Ethylene Content Research Articles

Kinetics controlled microstructure and composition in coordinative chain transfer copolymerization of ethylene–propylene

The wide applications of ethylene–propylene copolymers, which range from elastomers to oligomeric lubricants and additives can be expanded upon controlling the microstructure specifically its chemical composition. To account for that we use rac-Et(Ind)2ZrCl2 metallocene catalyst in combination with modified methylaluminoxane (MMAO) as the cocatalyst and ZnEt2 as the chain transfer agent (CTA) in a coordinative chain transfer copolymerization. The monotonic decline of molar mass and narrowing of its distribution in the presence of CTA suggest the establishment of the regenerative chain transfer reaction. The end-group analysis by 1H NMR spectroscopy demonstrates the depletion of β-H transfer and replacement of chain transfer to CTA. Microstructure analysis of copolymers by 13C NMR reveals a significant increase in ethylene content, which raises smoothly by CTA content, along with modification of the microstructure at the triad level, suggesting the prevalence of ethylenic sequences. This is in line with the decrease of the glass transition temperature and appearance of a broad melting peak between 30 and 90 °C. We explain these experimental observations by a computational study at the DFT level that compares three reaction pathways of ethylene and propylene insertion into an ethylene-ended propagating chain or chain transfer to the CTA. The outcome shows that propylene insertion is kinetically less feasible compared to ethylene insertion or chain transfer, while thermodynamically the chain transfer reaction is less favored. These results establish a new kinetics control over the chain microstructure in ethylene–propylene copolymers.

The relationship between ethylene-induced autophagy and reactive oxygen species in Arabidopsis root cells during the early stages of waterlogging stress.

The response of plants to waterlogging stress is a complex process, with ethylene playing a crucial role as a signaling molecule. However, it remains unclear how ethylene is initially triggered in response to waterlogging stress when plants are continuously waterlogged for less than 12 hours. Here, we have shown that ethylene-induced autophagy leads to the degradation of damaged mitochondria (the main organelles producing reactive oxygen species (ROS)) to reduce ROS production during oxidative stress in Arabidopsis thaliana, which improves the survival rate of root cells in the early stages of waterlogging stress. Waterlogging stress activated ethylene-related genes, including ACO2, ACS2, ERF72, ERF73, and EIN3, and ethylene content of plants increased significantly within 24 h of continuous waterlogging. As stress duration increased, increased amounts of ROS accumulated in Arabidopsis thaliana roots, and the activity of antioxidant enzymes initially increased and then decreased. Concurrently, the level of ethylene-induced autophagy, which participates in antioxidant defense, is higher in wild-type plants than in the octuple acs mutant cs16651 (acs2-1/acs4-1/acs5-2/acs6-1/acs7-1/acs9-1/amiRacs8acs11). Exogenous application of 1-aminocyclopropanecarboxylic acid (ACC), resulted in a more pronounced manifestation of autophagy in the stele of Arabidopsis roots. Compared with the waterlogging treatment group or the ACC treatment group, the waterlogging + ACC treatment can induce autophagy to occur earlier and expand the autophagic range to the epidermis of Arabidopsis thaliana roots. Overall, our results provide insight into the important role of ethylene-induced autophagy in enhancing the antioxidative capacity of Arabidopsis thaliana during the early stages of waterlogging stress. Furthermore, we suggest ethylene as a potential candidate for mitigating the deleterious effects caused by waterlogging in Arabidopsis thaliana.

