Ethylene Biosynthesis Inhibitor Research Articles

Salicylic Acid from Gandapura Oil as an Inhibitor of Ethylene ‎Biosynthesis in Malus sylvestris L. Mill

Local apple production, especially Anna's apples, continues to decline. One of the Causes of the decline in local apple production is due to the disproportionate use of chemicals, which causes ethylene production in plants to increase. The purpose of this study was to examine the effect of salicylic acid on reducing levels of ethylene concentrations in Anna apple plants. This study used a completely randomized design (CRD) with a single factor, namely the treatment of various salicylic acid concentrations (25 ppm, 50 ppm, 100 ppm, 200 ppm). The results showed that salicylic acid was able to reduce the value of ethylene concentration in plants. Provision of salicylic acid concentrations starting at 25 ppm was able to inhibit ethylene biosynthesis by more than 90%. The best results were shown in samples treated with 200 ppm salicylic acid concentration. By using salicylic acid alternatives, farmers are able to save around Rp3,040,400 in costs in one harvest period. The percentage of costs for salicylic acid in one harvest period is 3.39% of the total production costs, while the cost of the import promoter is 7.92% of the total production costs

Brassinosteroids play multiple roles in nodulation of pea via interactions with ethylene and auxin.

A comprehensive analysis of the role of brassinosteroids in nodulation, including their interactions with auxin and ethylene revealed thatbrassinosteroids inhibit infection, promote nodule initiation but do not influence nodule organogenesis or function. Nodulation, the symbiosis between legumes and rhizobial bacteria, is regulated by a suite of hormones including brassinosteroids. Previous studies have found that brassinosteroids promote nodule number by inhibiting ethylene biosynthesis. In this study, we examined the influence of brassinosteroids on the various stages of infection and nodule development. We utilise pea mutants, including brassinosteroid mutants lk, lka and lkb, the ethylene insensitive ein2 mutant and the lk ein2 double mutant, along with transgenic lines expressing the DR5::GUS auxin activity marker to investigate how brassinosteroids interact with ethylene and auxin during nodulation. We show that brassinosteroids inhibit the early stages of nodulation, including auxin accumulation, root hair deformation and infection thread formation, and demonstrate that infection thread formation is regulated by brassinosteroids in an ethylene independent manner. In contrast, brassinosteroids appear to act as promoters of nodule initiation through both an ethylene dependent and independent pathway. Although brassinosteroids positively influence the ultimate number of nodules formed, we found that brassinosteroid-deficiency did not influence nodule structure including the vascular pattern of auxin activity or nitrogen-fixation capacity. These findings suggest that brassinosteroids are negative regulators of infection but positive regulators of nodule initiation. Furthermore, brassinosteroids do not appear to be essential for nodule organogenesis or function. Given the influence of brassinosteroids on discreet stages of nodulation but not nodule function, manipulation of brassinosteroids may be an interesting avenue for future research on the optimisation of nodulation.

Ethylene-removing packaging: Basis for development and latest advances.

Produce is rapidly gaining market share worldwide. Ethylene is a gas molecule that causes detrimental changes in produce. Thus, it is crucial to reduce surrounding ethylene besides inhibiting ethylene biosynthesis to extend produce shelf life and reduce food waste. Ethylene-removing packaging (ERP) can reduce ethylene concentration surrounding produce during transportation and commercialization. The information found in the literature on the topic is minimal and incomplete compared to other types of active packaging. It focuses on compounds with an ethylene-removing capacity rather than on the packaging technology per se. The goal of this literature review is to compile and discuss information from peer-reviewed scientific papers and industry websites on the basics on ERP and on recent developments that can be used to build on and to advance this type of active packaging. This review first focuses on factors needed to design effective ERP including produce characteristics, in-package composition, material properties and their changes after compounding, remover properties, integration techniques, and environment. Next, this review presents a classification for ERP and provides a detailed analysis of various ethylene-removing compounds including their mechanisms of action, integration techniques, impacts on produce shelf life, advantages and drawbacks including safety, commercial applications, and combinations with other shelf-life extending technologies. Some ERP designs are more promising to extend produce shelf life than others, but there is still room for further research to advance this packaging strategy. Specific needs include investigation of ethylene removal for fresh-cut produce and exploring different integration techniques and materials for such integration.

