ACC Oxidase Research Articles

Inhibition of ethylene production by putrescine alleviates aluminium-induced root inhibition in wheat plants.

Inhibition of root elongation is one of the most distinct symptoms of aluminium (Al) toxicity. Although putrescine (Put) has been identified as an important signaling molecule involved in Al tolerance, it is yet unknown how Put mitigates Al-induced root inhibition. Here, the possible mechanism was investigated by using two wheat genotypes differing in Al resistance: Al-tolerant Xi Aimai-1 and Al-sensitive Yangmai-5. Aluminium caused more root inhibition in Yangmai-5 and increased ethylene production at the root apices compared to Xi Aimai-1, whereas the effects were significantly reversed by ethylene biosynthesis inhibitors. The simultaneous exposure of wheat seedlings to Al and ethylene donor, ethephon, or ethylene biosynthesis precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), increased ethylene production and aggravated root inhibition, which was more pronounced in Xi Aimai-1. In contrast, Put treatment decreased ethylene production and alleviated Al-induced root inhibition in both genotypes, and the effects were more conspicuous in Yangmai-5. Furthermore, our results indicated that Al-induced ethylene production was mediated by ACC synthase (ACS) and ACC oxidase, and that Put decreased ethylene production by inhibiting ACS. Altogether, these findings indicate that ethylene is involved in Al-induced root inhibition and this process could be alleviated by Put through inhibiting ACS activity.

NO Promotes Seed Germination and Seedling Growth Under High Salt May Depend on EIN3 Protein in Arabidopsis.

The gas molecule nitric oxide (NO) can cooperate with ethylene to tightly modulate plant growth and stress responses. One of the mechanism of their crosstalk is that NO is able to activate ethylene biosynthesis, possibly through post-translational modification of key enzymes such as ACC synthase and oxidase by S-nitrosylation. In this paper, we focus on the crosstalk of NO with ethylene signaling transduction transcription factor EIN3 (Ethylene Insensitive 3) and downstream gene expression in alleviating germination inhibition and growth damage induced by high salt. The Arabidopsis lines affected in ethylene signaling (ein3eil1) and NO biosynthesis (nia1nia2) were employed to compare with the wild-type Col-0 and overexpressing line EIN3ox. Firstly, the obviously inhibited germination, greater ratio of bleached leaves and enhanced electrolyte leakage were found in ein3eil1 and nia1nia2 lines than in Col-0 plants upon high salinity. However, the line EIN3ox obtained a notably elevated ability to germinate and improved seedling resistance. The experiment with SNP alone or plus high salt mostly enhanced the expression of EIN3 transcripts, compared with ACO4 and ACS2. The western blot and transcript analysis found that high-salt-induced EIN3 stabilization and EIN3 transcripts were largely attenuated in the NO biogenesis mutant nia1nia2 plants than in Col-0 ones. This observation was confirmed by simulation experiments with NO scavenger cPTIO to block NO emission. Taken together, our study provides insights that NO promotes seed germination and seedlings growth under salinity may depend on EIN3 protein.

1-Methylcyclopropene (1-MCP) inhibits ethylene production of durian fruit which is correlated with a decrease in ACC oxidase activity in the peel

Fruit of cv. Monthong durian (Durio zibethinus Murr.) were treated for 12h with 0 (control) and 500nLL−1 1-methylcyclopropene (1-MCP) at 25°C and were then stored at a temperature of 15°C. The fruit were transferred from a temperature of 15°C to a temperature of 25°C within a 3-day interval. 1-MCP treatment did not affect the relatively low rate of ethylene production in fruit stored at a temperature of 15°C. In contrast, 1-MCP delayed the dramatic increase in ethylene production in fruit that were transferred from a temperature of 15°C to a temperature of 25°C. It is well known that the peel (husk) produces much more ethylene than the pulp, hence, the effects of 1-MCP on the peel will likely overshadow any effect on the pulp. In the peel, 1-MCP had no effect on 1-aminocyclopropene-1-carboxylic acid (ACC) synthase activity, but decreased ACO activity. ACC levels in the peel were not affected by the treatment at 25°C. In the pulp, by contrast, ACO activity was not affected, but ACS activity was not inhibited at 25°C and ACC levels were found to be lower, after the 1-MCP treatment. It was concluded that 1-MCP seems to inhibit ethylene production of durian mainly by preventing an increase in ACC oxidase activity in the peel.

