Expression Of ETR1 Research Articles

Enhancing Medium-Chain Fatty Acid Ethyl Ester Production During Beer Fermentation Through EEB1 and ETR1 Overexpression in Saccharomyces pastorianus.

Esters are important flavor compounds in alcoholic beverages. Although they are present at trace levels, esters play a key role in the formation of flavors, especially fruity flavors, in beverages. Low ester contents result in bland beer and unpleasant flavor. In this study, three recombinant strains, ethanol O-acyltransferase encoding EEB1 overexpression strain (31194:: EEB1), 2-enoyl thioester reductase encoding ETR1 overexpression strain (31194:: ETR1), and EEB1- ETR1 co-overexpression strain (31194:: EEB1:: ETR1), were constructed. Ethyl hexanoate production by 31194:: EEB1 and 31194:: EEB1:: ETR1 was 106% higher than that by the parental strain. Further, ethyl octanoate production by 31194:: EEB1 and 31194:: EEB1:: ETR1 was enhanced by 47 and 41%, respectively, compared with that of parental strain 31194. However, no difference was observed between 31194:: ETR1 and the parental strain in terms of ethyl hexanoate and ethyl octanoate production. This indicates that although EEB1 overexpression in Saccharomyces pastorianus enhanced ethyl hexanoate and ethyl octanoate production, ETR1 expression levels did not affect the extracellular concentrations of these esters.

EFECTO DEL 1-METILCICLOPROPENO EN LA MADURACIÓN DE MANGO ATAULFO EN CONDICIÓN SIMULADA PARA EXPORTACIÓN A EUROPA

El objetivo de esta investigación fue evaluar el efecto del 1-metilciclopropeno (1-MCP) en el proceso de maduración y calidad de mango (Mangifera indica L.) var. Ataulfo almacenado 20 d a 13 ºC y 5 d a 25 ºC, que simulan el transporte y distribución en Europa, para generar conocimiento sobre la acción del 1-MCP en el metabolismo del etileno; así como para encontrar condiciones de aplicación de 1-MCP en esta variedad. Los frutos fueron tratados con 1-MCP (0, 300, 600 y 1000 nL L-1) con y sin tratamiento hidrotérmico (CH y SH). Se midió la velocidad de respiración (VR), producción de etileno (VPE), contenido de ácido aminociclopropano-1-carboxílico (ACC), actividad de ACC oxidasa, transcritos (receptor ETR1 de etileno y ACC oxidasa ACO), variables físicas y químicas. En los frutos testigo SH y CH, la máxima VR fue de 129.12 y 129.37 mL CO2 kg-1 h-1 (días 1 y 4 a 25 ºC), respectivamente; la VPE fue de 0.15 y 0.23 μL kg-1 h-1. La VR se redujo en los frutos SH con 1-MCP (86.17 mL CO2 kg-1 h-1), así como se redujeron la VPE (0.13 μL kg-1 h-1), la actividad de la ACC oxidasa y la expresión de los genes ETR1 y ACO después de su traslado a 25 ºC (4 a 5 d). En los frutos CH y con 1-MCP no se observaron estos cambios. Los mangos SH con 1000 nL L-1 fueron los que mantuvieron sus características físicas y químicas normales de maduración, por 5 d a 25 ºC, previo a 20 d a 13 ºC. Se concluyó que la aplicación de 1-MCP a 1000 nL L-1 por 24 h a 20 ºC y posterior almacenamiento de 20 d a 13 ºC puede ser una ayuda para transportar el mango Ataulfo a mercados lejanos donde no demandan el tratamiento hidrotémico.

ZAP1-mediated modulation of triacylglycerol levels in yeast by transcriptional control of mitochondrial fatty acid biosynthesis.