The karrikin signaling regulator SMAX1 controls Lotus japonicus root and root hair development by suppressing ethylene biosynthesis

An evolutionarily ancient plant hormone receptor complex comprising the α/β-fold hydrolase receptor KARRIKIN INSENSITIVE 2 (KAI2) and the F-box protein MORE AXILLARY GROWTH 2 (MAX2) mediates a range of developmental responses to smoke-derived butenolides called karrikins (KARs) and to yet elusive endogenous KAI2 ligands (KLs). Degradation of SUPPRESSOR OF MAX2 1 (SMAX1) after ligand perception is considered to be a key step in KAR/KL signaling. However, molecular events which regulate plant development downstream of SMAX1 removal have not been identified. Here we show that Lotus japonicus SMAX1 is specifically degraded in the presence of KAI2 and MAX2 and plays an important role in regulating root and root hair development. smax1 mutants display very short primary roots and elongated root hairs. Their root transcriptome reveals elevated ethylene responses and expression of ACC Synthase 7 (ACS7), which encodes a rate-limiting enzyme in ethylene biosynthesis. smax1 mutants release increased amounts of ethylene and their root phenotype is rescued by treatment with ethylene biosynthesis and signaling inhibitors. KAR treatment induces ACS7 expression in a KAI2-dependent manner and root developmental responses to KAR treatment depend on ethylene signaling. Furthermore, in Arabidopsis, KAR-induced root hair elongation depends on ACS7 Thus, we reveal a connection between KAR/KL and ethylene signaling in which the KAR/KL signaling module (KAI2-MAX2-SMAX1) regulates the biosynthesis of ethylene to fine-tune root and root hair development, which are important for seedling establishment at the beginning of the plant life cycle.

Effects of ethylene biosynthesis and signaling on oxidative stress and antioxidant defense system in Nelumbo nucifera G. under cadmium exposure.

Water contamination with cadmium (Cd) is a global environmental problem and its remediation becomes urgent. Phytoremediation using ornamental plants has attracted much attention for its advantages of cost-effectiveness and beautification of the environment. Nelumbo nucifera G. is a popular ornamental aquatic macrophyte with fast growth, large biomass, and high capacities for Cd accumulation and removal. However, information about Cd resistance and defense responses in N. nucifera is rather scarce, which restricts its large-scale utilization for phytoremediation. The phytohormone ethylene plays an important role in plant resistance to Cd stress, but the underlying mechanism remains unclear. In this study, we investigated morphophysiological responses of N. nucifera seedlings to Cd stress, and focused on the effects of ethylene on oxidative damage, Cd accumulation, and antioxidant defense system at the metabolic and transcript levels in leaves under Cd stress. Our results showed that Cd exposure led to leaf chlorosis and necrosis, coupled with an increase in contents of hydrogen peroxide, electrolyte leakage, and malondialdehyde, and decrease in chlorophyll content. Exogenous ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) application intensified Cd-induced stress responses and Cd accumulation, and increased ethylene production by inducing ACC synthase (ACS) gene NnACS. Such enhanced ethylene emission inhibited catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities, and modulated ascorbate (AsA) and glutathione (GSH) accumulation through transcriptional regulation of their respective metabolic genes. After ethylene action inhibitor silver thiosulfate (STS) supplementation, Cd-induced oxidative damage was abolished, and Cd content declined but still at a relatively high level. Blocking of ethylene perception by STS inhibited ethylene biosynthesis; enhanced CAT, APX, and GR activities and their transcript levels; increased AsA accumulation via inducing its biosynthetic genes; but reduced GSH content and NnGSH2 expression level. These results suggest that ethylene biosynthesis and signaling play an important role in N. nucifera response to Cd stress, and maintaining appropriate ethylene level and low ethylene sensitivity could improve its Cd tolerance via efficient antioxidant defenses.

Homeobox transcription factor OsZHD2 promotes root meristem activity in rice by inducing ethylene biosynthesis.