Cloning and expression of the 1-aminocyclopropane-1-carboxylic oxidase gene from Agrostis stolonifera.

A gene encoding 1-aminocyclopropane-1-carboxylic oxidase (ACO), which catalyzes the terminal step in ethylene biosynthesis, was isolated from Agrostis stolonifera. The AsACO gene is composed of 975 bp, encoding 324 amino acids. Three exons interspersed by two introns form AsACO gDNA. A BLAST search of the nucleotide sequence revealed a high level of similarity (79-91%) between AsACO and ACO genes of other plants. A phylogenetic tree was constructed via BLAST in the NCBI, and revealed the highest homology with wheat TaACO. The calculated molecular mass and predicted isoelectric point of AsACO were 36.25 and 4.89 kDa, respectively. Analysis of subcellular localization revealed that AsACO is located in the nucleus and cytoplasm. The Fe(II)-binding cofactors and cosubstrate were identified, pertaining to the ACO family. The expression patterns of AsACO were determined by quantitative real time PCR. AsACO expression was highest in the stem, and was strongly up-regulated in response to ethephon, methyl jasmonate, salicylic acid, and cold temperature, but down-regulated in response to drought and NaCl treatment. The protein encoded by AsACO exhibited ACC oxidase activity in vitro. Taken together, these findings suggest that AsACO contains domains common to the ACO family, and is induced in response to exogenous hormones. Conversely, some abiotic stress conditions can inhibit AsACO expression.

RFLP analysis reveals the genealogical relation of novel Japanese persimmon ‘Saijo’

‘Saijo’ Japanese persimmon (Diospyros kaki Thumb.) is one of the most popular and commercially important fruit cultivars in Japan. In 2000, origin-unknown ‘Saijo’-like cultivar was found at the Shimane farm and named as ‘M-3’. Although it has similar morphological and physiological characteristics with ‘Saijo’ cultivars, its fruit size is apparently bigger than ‘Saijo’ making them an attractive candidate as novel valuable fruit for farm household. In this study, to elucidate the genealogical relationship of ‘M-3’, we conducted the restriction fragment length polymorphism (RFLP) analysis using genomic DNA of Japanese persimmon (‘Saijo’ lines, pollinizers, and other cultivars that bloom a male flower) detected by cDNA probes involved in genes coding persimmon fruit ripening: 1-aminocyclopropane-1-carboxylate synthase 1 (ACCS-1), ACC oxidase 1 (ACCO-1), and polygalacturonase (PG-9). We demonstrated that ‘M-3’ line shares several RFLPs specific to ‘Saijo’ lines, pollinizers, and other cultivars. We found that morphological features of fruit and leaf in ‘M-3’ resembled that of ‘Saijo’ and pollinizer lines. These results strongly suggest that ‘M-3’ is likely the seedlings crossbred by ‘Saijo’ and pollinizer cultivars. Our findings provide first insight of genealogical origins of valuable newly identified persimmon cultivar and an important suggestion to establish a new valuable ‘Saijo’ cultivar by cross breeding with pollinizer lines.

