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Ethylene Production (ethylene + production)
Selected AbstractsEthylene production in plants during transformation suppresses vir gene expression in Agrobacterium tumefaciensNEW PHYTOLOGIST, Issue 3 2008Satoko Nonaka Summary ,,Ethylene evolution from plants inhibits Agrobacterium -mediated genetic transformation, but the mechanism is little understood. In this study, the possible role of ethylene in Agrobacterium -mediated genetic transformation was clarified. ,,It was tested whether or not plant ethylene sensitivity affected genetic transformation; the sensitivity might regulate bacterial growth during co-cultivation and vir gene expression in Agrobacterium tumefaciens. For these experiments, melon (Cucumis melo) was used, in which ethylene sensitivity was controlled by chemicals, and Arabidopsis ethylene-insensitive mutants. ,,Agrobacterium -mediated genetic transformation was inhibited in ethylene-sensing melon, whereas, in Arabidopsis ethylene-insensitive mutant, it was enhanced. However, the ethylene sensitivity did not affect bacterial growth. vir gene expression was inhibited by application of plant exudate from ethylene-sensitive plants. The inhibitory effect of the ethylene sensitivity on genetic transformation relieved the activation of vir gene expression in A. tumefaciens with vir gene inducer molecule (acetosyringone, AS) or A. tumefaciens mutant strain which has constitutive vir gene expression. ,,These results indicate that ethylene evolution from a plant inoculated with A. tumefaciens inhibited vir gene expression in A. tumefaciens through the ethylene signal transduction in the plant, and, as a result, Agrobacterium -mediated genetic transformation was inhibited. [source] The effects of 1-methylcyclopropene on peach fruit (Prunus persica L. cv. Jiubao) ripening and disease resistanceINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2005Hongxia Liu Summary In order to learn how 1-methylcyclopropene (1-MCP) affects ripening and disease-resistance of peach fruit (Prunus persica L. cv. Jiubao) after harvest, they were treated with 1-MCP and some were inoculated with Penicillium expansum. Treating peach fruit with 0.2 ,L L,1 of 1-MCP at 22 °C for 24 h effectively slowed the decline in fruit firmness. The minimal concentration of 1-MCP able to inhibit fruit softening was 0.6 ,L L,1. Changes in other parameters related to peach ripening, such as content of soluble solids, total soluble sugar, titratable acidity, soluble pectin and ethylene production were also significantly reduced or delayed by 1-MCP. Repeated treatment of peach with 1-MCP resulted in more effective inhibition of ripening. Post-harvest decay of peach fruit was reduced by treatment with 1-MCP and disease progress in fruit inoculated with P. expansum was reduced. The activities of phenylalanine ammonialyase, polyphenoloxidase and peroxidase in the inoculated fruit were also enhanced by 1-MCP. [source] ACTIVITIES OF ,-GALACTOSIDASE AND ,-L-ARABINOFURANOSIDASE, ETHYLENE BIOSYNTHETIC ENZYMES DURING PEACH RIPENING AND SOFTENINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2006CHANG-HAI JIN ABSTRACT A study was conducted to determine changes in firmness, ethylene and ethylene biosynthetic enzymes, and the activities of ,-galactosidase (,-GAL) and ,-L-arabinofuranosidase (,-AF) during peach ripening and softening. The activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, ACC oxidase and polygalacturonase increased in parallel with ethylene production and declined in firmness during peach ripening, and they appeared at maximum simultaneously at maturity IV. ,-GAL activity was high in unripe peach fruit and it experienced an overall decline during peach ripening. While ,-AF activity changed placidly at the initial stage (maturity I,III), after that it experienced a rapid increasing stage. The preliminary result indicated that ,-GAL and ,-AF, as well as ethylene biosynthetic enzymes, may be involved in the ripening and softening of peach fruit. [source] EFFECT OF 1-METHYLCYCLOPROPENE ON NUTRITIONAL QUALITY AND ANTIOXIDANT ACTIVITY OF TOMATO FRUIT (SOLANUM LYCOPERSICON L.) DURING STORAGEJOURNAL OF FOOD QUALITY, Issue 2 2010MENG WANG ABSTRACT The effect of 1-methylcyclopropene (1-MCP) on postharvest quality and nutritional compounds in tomato (Solanum lycopersicon Mill.) fruit during storage was determined. The green mature tomato was exposed to 1 µL/L 1-MCP for 24 h. Thereafter, the fruit were stored at 20C and 85,95% relative humidity for 20 days. The results indicated that 1-MCP treatment significantly delayed the decrease of firmness, total soluble solids, and titratable acidity, inhibited the increase of weight loss, and suppressed the rise in respiration rate and ethylene production. Moreover, 1-MCP treatment also inhibited the lycopene accumulation and chlorophyll degradation. Ascorbic acid and soluble phenolic contents in 1-MCP-treated fruit were significantly higher than those in the control fruit. 