR activity and GSH, photosynthesis, and plant dry mass. This signifies that melatonin-mediated salt stress tolerance was related to ethylene synthesis as it improved antioxidant activity and photosynthesis of plants under salt stress. Thus, the interaction of melatonin and ethylene bears a prominent role in salt stress tolerance in wheat and can be used to develop salt tolerance in other crops.

Transcriptome changes associated with boron applications in fruits of watercore-susceptible pear cultivar

Watercore is a common physiological disorder in pear and is closely related to the excessive accumulation of sorbitol and sucrose. Our previous research found that the incidence of watercore in 'Akibae' (Pyrus pyrifolia cv. Akibae) fruit significantly decreased after boron application (BA). Moreover, the foliar spray of boric acid also significantly improved fruit quality. However, the mechanisms underlying the pear fruit response to BA was still limited. A comprehensive transcriptome analysis of BA treatment 'Akibae' pear fruit was performed in this study. Transcriptome results revealed a total of 3146 up-regulated and 1145 down-regulated differentially expressed genes (DEGs) between control and treated fruits of 'Akibae' pear. BA significantly induced the expression of sorbitol metabolism and sucrose metabolism genes. In addition, BA also increased the expression of starch degradation, fatty acid synthesis, IAA (indole-3-acetic acid) degradation, and GA (gibberellin acid) synthesis genes and inhibited the expression of ethylene synthesis genes. These findings suggested that BA probably alleviates 'Akibae' watercore occurrence and improves fruit quality by regulating the decrease in sorbitol and sucrose, the increase in fatty acids and the balance of plant hormones. Our results provide further information for understanding the molecular mechanism of the effect of BA on pear fruit.

A very-long-chain fatty acid synthesis gene, SD38, influences plant height by activating ethylene biosynthesis in rice.

As an important trait in crop breeding, plant height is associated with lodging resistance and yield. With the identification and cloning of several semi-dwarfing genes, increasing numbers of semi-dwarf cultivars have emerged, which has led to a 'green revolution' in rice (Oryza sativa) production. In this study, we identified a rice semi-dwarf mutant, semi-dwarf 38 (sd38), which showed significantly reduced cell length. SD38 encodes a fatty acid elongase, β-ketoacyl-CoA synthase, which is involved in the synthesis of very-long-chain fatty acids (VLCFAs). Expression analysis showed that SD38 was localized on the membrane of the endoplasmic reticulum, and was expressed in all analyzed tissues with differential abundance. The mutation of SD38 affected lipid metabolism in the sd38 mutant. A functional complementarity test in Saccharomyces cerevisiae indicated that SD38 was capable of complementing the deficiency of ELO3p activity in BY4741-elo3 knockout yeast cells by participating in the synthesis of C24:0 VLCFA. Significant changes were observed in the expression of genes involved in ethylene synthesis, which resulted in reduced content of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in the sd38 mutant. Exogenously supplied VLCFA (C24:0) increased the expression levels of OsACS3, OsACS4, and OsACO7 and the plant height of sd38 mutant seedlings, similar to the effect of exogenous application of ACC and ethephon. These results reveal a relationship among VLCFAs, ethylene biosynthesis, and plant height and improve our understanding of plant height development in crops.

Differences in the Mode of Action of Florpyrauxifen-Benzyl between Barnyardgrass and Yerbadetajo

Barnyardgrass (a monocotyledon) and yerbadetajo (a dicotyledon) are the most troublesome weeds in rice fields in China. The synthetic auxin herbicide florpyrauxifen-benzyl can effectively control both weeds. The objective of this research was to clarify modes of action of florpyrauxifen-benzyl in barnyardgrass and yerbadetajo. Our results showed that yerbadetajo was more sensitive to florpyrauxifen-benzyl than barnyardgrass: the 50% growth rate inhibition in barnyardgrass and yerbadetajo was 4.14 and 0.38 g a.i. ha−1, respectively. Florpyrauxifen-benzyl induced the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and abscisic acid (ABA) in yerbadetajo within 24 h, while in barnyardgrass, the highest production occurred at 12 h and decreased at 24 h. ACC and ABA levels in yerbadetajo at 24 h of treatment were significantly higher than those in barnyardgrass at any time. There were less differentially expressed genes related to ethylene and ABA synthesis in barnyardgrass than in yerbadetajo. There were five genes induced to increase by florpyrauxifen-benzyl in barnyardgrass and eleven genes in yerbadetajo. More ACC oxidase genes (ACO) were induced in barnyardgrass and more ACC synthesis genes (ACS) in yerbadetajo, especially three ACS3 (>30 fold). We speculated that differences in gene expression caused differences in ethylene and ABA production, leading to differences in phytotoxicity.