The effect of chilling injury-inducing storage conditions on quality and consumer acceptance of different Prunus persica cultivars

Few information is available about how chilling injury-inducing storage affects quality and consumer acceptance of different peach/nectarine cultivars and its possible relationship with altered physiological or ripening-related events. Accordingly, this study investigated the effect of chilling injury (CI)-inducing temperatures (4°C during 21 days) on ethylene production, firmness loss, ACC oxidase (ACO) activity, antioxidant capacity, chilling injury symptoms such as mealiness or flesh browning, sensory attributes and consumer acceptance of six melting (‘Ambra’, ‘Nectaross’, ‘Rome Star’, ‘Big Top’, ‘Honey Royale’ and ‘Sweet Dream’) and a stony-hard (SH; ‘Ghiaccio-1’) peach/nectarine cultivars, over two consecutive seasons (2011–2012). Cold storage at 4°C induced greater ethylene production and ACO activity accompanied by greater firmness loss in all cultivars except for the SH phenotype. Antioxidant capacity slightly decreased in response to cold storage, but increased during shelf life (20°C) after 1 or 3 days to reach similar levels than those observed in non-cold stored fruit. The greatest capacity of the fruit to produce ethylene after cold storage was associated to lower mealiness incidence. For most cultivars, chilling injury-inducing storage negatively influenced the consumer acceptability. However, no clear relationships were found between the antioxidant capacity, the pattern of firmness loss and the development of chilling injury symptoms.

Genetic Transformation of Dendrobium 'Sonia Earsakul' with Antisense Carica papaya ACO1 Gene

<p><em>Dendrobium</em> orchid is one of the major export cut flowers not only in Thailand but also for several tropical countries. However, the production of ethylene by their flowers causes a shorter vase life. Flowers that contained lower levels of ethylene usually exhibited delayed senescence and consequently prolonged vase life. The transfer of antisense <em>ACC oxidase (ACO)</em> gene into orchid, in theory, may leads to decreased ethylene production because this gene can down regulates the ethylene biosynthesis pathway. This study focuses on the transformation and the existence and expression of the antisense <em>ACO</em>1 gene from papaya, namely (<em>CP-ACO</em>1), which was transferred in to <em>Dendrobium</em> 'Sonia Earsakul'. The successful stable transformation event obtained and the existence of the transferred gene was determined using PCR, dot blot hybridization and Southern blot hybridization techniques. The results revealed that antisense <em>CP-ACO</em>1 and <em>hygromycin phosphotransferase (hpt)</em> gene existed in all transgenic lines confirmed by PCR technique. The genomic dot blot confirmed the incorporation of the transgene in transgenic plant genome. Southern blot hybridization revealed the existed of one to four sets of the gene in transgenic lines. The expression of antisense <em>CP-ACO</em>1 gene was analyzed through the level of ACO enzyme activity and ethylene production in transgenic orchid. All of the transgenic lines had lower ACO enzyme activity and lower ethylene production than that of the non-transgenic orchid plants.<strong> </strong></p> <p> </p>

Glutathione Regulates 1-Aminocyclopropane-1-Carboxylate Synthase Transcription via WRKY33 and 1-Aminocyclopropane-1-Carboxylate Oxidase by Modulating Messenger RNA Stability to Induce Ethylene Synthesis during Stress.

Glutathione (GSH) plays a fundamental role in plant defense-signaling network. Recently, we have established the involvement of GSH with ethylene (ET) to combat environmental stress. However, the mechanism of GSH-ET interplay still remains unexplored. Here, we demonstrate that GSH induces ET biosynthesis by modulating the transcriptional and posttranscriptional regulations of its key enzymes, 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO). Transgenic Arabidopsis (Arabidopsis thaliana) plants with enhanced GSH content (AtECS) exhibited remarkable up-regulation of ACS2, ACS6, and ACO1 at transcript as well as protein levels, while they were down-regulated in the GSH-depleted phytoalexin deficient2-1 (pad2-1) mutant. We further observed that GSH induced ACS2 and ACS6 transcription in a WRKY33-dependent manner, while ACO1 transcription remained unaffected. On the other hand, the messenger RNA stability for ACO1 was found to be increased by GSH, which explains our above observations. In addition, we also identified the ACO1 protein to be a subject for S-glutathionylation, which is consistent with our in silico data. However, S-glutathionylation of ACS2 and ACS6 proteins was not detected. Further, the AtECS plants exhibited resistance to necrotrophic infection and salt stress, while the pad2-1 mutant was sensitive. Exogenously applied GSH could improve stress tolerance in wild-type plants but not in the ET-signaling mutant ethylene insensitive2-1, indicating that GSH-mediated resistance to these stresses occurs via an ET-mediated pathway. Together, our investigation reveals a dual-level regulation of ET biosynthesis by GSH during stress.