The transcriptional activator Zap1p maintains zinc homeostasis in Saccharomyces cerevisiae. In this study, we examined the role of Zap1p in triacylglycerol (TAG) metabolism. The expression of ETR1 is reduced in zap1Δ. The altered expression of ETR1 results in reduced mitochondrial fatty acid biosynthesis and reduction in lipoic acid content in zap1Δ. The transcription factor Zap1 positively regulates ETR1 expression. Deletion of ETR1 also causes the accumulation of TAG, and the introduction of ETR1 in zap1Δ strain rescues the TAG level. These results demonstrated that the compromised mitochondrial fatty acid biosynthesis causes a reduction in lipoic acid and loss of mitochondrial function in zap1Δ. Functional mitochondria are required for the ATP production and defect in mitochondria slow down the process which may channeled carbon towards lipid biosynthesis and stored in the form of TAG.

Soil drench treatment with ß-aminobutyric acid increases drought tolerance of potato.

The non-protein amino acid β-aminobutyric acid (BABA) is known to be a priming agent for a more efficient activation of cellular defence responses and a potent inducer of resistance against biotic and abiotic stresses in plants. Nevertheless, most of the studies on priming have been carried out in Arabidopsis. In potato, the effect of BABA was demonstrated only on biotic stress tolerance. We investigated the effect of BABA on the drought tolerance of potato and found that soil drenched with BABA at a final concentration of 0.3 mM improves the drought tolerance of potato. Water loss from the leaves of the primed plants is attenuated and the yield is increased compared to the unprimed drought-stressed plants. The metabolite composition of the tubers of the BABA-treated plants is less affected by drought than the tuber composition of the non-treated plants. Nitric oxide and ROS (reactive oxygen species) production is increased in the BABA-treated roots but not in the leaves. In the leaves of the BABA-treated plants, the expression of the drought-inducible gene StDS2 is delayed, but the expression of ETR1, encoding an ethylene receptor, is maintained for a longer period under the drought conditions than in the leaves of the non-treated, drought-stressed control plants. This result suggests that the ethylene-inducible gene expression remains suppressed in primed plants leading to a longer leaf life and increased tuber yield compared to the non-treated, drought-stressed plants. The priming effect of BABA in potato, however, is transient and reverts to an unprimed state within a few weeks.

Effect of ethylene and 1-MCP on expression of genes involved in ethylene biosynthesis and perception during ripening of apple fruit

Ethylene plays an important role in regulating fruit ripening and senescence and directly influences the development of the eating quality of fresh apples, including appearance, color, texture, and flavor. Apple fruit (Malus domestica Borkh.) is a well-known climacteric fruit and a good model system to study fruit ripening and senescence. To better understand fruit ripening and the role of ethylene perception and signal transduction, apples harvested at a pre-climacteric stage were allowed to naturally ripen, or ripening was either stimulated by treatment with 36μLL−1 ethylene for 24h or inhibited by 1-MCP treatment (1.0μLL−1 for 24h), respectively. Postharvest physiological indices including respiration and ethylene production were monitored for 22d for ethylene treatment and 47d for 1-MCP treatment. Based on an efficiency test, 20 genes in relation to ethylene biosynthesis and perception were investigated using real-time qPCR during the post-treatment period. The ETR2, ETR5, ERSs, EIL4, ERFs genes together with ACS1 and ACO1 genes were significantly up-regulated in fruit during ripening. Ethylene treatment further enhanced the expression of ACO2, ETR1, CTR1s and EIN2A genes, while the ACS3 and ACO3, and EIN2B genes were only slightly affected. 1-MCP treatment significantly inhibited expression of ACS1, ACO1 and ACO2 ethylene biosynthesis genes, which coincided with ethylene production. 1-MCP treatment also reduced expression of ETR1, ETR2, ETR5, ERSs, CTR1, EIN2A, EIL4 and ERFs genes, while having a limited effect on ACS3, ACO3, and EIN2B. This study demonstrated the complexity and dynamic changes of transcriptional profiles of ethylene perception and biosynthesis in response to fruit ripening, ethylene, and 1-MCP treatment. Understanding of the significant changes of these genes and their function may help to explore the mechanisms controlling apple fruit ripening and its response to exogenous ethylene stimuli and action inhibition at the receptor level during ripening and senescence.