1-MCP treatment enhanced the ferric reducing antioxidant power (FRAP) values and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. These results suggested that 1-MCP can be used as a commercial technology due to its ability to improve nutritional value of tomato fruit as well as to delay fruit ripening. PRACTICAL APPLICATIONS Tomato fruit are often harvested at mature green stage to minimize damage during transport to market, and then allowed to ripen before or during presentation in retail outlets. A limitation to marketing of tomato fruit is the time that ripe fruit remain in an acceptable condition for consumers. 1-Methylcyclopropene (1-MCP) can extend the storage life and improve postharvest quality of tomato fruit. Recently, nutritional quality is of increasing interest to the consumers because of their potential health benefits in protecting against various diseases. However, the effects of 1-MCP on nutritional compounds and antioxidant activity of tomato fruit are still unclear and need to be more precisely determined. This study can provide information on the effect of 1-MCP treatment on postharvest quality and nutritional compounds in tomato fruit during storage. The results could be applicable to improve the quality and nutritional value of tomato fruit for commercial purpose. [source] QUALITY OF FRESH-CUT TOMATOESJOURNAL OF FOOD QUALITY, Issue 3 2004ABDUL HAKIM ABSTRACT Tomato fruit at pink or light-red stages of ripening were cut into slices, rinsed with water containing 50 ,L.L,1 sodium hypochlorite and drained. They were stored in perforated polyethylene package at 1C in air or controlled atmosphere for five and ten days. Weight loss, chlorophyll and lycopene contents, seed discoloration, fungal infection, total soluble solids content, titratable acidity, sugar/acid ratio, pH, flavor and taste, firmness, ascorbic acid content, rate of respiration and ethylene production, and electrolyte leakage were evaluated after each storage period. The overall quality of controlled atmosphere-stored slices was better than that of air stored slices. Slices from light-red fruit had lower weight loss, minimum seed discoloration, lower [source] 1-Methylcyclopropene affects the antioxidant system of apricots (Prunus armeniaca L. cv. Búlida) during storage at low temperatureJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2010Isabel Egea Abstract BACKGROUND: Apricots (Prunus armeniaca cv. Búlida) were treated with 1 mL L,1 1-methylcyclopropene (1-MCP) immediately after harvest and stored in air at 2 °C for 21 days. Antioxidant levels (ascorbic acid and carotenoids), enzymatic antioxidant activities (superoxide dismutase (SOD) and unspecific peroxidase (POX)) and total antioxidant capacity (trolox equivalent antioxidant capacity (TEAC)) were determined. The level of oxidative stress was also established by measuring ion leakage during storage. The changes in the antioxidant potential of apricots were related to the capacity of 1-MCP to increase their commercial life. RESULTS: 1-MCP-treated fruits exhibited higher SOD activity, whereas POX activity was significantly higher only after 21 days at 2 °C. Treated fruits also exhibited better retention of ascorbate and carotenoids and higher TEAC during storage. In accordance with these observations, lower ion leakage values were detected in 1-MCP-treated apricots. CONCLUSION: Taken together, these results suggest that 1-MCP conferred a greater resistance to oxidative stress. This, along with the reduction in ethylene production, could contribute to the increase in commercial life and nutritional value observed in 1-MCP-treated apricots. Copyright © 2010 Society of Chemical Industry [source] Pre- or post-harvest applications of putrescine and low temperature storage affect fruit ripening and quality of ,Angelino' plumJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2008Ahmad S Khan Abstract BACKGROUND: Plum has a very short storage life. The role of pre- or post-harvest applications of putrescine (PUT) and low temperature storage on fruit ripening and quality was investigated in plum fruit (Prunus salicina Lindl. cv. Angelino). RESULTS: Pre- or post-harvest PUT treatments [(0.1, 1.0 or 2.0 mmol L,1) + 0.01% Tween-20 as a surfactant] delayed and suppressed the climacteric ethylene production and respiration rate irrespective of the method used to apply PUT. PUT-treated fruit following low temperature storage (0 ± 1 °C; 90 ± 5% RH), at the ripe stage exhibited higher fruit firmness and titratable acidity (TA), while soluble solids content (SSC), levels of ascorbic acid, total carotenoids and total antioxidants were lower than in untreated fruit. Fruit both sprayed with PUT and