Ethylene Biosynthesis Pathway Research Articles

Research progress on the effects of postharvest storage methods on melon quality

Background As an important global agricultural cash crop, melon has a long history of cultivation and a wide planting area. The physiological metabolism of melon after harvest is relatively strong; if not properly stored, melon is easily invaded by external pathogens during transportation, resulting in economic losses and greatly limiting its production, development and market supply. Therefore, the storage and freshness of melon are the main challenges in realizing the annual supply of melon, so postharvest storage has received increasing amounts of attention from researchers. Methods This study used academic, PubMed, and Web of Science resources to retrieve keywords related to postharvest storage and melon quality; read, refined, classified, and sorted the retrieved literature; sorted and summarized the relevant research results; and finally completed this article. Results This article reviews the mechanism and effects of physical, chemical and biological preservation techniques on the sensory quality, compound contents and respiratory physiological activities of different varieties of melon fruits. When maintaining normal metabolism and not producing physiological disorders, melon inhibits cell wall metabolism, reactive oxygen species metabolism and the ethylene biosynthesis pathway, etc., to the greatest extent during postharvest storage, thereby reducing the material consumption of fruits, delaying the ripening and senescence process, and prolonging the postharvest life and shelf life. Conclusion The literature provides a theoretical basis for postharvest preservation technology in the melon industry in the future and provides corresponding guidance for the development of the melon industry.

The response of Midknight Valencia oranges to ethephon degreening varies in the turning and regreening stages.

Late-ripening citrus plays an important role in the stability of the global citrus industry. However, the regreening phenomenon in Valencia oranges impacts the peel color and commercial value. Ethylene degreening is an effective technique to improve the color of citrus fruits, but this effect may be delayed in regreened oranges. To better clarify this phenomenon, plastid morphology, pigment and phytohormone content in ethephon-degreened Midknight Valencia oranges harvested in different stages were evaluated. Results showed that in fruits harvested at the turning stage, ethephon degreening treatment induced a chloroplast-to-chromoplast transition, and chlorophyll degradation and carotenoid accumulation were accelerated. Conversely, in fruits harvested at the regreening stage, the changes in plastid morphology were minimal, with delayed changes in chlorophyll and carotenoids. Genes related to ethylene biosynthesis and signaling pathways supported these responses. Variations in endogenous auxin, jasmonic acid, abscisic acid and gibberellins could partially explain this phenomenon. The response of Midknight Valencia oranges to ethephon degreening was delayed in the regreening stage, possibly due to the dynamic variations in endogenous phytohormones. © 2024 Society of Chemical Industry.

From the rhizosphere to plant fitness: Implications of microplastics soil pollution

Microplastics (MPs) are a widespread contaminant in the terrestrial environment, with potential impacts on the soil-plant system not yet well understood. This study explores the effects of oxidised low-density polyethylene-MPs (LDPE-MPs) on the rhizosphere ecology and plant fitness of Fragaria x ananassa (Duchesne ex Weston) Duchesne ex Rozier. The rhizospheric microbial community was investigated under the influence of 0,5 % LDPE-MPs by internal transcribed spacer (ITS) and 16 S rRNA metagenomic analysis; photosynthetic parameters, antioxidant enzyme activities, and nutrient accumulation were assessed to evaluate plant physiological and biochemical status. Genes related to jasmonic acid (JA), ethylene biosynthesis, and nitrate signalling pathways were analysed to define the plant molecular response. Our results showed a shift in the rhizosphere microbial community. We identified MPs molecular biomarkers in the contaminated rhizosphere (Fusarium, Thanatephorus and Pseudallescheria) with potential pathogenic functions and two novel molecular biomarkers (Ohtaekwangia and Ascobolus). MPs pollution negatively impacts plant fitness, which showed decreased chlorophyll a and b (40 and 48 %, respectively), a change in nutrient content (fluctuations between 14,42 and 26,7 %) at the leaf level and increased activity of antioxidant enzymes. Gene expression related to JA, ethylene biosynthesis, and nitrogen signalling pathways is enhanced in plants grown in contaminated soil, as well as the root endophytic and epiphytic microorganism interactions. Our results demonstrate that MPs pollution influences the rhizosphere microbial community and functions, and consequently, negatively impacts plant health.