Degreening behavior in ‘Fallglo’ and ‘Lee × Orlando’ is correlated with differential expression of ethylene signaling and biosynthesis genes

Two citrus types (‘Fallglo’ and ‘Lee × Orlando’) exhibiting differential fruit degreening response when treated with ethylene were selected. Fruit were harvested at commercial maturity but at different developmental periods (Harvest I, II and III). Rate of color change was greater in ‘Fallglo’ than in ‘Lee × Orlando’ when fruit were treated with 5 μL L −1 of ethylene for 24 h. After 24 h of transfer of fruit to ethylene-free storage, rate of change decreased in ‘Fallgo’ and exhibited varied response in ‘Lee × Orlando’ depending on harvest date. ‘Fallglo’ fruit from Harvests I and II were completely degreened at the end of storage for 7 d; however ‘Lee × Orlando’ were not and were green in color. No difference in seedling triple response was observed between ‘Fallglo’ and ‘Lee × Orlando’ and sequences of the four ethylene receptors were identical between them. Expression of genes involved in ethylene biosynthesis and signaling pathways were studied in flavedo to test if differences in these pathways were correlated with differential ethylene sensitivity of the citrus types. Basal levels of ACS2 and ACO expressions declined as maturity progressed, and ethylene-induced expression of ACS1 and ACO were influenced by fruit maturity. At Harvests I and II, ethylene-induced increase in ACS1 and ACO expressions and ACC levels were greater in ‘Fallglo’ than in ‘Lee × Orlando’. Ethylene treatment influenced MACC content only during Harvest I in ‘Lee × Orlando’. MACC levels were generally higher in ‘Lee × Orlando’ than in ‘Fallglo’. Expressions of ETR1 and ETR2 were ethylene responsive in ‘Fallglo’ and only ETR1 expression was ethylene responsive in ‘Lee × Orlando’. Ethylene had more impact on ETR1 expression in ‘Fallglo’ than in ‘Lee × Orlando’. Ethylene had a negative effect on ETR3 expression which was more pronounced in ‘Lee × Orlando’ than in ‘Fallglo’. Expressions of ERS1, CTR1, EIN2, EIL1 and EIL2 were not affected by ethylene in both citrus types. Expression of chlorophyllase gene and rate of total chlorophyll degradation were higher in ‘Fallglo’ than in ‘Lee × Orlando’ during ethylene treatment. Differential degreening behavior of ‘Fallglo’ and ‘Lee × Orlando’ correlated with peel maturity, and factor(s) downstream of ethylene signaling but upstream of ethylene biosynthesis play a role in the differential sensitivity.

Ethylene perception is involved in female cucumber flower development

It is well established that ethylene promotes female flower development in cucumber. However, little is known about how the gaseous hormone selectively affects female flowers, and what mechanism it uses. Previously, we found organ-specific DNA damage in the primordial anther of female cucumber flowers. This finding led to a hypothesis that ethylene might promote female flower development via the organ-specific induction of DNA damage in primordial anthers. In this study, we tested this hypothesis first by demonstrating ethylene induction of DNA damage via the ethylene signaling pathway using cucumber protoplasts. Then, using representative component genes of the ethylene signaling pathway as probes, we found that one of the ethylene receptors, CsETR1, was temporally and spatially downregulated in the stamens of stage-6 female cucumber flowers, especially along with the increase of the nodes. Furthermore, by constructing transgenic Arabidopsis plants with organ-specific expression of antisense CsETR1 under the control of an AP3 promoter to downregulate ETR1 expression in the stamens, we generated Arabidopsis 'female flowers', in which the abnormal stamens mimic those of female cucumber flowers. Our data suggest that ethylene perception is involved in the arrest of stamen development in female cucumber flowers through the induction of DNA damage. This opens up a novel perspective and approach to solve the half-century-long puzzle of how gaseous ethylene selectively promotes female flowers in the monoecious cucumber plant.