Integrative metabolomics and transcriptomics analyses reveal pivotal regulatory mechanisms of 1-methylcyclopropene in maintaining postharvest storage quality of ‘Fuji’ apples

Abstract In this study, integrative metabolomics and transcriptomics analyses were conducted to investigate the effects of 1-methylcyclopropene (1-MCP) on apple fruit quality during long-term cold storage. The results showed that 1-MCP (1 μL/L) treatment could maintain fruits apparent quality (i.e. external color and firmness), inhibit the increase of rot rate and soluble solids content/titratable acidity ratio, decrease ethylene release, and respiratory intensity during cold storage, and extend shelf life. Moreover, 1-MCP had long-term effects on the accumulation of many qualities related to metabolite and gene expression in fruits. 1-MCP affected genes related to metabolism at the early stage of storage, specifically those of the glycolysis and tricarboxylic acid cycle pathways. Genes related to the degradation of sucrose, starch, and cellulose were inhibited, and some starch and cellulose synthesis genes were up-regulated by 1-MCP. Apart from ethylene synthesis and signal transduction being inhibited by 1-MCP, several enzymes (pectinesterase, pectate lyase, polygalacturonase) were involved in pectin degradation, and degradation products of the cell wall (i.e. d-galacturonic acid and d-glucuronic acid) were also strongly inhibited, further maintaining fruit firmness. Cysteine, as precursor glutathione (GSH) related to plant resistance, up-regulated the synthase gene. However, the expression of genes related to cyanoalanine synthase and amino acid utilization pathways was suppressed by 1-MCP. Collectively, 1-MCP could maintain the postharvest quality of apple fruits.

Silver nitrate reduces hyperhydricity in shoots regenerated from the hypocotyl of snapdragon cv. Maryland Apple Blossom

We developed an efficient protocol for shoot regeneration from hypocotyl explants in snapdragon (Antirrhinum majus L.) cv. Maryand Apple Blossom by plant growth regulators (PGRs), followed by ethylene synthesis inhibitor Aminoethoxyvinylglycine (AVG), ethylene precursor 1-Aminocyclopropane-1-carboxylate (ACC), and ethylene action inhibitor silver nitrate (AgNO3). The combination of benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D) did not induce shoots, whereas naphthaleneacetic acid (NAA) and Zeatin (Zt) induced shoots. The combination of 0.05 mg/L NAA and 2.5 mg/L Zt resulted in the maximum shoot regeneration percentage and a reasonable number of shoots per explant. However, the regenerated shoots exhibited hyperhydricity and failed to develop into normal plants when introduced into plant growth media. Addition of ACC and AVG to the media containing 0.05 mg/L NAA and 2.5 mg/L Zt inhibited shoot regeneration, while AgNO3 (2.0 mg/L) marginally improved shoot regeneration and successfully reduced hyperhydricity. Shoots grown in AgNO3-containing media showed a reduction in ethylene related gene expression and reactive oxygen species (ROS) accumulation; the leaves showed reduced intercellular space as well as an increase in the number of open stomata under AgNO3 treatment. Moreover, shoots regenerated from AgNO3-containing media easily developed into normal plants in plant growth medium. This study highlights the importance of specific PGRs in shoot regeneration, as well as the role of AgNO3 in reducing the hyperhydricity of shoots regenerated in vitro. These findings will contribute to a better understanding of the hyperhydricity mechanism. We expect this protocol to be useful for in vitro shoot regeneration and genetic transformation of the snapdragon cultivar used in this study.