A UPLC-MS/MS method for quantification of metabolites in the ethylene biosynthesis pathway and its biological validation in Arabidopsis.

The plant hormone ethylene is of vital importance in the regulation of plant development and stress responses. Recent studies revealed that 1-aminocyclopropane-1-carboxylic acid (ACC) plays a role beyond its function as an ethylene precursor. However, the absence of reliable methods to quantify ACC and its conjugates malonyl-ACC (MACC), glutamyl-ACC (GACC), and jasmonyl-ACC (JA-ACC) hinders related research. Combining synthetic and analytical chemistry, we present the first, validated methodology to rapidly extract and quantify ACC and its conjugates using ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Its relevance was confirmed by application to Arabidopsis mutants with altered ACC metabolism and wild-type plants under stress. Pharmacological and genetic suppression of ACC synthesis resulted in decreased ACC and MACC content, whereas induction led to elevated levels. Salt, wounding, and submergence stress enhanced ACC and MACC production. GACC and JA-ACC were undetectable in vivo; however, GACC was identified in vitro, underscoring the broad applicability of the method. This method provides an efficient tool to study individual functions of ACC and its conjugates, paving the road toward exploration of novel avenues in ACC and ethylene metabolism, and revisiting ethylene literature in view of the recent discovery of an ethylene-independent role of ACC.

How the Ethylene Biosynthesis Pathway of Semi-Halophytes Is Modified with Prolonged Salinity Stress Occurrence?

The mechanism of ethylene (ET)-regulated salinity stress response remains largely unexplained, especially for semi-halophytes and halophytes. Here, we present the results of the multifaceted analysis of the model semi-halophyte Mesembryanthemum crystallinum L. (common ice plant) ET biosynthesis pathway key components' response to prolonged (14 days) salinity stress. Transcriptomic analysis revealed that the expression of 3280 ice plant genes was altered during 14-day long salinity (0.4 M NaCl) stress. A thorough analysis of differentially expressed genes (DEGs) showed that the expression of genes involved in ET biosynthesis and perception (ET receptors), the abscisic acid (ABA) catabolic process, and photosynthetic apparatus was significantly modified with prolonged stressor presence. To some point this result was supported with the expression analysis of the transcript amount (qPCR) of key ET biosynthesis pathway genes, namely ACS6 (1-aminocyclopropane-1-carboxylate synthase) and ACO1 (1-aminocyclopropane-1-carboxylate oxidase) orthologs. However, the pronounced circadian rhythm observed in the expression of both genes in unaffected (control) plants was distorted and an evident downregulation of both orthologs' was induced with prolonged salinity stress. The UPLC-MS analysis of the ET biosynthesis pathway rate-limiting semi-product, namely of 1-aminocyclopropane-1-carboxylic acid (ACC) content, confirmed the results assessed with molecular tools. The circadian rhythm of the ACC production of NaCl-treated semi-halophytes remained largely unaffected by the prolonged salinity stress episode. We speculate that the obtained results represent an image of the steady state established over the past 14 days, while during the first hours of the salinity stress response, the view could be completely different.

Two key enzyme genes associated with ethylene bio-synthesis, LbACS and LbACO, are involved in the regulation of lily flower senescence

Ethylene plays an important role in regulating the growth and development of flowers and determines the flower life span of ornamental plants. In this study, the lily variety 'Manissa' was used to elucidate the mechanism associated with the regulation of lily senescence by the genes for 1-aminocyclopropane-1-carboxylic acid synthetase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), which are key enzymes in the ethylene biosynthesis pathway. The results showed that ethylene release increased, the relative water content first increased and then decreased, and relative conductivity continuously increased as lily bud development progressed. LbACS1 transcription was highest at the blooming stage, LbACS7 transcription was highest at the green bud stage, and LbAC03 and LbAC04 levels both peaked at the yellow bud stage and the blooming stage. After treating cut lily flowers with ethephon and ethylene inhibitor 1-methylcyclopropene (1-MCP), the results showed that ethephon promoted the senescence of cut flowers, ethylene release, and the transcription levels of the four Lb genes. 1-MCP treatment also delayed the aging of cut flowers, but reduced ethylene release and inhibited the transcription of LbAC03 and LbAC04 when the treatment was applied during the later stages of bud development. This study provided evidence for the role of ethylene and the functions of LbACS and LbAC0 in the aging process associated with cut lily flowers.