stored in low temperature for 6 weeks, at the ripe stage showed reduced respiration rate, delayed changes in the SSC:TA ratio and levels of total carotenoids compared to post-harvest PUT application. CONCLUSION: Pre-harvest application of 2.0 mmol L,1 PUT 1 week before the anticipated commercial harvest was more effective in delaying plum fruit ripening and can be used to extend the storage (0 ± 1 °C) life of plums for up to 6 weeks with minimum losses in fruit quality. Copyright © 2008 Society of Chemical Industry [source] Use of alginate or zein as edible coatings to delay postharvest ripening process and to maintain tomato (Solanum lycopersicon Mill) qualityJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2008Pedro Javier Zapata Abstract BACKGROUND: Edible coatings could be effective tools for delaying the ripening process of fruits. Alginate or zein as edible coatings were assayed in tomato in order to maintain parameters related to quality during postharvest storage. RESULTS: Coated tomatoes showed lower respiration rate and ethylene production than control ones, with a twofold lower concentration of ethylene precursor. In addition, the evolution of parameters related to tomato quality losses, such as softening, colour evolution and weight loss, was significantly delayed (4,6 days on average) in coated tomatoes as compared to controls. Thereafter, sugars, organic acids (and especially ascorbic acid) and scores from sensory analysis remained at much higher levels at the end of storage in treated than in control tomatoes. CONCLUSIONS: Coatings based on alginate or zein could be effective tools for delaying the tomato-ripening process during postharvest storage, and in turn maintaining tomato quality and its acceptability by consumers. Copyright © 2008 Society of Chemical Industry [source] Keeping quality of tomato fruit by high electrostatic field pretreatment during storageJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2008Yu Wang Abstract BACKGROUND: High electrostatic field, as a feasible and non-chemical technique, applied to food preservation is a new area of study. The present article intensively investigated this new preservation method, together with its effects on post-harvest physiology and quality of tomato. RESULTS: Green mature tomatoes were exposed to negative (or positive) high electrostatic field for 2 h at 20 °C and then stored for 30 days at 13 ± 1 °C, 85,90% RH. Our results indicated that negative high electrostatic field (,2 kV cm,1) could delay the decline of firmness and the change in color, total soluble sugar and titratable acidity of tomato fruit during storage. The peak of respiration and ethylene production of tomato fruit during storage were delayed by negative high electrostatic field treatment for 6 days and 3 days, respectively. Increases of malondialdehyde content and electrical conductivity in tomato fruit were inhibited significantly by negative high electrostatic field treatment during storage (P < 0.05). CONCLUSION: A high electrostatic field of , 2 kV cm,1 can be used to keep the qualities and extend the shelf-life of tomato fruit. Further research should be highly recommended to understand the mechanisms improving the storability of tomato fruit by negative high electrostatic field. Copyright © 2007 Society of Chemical Industry [source] Postharvest response of ,Brown Turkey' figs (Ficus carica L.) to the inhibition of ethylene perceptionJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2005Gabriel O Sozzi Abstract The potential use of 1-methylcyclopropene (1-MCP) alone or as a supplement to cold storage to delay the softening of ,Brown Turkey' figs (Ficus carica L.) was studied. Figs were treated with 0, 0.25, 0.5 or 5 µl l,1 1-MCP at 25 °C for 8 h and stored at 20 °C until evaluated. Figs treated with 0.5 or 5 µl l,1 1-MCP had higher ethylene production and respiration rates but slower softening than untreated fruit and those treated with 0.25 µl l,1 1-MCP. Early-harvested firm figs and late-harvested soft figs were untreated or treated with 0.5 or 5 µl l,1 1-MCP at 25 °C and stored at 0 °C for 19 days. Firm figs treated with 1-MCP showed an early peak in ethylene synthesis, higher respiration rate and were firmer than control fruit. In contrast, soft figs did not respond to 1-MCP except for a late increase in respiration rates of fruit treated with 5 µl l,1 1-MCP. 1-MCP appeared to have a relatively limited effect on slowing ripening of ,Brown Turkey' figs and its effect was influenced by ripening stage. Copyright © 2005 Society of Chemical Industry [source] Effect of benzyl isothiocyanate on tomato fruit infection development by Alternaria alternataJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2005R Troncoso-Rojas Abstract Benzyl isothiocyanate (BITC) is known to be a strong antifungal compound in vitro against different