Root meristem activity is the most critical process influencing root development. Although several factors that regulate meristem activity have been identified in rice, studies on the enhancement of meristem activity in roots are limited. We identified a T-DNA activation tagging line of a zinc-finger homeobox gene, OsZHD2, which has longer seminal and lateral roots due to increased meristem activity. The phenotypes were confirmed in transgenic plants overexpressing OsZHD2. In addition, the overexpressing plants showed enhanced grain yield under low nutrient and paddy field conditions. OsZHD2 was preferentially expressed in the shoot apical meristem and root tips. Transcriptome analyses and quantitative real-time PCR experiments on roots from the activation tagging line and the wild type showed that genes for ethylene biosynthesis were up-regulated in the activation line. Ethylene levels were higher in the activation lines compared with the wild type. ChIP assay results suggested that OsZHD2 induces ethylene biosynthesis by controlling ACS5 directly. Treatment with ACC (1-aminocyclopropane-1-carboxylic acid), an ethylene precursor, induced the expression of the DR5 reporter at the root tip and stele, whereas treatment with an ethylene biosynthesis inhibitor, AVG (aminoethoxyvinylglycine), decreased that expression in both the wild type and the OsZHD2 overexpression line. These observations suggest that OsZHD2 enhances root meristem activity by influencing ethylene biosynthesis and, in turn, auxin.

Supplementary Red light results in the earlier ripening of tomato fruit depending on ethylene production

In greenhouse tomato production, the lower canopy of tomato plants is often shaded by the neighbouring tomato plants. Supplementary lighting can be used to provide sufficient light energy for plants. Red light is regarded as the most efficient spectrum in supplementary lighting. Whether and how supplementary red light in the ambient of sunlight affect the ripening of tomato remain to be elucidated. In this research, the impacts of supplementary red light on tomato ripening were examined by comparing the impacts of supplementary red light on ripening-related regulators, ethylene synthesis, ethylene signaling, carotenoid synthesis and light signaling in Micro-Tom wild type tomato fruit and ripening-inhibitor (rin) mutant. Supplementary red light did not affect the fruit ripening of rin mutant, because the deficiency of SlRIN resulted in down-regulation of genes encoding ripening-related regulators and suppression of ethylene biosynthesis. The wild type tomato fruit under supplementary red light showed accelerated color transition during ripening, which was associated with the increased expressions of genes encoding ripening-related regulators and ethylene biosynthesis. The increased expressions of genes encoding phytochrome in wild type tomato fruit under supplementary red light might reduce the level of phytochrome-interacting factors, resulting in higher activation of the phytoene synthase and overaccumulation of phytoene. Supplementary red light in ambient sunlight resulted in the accumulation of phytoene and the earlier ripening in tomato fruit, which depended on ethylene production.

The Ethylene Precursor ACC Affects Early Vegetative Development Independently of Ethylene Signaling.

The plant hormone ethylene plays a pivotal role in virtually every aspect of plant development, including vegetative growth, fruit ripening, senescence, and abscission. Moreover, it acts as a primary defense signal during plant stress. Being a volatile, its immediate biosynthetic precursor, 1-aminocyclopropane-1-carboxylic acid, ACC, is generally employed as a tool to provoke ethylene responses. However, several reports propose a role for ACC in parallel or independently of ethylene signaling. In this study, pharmacological experiments with ethylene biosynthesis and signaling inhibitors, 2-aminoisobutyric acid and 1-methylcyclopropene, as well as mutant analyses demonstrate ACC-specific but ethylene-independent growth responses in both dark- and light-grown Arabidopsis seedlings. Detection of ethylene emanation in ethylene-deficient seedlings by means of laser-based photoacoustic spectroscopy further supports a signaling role for ACC. In view of these results, future studies employing ACC as a proxy for ethylene should consider ethylene-independent effects as well. The use of multiple knockout lines of ethylene biosynthesis genes will aid in the elucidation of the physiological roles of ACC as a signaling molecule in addition to its function as an ethylene precursor.

Redox Control on Stem Cell Fate and Maintenance in the Root

Root growth depends on stem cells and the quiescence center (QC) in the root apical meristem (RAM). QC inhibits the differentiation of stem cells. A large amount of evidence showed that ASC/DHA and GSH/GSSG homeostasis have an important role in the QC and RAM activity. Mitochondria-localized APP1, ABO9, and PHB8 control the maintenance of the RAM through changing ROS homeostasis. Peptide RGF1 and its receptors RGFR1/2/3 establish ROS gradient in the root and maintain the root stem cells. Brassinosteroid (BR) might activate QC by inhibiting BRAVO which binds to BZR1 oxidized by BR-induced H2O2 and/or by inhibiting ethylene biosynthesis and peroxidase. Because ROS level is tightly controlled by antioxidants and ROS processing systems such as glutaredoxins (GRXs) and thioredoxins (TRXs), redox status might control the mitotic activity of the RAM, stemness of the initials, and proliferation and differentiation of root cells. Redox might interfere with the biosynthesis, transport, and action of auxin. The recent findings of the role of ROS in root stem cell regulation will be discussed with the background of this specific field and opened questions are addressed.