Exploring ethylene-related genes in Cannabis sativa: implications for sexual plasticity.

Presented here are model Yang cycle, ethylene biosynthesis and signaling pathways in Cannabis sativa. C. sativa floral transcriptomes were used to predict putative ethylene-related genes involved in sexual plasticity in the species. Sexual plasticity is a phenomenon, wherein organisms possess the ability to alter their phenotypic sex in response to environmental and physiological stimuli, without modifying their sex chromosomes. Cannabis sativa L., a medically valuable plant species, exhibits sexual plasticity when subjected to specific chemicals that influence ethylene biosynthesis and signaling. Nevertheless, the precise contribution of ethylene-related genes (ERGs) to sexual plasticity in cannabis remains unexplored. The current study employed Arabidopsis thaliana L. as a model organism to conduct gene orthology analysis and reconstruct the Yang Cycle, ethylene biosynthesis, and ethylene signaling pathways in C. sativa. Additionally, two transcriptomic datasets comprising male, female, and chemically induced male flowers were examined to identify expression patterns in ERGs associated with sexual determination and sexual plasticity. These ERGs involved in sexual plasticity were categorized into two distinct expression patterns: floral organ concordant (FOC) and unique (uERG). Furthermore, a third expression pattern, termed karyotype concordant (KC) expression, was proposed, which plays a role in sex determination. The study revealed that CsERGs associated with sexual plasticity are dispersed throughout the genome and are not limited to the sex chromosomes, indicating a widespread regulation of sexual plasticity in C. sativa.

The Ethylene Biosynthetic Enzymes, 1-Aminocyclopropane-1-Carboxylate (ACC) Synthase (ACS) and ACC Oxidase (ACO): The Less Explored Players in Abiotic Stress Tolerance.

Ethylene is an essential plant hormone, critical in various physiological processes. These processes include seed germination, leaf senescence, fruit ripening, and the plant's response to environmental stressors. Ethylene biosynthesis is tightly regulated by two key enzymes, namely 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO). Initially, the prevailing hypothesis suggested that ACS is the limiting factor in the ethylene biosynthesis pathway. Nevertheless, accumulating evidence from various studies has demonstrated that ACO, under specific circumstances, acts as the rate-limiting enzyme in ethylene production. Under normal developmental processes, ACS and ACO collaborate to maintain balanced ethylene production, ensuring proper plant growth and physiology. However, under abiotic stress conditions, such as drought, salinity, extreme temperatures, or pathogen attack, the regulation of ethylene biosynthesis becomes critical for plants' survival. This review highlights the structural characteristics and examines the transcriptional, post-transcriptional, and post-translational regulation of ACS and ACO and their role under abiotic stress conditions. Reviews on the role of ethylene signaling in abiotic stress adaptation are available. However, a review delineating the role of ACS and ACO in abiotic stress acclimation is unavailable. Exploring how particular ACS and ACO isoforms contribute to a specific plant's response to various abiotic stresses and understanding how they are regulated can guide the development of focused strategies. These strategies aim to enhance a plant's ability to cope with environmental challenges more effectively.

Discovery of candidate genes involved in ethylene biosynthesis and signal transduction pathways related to peach bud cold resistance.