fungi. The effectiveness of benzyl isothiocyanate to control Alternaria alternata growth in vitro and in vivo was tested. BITC in vitro activity was evaluated in A alternata growing on potato dextrose agar and exposed to 0.025, 0.05, 0.1, 0.2 or 0.4 mg ml,1. In vivo activity was evaluated by exposing A alternata -inoculated tomato fruits for either 18 or 36 h to 0.28 or 0.56 mg ml,1 BITC packed on low-density polyethylene film (LDPF) bags. Additionally, the effect of BITC on post-harvest physiology and tomato quality throughout storage at 20 °C was evaluated daily by monitoring respiration rate and ethylene production, whereas total soluble solids, pH, titratable acidity and fresh weight loss were measured every 3 days. Results showed that the minimal inhibitory concentration of BITC in vitro was 0.1 mg ml,1. A combined use of 0.56 mg ml,1 BITC with LDPF for 18 h was the optimum treatment to control Alternaria rot in packed tomato fruit. No effect of BITC on respiration rate, ethylene production, total soluble solids, pH, weight loss and titratable acidity was observed. Results suggest that BITC can be used as a post-harvest treatment to control Alternaria rot in tomato fruit without detrimental effects on the tomato post-harvest quality. Copyright © 2005 Society of Chemical Industry [source] Effect of preharvest sprays containing calcium, magnesium and titanium on the quality of peaches and nectarines at harvest and during postharvest storageJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2004María Serrano Abstract Peach and nectarine trees were foliar sprayed with a formulation containing Ca2+, Mg2+ and Ti4+. Parameters related to fruit quality were evaluated at harvest, after 7,28 days of cold storage and after subsequent ripening for 4 days at 20 °C (shelf life). At harvest, treated fruits from both cultivars had higher weight and pulp firmness than control fruits, while no effect was observed for either colour, total soluble solid content (TSS) and titratable acidity (TA) or the time required to ripen on the tree. During cold storage, lower levels of weight loss, colour evolution, TSS/TA ratio and ethylene production and higher pulp firmness were found in treated peaches and nectarines compared with control fruits. Also, the storability of treated fruits was extended for up to 14 days more than that of control fruits. During ripening at 20 °C after different periods of cold storage, parameters related to ripening evolved faster in control than in treated fruits. Also, the occurrence of the climacteric peak of ethylene production was delayed and its intensity was lower in treated peaches and nectarines than in controls. Copyright © 2004 Society of Chemical Industry [source] Papaya fruit softening, endoxylanase gene expression, protein and activityPHYSIOLOGIA PLANTARUM, Issue 3 2007Ashariya Manenoi Papaya (Carica papaya L.) cell wall matrix polysaccharides are modified as the fruit starts to soften during ripening and an endoxylanase is expressed that may play a role in the softening process. Endoxylanase gene expression, protein amount and activity were determined in papaya cultivars that differ in softening pattern and in one cultivar where softening was modified by the ethylene receptor inhibitor 1-methylcyclopropene (1-MCP). Antibodies to the endoxylanase catalytic domain were used to determine protein accumulation. The three papaya varieties used in the study, ,Line 8', ,Sunset', and ,Line 4-16', differed in softening pattern, respiration rate, ethylene production and showed similar parallel relationships during ripening and softening in endoxylanase expression, protein level and activity. When fruit of the three papaya varieties showed the respiratory climacteric and started to soften, the level of endoxylanase gene expression increased and this increase was related to the amount of endoxylanase protein at 32 kDa and its activity. Fruit when treated at less than 10% skin yellow stage with 1-MCP showed a significant delay in the respiratory climacteric and softening, and reduced ethylene production, and when ripe was firmer and had a ,rubbery' texture. The 1-MCP-treated fruit that had the ,rubbery' texture showed suppressed endoxylanase gene expression, protein and enzymatic activity. Little or no delay occurred between endoxylanase gene expression and the appearance of activity during posttranslational processing from 65 to 32 kDa. The close relationship between endoxylanase gene expression, protein accumulation and activity in different varieties and the failure of the 1-MCP-treated fruit to fully soften, supported de novo synthesis of endoxylanase, rapid posttranslation processing and a role in papaya fruit softening. [source] Molecular control of ethylene production by cyanide in Arabidopsis thalianaPHYSIOLOGIA PLANTARUM, Issue 2 2000Jennifer McMahon Smith Although