Ethylene signaling plays a pivotal role in mechanical-stress-induced root-growth cessation in Arabidopsis thaliana

ABSTRACTPlant roots show growth cessation as a primary response to mechanical stress. To clarify the molecular basis of this response, we have previously established an assay system to monitor the root growth response of Arabidopsis seedlings to mechanical stimuli using dialysis membrane-covered agar media. Here we examined the effect of plant hormones and their related molecules on this response. Amino-cyclopropane carboxylate, a precursor of ethylene, remarkably enhanced the growth reduction while silver ions, which block ethylene perception, nullified the response. Furthermore, salicylic acid, which inhibits ethylene biosynthesis, alleviated the root growth reduction, whereas methyl jasmonate had no apparent effect on the response. These results suggest that the root-growth cessation observed in response to mechanical stress involves ethylene signaling; however, this response may be independent from the pathway that integrates signals from ethylene and jasmonate.

New technology of protecting apple fruits from bitter pit and other physiological diseases during storage

The work was performed in the I. V. Michurin Federal Scientifi c Center (Tambov region, Russia) in 2015-2018. The fruits of Sinap Orlovsky variety with high susceptibility to bitter pit, medium – to superfi cial scald and CO2 -skin injuries were used. The main post-harvest strategy of protecting fruits from bitter pit (BP) is storage in a controlled atmosphere (CA), short-term low oxygen storage (10 days, O2<1 %) reduces losses from scald and BP, but does not provide protection from diseases of varieties with high susceptibility; post-harvest treatment with ethylene biosynthesis inhibitor (1-MCP) provides protection from scald, but has an ambiguous effect on the development of BP, and may increase the degree of disease appearance. The purpose of the research is the development of innovative technology of managing of bitter pit and other post-harvest pathological diseases. In the experiment, the control and 1-MCP-treated fruits were stored at 0 + 1 °C under regular (RA) and controlled atmosphere (CA) conditions: CA-1 (CO2 – 1.2-1.5 %, O2 – 1.2-1.5 %), CA-2 (СО2<0.1 %, О2 – 1.2-1.5 %), under conditions of short (10 days) post-harvest impact of controlled factors: temperature 18-20 °С, О2 – 1.2-1.5 %, CO2<0.1 % and further storage in regular atmosphere (LO2 ). Ethylene, α-farnesen and its oxidation products (CТ281), phenolic compounds were determined in fruits, losses from bitter pit, scald, CO2 -skin injuries, quality (fi rmness) were estimated. 1-MCP-treatment ensured a low level of ethylene and CT281 accumulation in fruits, protection from scald, preservation of fi rmness in all variants of fruit storage, with maximum effi ciency of variants CA-2, CA-1 and LO2 . Fruit protection from bitter pit was provided by CA-2 technology, a signifi cant reduction of losses – LO2 . When using the technology of CA-2, losses from CO2 -skin injuries, noted in the conditions of CA-1, were excluded. The maximum efficiency of protection of fruits from BP, scald, CO2 -injuries is provided by the developed technology CA-2 (CO2<0.1 %, O2 — 1.2-1.5 %).

Transcriptional regulation of chlorophyll-catabolic genes associated with exogenous chemical effects and genotypic variations in heat-induced leaf senescence for perennial ryegrass