The SlWRKY6-SlPROPEP-SlPep module confers tomato resistance to Phytophthora infestans

Tomato constitutes a primary agricultural industry, but its production is severely impaired by Phytophthora infestans (P. infestans). Although identifying numerous resistance genes, the molecular mechanisms underlying tomato resistance to P. infestans remain elusive. Here, we identified SlPep, a plant elicitor peptide that confers resistance to P. infestans in tomato. SlPep originates from the C terminus of the precursor protein, SlPROPEP, in tomato. The expression of SlPROPEP was transcriptionally induced upon P. infestans infection. And, transiently overexpressing of SlPROPEP enhanced tomato resistance by elevating the levels of reactive oxygen species and pathogenesis-related genes, whereas silencing of SlPROPEP impaired resistance. Moreover, we demonstrated that SlWRKY6 could enhance tomato resistance via up-regulating the expression of SlPROPEP. Additionally, we observed that the exogenous application of SlPep promoted jasmonic acid and ethylene contents, inducing tomato resistance towards P. infestans. Overall, our findings shed light on the molecular roles of the SlWRKY6-SlPROPEP-SlPep module in tomato-P. infestans interactions, providing novel insights into horticultural crop improvement.

Xylem Functionality Is Not a Direct Indicator of Apple Preharvest Fruit Drop

Apple (Malus ×domestica) growers can incur significant economic losses when fruit drop before they can be harvested [preharvest fruit drop (PFD)]. In some years and cultivars, more than 30% of potential yield can be lost. Growers frequently apply plant bioregulators to reduce PFD, either via delay in maturity [aminoethoxyvinylglycine (AVG), 1-methylcycolpropene] or via inhibition in production of cell hydrolysis enzymes in the fruit pedicel [naphthalene acetic acid (NAA)]. Finding a physiological indicator of PFD would allow growers to assess the susceptibility of fruit to PFD. Due to its lignification, xylem is believed to be the last tissue to break down in the fruit pedicel, leading to PFD. To determine whether loss in xylem functionality can be used as an indicator of PFD potential, studies were conducted in 2020 and 2021 with ‘Red Delicious’ treated with AVG (132 µL·L−1), NAA (10 µL·L−1), and an ethylene-producing compound [ethephon (150 µL·L−1 in 2020, 200 µL·L−1 in 2021)] to generate a range of PFD potentials. Xylem functionality was assessed in the fruit cortex. Internal ethylene content (IEC), fruit maturity indices, and PFD rates were quantified weekly throughout the harvest period. Expression of genes encoding for cell hydrolysis enzymes (MdEG1 and MdPG2) was quantified to relate xylem functionality to fruit abscission mechanisms. In 2020 and 2021, AVG reduced PFD compared with the untreated control by decreasing IEC. Although ethephon did not result in higher PFD than untreated fruit, NAA reduced PFD in 2020 but not 2021. For all treatments in both years, there was a linear decrease in xylem functionality throughout the measurement period. Cumulative PFD exponentially decreased as xylem functionality neared zero and the climacteric rise in ethylene began. Concurrent with the rise in IEC and PFD was an increase in the expression of MdEG1 and MdPG2 in the fruit pedicel of the control compared with AVG-treated fruit. AVG-treated fruit lost xylem functionality at a similar rate to the untreated control but had lower expression of MdEG1 and MdPG2. These results indicate that xylem functionality is not a sole direct indicator of PFD. The concurrent increase in PFD and expression of MdEG1/MdPG2 supports previous research indicating that these two genes may serve as potential markers for PFD.

Investigation of the Rheological Properties and Storage Stability of Waste Polyethylene/Ethylene-Vinyl Acetate-Modified Asphalt with Crosslinking and a Silicone Coupling Agent.

As the market for polyethylene consumption continues to expand, the amount of waste polyethylene is also increasing. Modifying asphalt with waste polyethylene (PE) is economical and environmentally friendly. The low-temperature performance and storage stability of PE-modified asphalt has long been an insurmountable problem. The high vinyl acetate (VA) content of ethylene-vinyl acetate (EVA) and PE blended into asphalt can improve the compatibility of PE and asphalt. It compensates for the high VA content of EVA brought about by the lack of high-temperature resistance to permanent deformation but is still not conducive to the stable storage of PE at high temperatures. The effect of furfural extraction oil, a crosslinking (DCP) agent, a silicone coupling agent (KH-570), and calcium carbonate (CaCO3) on the rheological properties and compatibility of PE/EVA-modified asphalt was investigated in this study. The conventional physical properties of PE/EVA-modified asphalt were tested after introducing furfural extraction oil, DCP, KH570, and CaCO3 to determine the correlations of these materials. In addition, frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS) were utilized to characterize the rheological properties and fatigue behavior. The results reveal that the addition of suitable ratios of furfural extract oil, DCP, KH-570, and CaCO3 to PE/EVA-modified asphalt produces a remarkable improvement in the viscoelastic characteristics and viscosity compared with PE/EVA-modified asphalt. Furthermore, fluorescence microscopy (FM) was utilized to evaluate the modification mechanism, which shows that PE/EVA undergoes significant crosslinking in asphalt, forming a three-dimensional network structure that dissolves in the asphalt. The storage stability of the PE-modified bitumen was fully determined, and its high-temperature rheology was substantially improved.