Responses of Dendrobium 'darrenn glory' and Mokara 'calypso jumbo' orchids to 1-methylcyclopropene and aqueous ozone postharvest treatments

Orchids possess a very special place amongst ornamental plants. But high ethylene sensitivity and early flower senescence of orchid result in a short vase life and rapid quality deterioration which is of great concern for the growers, traders and consumers. An attempt was made to study the influence of 1-methylcyclopropene (1-MCP) (0 and 300 nL L -1 ) and аquеous ozone (0 and 5.2 nL L -1 ) in prolonging vase life and maintaining quality of two cut orchid hybrids Dendrobium 'Darren Glory' (DDG) and Mokara Calypso Jumbo (MCJ). Results showed that orchid hybrids exhibited differences in their ethylene sensitivity, vase life, 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC oxidase activities. Pre-treatment with 1-MCP resulted in reduced ethylene production, vase life, ACC content and ACC oxidase activities, but increased bud opening %. Pre-treatment with аquеous ozone failed to influence all those parameters except bud opening %. Interaction effects of hybrid and 1-MCP were significant for ethylene production, hybrid and ozone for vas life, 1-MCP and ozone for bud opening %, and hybrid, 1-MCP and ozone for ethylene production and vase life. Aqueous ozone markedly contributed to the inhibition of microbial growth in vase solution. Pre-treatment of the cut orchid flowers with 300 nL L -1 1-MCP, followed by using 5.2 mg L -1 aqueous ozone as the vase solution could be recommended to maintain quality and extend vase life of both the DDG and MCJ orchid hybrids.

Aminoethoxyvinylglycine: isolated and combined with other growth regulators on quality of ‘Brookfield’ apples after storage

Growth regulators are used in the production of apples worldwide, especially to extend the harvest period and maintain postharvest quality. This study aimed to investigate the effects of applying aminoethoxyvinylglycine (AVG) in isolation as well as in combination with other growth regulators and postharvest techniques on the harvest quality and storage potential of ‘Brookfield’ apples (Malus domestica), a ‘Gala’ strain. Fruit receiving AVG only had the highest starch content and the highest titratable acidity at harvest. After 8 months of storage, the AVG + 1-MCP (1-methylcyclopropene) and AVG + ABS (ethylene absorption) conserved higher flesh firmness than to all the other treatments. Naphthaleneacetic acid (NAA) application induced ACC oxidase enzyme activity at harvest, but not after storage. AVG application, with or without the aid of another technique, did not decrease the red skin color of ‘Brookfield’ apples. Low mealiness and a high healthy fruit percentage was obtained when the fruits were submitted to pre-harvest AVG application combined with NAA, 1-MCP and ABS. Internal carbon dioxide had an inverse correlation with the quantity of healthy fruit and was directly correlated with mealiness.

Effects of Temperature and Ethylene Response Inhibitors on Growth and Flowering of Passion Fruit