cyanide has long been recognized as a co-product of ethylene synthesis, little attention has been given to its potential physiological and molecular roles. In the present work, the long-term effects of cyanide on growth and development were observed in Arabidopsis thaliana. Two days after a single 20-min application of cyanide, plants demonstrated visible signs of stress. Long-term detrimental effects on growth and photosynthetic capabilities were noted, including low chlorophyll accumulation and stunted growth. Because of the relationship between cyanide and ethylene production, we chose to evaluate the results of cyanide treatment on genes encoding proteins involved in ethylene synthesis. We have found that only the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase gene, ACS6, is rapidly activated in response to cyanide treatment, while other ACS genes were unaffected. This same gene has previously been shown to be transcriptionally activated in response to touch and other environmental stimuli. Cyanide was capable of activating ACS6 transcription within 10 min of treatment, and the amount of transcript correlated positively with the cyanide dosage. Due to the toxic nature of cyanide, plant in vivo concentrations are generally maintained lower than 10 ,M, but can increase under certain stresses. In the present work, we observed that physiologically relevant concentrations as low as 1 ,M HCN, considered metabolically ,safe', were capable of initiating ACS6 transcription. ACS6 transcripts were not substantially reduced as a result of multiple cyanide treatments, which is in contrast with the effects of mechanical stimulation on transcription. Our results suggest a relationship between cyanide production during ethylene synthesis and the molecular control of ethylene synthesis. This work corresponds with earlier experiments that have demonstrated that ethylene and cyanide can elicit some similar physiological responses. It is possible that cyanide may play an active role in ethylene regulation under conditions where rapid cyanide accumulation occurs. Since cyanide can rapidly activate ethylene synthesis, it is possible that it is involved in the positive-feedback regulation of ethylene that occurs in some plant tissues. [source] Conditioning period, CO2 and GR24 influence ethylene biosynthesis and germination of Striga hermonthicaPHYSIOLOGIA PLANTARUM, Issue 1 2000Abdel Gabbar T. Babiker Germination of witchweed (Striga hermonthica [Del.] Benth), an important root parasite on poaceous crops, requires pretreatment ,conditioning' in a warm moist environment and a subsequent exposure to a stimulant. The roles of conditioning period, CO2 and a strigol analogue (GR24) in ethylene biosynthesis and germination of the parasite were investigated. Conditioning increased the seeds' capacity to oxidize exogenous 1-aminocyclopropane-1-carboxylic acid (ACC). Exogenous CO2 increased the seeds capacity to oxidize ACC by 3- to 9-fold. A combination of GR24 and ACC increased ethylene production by more than 3-fold in comparison with the rates obtained using these compounds separately. Aminoethoxyvinylglycine (AVG) completely inhibited ethylene induction by GR24, but not by ACC. A GR24 treatment, made subsequent to conditioning in GR24, did not induce ethylene. However, seeds conditioned in GR24 and then given 1 mM ACC produced 293 nl l,1 ethylene. ACC oxidase (ACCO) activity in crude extracts was increased by conditioning and CO2. The enzyme displayed an absolute requirement for ascorbate. Absence of exogenous Fe2+ reduced enzyme activity only by 14%. GR24 applied during conditioning reduced germination in response to a subsequent GR24 treatment. ACC was, invariably, less effective in inducing S. hermonthica germination than GR24 even at concentrations which induce more ethylene than concurrent GR24 treatments. The results are consistent with a model in which conditioning removes a restriction on the ethylene biosynthetic pathway in S. hermonthica seeds. GR24 modulates the key enzymes in ethylene biosynthesis. The stimulant suppresses ethylene biosynthesis in unconditioned seeds and promotes it in conditioned ones. Germination of S. hermonthica results from the joint action of GR24 and the ethylene it induces. [source] Effects of exogenous GABA on gene expression of Caragana intermedia roots under NaCl stress: regulatory roles for H2O2 and ethylene productionPLANT CELL & ENVIRONMENT, Issue 2 2010SHENG-QING SHI ABSTRACT , -aminobutyric acid (GABA) is a four-carbon non-protein amino acid presented in a wide range of organisms. In this study, a suppression subtractive hybridization (SSH) library was constructed using roots of a legume shrub, Caragana intermedia, with the combined treatment of 300 mm NaCl and 300 mm NaCl + 10 mm GABA. We obtained 224 GABA-regulated unique expressed sequence tags (ESTs) including signal transduction, transcriptional regulation, hormone biosynthesis, reactive oxygen species (ROS) and polyamine metabolism, etc. The key H2O2 -generated genes, NADPH oxidase (CaGR60), peroxidase (CaGR61) and amine oxidase (CaGR62), were regulated at the mRNA level by 10 mm GABA, which clearly inhibited H2O2 accumulation brought about by NaCl stress in roots and leaves with the observation of 3,3,-diaminobenzidine (DAB) staining. Similarly, 10 mm GABA also regulated the expression of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) genes (CaGR30 and CaGR31) and ethylene production in NaCl-treated roots. Surprisingly, these H2O2 -generated genes were enhanced at the mRNA level by a lower concentration of GABA, at 0.25 mm, but not other alternative nitrogen sources, and endogenous GABA accumulated largely just by the application of GABA at either concentration. Our results further proved that GABA, as a signal molecule, participates in regulating the expression of genes in plants under salt stress. [source] Ethylene insensitivity impedes a subset of responses to phosphorus deficiency in tomato and petuniaPLANT CELL & ENVIRONMENT, Issue 12 2008HYE-JI KIM ABSTRACT The role of ethylene in growth and developmental responses to low phosphorus stress was evaluated using ethylene-insensitive ,Never-ripe' (Nr) tomato and etr1 petunia plants. Low phosphorus increased adventitious root formation in ,Pearson' (wild-type) tomato plants, but not in Nr, supporting a role for ethylene in adventitious root development and showing that ethylene is important for this aspect of phosphorus response. Low phosphorus reduced ethylene production by adventitious roots of both genotypes, suggesting that ethylene perception , not production , regulates carbon allocation to adventitious roots at the expense of other roots under low phosphorus stress. With the exception of its effect on adventitious rooting, Nr had positive effects on growth and biomass accumulation in tomato whereas etr1 tended to have negative effects on petunia. This was particularly evident during the recovery from transplanting, when the effective quantum yield of photosystem II of etr1 petunia grown with low phosphorus was significantly lower than ,Mitchell Diploid', suggesting that etr1 petunia plants may undergo more severe post-transplant stress at low phosphorus availability. Our results demonstrate that ethylene mediates adventitious root formation in response to phosphorus stress and plays an important role for quick recovery of plants exposed to multiple environmental stresses, i.e. transplanting and low phosphorus. [source] Ethylene-induced hyponastic growth in Arabidopsis thaliana is controlled by ERECTATHE PLANT JOURNAL, Issue 1 2010Martijn Van Zanten Summary Plants can respond quickly and profoundly to detrimental changes in their environment. For example, Arabidopsis thaliana can induce an upward leaf movement response through differential petiole growth (hyponastic growth) to outgrow complete submergence. This response is induced by accumulation of the phytohormone ethylene in the plant. Currently, only limited information is available on how this response is molecularly controlled. In this study, we utilized quantitative trait loci (QTL) analysis of natural genetic variation among Arabidopsis accessions to isolate novel factors controlling constitutive petiole angles and ethylene-induced hyponastic growth. Analysis of mutants in various backgrounds and complementation analysis of naturally occurring mutant accessions provided evidence that the leucin-rich repeat receptor-like Ser/Thr kinase gene, ERECTA, controls ethylene-induced hyponastic growth. Moreover, ERECTA controls leaf positioning in the absence of ethylene treatment. Our data demonstrate that this is not due to altered ethylene production or sensitivity. [source] The N-terminal region of Pseudomonas type III effector AvrPtoB elicits Pto-dependent immunity and has two distinct virulence determinantsTHE PLANT JOURNAL, Issue 4 2007Fangming Xiao Summary Resistance to bacterial speck disease in tomato is activated by the physical interaction of the host Pto kinase with either of the sequence-dissimilar type III effector proteins AvrPto or AvrPtoB (HopAB2) from Pseudomonas syringae pv. tomato. Pto-mediated immunity requires Prf, a protein with a nucleotide-binding site and leucine-rich repeats. The N-terminal 307 amino acids of AvrPtoB were previously reported to interact with the Pto kinase, and we show here that this region (AvrPtoB1-307) is sufficient for eliciting Pto/Prf-dependent immunity against P. s. pv. tomato. AvrPtoB1-307 was also found to be sufficient for a virulence activity that enhances ethylene production and increases growth of P. s. pv. tomato and severity of speck disease on susceptible tomato lines lacking either Pto or Prf. Moreover, we