Melatonin stimulates postharvest ripening of apples by up-regulating gene expression of ethylene synthesis enzymes

Melatonin has been implicated in the regulation of ripening in several types of climacteric fruits, but its role in apple is poorly understood. In this study, the effectiveness of melatonin in influencing postharvest ripening in apples and interacting with ethylene biosynthesis process was investigated. Apples of four local cultivars (Golden, Reineta, Blanquina and Rabiosa) were harvest at an immature green stage and immersed for 120 min in a solution with water (control), melatonin 50 µM, ACC 1 mM, and melatonin 50 µM + ACC 1 mM. The evolution of apple quality parameters and ethylene production was assessed in all cultivars for 35 days after treatment. In addition, Golden apple was used to examine the transcript abundance of ethylene biosynthesis enzymes genes in the skin and flesh. Exogenous melatonin improved apple quality during postharvest ripening and stimulated ethylene production in all cultivars studied, advancing the timing of the climacteric burst. Melatonin-induced changes in ethylene production correlated well with changes in fruit quality and were in part similar to those induced by the ethylene precursor ACC, so ethylene appears to be a target of melatonin. In Golden apple, melatonin stimulated the expression of MdACS1 and MdACO1 genes, which showed a climacteric profile similar to that of ethylene. The transcriptional effects of exogenous melatonin on ethylene-related genes was also more notable in the skin than in the flesh, suggesting an initiating role of the former in the biosynthesis of the phytohormone. Taken together, the results point to the fact that exogenous melatonin may be useful in improving apple quality during postharvest ripening by promoting colour and flavour change and extending fruit firmness. The effect of melatonin appears to be mediated in part by up-regulation of the transcriptional activity of the MdACS1 and MdACO1 genes during the climacteric peak, thus contributing to an increase in ethylene availability.

Salicylic acid treatment inhibits ethylene synthesis and starch-sugar conversion to maintain apple fruit quality during shelf life

Starch and sugars are widely acknowledged as taste determinants, energy substances, and signal molecules in fruits. Salicylic acid (SA) regulates many physiological and biochemical processes during fruit ripening. In this work, we investigated the effects of SA treatment on physiological parameters and SA synthesis, ethylene production, and starch-sugar metabolism of apples during shelf life. Results showed that SA maintained fruit firmness, reduced weight loss, and inhibited starch to sugar conversion during shelf life. The endogenous SA level was increased in SA-treated fruits, mediated by MdPAL, MdICS2, and MdNPR1, thus decreasing MdACS1 and MdACO1 expressions and inhibiting ethylene biosynthesis. Furthermore, the expression of starch and sugar-related genes, MdAMY, MdBam5, MdBam8, MdSPS, MdSUSY, MdNINV, and MdAINV, were inhibited by SA treatment during shelf life. It was inferred that exogenous SA could inhibit ethylene synthesis and starch-sugar conversion, maintain the quality, and prolong the shelf life of apples

Proteomic and metabolomic studies on chilling injury in peach and nectarine.

Peaches and nectarines are temperate climate stone fruits, which should be stored at 0°C to prevent the ripening of these climacteric fruits. However, if stored for too long or if stored at a higher temperature (4 or 5°C), they develop chilling injury. Chilling injury damage includes (1) dry, mealy, wooly (lack of juice) fruits, (2) hard-textured fruits with no juice (leatheriness), (3) flesh browning, and (4) flesh bleeding or internal reddening. There are genetic components to these disorders in that early season fruits are generally more resistant than late season fruits, and white-fleshed fruits are more susceptible to internal browning than yellow-fleshed fruits. A recent review covered the recent research in genomic and transcriptomic studies, and this review examines findings from proteomic and metabolomics studies. Proteomic studies found that the ethylene synthesis proteins are decreased in cold compromised fruits, and this affects the processes initiated by ethylene including cell wall and volatile changes. Enzymes in metabolic pathways were both higher and lower in abundance in CI fruits, an indication of an imbalance in energy production. Stress proteins increased in both fruits with or without CI, but were higher in damaged fruits. Metabolomics showed the role of levels of sugars, sucrose, raffinose, galactinol, and glucose-6-phosphate in protection against chilling injury, along with other membrane stabilizers such as polyamines. Amino acid changes were inconsistent among the studies. Lipid species changes during storage could be correlated with sensitivity or resistance to CI, but more studies are needed.