This study examined the effects of different day/night temperature regimes or silver ion on growth and flowering of passion fruit ‘Tai-nung No.1’. Low temperature treatment (20/15℃) caused passion fruit cultivar ‘Tai-nung No.1’ to fail to flower. Flowering induction occurred within a temperature range of 20-30℃, with no significant difference in the days to first flower bud and the total number of flower buds between plants grown at 30/25℃ and 25/20℃. However, plants grown at 30/25℃ exhibited their first flower buds set on the higher nodes and had higher abortion rates of flower buds than those at 25/20℃. Plants grown at 30/25℃ had the most rapid growth and the shortest plastochron. We also evaluated the effect of the ethylene response inhibitors silver nitrate (AgNO₃) and silver thiosulfate (STS) on growth and flowering of potted passion fruit ‘Tai-nung No.1’, when they were exposed to low temperature conditions (20/15℃) following chemical treatments (AgNO₃ or STS, at 0.5 or 1.0 mM). AgNO₃ and STS treatments induced flower formation and initial flower bud formation within approximately two weeks at 20/15℃ whereas non-treated control plants exhibited no flower formation. ACC content and activity of ACC oxidase in the leaves of passion fruit ‘Tai-nung No.1’exposed to low temperature conditions (20/15℃) were significantly inhibited by the ethylene inhibitor treatments. These results indicate that ethylene, which is produced under low temperature conditions, plays an important role in inhibiting flower formation in passion fruit.

Effects of the combination treatment of 1-MCP and ethylene on the ripening of harvested banana fruit

1-methylcyclopropene (1-MCP) has obvious effects on delaying the ripening of harvested banana fruit. However, improper concentration, treatment time and handling methods could affect normal ripening, yellowing, softening and formation of volatiles, which are important components of banana fruit quality. This study was performed to screen and test the effect of a combination of low concentration ethephon with 1-MCP on the ripening of banana fruit, as well as on physiological and biochemical changes. The results showed that a combination of 50μLL−1 ethephon with 400nLL−1 1-MCP (16h) was the most suitable treatment, which significantly delayed the ripening and maintained the commodity value of harvested banana fruit without detrimentally affecting normal ripening after ripening acceleration treatment. This treatment effectively delayed and decreased respiration rate and ethylene production, inhibited the activity of pectin lyase (PL), pectin methylesterase (PME), cellulase (CX) and polygalacturonase (PG), and delayed the peak activity of ACC synthase (ACS) and ACC oxidase (ACO). It also delayed the formation of volatile compounds, but did not detrimentally affect the amount of volatiles, especially the esters. The combined treatment significantly delayed the ripening and prolonged the shelf life of banana fruit with normal coloring and volatile development, which effectively maintained the commercial value of banana fruit.

Phytohormonal networks promote differentiation of fiber initials on pre-anthesis cotton ovules grown in vitro and in planta.

The number of cotton (Gossypium sp.) ovule epidermal cells differentiating into fiber initials is an important factor affecting cotton yield and fiber quality. Despite extensive efforts in determining the molecular mechanisms regulating fiber initial differentiation, only a few genes responsible for fiber initial differentiation have been discovered. To identify putative genes directly involved in the fiber initiation process, we used a cotton ovule culture technique that controls the timing of fiber initial differentiation by exogenous phytohormone application in combination with comparative expression analyses between wild type and three fiberless mutants. The addition of exogenous auxin and gibberellins to pre-anthesis wild type ovules that did not have visible fiber initials increased the expression of genes affecting auxin, ethylene, ABA and jasmonic acid signaling pathways within 1 h after treatment. Most transcripts expressed differentially by the phytohormone treatment in vitro were also differentially expressed in the ovules of wild type and fiberless mutants that were grown in planta. In addition to MYB25-like, a gene that was previously shown to be associated with the differentiation of fiber initials, several other differentially expressed genes, including auxin/indole-3-acetic acid (AUX/IAA) involved in auxin signaling, ACC oxidase involved in ethylene biosynthesis, and abscisic acid (ABA) 8'-hydroxylase an enzyme that controls the rate of ABA catabolism, were co-regulated in the pre-anthesis ovules of both wild type and fiberless mutants. These results support the hypothesis that phytohormonal signaling networks regulate the temporal expression of genes responsible for differentiation of cotton fiber initials in vitro and in planta.

Transcriptomic profiling of Arabidopsis thaliana mutant pad2.1 in response to combined cold and osmotic stress.