Background: Low temperature pose significant challenges to peach cultivation, causing severe damage to peach buds and restricting production and distribution. Ethylene, an important phytohormone, plays a critical role in enhancing plant cold resistance. Structural genes and transcription factors involved in ethylene biosynthesis and signal transduction pathways are associated with cold resistance. However, no research has specifically addressed their roles in peach cold resistance. Methods: In this study, we aimed for cold-resistance gene discovery in cold-sensitive peach cultivar "21Shiji" (21SJ) and cold-resistance cultivar "Shijizhixing" (SJZX) using RNA-seq and gas chromatography. Results: The findings revealed that under cold stress conditions, ethylene biosynthesis in "SJZX" was significantly induced. Subsequently, a structural gene, PpACO1-1, involved in ethylene biosynthesis in peach buds was significantly upregulated and showed a higher correlation with ethylene release rate. To identify potential transcription factors associated with PpACO1-1 expression and ethylene signal transduction, weighted gene co-expression network analysis was conducted using RNA-seq data. Four transcription factors: PpERF2, PpNAC078, PpWRKY65 and PpbHLH112, were identified. Conclusion: These findings provide valuable theoretical insights for investigating the regulatory mechanisms of peach cold resistance and guiding breeding strategies.

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.

The Potential of Essential Oils from Active Packaging to Reduce Ethylene Biosynthesis in Plant Products. Part 1: Vegetables (Broccoli and Tomato).

Essential oils (EOs) extracted from plants have a high potential to reduce ethylene biosynthesis, although their effects have not been deeply studied yet on the key components of the ethylene biosynthesis pathway: l-aminocyclopropane-1-carboxylic (ACC) oxidase activity, ACC synthase activity, and ACC content. Hence, the present study aimed to elucidate the effects of released EOs from active packaging (with different EO doses ranging from 100 to 1000 mg m-2) on the ethylene biosynthesis key components of broccoli and tomato under different storage temperature scenarios. The largest ethylene inhibitory effects on broccoli and tomatoes were demonstrated by grapefruit EO and thyme essential EO (up to 63%), respectively, which were more pronounced at higher temperatures. Regarding EO doses, active packaging with a thyme EO dose of 1000 mg m-2 resulted in the strongest reduction (33-38%) of ethylene production in tomatoes. For broccoli, identical results were shown with a lower grapefruit EO dose of 500 mg m-2. The studied EO-active packaging decreased ACC synthase and ACC oxidase activities by 40-50% at 22 °C. Therefore, this EO-active packaging is a natural and effective technology to reduce ethylene biosynthesis in broccoli and tomatoes when they are stored, even in unsuitable scenarios at high temperatures.

MaMADS1-MaNAC083 transcriptional regulatory cascade regulates ethylene biosynthesis during banana fruit ripening.

The hormone ethylene is crucial in the regulation of ripening in climacteric fruit, such as bananas. The transcriptional regulation of ethylene biosynthesis throughout banana fruit ripening has received much study, but the cascaded transcriptional machinery of upstream transcriptional regulators implicated in the ethylene biosynthesis pathway is still poorly understood. Here we report that ethylene biosynthesis genes, including MaACS1, MaACO1, MaACO4, MaACO5, and MaACO8, were upregulated in ripening bananas. NAC (NAM, ATAF, CUC) transcription factor, MaNAC083, a ripening and ethylene-inhibited gene, was discovered as a potential binding protein to the MaACS1 promoter by yeast one-hybrid screening. Further in vitro and in vivo experiments indicated that MaNAC083 bound directly to promoters of the five ethylene biosynthesis genes, thereby transcriptionally repressing their expression, which was further verified by transient overexpression experiments, where ethylene production was inhibited through MaNAC083-modulated transcriptional repression of ethylene biosynthesis genes in banana fruits. Strikingly, MaMADS1, a ripening-induced MADS (MCM1, AGAMOUS, DEFICIENS, SRF4) transcription factor, was found to directly repress the expression of MaNAC083, inhibiting trans-repression of MaNAC083 to ethylene biosynthesis genes, thereby attenuating MaNAC083-repressed ethylene production in bananas. These findings collectively illustrated the mechanistic basis of a MaMADS1-MaNAC083-MaACS1/MaACOs regulatory cascade controlling ethylene biosynthesis during banana fruit ripening. These findings increase our knowledge of the transcriptional regulatory mechanisms of ethylene biosynthesis at the transcriptional level and are expected to help develop molecular approaches to control ripening and improve fruit storability.