Effect of Wounding Intensity on Edible Quality by Regulating Physiological and ROS Metabolism in Fresh-Cut Pumpkins

Fresh-cut pumpkin is favored by consumers for its environmental protection, safety, and convenience at home and abroad. To investigate the effect of different wounding intensities (piece, strip and slice, corresponding to 1.90, 3.53 and 6.29 m2 kg−1) on the quality of fresh-cut pumpkin, the critical indexes involved in reactive oxygen species (ROS) metabolism, vitamin C-glutathione cycle, phenylpropanoid metabolism and membrane lipid peroxidation were monitored for pumpkin during storage at 4 °C for 6 d. The results showed that with the increase in cutting injury strength, the lightness, whiteness index, respiration rate, ethylene content, lipoxygenase activity and malondialdehyde content of fresh-cut pumpkin increased, while the hardness, sensory quality, appearance and total soluble solid content continuously decreased. The quality deterioration was the most severe in the slice group, while a higher sensory quality was maintained in the piece after 6 d of storage. However, the activity of phenylalanine ammonia-lyase increased and then contributed to the synthesis of the phenolic compound, which resulted in enhancements of 79.13%, 29.47% and 16.14% in piece, strip and slice, respectively. Meanwhile, cutting enhanced the activity of antioxidant enzymes including ascorbate peroxidase, glutathione reductase, superoxide dismutase and catalase, resulting in the enhancement of antioxidant activity in fresh-cut pumpkin. The collected results showed that the wounding intensities have an obvious influence on the quality by regulating physiological and ROS metabolism.

Mechanism insight into ethylene oligomerization on zeolite K-LTA surface: A DFT and kMC study

The regeneration gas used in the K-LTA zeolite dryer of the MTO plant is planning to be changed from high purity nitrogen to the top gas of the demethanizer tower with high ethylene content, which is helpful to energy saving and emission reduction. However, there is a risk of ethylene oligomerization and carbon deposition when the regeneration gas passes through the K-LTA zeolite. The reaction mechanism of ethylene oligomerization on the K-LTA zeolite surface must be clarified. DFT calculations showed that ethylene could be physically adsorbed on Si–OH, Al–OH, the incomplete α- and β-cage on [100]-D4R-e surface. Butoxide forms through ethylene dimerization by stepwise and concerted mechanisms first. Then the reaction of ethylene and butoxide to n-hexyloxide leads to the continued growth of the carbon chain. The oligomerization reaction barriers of rate-determining steps are between 1.65∼1.75 eV, which is more difficult to occur than other zeolites. The ethylene oligomerization reaction can be divided into stepwise polymerization path, concerted polymerization path and concerted butene path. kMC simulation found that the dominant reaction paths are different under different temperatures. When the regeneration temperature reaches 473 K, trace n-butene is generated. At 513 K, ethylene oligommerization occurs and carbon deposition is formed. The results put forward higher requirements for strictly controlling the temperature of the dryer to ensure the excellent performance of K-LTA zeolite.