Heat-induced leaf senescence is hallmarked with accelerated chlorophyll (Chl) catabolism. The involvement of Chl catabolic genes (CCGs) in heat-induced leaf senescence is not well characterized. The objectives of this study were to investigate transcriptional changes in CCGs associated with exogenous chemical effects and genotypic variations during heat-induced leaf senescence in perennial ryegrass (Lolium perenne L.), and to characterize its underlying mechanisms. Perennial ryegrass plants of ‘Buena Vista’ and ‘Pinnacle’ differing in heat tolerance were exposed to heat stress at 35/30 °C (day/night) and control condition at 25/20 °C (day/night) in growth chambers and foliar sprayed with the following chemicals: salicylic acid (SA), 6-benzylaminopurine (6-BA; a cytokinin), calcium dichloride (CaCl2), aminoethoxyvinylglycine (AVG; an ethylene biosynthesis inhibitor), sodium nitroprusside (SNP, a nitric oxide donor), and urea (N, nitrogen source). Higher Chl content, photochemical efficiency and membrane stability were found in ‘Buena Vista’ than ‘Pinnacle’ whereas lower expression levels of three CCGs (LpNYC1, LpNOL, and LpPPH) were detected in the former genotype under heat stress. Exogenous application of SA, 6-BA, CaCl2, AVG, SNP, and N suppressed heat-induced Chl decline and expression of CCGs in heat sensitive genotype ‘Pinnacle’ under heat stress. Heat-induced oxidative damage was alleviated by these compounds, as indicated by significantly lower reactive oxygen species (ROS) content and higher activities of ROS scavenging enzymes. The expression levels of CCGs were negatively correlated to ROS level, including O2− and H2O2, while positively correlated to activities of ROS scavenging enzymes, such as CAT and SOD. The current results suggest that the transcript levels of LpNYC1, LpNOL, and LpPPH were negatively correlated with heat-induced leaf senescence, and down-regulation of CCGs genes could suppress heat-induced leaf senescence and oxidative damages, conferring heat tolerance in perennial ryegrass.

Ethylene synthesis in mango ‘Palmer’ production

Ethylene is an important hormone in the floral induction process of the mango tree. However, climatic conditions such as the high temperatures that occur in the Brazilian semi-arid can raise the levels of ethylene and cause abortion of flowers and fruits, impairing the production. Thus, the goal of this study was to evaluate the effect of the ethylene biosynthesis inhibitor complex (Ni, Co and Mo) on flowering and ‘Palmer’ mango production. The experiment was set up in a randomized block design with six treatments and four replications. The treatments were five increasing levels of the commercial product Profol NiCoMo Dry® (Ni: 2.4%, Co: 1.2% and Mo: 26%) at concentrations of 0.25, 0.50, 0.75, 1.00 and 1.25 g L(‑1) and a control, in a volume of 800 L ha(‑1), at pre-flowering. Three weekly applications were carried out, starting with the second application of nitrate for floral induction. Evaluations were made for the number and length of panicles; number of fruits branch(‑1) of the sun rising side (NFRN), of the west side (NFRP) and total (NFR); length, diameter and fruit mass. The increase in the levels of Profol NiCoMo Dry up to 1.25 g L(‑1) promoted a linear increase in panicle length, fruit set and total number of fruit plant‑1, resulting in a linear reduction of fruit size (mass), without compromising the commercial standard. Increasing levels of Profol NiCoMo Dry up to 1.25 g L(‑1) promoted a cubic response in fruit yield, with the lowest obtained (23.30 t ha‑1) when using 0.1 g L(‑1) and the maximum (36.20 t ha(‑1)) for the level of 1.23 g L(‑1).

Synergistic effect of nitric oxide with hydrogen sulfide on inhibition of ripening and softening of peach fruits during storage

The effects of fumigation with NO, H2S and combination of both on the quality, ethylene biosynthesis and softening of postharvest ‘Dahong’ peach fruit were investigated in current study. Results showed that NO or H2S significantly inhibited the increase of rot index, soluble solid contents, decrease of firmness along with titratable acid contents (P < 0.05). Combinatorial treatment (NO+H2S) further inhibited ripening of peach fruits, moreover it also showed significant decline in ACC content, ACC synthase and oxidase activities compared to individual treatments, was mainly linked with reduced ethylene production. The combined treatment significantly inhibited the increase of water-soluble and CDTA-soluble cell wall fractions, the decrease of Na2CO3-soluble fractions in peach fruit with significantly reduced softening related enzymes activities. These observations suggested the existence of synergistic functions between NO and H2S in inhibiting ethylene biosynthesis and cell wall metabolism in order to maintain superior quality of peach fruits.

Endosymbiotic Sinorhizobium meliloti modulate Medicago root susceptibility to secondary infection via ethylene.