GENOME-WIDE BIOINFORMATICS ANALYSIS OF 1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASE (ACS), 1-AMINOCYCLOPROPANE-1-CARBOXYLATE OXIDASE (ACO) AND ETHYLENE OVERPRODUCER 1 (ETO1) GENE FAMILY OF FRAGARIA VESCA (WOODLAND STRAWBERRY)

This study was made on three genes ACS, ACO, and ETO, which are involved in ethylene biosynthesis pathway in Fragaria vesa plant, to know about evolution, conserved motifs and domains, gene expressions, and phylogeny of these genes. After carefully screening using Phytozome plant gene database, NCBI gene database, Motif finder, and MegaX phylogenetic tree 10 gene sequences of ACS, 5 gene sequences of ACO and 3 gene sequences of ETO were identified. Four ETO gene sequences of Arabidopsis thaliana were also used to authenticate this research because only 3 ETO gene sequences of Fragaria vesca analyses cannot be done. MegaX evolutionary analysis, TB tools domain analysis, Meme motif analysis, Cis-regulatory analysis, Wolf analysis were made on these sequences to acquire detailed knowledge. The presence of light, anaerobic induction, abscisic acid, MeJA, gibberellin, low temperature, drought, cell cycle, and endosperm expression responsive elements were identified in FeACS, FeACO, and FeETO genes by cis-regulatory analysis. This study will help for further practical experimentation on ethylene regulators. The bioinformatics-based genome-wide assessment of the family of Fragaria vesca attempted in the present study could be a significant step for further practical investigation on ethylene regulators based on genome-wide expression profiling.

Transcriptome analysis during vernalization in wheat (Triticum aestivum L.)

BackgroundVernalization, as a vital process in the life cycle of winter cereal, has important effects on floral organ formation and flowering time. Many morphological changes together with molecular changes occur during the vernalization period. Here, we used transcriptome sequencing to analyze the transcriptomic changes in wheat leaves before, during and after vernalization using the winter wheat cultivar ‘Shiluan02-1’.ResultsA total of 16,370 differentially expressed genes were obtained across different vernalization periods. Gene Ontology enrichment analysis revealed that photoperiodism, photoprotection, photosynthesis, lipid transport and biosynthetic process, and chlorophyll metabolic process were closely related to vernalization. In addition, AP2/ERF, C2H2, bHLH, WRKY, MYB, MYB-related, and NAC transcription factors were significantly enriched during vernalization, and the transcription factor expression patterns suggested the intricate regulation of transcription factor modules in plant vernalization pathways. Analysis of gene expression patterns of the MADS-box transcription factor genes showed different expression patterns during vernalization phases, among which VERNALIZATION1 (VRN1) genes were found to gradually increase during vernalization periods from V0 to V35, while decline in the V42 phase, then increase after vernalization. The Tavrt-2 gene cooperated with Tavrn1 to regulate flowering induced by vernalization, and its expression level was rapidly increased by vernalization but declined in the V42 phase and then increased after vernalization. Some genes from the ICE-CBF-COR pathway were also identified, and additional analysis indicated that some key genes related to phytohormone biosynthesis and signal transduction were enriched during the vernalization period, such as gibberellic acid, ethylene, abscisic acid and jasmonic acid biosynthesis and signaling pathway genes.ConclusionsOur study provides valuable molecular information for future studies on wheat vernalization regulation and also serves as an excellent reference for future wheat breeding.

Physiological Changes and Transcriptomic Analysis throughout On-Tree Fruit Ripening Process in Persimmon (Diospyros kaki L.).