The contribution of glutathione (GSH) in stress tolerance, defense response and antioxidant signaling is an established fact. In this study transcriptome analysis of pad2.1, an Arabidopsis thaliana mutant, after combined osmotic and cold stress treatment has been performed to explore the intricate position of GSH in the stress and defense signaling network in planta. Microarray data revealed the differential regulation of about 1674 genes in pad2.1 amongst which 973 and 701 were significantly up- and down-regulated respectively. Gene enrichment, functional pathway analysis by DAVID and MapMan analysis identified various stress and defense related genes viz. members of heat shock protein family, peptidyl prolyl isomerase (PPIase), thioredoxin peroxidase (TPX2), glutathione-S-transferase (GST), NBS-LRR type resistance protein etc. as down-regulated. The expression pattern of the above mentioned stress and defense related genes and APETALA were also validated by comparative proteomic analysis of combined stress treated Col-0 and pad2.1. Functional annotation noted down-regulation of UDP-glycosyl transferase, 4-coumarate CoA ligase 8, cinnamyl alcohol dehydrogenase 4 (CAD4), ACC synthase and ACC oxidase which are the important enzymes of phenylpropanoid, lignin and ethylene (ET) biosynthetic pathway respectively. Since the only difference between Col-0 (Wild type) and pad2.1 is the content of GSH, so, this study suggested that in addition to its association with specific stress responsive genes and proteins, GSH provides tolerance to plants by its involvement with phenylpropanoid, lignin and ET biosynthesis under stress conditions.

Gamma radiation control quality and lignification of bamboo shoots (Phyllostachys praecox f. prevernalis.) stored at low temperature

Bamboo shoots are highly nutritious but possess poor shelf life after harvest due to rapid decline of tenderness mostly result from lignification processes. Present investigation was performed to evaluate the potential of gamma radiation as a postharvest technology to preserve bamboo shoots. The effects of 0.5kGy gamma radiation on quality and lignification of bamboo shoots during storage at 2°C were investigated. The results showed that gamma radiation reduced the decay rate of bamboo shoots by 71% at the end of storage. It also significantly retarded ethylene production through controlling the activities of ACC synthase (ACS) and ACC oxidase (ACO), which may contribute to inhibition of lignin synthesis. Meanwhile, gamma radiation decreased the activities of phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD), which are associated with lignin accumulation, thus reduced lignin content by 12.5% than that of the control after twenty-eight days of storage. These results demonstrated the potential of the gamma radiation as a promising postharvest technique to maintain the quality and inhibit the lignification of bamboo shoots.

UV-C radiation modifies the ripening and accumulation of ethylene response factor (ERF) transcripts in tomato fruit

Ultraviolet-C (UV-C) radiation is used as a postharvest treatment to prolong the shelf life of fruit. However, this stressful process may also affect ethylene production and, consequently, the expression of genes encoding ethylene response factors (ERFs). To test this hypothesis, MicroTom tomatoes harvested at the breaker stage were subjected to: 1 – application of 3.7kJm−2 UV-C radiation, 2 – application of 2μLL−1 1-methylcyclopropene (1-MCP) followed by UV-C radiation; and 3 – without 1-MCP or UV-C (control treatment). After treatment all fruit were stored for 12d at 21±2°C and 80±5% relative humidity (RH). Although UV-C radiation increased ACC oxidase transcripts and stimulated ethylene production, the ripening evolution was delayed. Fruit treated with UV-C showed lower accumulation of lycopene, β-carotene, lutein+zeaxanthin and δ-tocopherol; but retained higher levels of chlorogenic acid, ρ-coumaric acid and quercetin after 6d. Additionally, UV-C treated fruit had higher contents of polyamines (putrescine and spermidine). Among the 14 ERFs studied, 11 (Sl-ERF A.1, Sl-ERF A.3, Sl-ERF B.1, Sl-ERF B.2, Sl-ERF B.3, Sl-ERF C.6, Sl-ERF D.1, Sl-ERF D.3, Sl-ERF E.1, Sl-ERF F.5, Sl-ERF G.2) exhibited increased transcript accumulation, 2 ERFs (Sl-ERF E.2 and Sl-ERF E.4) showed decreased transcript accumulation and only 1 ERF (Sl-ERF E.3) was not significantly affected by UV-C treatment. As expected, the transcript profiles of 1-MCP and/or UV-C-treated tomatoes demonstrate that ethylene plays an important role in the expression of ERFs. The delay in fruit ripening may be caused by the activation of ERFs that could act as regulators of metabolic pathways during ripening. However, this hypothesis needs to be better tested. In conclusion, a relationship has been established between UV-C treatment and ripening delay, correlated to changes in 13 ERF transcripts evaluated during postharvest treatment.