A complex network of pathways coordinates nodulation and epidermal root hair infection in the symbiotic interaction between rhizobia and legume plants. Whereas nodule formation was known to be autoregulated, it was so far unclear whether a similar control is exerted on the infection process. We assessed the capacity of Medicago plants nodulated by Sinorhizobium meliloti to modulate root susceptibility to secondary bacterial infection or to purified Nod factors in split-root and volatile assays using bacterial and plant mutant combinations. Ethylene implication in this process emerged from gas production measurements, use of a chemical inhibitor of ethylene biosynthesis and of a Medicago mutant affected in ethylene signal transduction. We identified a feedback mechanism that we named AOI (for Autoregulation Of Infection) by which endosymbiotic bacteria control secondary infection thread formation by their rhizospheric peers. AOI involves activation of a cyclic adenosine 3',5'-monophosphate (cAMP) cascade in endosymbiotic bacteria, which decreases both root infectiveness and root susceptibility to bacterial Nod factors. These latter two effects are mediated by ethylene. AOI is a novel component of the complex regulatory network controlling the interaction between Sinorhizobium meliloti and its host plants that emphasizes the implication of endosymbiotic bacteria in fine-tuning the interaction.

Induction of ethylene inhibits development of soybean sudden death syndrome by inducing defense-related genes and reducing Fusarium virguliforme growth.

Ethylene is a gaseous hormone that regulates plant responses to biotic and abiotic stresses. To investigate the importance of ethylene in soybean resistance to Fusarium virguliforme (Fv), the causal agent of sudden death syndrome (SDS), soybean cultivars Williams 82 (SDS-susceptible) and MN1606 (SDS-resistant) were treated 24 h before and 24h after Fv inoculation with either ethephon (ethylene inducer), cobalt chloride (ethylene biosynthesis inhibitor), or 1-MCP (ethylene perception inhibitor). Inoculated plants were grown for 21 days at 24°C in the greenhouse and then evaluated for SDS severity and expression of soybean defense genes. In both cultivars, plants treated with ethephon showed lower SDS foliar severity compared to the other treatments, whereas those treated with cobalt chloride or 1-MCP showed the same or higher SDS foliar severity compared to the water-treated control. Ethephon application resulted in activation of genes involved in ethylene biosynthesis, such as ethylene synthase (ACS) and ethylene oxidase (ACO), and genes involved in soybean defense response, such as pathogenesis-related protein (PR), basic peroxidase (IPER), chalcone synthase (CHS), and defense-associated transcription factors. Cobalt chloride and 1-MCP treatments had little or no effect on the expression of these genes. In addition, ethephon had a direct inhibitory effect on in-vitro growth of Fv on PDA media. Our results suggest that ethephon application inhibits SDS development directly by slowing Fv growth and/or by inducing soybean ethylene signaling and the expression of defense related genes.

Chlorine Dioxide Generation Method and Its Action Mechanism for Removing Harmful Substances and Maintaining Quality Attributes of Agricultural Products

Agricultural products are perishable and easily contaminated by spoilage microorganisms or foodborne pathogens, causing decay of food and illness in consumers. Chlorine dioxide (ClO2) has many advantages as a fungicide in comparison to chlorine, NaClO, and ozone, and it can be used for sterilization and preservation due to its strong oxidizing properties. ClO2 gas is more widely used in food safety and food preservation than its aqueous solutions. However, the ClO2 gas produced on a large scale from a chemical reactor cannot be applied to food in small packages. Several recent reports have discussed the use of ClO2 self-releasing packaging. This article highlights the systematic evaluation of the performance of ClO2 alone and in combination with other treatments, such as 1-MCP, chitosan, and UV irradiation, in maintaining food safety and freshness of agricultural products. This article also focuses on the biological functions and mechanisms of ClO2-mediated preservation of plant or animal food, including damage to the cell wall and the membrane of pathogens, inhibition of ethylene biosynthesis, restoration of redox balance, and change of the compound structure of toxins, such as pesticides, insecticides, and mycotoxins.