Effects of chitosan nanoparticles coating on delaying of seed soybean (Gycine max) deterioration

High-quality seed is always demanded by farmers and may result in up to a 30% increase in crop yields. One of the major constraints ofsoybean cultivation is that soybean seeds quickly deteriorate in storage due to high lipid and protein content. Coating technology withvarious coating formulas is needed to extend seeds’ shelf life. This research aimed to determine the effects of CSNPs (chitosan-waxnanoparticles) and CS (chitosan-wax) as active coating ingredients in delaying the Deterioration of soybean seed quality. Two varietiesof soybean seed and three coating treatments (control, CS, and CSNPs) were used during storage for six months. Each treatment wasreplicated four times, and the observation was conducted monthly. The result showed that coating treatment could significantly suppressthe increase in water content and the decrease in protein and fat levels compared to the control. Moreover, the coating also suppresses therespiration rate, ethylene content, and MDA concentration during storage, especially for the Grobogan variety. The coated seed showeda higher vigor index and germination than the controls, particularly in the Dega variety. The CSNPs performed better than CS and controlfor all the experimental parameters. The germination percentage of the Dega variety soybean seeds after six months of storage at CS andCSNPs coating treatments were 93.33 and 92.67%, respectively, much higher than the Grobogan variety. The initial mositure contentmuch influenced the seed’s physical, chemical, and viability during storage.

SlMAPK3 Positively Regulates the Ethylene Production of Postharvest Tomato Fruits and Is Involved in Ethylene-Mediated Cold Tolerance.

Mitogen-activated protein kinase (MAPK) cascades and ethylene are crucial for plant growth, development, and stress responses, but their potential mechanisms in cold resistance remain unclear. We revealed that SlMAPK3 transcript levels were dramatically induced by cold treatment in an ethylene-dependent manner. Under cold stress, the proline content of SlMAPK3-overexpression fruit was 96.5 and 115.9% higher than that of wild-type fruit (WT), respectively, while the ion leakage was 37.3 and 32.5% lower than that of WT. RNA sequencing revealed that overexpression of SlMAPK3 caused upregulation of genes that are enriched in the ethylene-activated signaling pathway (GO:0009873), cold signaling pathway (GO:0009409), and heat signaling pathway (GO:0009408). RT-qPCR demonstrated that the expression levels of SlACS2, SlACS4, SlSAHH, SlCBF1, SlDREB, SlGolS1, and SlHSP17.7 in the OE.MAPK3 fruits were consistent with the RNA sequencing results. Meanwhile, the knockout of SlMAPK3 reduced the ethylene content, ACC content, and ACS activity. Moreover, the knockout of SlMAPK3 reduced the positive effect of ethylene in cold stress, while suppressing the expression of SlICE1 and SlCBF1. In conclusion, our study demonstrated a novel mechanism by which SlMAPK3 positively regulates the ethylene production of postharvest tomato fruits and is involved in ethylene-mediated cold tolerance.

Fiber-specific increase of carotenoid content promotes cotton fiber elongation by increasing abscisic acid and ethylene biosynthesis

Cotton fiber is a raw material for the global textile industry and fiber quality is essential to its industrial application. Carotenoids are plant secondary metabolites that may serve as dietary components, regulate light harvesting, and scavenge reactive oxygen species. Although carotenoids accumulate predominantly in rapidly elongating cotton fibers, their roles in cotton fiber development remain poorly understood. In this study, a fiber-specific promoter proSCFP was applied to drive the expression of GhOR1Del, a positive regulator of carotenoid accumulation, to upregulate the carotenoid level in cotton fiber in planta. Fiber length, strength, and fineness were increased in proSCFP:GhOR1Del transgenic cotton and abscisic acid (ABA) and ethylene contents were increased in elongating fibers. The ABA downstream regulator GhbZIP27a stimulated the expression of the ethylene synthase gene GhACO3 by binding to its promoter, suggesting that ABA promoted fiber elongation by increasing ethylene production. These findings suggest the involvement of carotenoids and ABA signaling in promoting cotton fiber elongation and provide a strategy for improving cotton fiber quality.