Subcellular co‐localization of Arabidopsis RTE1 and ETR1 supports a regulatory role for RTE1 in ETR1 ethylene signaling

Ethylene is an important plant growth regulator perceived by membrane-bound ethylene receptors. The ETR1 ethylene receptor is positively regulated by a predicted membrane protein, RTE1, based on genetic studies in Arabidopsis. RTE1 homologs exist in plants, animals and protists, but the molecular function of RTE1 is unknown. Here, we examine RTE1 expression and subcellular protein localization in order to gain a better understanding of RTE1 and its function in relation to ETR1. Arabidopsis plants transformed with the RTE1 promoter fused to the beta-glucuronidase (GUS) reporter gene revealed that RTE1 expression partly correlates with previously described sites of ETR1 expression or sites of ethylene response, such as the seedling root, root hairs and apical hook. RTE1 transcript levels are also enhanced by ethylene treatment, and reduced by the inhibition of ethylene signaling. For subcellular localization of RTE1, a functional RTE1 fusion to red fluorescent protein (RFP) was expressed under the control of the native RTE1 promoter. Using fluorescence microscopy, RTE1 was observed primarily at the Golgi apparatus and partially at the endoplasmic reticulum (ER) in stably transformed Arabidopsis protoplasts, roots and root hairs. Next, a functional ETR1 fusion to a 5xMyc epitope tag was expressed under the control of the native ETR1 promoter. Immunohistochemistry of root hairs not only showed ETR1 residing at the ER as previously reported, but revealed substantial localization of ETR1 at the Golgi apparatus. Lastly, we demonstrated the subcellular co-localization of RTE1 and ETR1. These findings support and enhance the genetic model that RTE1 plays a role in regulating ETR1.

Ligand-induced Degradation of the Ethylene Receptor ETR2 through a Proteasome-dependent Pathway in Arabidopsis

Protein degradation plays an important role in modulating ethylene signal transduction in plants. Here we show that the ethylene receptor ETR2 is one such target for degradation and that its degradation is dependent upon perception of the signaling ligand ethylene. The ETR2 protein is initially induced by ethylene treatment, consistent with an increase in transcript levels. At ethylene concentrations above 1 mul/liter, however, ETR2 protein levels subsequently decrease in a post-transcriptional fashion. Genetic and chemical approaches indicate that ethylene perception by the receptors initiates the reduction in ETR2 protein levels. The ethylene-induced decrease in ETR2 levels is not affected by cycloheximide, an inhibitor of protein biosynthesis, but is affected by proteasome inhibitors, indicating a role for the proteasome in ETR2 degradation. Ethylene-induced degradation still occurs in seedlings treated with brefeldin A, indicating that degradation of ETR2 does not require exit from its subcellular location at the endoplasmic reticulum. These data support a model in which ETR2 is degraded by a proteasome-dependent pathway in response to ethylene binding. Implications of this model for ethylene signaling are discussed.

RTE1 Is a Golgi-Associated and ETR1-Dependent Negative Regulator of Ethylene Responses

Arabidopsis (Arabidopsis thaliana) RTE1 encodes a membrane protein and negatively regulates ethylene responses. Genetic and transformation studies suggest that the function of the wild-type RTE1 is primarily dependent on ETR1 and can be independent on the other receptors. Ethylene insensitivity caused by the overexpression of RTE1 is largely masked by the etr1-7 mutation, but not by any other receptor mutations. The wild-type ETR1 N terminus is sufficient to the activation of the RTE1 function and the ectopic expression of etr1(1-349) restored ethylene insensitivity conferred by 35SgRTE1 in etr1-7. The RTE1 N terminus is not essential to the etr1-2 function and the expression of rte1(NDelta49), which has an N-terminal deletion of 49 amino acid residues, restored ethylene insensitivity in etr1-2 rte1-2. The ectopic expression of GREEN FLUORESCENT PROTEIN (GFP)-RTE1 conferred ethylene insensitivity in wild type and the GFP fusion displayed fast movement within the cytoplasm. The GFP-RTE1 and EYFP-NAG proteins colocalized and the Brefeldin A treatment caused aggregation of GFP-RTE1, suggesting RTE1 is a Golgi-associated protein. Our results suggest specificity of the RTE1 function to ETR1 and that endomembranes may play a role in the ethylene signal transduction.