Eficacia de aviglicina en la reducción de la floración natural en piña en Costa Rica

The naturally differentiated flowering (NDF for its acronym in English) in Ananas comosus is regulated by low temperature and short days, stimulating greater ethylene biosynthesis. The efficacy of aviglycine (AVG) as an inhibitor of ethylene biosynthesis during the period of highest susceptibility of ‘MD-2’ pineapple plants in the Huetar Norte region of Costa Rica was evaluated. Three doses of the PinCor® 20 SL formulation were studied in high volume (2,000 L ha(-1)) and low volume (25 L ha-1) in plants from 213 to 225 days of age and from 1.7 to 1.87 kg of fresh weight, through applications with a seven-day interval between weeks 48 of 2015 and eight of 2016. PinCor® 20 SL (AVG) (0.25, 0.50 and 1.0 L ha(-1)) at 25 L ha(‑1) (2,000, 4,000 and 8,000 ppm) and at 2,000 L ha(-1) (25, 50 and 100 ppm) reduced natural flowering from 43.7 to 6.9% without affecting sensitivity to exogenous ethylene applied foliar, although the magnitude of the phenomenon could be influenced by the microenvironment. The volume applied did not affect the efficacy, while as the dose was increased the incidence was significantly lower and at 8,000 ppm it suppressed the natural flowering at 100%, although at high concentrations it generated symptoms of mild temporary chlorotic reaction in the plants. 100% natural flowering was expressed between weeks two and eight of 2016, coinciding with the exposure of the plantation for more than 50 min a day to a temperature lower than 20°C associated with a day-night temperature amplitude lower than 4°C; the incidence of NFD tending to increase as the period of foliar exposure increased.

Ethylene mediates repression of anthocyanin accumulation in black rice pericarps in the absence of light

The antioxidant properties of black rice are attributed to the high anthocyanin content in the pericarp. Light-dependent regulation of anthocyanin biosynthesis and the associated regulatory genes have been extensively studied in many plant species, including rice. Light is considered indispensable for anthocyanin accumulation in plants. Here, we report that anthocyanin biosynthesis and accumulation in the dark is negatively regulated by ethylene, as the ethylene biosynthesis inhibitor aminoethoxyvinylglycine hydrochloride (AVG)-treated samples in the dark exhibited significantly higher transcript levels of biosynthesis genes, including CHI, DFR, ANS, ANR, F3H, F’3H, CHS and UGFT, compared to untreated controls. Upregulation of these biosynthesis genes was accompanied by simultaneous de-repression of the R2-R3 domain and bHLH-containing transcription factors Kala3 and Kala4 at the transcript level. Additionally, bHLH152, which shows high similarity to Arabidopsis PIF3, is involved in the regulation of anthocyanin. These findings highlight the role of ethylene in modulating tissue-specific regulation of anthocyanin biosynthesis genes in the dark.

Mutation in a putative glycosyltransferase-like gene causes programmed cell death and early leaf senescence in rice

Leaf senescence is a genetically regulated, highly complex and ordered process. Although it has been extensively studied, the mechanism of leaf senescence is not well understood. In this study, we isolated a rice mutant, designated as premature senescence leaf (psl), which exhibits early senescence and spontaneous lesion mimic phenotype after flowering. The psl mutant displays programmed cell death with elevated accumulation of reactive oxygen species (ROS). Molecular and genetic analyses revealed that the phenotypes were caused by a phenylalanine deletion in the OsPSL (LOC_Os12g42420) that encode a putative core 2/I branching beta-1,6-N-acetylglucosaminyl transferase predicted to be involved in protein glycosylation modification. OsPSL mRNA levels increased as senescence progressed, with maximum accumulation of transcripts at late senescence stages in WT plants. Moreover, remarkedly down-regulated transcriptional levels of O-linked N-acetylglucosamine (O-GlcNAc) transferases (OGTs) genes were observed in psl mutant, supporting the occurrence of impaired O-glycosylation modification. Proteomic analysis showed that ethylene-related metabolic enzymes including S-adenosyl methionine (SAM) synthetase (SAMS) were significantly upregulated in the psl mutant compared with WT. Consistent with the proteomic results, ethylene concentration is higher in psl mutant than in wild-type plants, and transcript levels of ethylene synthesis and signal transduction genes were induced in psl mutant. The early leaf senescence of psl can be partially rescued by ethylene biosynthesis inhibitor aminoethoxyvinylglycine treatment. These results highlight the importance of protein O-glycosylation in PCD and leaf senescence, and suggest a possible role of OsPSL in ethylene signaling.