Alcoholysis of ethylene-vinyl acetate copolymer catalyzed by alkaline: A kinetic study based on in situ FTIR spectroscopy

Controlled alcoholysis of ethylene–vinyl acetate copolymer (EVA) is very important both to industry and academic research. To this end, accurate kinetic model is an important tool, but traditional methods for studying reaction kinetics involving polymers are usually laborious and time consuming due to the need of product purification. Therefore, we developed a new method to study the alcoholysis of EVA with 32 mol% ethylene content based on in situ FTIR spectroscopy. The feasibility and accuracy of this method was carefully studied. A kinetic model for predicting reaction rate was obtained using this method. The applicability of the kinetic model was further verified by performing flow alcoholysis in microflow reactor. It was found that this kinetic model is pretty accurate for conversions up to around 60 %, even at a relatively high temperature. The in situ FTIR method may also be suitable for monitoring industrial production process and other alcoholysis systems like PVA.

Transcriptomic and Physiological Analyses Reveal the Molecular Mechanism through Which Exogenous Melatonin Increases Drought Stress Tolerance in Chrysanthemum

Chrysanthemum (Chrysanthemum morifolium (Ramat.) Hemsl.) is an important species in China's flower industry, and drought stress seriously affects the growth, quality, yield, and geographical distribution of this species. Melatonin (MT) plays a key role in regulating plant abiotic stress responses and stress resistance, but the mechanism through which exogenous MT regulates drought resistance in chrysanthemum remains unclear. This study explored the protective effect of MT on chrysanthemum drought tolerance and its key regulatory pathways. Exogenous MT application increased the photosynthetic capacity (Tr increased by 18.07%; Pn increased by 38.46%; and Gs increased by 26.52%) of chrysanthemum and attenuated decreases in its chlorophyll (19.89%) and relative water contents (26.94%). Moreover, MT increased the levels of osmolarity-related compounds such as soluble sugars (43.60%) and soluble protein (9.86%) under drought stress and increased antioxidant enzyme activity (SOD increased by 20.98%; POD increased by 35.04%; and CAT increased by 26.21%). Additionally, MT increased the endogenous MT (597.96%), growth hormone (45.31% and 92.09%), gibberellic acid (75.92% and 3.79%), salicylic acid (33.02%), and cytokinin contents (1400.00%) under drought stress while decreasing the abscisic acid (50.69% and 56.79%), jasmonate contents (62.57% and 28.31%), and ethylene contents (9.28%). RNA-seq analysis revealed 17,389, 1466, and 9359 differentially expressed genes (DEGs) under three treatments (PEG, MT, and MT _ PEG, respectively) compared with the control. Enrichment analyses of the DEGs identified more than 10 GO terms and 34 KEGG pathways. Nitrogen metabolism, sulfur metabolism, and alanine, aspartate, and glutamate metabolism were significantly increased under all three treatments. The DEGs included many transcription factors, such as MYB, WRKY, and NAC proteins. Our results preliminarily classify candidate genes and metabolic pathways with active roles in the interaction between MT and drought stress and advance the understanding of the molecular mechanism of the response to drought stress under MT conditions, thereby providing a theoretical basis for the breeding of drought-resistant chrysanthemum.

Anatomical and Physiological Characteristics of Awn Development in Elymus nutans, an Important Forage Grass in Qinghai-Tibet Plateau

Awns are the important structures of inflorescence in many crops that belong to the Poaceae family. In addition, they actively participate in photosynthesis, transpiration, seed dispersal, and self-planting. The Elymus nutans Griseb. is an important, self-pollinated, allohexaploid (2n = 6x = 42) and perennial native forage grass in Qinghai-Tibet Plateau that shows variation in awns length. However, the changes in the anatomical structure, physiological traits, and biochemical characteristics during awn development remain unclear in E. nutans. Therefore, this study investigated the changes in anatomical structures, enzymatic activities, and hormonal regulations of awns at four developmental stages, i.e., booting, heading, flowering, and maturity stages of three E. nutans accessions having different awn lengths. The results showed that the cross-sections of E. nutans awns had an acute triangular shape and structural similarities to wheat awns. In addition, the growth of long awns was recorded faster than short awns at the heading stage, but no significant differences in awns lengths were found at the heading, flowering, and maturity stages. The differences in the sizes of barbs and stomata of three accessions were statistically non-significant; however, the accession with long awns had more stomata than the accession with shorter awns at all developmental stages. In addition, the content of cytokinin (CTK), abscisic acid (ABA), and ethylene (ETH), and activities of superoxide dismutase (SOD) and peroxidase (POD) were significantly related to the development of awn. At the flowering stage, the content of CTK, and activities of SOD and POD of long awn accession were significantly higher than the short awn accession. Therefore, the obtained results provide a sound basis for future research on the molecular mechanisms of awn development and their potential role in E. nutans.