Synergistic Effects of the Combined Application of MCP and Low O2 on Apple Fruit Ripening

We have studied the effects of MCP and low O2, applied singly and in combination, on apple fruit ripening at 1, 7, and 18 °C. The single application of 2 ppm MCP is more effective in delaying the onset of the C2H4 climacteric than is 1% O2. However, the combined application has a much larger effect than the single applications of either MCP or 1% O2. For instance, at 7 °C, the onset of the C2H4 climacteric occurs at 15, 50, and 90–95 days for the controls, 1% O2 and 2 ppm MCP, respectively, whereas the combined application of 2 ppm MCP and 1% O2 suppressed the initiation of the C2H4 climacteric for 200 days, the duration of the experiment. The retardation of the climacteric onset by the treatments is associated with the suppression of ACC-synthase (ACS1) and the putative receptor ERS1. The accumulation of their transcripts is critically dependent on the rate of C2H4 evolution. As expected, the combined application of MCP and 1% O2 completely suppressed the expression of both genes. Yet when the fruits were transferred to 18 °C in air, they ripened normally. A similar pattern of inhibition in response to the above treatments was also observed with a C2H4-dependent MAPK. The expression of ETR1, ETR2 and ACC-oxidase was not affected by the treatments. The nature of this strong effect of the combined application of MCP and low O2 is not clear. It should be pointed out that MCP does not inhibit the induction of hypoxic proteins such as ADH.

Effect of ethylene pathway mutations upon expression of the ethylene receptor ETR1 from Arabidopsis.

The ethylene receptor family of Arabidopsis consists of five members, one of these being ETR1. The effect of ethylene pathway mutations upon expression of ETR1 was examined. For this purpose, ETR1 levels were quantified in mutant backgrounds containing receptor loss-of-function mutations, ethylene-insensitive mutations, and constitutive ethylene response mutations. Ethylene-insensitive mutations of ETR1 resulted in a posttranscriptional increase in levels of the mutant receptor. Treatment of seedlings with silver, which leads to ethylene insensitivity, also resulted in an increase in levels of ETR1. Loss-of-function mutations of ETR1 resulted in both transcriptional and posttranscriptional changes in levels of the receptor. Most other ethylene pathway mutations, including a newly isolated T-DNA insertion mutation in the gene encoding the ethylene receptor ERS1, had relatively minor effects upon the expression of ETR1. Our results indicate that mutations in ETR1 can affect expression at the posttranscriptional level, and suggest that these posttranscriptional changes may contribute to the phenotypes observed in the mutants. Our results also refine the model on how mutations in ethylene receptors are able to confer dominant ethylene insensitivity upon plants.

Regulation of differential growth in the apical hook of Arabidopsis.

Arabidopsis seedlings develop a hook-like structure at the apical part of the hypocotyl when grown in darkness. Differential cell growth processes result in the curved hypocotyl hook. Time-dependent analyses of the hypocotyl showed that the apical hook is formed during an early phase of seedling growth and is maintained in a sequential phase by a distinct process. Based on developmental genetic analyses of hook-affected mutants, we show that the hookless mutants (hls1, cop2) are involved in an early aspect of hook development. From time-dependent analyses of ethylene-insensitive mutants, later steps in hook maintenance were found to be ethylene sensitive. Regulation of differential growth was further studied through examination of the spatial pattern of expression of two hormone-regulated genes: an ethylene biosynthetic enzyme and the ethylene receptor ETR1. Accumulation of mRNA for AtACO2, a novel ACC (1-aminocyclopropane-1-carboxylic acid) oxidase gene, occurred within cells predominantly located on the outer-side of the hook and was tightly correlated with ethylene-induced exaggeration in the curvature of the hook. ETR1 expression in the apical hook, however, was reduced by ethylene treatment. Based on the expression pattern of ETR1 and AtACO2 in the hook-affected mutants, a model for hook development and maintenance is proposed.