Effects of edible coatings on the quality and storage of early harvested guava

Guava is a world-renowned fruit of climacteric nature. It is characterized as a perishable fruit and has a short post-harvest shelf life when stored at room temperature. The objective of this work is to study the effects of coatings on the physiology and shelf life of 'Pedro Sato' guavas harvested early. For this, the effect of edible coatings based on hydroxypropyl methylcellulose (HPMC) and beeswax (BW) applied to guavas harvested green and stored for eight days at 22 °C was evaluated. Guavas were coated with HPMC+10% BW; HPMC+20% BW; HPMC+40% BW and Control-uncoated. The coatings reduced the respiration rate, inhibited ethylene synthesis and slowed the ripening process. The main benefits were the reduction in mass loss, maintenance of green color and firmness retention. The treatment with HPMC+20% BW presented the best results in maintaining the quality of the fruits, reducing the activity of the PG enzyme and delaying the ripening of 'Pedro Sato' guavas without promoting the activity of the ADH enzyme and consequently the fermentation of the fruits. fruits. The fruits treated with HPMC+20% CA showed a gain in shelf life of at least six days and despite being harvested green, no disorder affected the ripening process and its quality.

Programmed cell death associated with the formation of schizo-lysigenous aerenchyma in Nelumbo nucifera root.

Nelumbo nucifera (N. nucifera) is an important aquatic economic crop with high edible, medicinal, ornamental, and ecological restoration values. Aerenchyma formation in N. nucifera root is an adaptive trait to the aquatic environment in long-term evolution. In this study, light microscopy, electron microscopy, and molecular biology techniques were used to study the process of the aerenchyma development and cytological events in N. nucifera root and the dynamic changes of aerenchyma formation under the treatment of exogenous 21% oxygen, ethylene (ET), and ET synthesis i + nhibitor 1-methylcyclopropene (1-MCP). The results showed that programmed cell death (PCD) occurred during the aerenchyma formation in N. nucifera root. Plasmalemma invagination and vacuole membrane rupture appeared in the formation stage, followed by nuclear deformation, chromatin condensation and marginalization, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) detection was positive at this time. In the expansion stage of the aerenchyma development, cytoplasmic degradation and many vesicles appeared in the cytoplasm, and organelles began to degrade. Then the plasma membrane began to degrade, and the degradation of the cell wall was the last PCD step. After 21% oxygen was continuously filled in the rhizosphere environment of N. nucifera roots, the area of aerenchyma in N. nucifera roots was smaller than that in the control group. Moreover, ET induced the earlier occurrence of aerenchyma in N. nucifera root, but also, the area of aerenchyma became larger than that of the control. On the contrary, 1-MCP inhibited the occurrence of aerenchyma to some extent. Therefore, the formation of aerenchyma in N. nucifera root resulted from PCD, and its formation mode was schizo-lysigenous. A hypoxic environment could induce aerenchyma formation in plants. ET signal was involved in aerenchyma formation in N. nucifera root and had a positive regulatory effect. This study provides relevant data on the formation mechanism of plant aerenchyma and the cytological basis for exploring the regulation mechanism of plant aerenchyma formation.

Ammonium improved cell wall and cell membrane P reutilization and external P uptake in a putrescine and ethylene dependent pathway

Ammonium promotes rice P uptake and reutilization better than nitrate, under P starvation conditions; however, the underlying mechanism remains unclear. In this study, ammonium treatment significantly increased putrescine and ethylene content in rice roots under P deficient conditions, by increasing the protein content of ornithine decarboxylase and 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase compared with nitrate treatment. Ammonium treatment increased rice root cell wall P release by increasing pectin content and pectin methyl esterase (PME) activity, increased rice shoot cell membrane P release by decreasing phosphorus-containing lipid components, and maintained internal P homeostasis by increasing OsPT2/6/8 expression compared with nitrate treatment. Ammonium also improved external P uptake by regulating root morphology and increased rice grain yield by increasing the panicle number compared with nitrate treatment. The application of putrescine and ethylene synthesis precursor ACC further improved the above process. Our results demonstrate for the first time that ammonium increases rice P acquisition, reutilization, and homeostasis, and rice grain yield, in a putrescine- and ethylene-dependent manner, better than nitrate, under P starvation conditions.