Effects of intermittent warming on aroma-related esters of 1-methylcyclopropene-treated ‘Nanguo’ pears during ripening at room temperature

Refrigeration combined with 1-methylcyclopropene (1-MCP) treatment is an effective method for the long-term storage of climacteric fruit, but this benefit is offset by a loss of aroma when the fruit is then ripened at room temperature. The pear cv. ‘Nanguo’ (Pyrus ussuriensis Maxim.) was treated with 1-MCP and continuously stored at 0±0.5°C or exposed to the same storage temperature alternated with 20±1°C for 1 d every 20 d during storage (namely, intermittent warming [IW]). Changes in aroma-related esters, levels of fatty acids, and the activity and gene expression of alcohol acyltransferase (AAT) and lipoxygenase (LOX) were investigated. Changes in the gene expression of the enzymes (1-aminocyclopropane-carboxylase (ACC) synthase (ACS) and ACC oxidase (ACO)) involved in ethylene biosynthesis and the expression of genes involved in ethylene signal transduction were also studied. Significantly higher ester content was found in IW-treated fruit. Increased activity and gene expression of AAT, LOX, and accumulated polyunsaturated fatty acids were associated with enhanced aroma quality in IW-treated fruit. The increased translation levels of PuACS1 and PuACO1 contributed to the elevated ethylene levels in IW-treated fruit. IW treatment seemed to have no significant effect on the induction of the expression of PuETR1 and merely stimulated the expression of PuCTR1 during the prior period of the shelf life at 20°C. Treatment with IW effectively prevented the loss of aroma-related esters from 1-MCP-treated ‘Nanguo’ pears, and possible mechanisms for this were discussed.

Ethylene is integrated into the nitric oxide regulation of Arabidopsis somatic embryogenesis.

The study confirms the role of the two Arabidopsis hemoglobin genes (Glb1 and Glb2) during somatic embryogenesis and proposes the involvement of ethylene in the regulation of embryo development. Suppression of both Glb1 and Glb2 results in accumulation of nitric oxide (NO) and a different embryogenic response. Compared to WT tissue, down-regulation of Glb1 (Glb1 RNAi line) compromises the embryogenic process, while repression of Glb2 (Glb2−/− line) increases the number of embryos. These differences were ascribed to the differential accumulation of NO in the two lines, as Glb1 is a more effective NO scavenger compared to Glb2. A high elevation of NO level [achieved pharmacologically using the NO donor sodium nitroprusside (SNP), or genetically using the Glb1 suppressing line], activated the two ethylene biosynthetic genes 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase). Ethylene accumulation repressed embryogenesis, as shown by the decreased embryo number observed in tissue treated with the ethylene releasing agent Ethephon (ETH), as well as by the increased embryo production obtained with the two ethylene insensitive mutant lines (ein2-1 and ein3-1). A repression in ethylene level increased the expression of many auxin biosynthetic genes and favored the accumulation of the auxin indole-acetic acid (IAA) at the sites of the explants where embryogenic tissue will form. Collectively these data reveal that high levels of NO, generated by the Glb1 suppressing line, but not by the Glb2 suppressing line, might increase the level of ethylene, which represses the production of auxin. Auxin is the inductive signal required for the formation of the embryogenic tissue.