Physiochemical Changes of European Pear cv. Conference and Asian Pear cv. Yali during Cold Storage

This study evaluated the physiochemical changes of one commercial European pear variety ‘Conference’ and one Asian pear variety ‘Yali’ during 60 days of storage at 1 °C. Content of organic acids, ethylene and formation of CO2 were determined using HPLC/UV-VIS and GC/FID and TCD detectors, respectively. This study presents an evaluation of the influence of the above-mentioned factors and long-term storage on quality parameters, including the antioxidant capacity of an important European and Asian pear cultivar. There was a significant effect of temperature on respiration rate in both varieties. Development of the respiration intensity had a similar course in European and Asian pears. The high values of CO2 production at the beginning of storage for the variety ‘Conference’ (14.08 mg·kg−1·h−1) and ‘Yali’ (23.37 mg·kg−1·h−1) were followed by a sharp decline of 80% and 83% at later stages of storage at 1 °C, respectively. Ethylene formation in fruit increased with storage time and was the highest after 60 days in cold storage, especially in ‘Yali’ (7.14 µL·kg−1·h−1). The results show the relation between ethylene formation and ripening-related fruit parameters. The ‘Yali’ variety showed negligible changes in soluble solids content and flesh firmness during storage ranging from 0.35 to 0.60 MPa. The most represented sugar determined enzymatically was fructose and malic acid was the dominant organic acid in pear fruit. Antioxidant activity determined using the FRAP and DPPH methods did not change significantly during 60 days of storage.

Evaluation of the Effect of 1-MCP Treatment on Flesh and Surface Color of Selected European and Asian Plum Fruit Using Machine Vision

The aim of this work was to evaluate how 1-methylcyclopropene (1-MCP) treatment affects appearance of plum fruit. Fruit of ‘Angeleno’ and ‘Topend’ cultivars were treated with 625 ppb gaseous 1-MCP at 1 °C for 24 h after harvest. Samples without treatment, called control, and those subjected to the treatment were stored at 1 °C for 8 weeks (Topend) and 10 weeks (Angeleno). The subgroup of initial samples and those withdrawn from cold storage were also measured after 7 d storage at 20 °C. According to measured parameters of ethylene, CO2 production, firmness, and total soluble solids content, there was a clear difference between 1-MCP- treated and control samples for both cultivars. Color attributes of hue angle and saturation changed significantly during storage, especially for flesh color measured on fruit cut in half. The comparison revealed that saturation responded more sensitively to changes. Firmness correlated significantly with color attributes, and flesh saturation reached the highest value of Pearson’s correlation of r = 0.608 (p < 0.01) and Spearman’s rank correlation of ρ = 0.636 (p < 0.01). The specific plum color was also evaluated with a normalized blue value, which obtained significant linear correlation with firmness (r = −0.7414, p < 0.001). There was significant difference between cultivars in terms of surface color and its correlation with firmness as Pearson’s correlation obtained r = 0.833 (p < 0.001) for ‘Topend’ and r = 0.556 (p > 0.05) for ‘Angeleno’.