The involvement of effectors and transcriptional regulators in persimmon fruit maturation has been mostly approached by the literature under postharvest conditions. In order to elucidate the participation of these genes in the on-tree fruit maturation development, we have collected samples from seven persimmon germplasm accessions at different developmental stages until physiological maturation. This study has focused on the expression analysis of 13 genes involved in ethylene biosynthesis and response pathways, as well as the evolution of important agronomical traits such as skin colour, weight, and firmness. Results revealed different gene expression patterns, with genes up- and down-regulated during fruit development progression. A principal component analysis was performed to correlate gene expression with agronomical traits. The decreasing expression of the ethylene biosynthetic genes DkACO1, DkACO2, and DkACS2, in concordance with other sensing (DkERS1) and transduction genes (DkERF18), provides a molecular mechanism for the previously described high production of ethylene in immature detached fruits. On the other side, DkERF8 and DkERF16 are postulated to induce fruit softening and skin colour change during natural persimmon fruit ripening via DkXTH9 and DkPSY activation, respectively. This study provides valuable information for a better understanding of the ethylene signalling pathway and its regulation during on-tree fruit ripening in persimmon.

The effect of cold stress on ethylene biosynthesis and sensitivity in cut lily ‘Marlon’

Fresh cut lily flowers often have a long postharvest life and produce undetectable levels of ethylene. This changes after cold storage, when lilies produce a higher amount of ethylene with a very early leaf and then flower senescence. Such changes to postharvest physiology are likely ethylene-dependant, either due to a higher level of ethylene production or a change in ethylene sensitivity as a result of alteration in the expression of genes involved in the biosynthesis, perception and signalling of ethylene. Therefore, we investigated the transcriptional regulation of ethylene biosynthesis, perception, and signalling pathways in response to cold storage in the cut lily cultivar ‘Marlon’. Cut lily stems were treated as follows: 1) control (no treatments), 2) 1-Methylcyclopropene (1-MCP; an ethylene action inhibitor) (10 nL L−1), 3) ethylene (10 μL L−1), and 4) 1-MCP (10 nL L−1) + ethylene (10 μL L−1) for 12 h, thereafter, half of each treated group were cold stored at 5 °C in 12 h light/dark condition for 7 days. We assessed quality characteristics, ethylene production, and the expression of its biosynthesis, perception, and signalling genes. Ethylene and 1-MCP treatments had no effects on non-cold-stored plants. Cold storage led to much earlier leaf yellowing (from 8 to 4 days), and flowers senesced and abscised 3 days earlier. In cold-stored plants, flower senescence and abscission were hastened by ethylene and delayed by 1-MCP. These findings indicate that ethylene does influence flower senescence following cold storage but leaf senescence is under the control of other factors. Our results suggest that treatments that focus on ethylene blockers to prolong postharvest life in lilies will be effective for flowers but not leaves.

EcAGL enhances cadmium tolerance in transgenic Arabidopsis thaliana through inhibits cadmium transport and ethylene synthesis pathway

Cadmium (Cd) is a highly toxic heavy metal with severe impacts on plant growth and development. Although a multitude of plants have acquired strong tolerance to Cd stress, the underlying molecular mechanism has not been fully elucidated. Here, we identified a Agamous-like MADS-box gene (EcAGL) from Erigeron canadensis. The expression of EcAGL was obviously raised under Cd stress and subcellular localization indicated EcAGL was localized in the nucleus. Overexpression of EcAGL in Arabidopsis thaliana showed marked alleviation of the Cd-induced reduction; Compared to wild-type lines, the antioxidant enzymes activities were increased in EcAGL overexpressing lines under Cd stress. The roots Cd content of transgenic lines was not different with the control plants, whereas significant reduction in shoots Cd content was detected in the transgenic lines, indicating that this gene can enhance Cd tolerance by reducing Cd accumulation in Arabidopsis. Moreover, the expression levels of heavy metal ATPase (AtHMA2 and AtHMA3) and natural resistance-associated macrophage protein (AtNRAMP5) genes in the root of transgenic lines decreased under Cd stress, indicating that EcAGL likely hampered the Cd transport pathway. Gene expression profiles in shoot showed that EcAGL likely modulates the expression of 1-aminocyclopropane-1-carboxylic acid synthase gene (AtACS2), which is involved in the ethylene synthesis pathway, to strengthen the tolerance to Cd. Collectively, these results indicate that EcAGL plays a significant role in regulating Cd tolerance in E. canadensis by alleviating oxidative stress, Cd transport and affecting the ethylene biosynthesis pathway, providing new insight into the molecular mechanism underlying plant tolerance to Cd stress.