Design of aminoethoxyvinylglycine functional analogues to delay postharvest ripening of tomato fruit

Ethylene is a key hormone in regulating fruit ripening, thus inhibiting ethylene production is an effective way to delay postharvest ripening of fruit. Aminoethoxyvinylglycine (AVG) is a competitively ethylene synthesis inhibitor that can significantly delay the fruit softening at postharvest stage and prolong the fruit shelf life. However, the high production cost of AVG limits its widespread use. In this study, nine AVG analogues with simple structures were designed and synthesized based on the 1-aminocyclo-propane-1-carboxylic acid synthase (ACS) enzyme ACS2 (Protein Data Bank ID: 1AIY) of tomato. The molecular docking analysis of ACS2 with AVG analogues showed that the compounds 2i, 2k, and 2 n have higher predicted binding activity than the other analogues, which form hydrogen bonds with the key amino acids Ala54 and Arg412 of ACS2. Compounds 2i, 2k, and 2 n reduce ethylene production and delay the postharvest ripening of tomato fruit in varying degrees, and 2 n is the most effective AVG analogue, suggesting that the function of these analogues is basically associated with their predicted binding activity with ACS2. This study developed a new class of ethylene synthesis inhibitors with significant effects on the control of ethylene action and prolonging fruit shelf life. This work also has crucial implications for research on structure-activity relationship and development of more potential AVG functional analogues.

Phosphorus Regulates the Level of Signaling Molecules in Rice to Reduce Cadmium Toxicity.

Phosphorus treatment can reduce Cd accumulation and Cd toxicity in rice, but alterations in the internal regulatory network of rice during this process have rarely been reported. We have removed the effect of cadmium phosphate precipitation from the hydroponic system, treated a pair of different Cd-response rice varieties with different levels of phosphorus and cadmium and examined the changes in physiological indicators and regulatory networks. The results demonstrated that phosphorus treatment significantly reduced Cd accumulation in both types of rice, although the antioxidant systems within the two types of rice produced opposite responses. Overall, 3 mM phosphorus treatment to Cd-N decreased the expression of OsIAA17 and OsACO1 by 32% and 37%, respectively, while increasing the expression of OsNR2 by 83%; these three genes regulate the synthesis of auxin, ethylene, and nitric oxide in rice. IAA and NO levels in rice shoots increased by 24% and 96%, respectively, and these changes contribute to Cd detoxification. The cadmium transporter genes OsHMA2, OsIRT1, and OsABCC1 were significantly down-regulated in Cd-N roots after triple phosphorus treatment. These data suggest that phosphorus treatment can reduce Cd accumulation and enhance Cd resistance in rice by affecting the expression of signaling molecules.

A comprehensive insight on the main physiological biochemical and related genes expression changes during the development of superficial scald in "Yali" pear.

Superficial scald is a serious physiological disorder in “Yali” pear (Pyrus bretschneideri Rehd. cv. Yali) after long-term cold storage. Changes in superficial scald, ethylene production, α-farnesene and phenylpropane metabolism with associated gene expression in “Yali” pear treated with and without (control) 1-methylcyclopropene (1-MCP) were investigated. Compared with the control group (without 1-MCP), 1-MCP (1.0 μl L–1) significantly lowered the superficial scald index after 180 days of cold storage. During cold storage and shelf life, the contents of α-farnesene, conjugated trienols, chlorogenic acid, and epicatechin in the peel were reduced, while quercetin was enhanced in 1-MCP-treated fruit, and the expression of genes associated with ethylene synthesis (ACS1, ACO1), receptors (ETR2, ERS1) and signal transduction (ERF1), α-farnesene metabolism (AFS1, HMGR2, GST7), phenolic biosynthesis (PAL1, C4H1, C4H2, HCT3, 4CL2, C3H), and oxidases (PPO1, PPO5, and LAC7) were significantly downregulated by 1-MCP. These results suggested that the onset and development of superficial scald was closely related to the ethylene receptor, conjugated trienols, chlorogenic acid and epicatechin and related genes expression in “Yali” pear.