Dissecting the effect of ethylene in the transcriptional regulation of chilling treatment in grapevine leaves

Ethylene (ETH) plays important roles in various development programs and stress responses in plants. In grapevines, ETH increased dramatically under chilling stress and is known to positively regulate cold tolerance. However, the role of ETH in transcriptional regulation during chilling stress of grapevine leaves is still not clear. To address this gap, targeted hormone profiling and transcriptomic analysis were performed on leaves of Vitis amurensis under chilling stress with and without aminoethoxyvinylglycine (AVG, a inhibitor of ETH synthesis) treatment. APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) and WRKY transcription factors (TF) were only the two highly enriched TF families that were consistently up-regulated during chilling stress but inhibited by AVG. The comparison of leaf transcriptomes between chilling treatment and chilling with AVG allowed the identification of potential ETH-regulated genes. Potential genes that are positively regulated by ETH are enriched in solute transport, protein biosynthesis, phytohormone action, antioxidant and carbohydrate metabolism. Conversely, genes related to the synthesis and signaling of ETH, indole-3-acetic acid (IAA), abscisic acid (ABA) were up-regulated by chilling treatment but inhibited by AVG. The contents of ETH, ABA and IAA also paralleled with the transcriptome data, which suggests that the response of ABA and IAA during chilling stress may regulate by ETH signaling, and together may belong to an integrated network of hormonal signaling pathways underpinning chilling stress response in grapevine leaves. Together, these findings provide new clues for further studying the complex regulatory mechanism of ETH under low-temperature stress in plants more generally and new opportunities for breeding cold-resilient grapevines.

Subsurface aeration mitigates organic material mulching-induced anaerobic stress via regulating hormone signaling in Phyllostachys praecox roots.

Organic material mulching has been used extensively to allow Phyllostachys praecox to promote growth and development of shoots. However, the bamboo forest always showed a significant degradation, probably due to anaerobic damage caused by the mulching after several years. Therefore, we have innovatively proposed an improvement measure to aerate the underground pipes for the first time. We investigated the role of subsurface pipe aeration in regulating root hypoxia to reduce the stress and to identify the degradation mechanism. Results showed that aeration increased oxygen concentration, shoot yield and root growth compared with mulching, and the aeration enhanced the concentration of indole-3-acetic acid (IAA) and the expression of Aux/IAAs (Aux1, Aux2, Aux3, and Aux4). Aeration reduced gibberellin (GA), ethylene (ETH), and abscisic acid (ABA) contents as well as anaerobic enzyme activities (alanine transaminase, AlaAT; alcohol dehydrogenase, ADH; pyruvate decarboxylase, PDC; and lactate dehydrogenase, LDH), which alleviated root damage in anoxic conditions. Furthermore, correlation showed that the activities of ADH, LDH, PDC, and AlaAT showed significant linear correlations with soil oxygen levels. RDA analyses showed that ABA, IAA, and ETH were found as the key driving hormones of Aux/IAAs in the root of the forest mulched with organic material. Here we show that subsurface aeration increases soil oxygen concentration, shoot yield, root growth and regulates phytohormone concentrations and Aux/IAAs expression, which reduces anaerobic enzyme activities. Consequently, subsurface pipe aeration is an effective measure to mitigate the degradation of bamboo forests caused by soil hypoxia that results from organic material mulching.

S‐adenosylmethionine synthase (BtSAMS) from Balsas teosinte confers resistance to peach aphids in Arabidopsis

AbstractThe purpose of this study was to clone S‐adenosylmethionine synthase (BtSAMS) from Balsas teosinte (Zea mays ssp. parviglumis) and investigate its function via heterologous expression in Arabidopsis plants. The BtSAMS coding sequence was cloned and its length is 1185 bp. The expression of BtSAMS in Z. mays ssp. parviglumis was a 12.2‐fold increase after aphid infestation. Transgenic Arabidopsis plants heterologously expressing BtSAMS were generated and their morphological characters were observed. A prolonged vegetative growth period was displayed by BtSAMS‐OX plants. The more and longer trichomes were observed on the upper surface of BtSAMS seedlings. The ethylene content in BtSAMS‐OX plants was not significantly different compared with the untransformed controls. These BtSAMS‐OX transgenic plants showed greater resistance to peach aphids compared with the untransformed control plants. Peach aphids appeared to prefer the untransformed controls in that aphids number reduced by more than 50% on BtSAMS plants compared to controls. When sprayed with the insecticide avi‐imidacloprid, the number of peach aphids decreased on BtSAMS‐OX plants and untransformed controls by 91.6% and 80.5%, respectively. Peach aphids also showed lower reproduction ability when forced to feed on the transgenic plants. The number of newly born nymphs on BtSAMS plants was less than 50% of that on the untransformed control. We therefore propose that BtSAMS may be a suitable candidate gene to confer resistance to peach aphids in plants.