Shedding light on ethylene metabolism in higher plants.

Ethylene metabolism in higher plants is regulated by a wide array of endogenous and environmental factors. During most physiological processes, ethylene levels are mainly determined by a strict control of the rate-limiting biosynthetic steps responsible for the production of 1-aminocyclopropane-1-carboxylic acid (ACC) and its subsequent conversion to ethylene. Responsible for these reactions, the key enzymes ACC synthase and ACC oxidase are encoded by multigene families formed by members that can be differentially regulated at the transcription and post-translational levels by specific developmental and environmental signals. Among the wide variety of environmental cues controlling plant ethylene production, light quality, duration, and intensity have consistently been demonstrated to influence the metabolism of this plant hormone in diverse plant tissues, organs, and species. Although still not completely elucidated, the mechanisms underlying the interaction between light signal transduction and ethylene evolution appears to involve a complex network that includes central transcription factors connecting multiple signaling pathways, which can be reciprocally modulated by ethylene itself, other phytohormones, and specific light wavelengths. Accumulating evidence has indicated particular photoreceptors as essential mediators in light-induced signaling cascades affecting ethylene levels. Therefore, this review specifically focuses on discussing the current knowledge of the potential molecular mechanisms implicated in the light-induced responses affecting ethylene metabolism during the regulation of developmental and metabolic plant responses. Besides presenting the state of the art in this research field, some overlooked mechanisms and future directions to elucidate the exact nature of the light–ethylene interplay in higher plants will also be compiled and discussed.

Transcriptomic analysis of the late stages of grapevine (Vitis vinifera cv. Cabernet Sauvignon) berry ripening reveals significant induction of ethylene signaling and flavor pathways in the skin.

BackgroundGrapevine berry, a nonclimacteric fruit, has three developmental stages; the last one is when berry color and sugar increase. Flavors derived from terpenoid and fatty acid metabolism develop at the very end of this ripening stage. The transcriptomic response of pulp and skin of Cabernet Sauvignon berries in the late stages of ripening between 22 and 37 °Brix was assessed using whole-genome micorarrays.ResultsThe transcript abundance of approximately 18,000 genes changed with °Brix and tissue type. There were a large number of changes in many gene ontology (GO) categories involving metabolism, signaling and abiotic stress. GO categories reflecting tissue differences were overrepresented in photosynthesis, isoprenoid metabolism and pigment biosynthesis. Detailed analysis of the interaction of the skin and pulp with °Brix revealed that there were statistically significantly higher abundances of transcripts changing with °Brix in the skin that were involved in ethylene signaling, isoprenoid and fatty acid metabolism. Many transcripts were peaking around known optimal fruit stages for flavor production. The transcript abundance of approximately two-thirds of the AP2/ERF superfamily of transcription factors changed during these developmental stages. The transcript abundance of a unique clade of ERF6-type transcription factors had the largest changes in the skin and clustered with genes involved in ethylene, senescence, and fruit flavor production including ACC oxidase, terpene synthases, and lipoxygenases. The transcript abundance of important transcription factors involved in fruit ripening was also higher in the skin.ConclusionsA detailed analysis of the transcriptome dynamics during late stages of ripening of grapevine berries revealed that these berries went through massive transcriptional changes in gene ontology categories involving chemical signaling and metabolism in both the pulp and skin, particularly in the skin. Changes in the transcript abundance of genes involved in the ethylene signaling pathway of this nonclimacteric fruit were statistically significant in the late stages of ripening when the production of transcripts for important flavor and aroma compounds were at their highest. Ethylene transcription factors known to play a role in leaf senescence also appear to play a role in fruit senescence. Ethylene may play a bigger role than previously thought in this non-climacteric fruit.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0370-8) contains supplementary material, which is available to authorized users.