found that residues 308,387 of AvrPtoB are required for the previously reported ability of AvrPtoB to suppress pathogen-associated molecular patterns-induced basal defenses in Arabidopsis. Thus, the N-terminal region of AvrPtoB has two structurally distinct domains involved in different virulence-promoting mechanisms. Random and targeted mutagenesis identified five tightly clustered residues in AvrPtoB1-307 that are required for interaction with Pto and for elicitation of immunity to P. s. pv. tomato. Mutation of one of the five clustered residues abolished the ethylene-associated virulence activity of AvrPtoB1-307. However, individual mutations of the other four residues, despite abolishing interaction with Pto and avirulence activity, had no effect on AvrPtoB1-307 virulence activity. None of these mutations affected the basal defense-suppressing activity of AvrPtoB1-387. Based on sequence alignments, estimates of helical propensity, and the previously reported structure of AvrPto, we hypothesize that the Pto-interacting domains of AvrPto and AvrPtoB1-307 have structural similarity. Together, these data support a model in which AvrPtoB1-307 promotes ethylene-associated virulence by interaction not with Pto but with another unknown host protein. [source] A role for ethylene in the phytochrome-mediated control of vegetative developmentTHE PLANT JOURNAL, Issue 6 2006Eloise Foo Summary Members of the phytochrome family of photoreceptors play key roles in vegetative plant development, including the regulation of stem elongation, leaf development and chlorophyll accumulation. Hormones have been implicated in the control of these processes in de-etiolating seedlings. However, the mechanisms by which the phytochromes regulate vegetative development in more mature plants are less well understood. Pea (Pisum sativum) mutant plants lacking phytochromes A and B, the two phytochromes present in this species, develop severe defects later in development, including short, thick, distorted internodes and reduced leaf expansion, chlorophyll content and CAB gene transcript level. Studies presented here indicate that many of these defects in phyA phyB mutant plants appear to be due to elevated ethylene production, and suggest that an important role of the phytochromes in pea is to restrict ethylene production to a level that does not inhibit vegetative growth. Mutant phyA phyB plants produce significantly more ethylene than WT plants, and application of an ethylene biosynthesis inhibitor rescued many aspects of the phyA phyB mutant phenotype. This deregulation of ethylene production in phy-deficient plants appears likely to be due, at least in part, to the elevated transcript levels of key ethylene-biosynthesis genes. The phytochrome A photoreceptor appears to play a prominent role in the regulation of ethylene production, as phyA, but not phyB, single-mutant plants also exhibit a phenotype consistent with elevated ethylene production. Potential interactions between ethylene and secondary plant hormones in the control of the phy-deficient mutant phenotype were explored, revealing that ethylene may inhibit stem elongation in part by reducing gibberellin levels. [source] The effect of plant cytokinin hormones on the production of ethylene, nitric oxide, and protein nitrotyrosine in ageing tobacco leavesBIOFACTORS, Issue 1-4 2006N. Wilhelmová Abstract Transgenic plants with genetically increased or decreased levels of cytokinins were used to investigate the effect of cytokinin level on the production of ethylene, a plant hormone with suggested role in senescence, and the production of nitric oxide, potentially important signalling and regulatory molecule. The production of these gases was followed during the course of leaf development and senescence. The production of ethylene and nitric oxide is under genetic control of genes other than those involved in regulation of senescence. The difference in basic ethylene and NO levels in different tobacco cultivars was higher than their changes in senescence. The results of this study did not indicate a direct link between ethylene production and cytokinin levels. However, there was a decreased production of NO in senescent leaves. Low cytokinins level was associated with increased NO production during leaf development. Protein nitrotyrosine proved to be a better indicator of the reactive nitrogen species than measuring of the NO production. Higher nitrotyrosine concentrations were found in insoluble proteins than in the soluble ones, pointing to membrane proteins as the primary targets of the reactive nitrogen species. In plants with elevated cytokinin levels the content of nitrated proteins decreased both in soluble and insoluble fractions. This finding indicates an antioxidative function of cytokinins against reactive nitrogen species. [source] | |||||||||||||