A D-cysteine desulfhydrase, SlDCD2, participates in tomato fruit ripening by modulating ROS homoeostasis and ethylene biosynthesis.

Hydrogen sulfide (H2S) is involved in multiple processes during plant growth and development. D-cysteine desulfhydrase (DCD) can produce H2S with D-cysteine as the substrate; however, the potential developmental roles of DCD have not been explored during the tomato lifecycle. In the present study, SlDCD2 showed increasing expression during fruit ripening. Compared with the control fruits, the silencing of SlDCD2 by pTRV2-SlDCD2 accelerated fruit ripening. A SlDCD2 gene-edited mutant was constructed by CRISPR/Cas9 transformation, and the mutant exhibited accelerated fruit ripening, decreased H2S release, higher totalcysteine and ethylene contents, enhanced chlorophyll degradation and increased carotenoid accumulation. Additionally, the expression of multiple ripening-related genes, including NYC1, PAO, SGR1, PDS, PSY1, ACO1, ACS2, E4, CEL2, and EXP was enhanced during the dcd2 mutant tomato fruit ripening. Compared with the wild-type fruits, SlDCD2 mutation induced H2O2 and malondialdehyde (MDA) accumulation in fruits, which led to an imbalance in reactive oxygen species (ROS) metabolism. A correlation analysis indicated that H2O2 content was strongly positively correlated with carotenoids content, ethylene content and ripening-related gene expression and negatively correlated with the chlorophyll content. Additionally, the dcd2 mutant showed earlier leaf senescence, which may be due to disturbed ROS homeostasis. In short, our findings show that SlDCD2 is involved in H2S generation and that the reduction in endogenous H2S production in the dcd2 mutant causes accelerated fruit ripening and premature leaf senescence. Additionally, decreased H2S in the dcd2 mutant causes excessive H2O2 accumulation and increased ethylene release, suggesting a role of H2S and SlDCD2 in modulating ROS homeostasis and ethylene biosynthesis.

Salicylic acid delays pear fruit senescence by playing an antagonistic role toward ethylene, auxin, and glucose in regulating the expression of PpEIN3a.

Salicylic acid (SA) and ethylene (ET) are crucial fruit senescence hormones. SA inhibited ET biosynthesis. However, the mechanism of SA delaying fruit senescence is less known. ETHYLENE INSENSITIVE 3 (EIN3), a key positive switch in ET perception, functions as a transcriptional activator and binds to the primary ET response element that is present in the promoter of the ETHYLENE RESPONSE FACTOR1 gene. In this study, a gene encoding putative EIN3 protein was cloned from sand pear and designated as PpEIN3a. The deduced PpEIN3a contains a conserved EIN3 domain. The evolutionary analysis results indicated that PpEIN3a belonged to the EIN3 superfamily. Real-time quantitative PCR analysis revealed that the accumulation of PpEIN3a transcripts were detected in all tissues of this pear. Moreover, PpEIN3a expression was regulated during fruit development. Interestingly, the expression of PpEIN3a was downregulated by SA but upregulated by ET, auxin, and glucose. Additionally, the contents of free and conjugated SA were higher than those of the control after SA treatment. While the content of ET and auxin (indole-3-acetic acid, IAA) dramatically decreased after SA treatment compared with control during fruit senescence. The content of glucose increased when fruit were treated by SA for 12h and then there were no differences between SA treatment and control fruit during the shelf life. SA also delayed the decrease in sand pear (Pyrus pyrifolia Nakai. 'Whangkeumbae') fruit firmness. The soluble solid content remained relatively stable between the SA treated and control fruits. This study showed that SA plays an antagonistic role toward ET, auxin, and glucose in regulating the expression of PpEIN3a to delay fruit senescence.