Tuning the acidity by addition of transition metal to Mn modified hollow silica spheres and their catalytic activity in ethanol dehydration to ethylene

Due to the currently worldwide petrochemical feedstock shortage, the ethylene synthesis from renewable non-oil sources becomes of high interest. The catalysts were prepared in two steps: (i) formation of spheres containing the carbon-coated Mn core by hydrothermal method, (ii) formation of the Si-Zr oxide shell by sol-gel method. The prepared catalysts were characterized by N2 physisorption, SEM-EDX, XRD, XPS, and NH3-TPD. The catalytic results have shown that Fe, Zn or Ni modified Mn core exhibited superior activity compared to the catalysts containing only Mn in the core. With 75% yield and 98% ethanol conversion at 350 °C and WHSV of 1.4 h–1, MnNi@SiZr was the best catalyst. These results are due to an increased number of acid sites compared to the other materials and an optimal ratio of weak/medium acid sites. Our findings suggest new lines for developing active and stable catalysts for ethylene synthesis from ethanol.

Acetylsalicylic acid and salicylic acid alleviate postharvest leaf senescence in Chinese flowering cabbage (Brassica rapa var. parachinensis)

The leaves of ‘Ningxia Chinese flowering cabbage’ readily become yellow and senesce after harvest. To test the effects of acetylsalicylic acid (ASA) and salicylic acid (SA) on postharvest leafy vegetables, Chinese flowering cabbages were sprayed with 2 mmol L−1 ASA and 1.5 mmol L−1 SA, and stored at 15 °C. Compared with the controls, during storage, ASA- and SA-treated cabbages retained higher levels of total chlorophyll (Chl), Chl a, and Chl b, and lower activities of chlorophyllase, Mg dechelatase, pheophytinase, and Chl-degrading peroxidase, and had more intact chloroplasts. Furthermore, ASA and SA repressed respiration intensity, ethylene rate, the activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase, and ACC content, decreased reactive oxygen species (ROS) levels, and increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, phenylalanine ammonia lyase, cinnamate 4-hydroxylase, 4-coumarate-CoA ligase, chalcone synthase, chalcone isomerase, and cinnamyl alcohol dehydrogenase, promoting the accumulation of phenolics and flavonoids. Using principal component and hierarchical clustering analyses, leaf senescence was attributed to higher respiration, ethylene synthesis, and ROS levels, while the delay of senescence in treated cabbages resulted from the cooperation of ROS metabolism and the phenylpropanoid pathway. ASA and SA slowed leaf degreening and senescence. Between the two treatments, 2 mmol L−1 ASA was the most effective.

Label-Free Quantitative Proteomics Reveal the Involvement of PRT6 in Arabidopsis thaliana Seed Responsiveness to Ethylene

In Arabidopsis thaliana, the breaking of seed dormancy in wild type (Col-0) by ethylene at 100 μL L−1 required at least 30 h application. A mutant of the proteolytic N-degron pathway, lacking the E3 ligase PROTEOLYSIS 6 (PRT6), was investigated for its role in ethylene-triggered changes in proteomes during seed germination. Label-free quantitative proteomics was carried out on dormant wild type Col-0 and prt6 seeds treated with (+) or without (−) ethylene. After 16 h, 1737 proteins were identified, but none was significantly different in protein levels in response to ethylene. After longer ethylene treatment (30 h), 2552 proteins were identified, and 619 Differentially Expressed Proteins (DEPs) had significant differences in protein abundances between ethylene treatments and genotypes. In Col, 587 DEPs were enriched for those involved in signal perception and transduction, reserve mobilization and new material generation, which potentially contributed to seed germination. DEPs up-regulated by ethylene in Col included S-adenosylmethionine synthase 1, methionine adenosyltransferase 3 and ACC oxidase involved in ethylene synthesis and of Pyrabactin Resistance1 acting as an ABA receptor, while DEPs down-regulated by ethylene in Col included aldehyde oxidase 4 involved in ABA synthesis. In contrast, in prt6 seeds, ethylene did not result in strong proteomic changes with only 30 DEPs. Taken together, the present work demonstrates that the proteolytic N-degron pathway is essential for ethylene-mediated reprogramming of seed proteomes during germination.