The role of ethylene in plant temperature stress response.

Temperature influences the seasonal growth and geographical distribution of plants. Heat or cold stress occur when temperatures exceed or fall below the physiological optimum ranges, resulting in detrimental and irreversible damage to plant growth, development, and yield. Ethylene is a gaseous phytohormone with an important role in plant development and multiple stress responses. Recent studies have shown that, in many plant species, both heat and cold stress affect ethylene biosynthesis and signaling pathways. In this review, we summarize recent advances in understanding the role of ethylene in plant temperature stress responses and its crosstalk with other phytohormones. We also discuss potential strategies and knowledge gaps that need to be adopted and filled to develop temperature stress-tolerant crops by optimizing ethylene response.

Targeted system approach to ethylene biosynthesis and signaling of a heat tolerant tomato cultivar; the impact of growing season on fruit ripening.

Growing tomato in hot weather conditions is challenging for fruit production and yield. Tomato cv. Savior is a heat-tolerant cultivar which can be grown during both the Vietnamese winter (mild condition) and summer (hot condition) season. Understanding the mechanisms of ethylene biosynthesis and signaling are important for agriculture, as manipulation of these pathways can lead to improvements in crop yield, stress tolerance, and fruit ripening. The objective of this study was to investigate an overview of ethylene biosynthesis and signaling from target genes to proteins and metabolites and the impact of growing season on a heat tolerant tomato cultivar throughout fruit ripening and postharvest storage. This work also showed the feasibility of absolute protein quantification of ethylene biosynthesis enzymes. Summer fruit showed the delayed peak of ethylene production until the red ripe stage. The difference in postharvest ethylene production between winter and summer fruit appears to be regulated by the difference in accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC) which depends on the putative up-regulation of SAM levels. The lack of differences in protein concentrations between winter and summer fruit indicate that heat stress did not alter the ethylene biosynthesis-related protein abundance in heat tolerant cultivar. The analysis results of enzymatic activity and proteomics showed that in both winter and summer fruit, the majority of ACO activity could be mainly contributed to the abundance of ACO5 and ACO6 isoforms, rather than ACO1. Likewise, ethylene signal transduction was largely controlled by the abundance of ethylene receptors ETR1, ETR3, ETR6, and ETR7 together with the constitute triple response regulator CTR1 for both winter and summer grown tomatoes. Altogether our results indicate that in the heat tolerant tomato cv. Savior, growing season mainly affects the ethylene biosynthesis pathway and leaves the signaling pathway relatively unaffected.

Peronophythora litchii RXLR effector P. litchii avirulence homolog 202 destabilizes a host ethylene biosynthesis enzyme.

Oomycete pathogens can secrete hundreds of effectors into plant cells to interfere with the plant immune system during infection. Here, we identified a Arg-X-Leu-Arg (RXLR) effector protein from the most destructive pathogen of litchi (Litchi chinensis Sonn.), Peronophythora litchii, and named it P. litchii avirulence homolog 202 (PlAvh202). PlAvh202 could suppress cell death triggered by infestin 1 or avirulence protein 3a/resistance protein 3a in Nicotiana benthamiana and was essential for P. litchii virulence. In addition, PlAvh202 suppressed plant immune responses and promoted the susceptibility of N. benthamiana to Phytophthora capsici. Further research revealed that PlAvh202 could suppress ethylene (ET) production by targeting and destabilizing plant S-adenosyl-L-methionine synthetase (SAMS), a key enzyme in the ET biosynthesis pathway, in a 26S proteasome-dependent manner without affecting its expression. Transient expression of LcSAMS3 induced ET production and enhanced plant resistance, whereas inhibition of ET biosynthesis promoted P. litchii infection, supporting that litchi SAMS (LcSAMS) and ET positively regulate litchi immunity toward P. litchii. Overall, these findings highlight that SAMS can be targeted by the oomycete RXLR effector to manipulate ET-mediated plant immunity.