The Experts below are selected from a list of 897 Experts worldwide ranked by ideXlab platform
James W Buck - One of the best experts on this subject based on the ideXlab platform.
-
Resistance of Daylily Cultivars to the Daylily Rust Pathogen, Puccinia
2020Co-Authors: Jean L. Williams-woodward, James W BuckAbstract:Daylilies (Hemerocallis sp.) have traditionally been considered to be pest-free. However, a rust disease caused by Puccinia hemerocallidis Thum. has become an in- creasing problem in the United States since 2000. The objective of this study was to evaluate Daylily cultivars for resistance to Daylily rust. From a greenhouse evaluation of 84 inoculated cultivars, 14 (17%) were classified as resistant; 13 (15%) were classified as moderately resistant; 22 (26%) were classified as moderately susceptible; and 35 (42%) were classified as fully susceptible. Several cultivars displayed very high levels of resistance and may be utilized by breeders to develop cultivars with improved resistance to Daylily rust. Information about the resistance and susceptibility of cultivars also will help com- mercial growers and gardeners select cultivars that have the potential to dramatically reduce damaging outbreaks of rust.
-
management of Daylily rust with different fungicide combinations and spray intervals
Plant Disease, 2016Co-Authors: Robert S Emmitt, K L Stevenson, T B Brenneman, James W BuckAbstract:Daylily (Hemerocallis spp.) is a popular herbaceous perennial plant and was considered to be relatively disease free until 2000, when Daylily rust, caused by Puccinia hemerocallidis, was first detected in the United States. Management of Daylily rust in nurseries is dependent on the use of fungicides, which are typically applied to the foliage of large blocks of plants at 21- or 28-day intervals. The objectives of this study were to determine the most effective fungicides or fungicide combinations and application intervals for managing Daylily rust in the field. Foliar sprays of azoxystrobin alone at 14-, 21-, or 28-day intervals, combinations of azoxystrobin + propiconazole, azoxystrobin + chlorothalonil, propiconazole + chlorothalonil, and chlorothalonil + thiophanate-methyl applied at intervals of 21or 28 days, and a nontreated control were evaluated under high disease pressure, at three locations in Griffin, GA in 2014. In all three fields, all treatments that included azoxystrobin were effective at r...
-
identification of pathotypes in the Daylily rust pathogen puccinia hemerocallidis
Journal of Phytopathology, 2013Co-Authors: James W BuckAbstract:Daylily rust, caused by Puccinia hemerocallidis, has been present in the United States since 2000. In 2003, inoculations with a single isolate of P. hemerocallidis identified Daylily cultivars with high levels of resistance to the fungus. The present study was carried out to determine if pathotypes of P. hemerocallidis are present in the south eastern United States. Sixteen isolates of P. hemerocallidis were each inoculated onto leaf segments from 19 Daylily cultivars and the resulting disease phenotype assessed. A significant effect of rust isolate on host reaction phenotype was observed for nine of the 19 Daylily cultivars. Five of the nine cultivars displayed reaction phenotypes with different isolates of P. hemerocallidis that included at least one susceptible or moderately susceptible and also resistant phenotypes. These results indicate that different pathotypes of the fungus are present in the south east United States. Daylily hybridizers interested in screening for host resistance to P. hemerocallidis will need to include multiple isolates of the fungus to allow for this host specialization.
-
management of Daylily rust with different fungicides and application methods
Plant Disease, 2013Co-Authors: W B Dong, Steven N Jeffers, James W BuckAbstract:Abstract The objectives of this study were to assess the efficacy of various fungicides applied as root dips, soil drenches, or foliar sprays to Daylily plants grown in containers and planted in the field to manage rust caused by Puccinia hemerocallidis. Soil drenches and foliar sprays were evaluated in field experiments in Griffin, GA in 2010 and 2011. Dipping bare-root Daylily plants for 5 min in azoxystrobin, tebuconazole, or thiophanate-methyl significantly reduced lesion development compared with nontreated control plants. Drenches with azoxystrobin, fluoxastrobin, or tebuconazole, each at three rates (0.06, 0.12, and 0.24 g of active ingredient [a.i.]/container), significantly reduced development of rust lesions on container-grown Daylily plants for up to 9 weeks after treatment and 6 weeks after inoculation. One early-season drench of azoxystrobin at 0.12 g a.i‥/plant provided season-long reduction in disease incidence and disease progress that was comparable with foliar sprays with azoxystrobin or...
-
effect of light on in vivo urediniospore germination lesion development and sporulation of puccinia hemerocallidis on Daylily and puccinia pelargoniizonalis on geranium
Mycologia, 2011Co-Authors: Weibo Dong, James W BuckAbstract:The presence of rusts of Daylily and geranium caused respectively by Puccinia hemerocalli- dis and P. pelargonii-zonalis can result in reduced value of these ornamental crops. Experiments were conducted to determine the effects of fluorescent light and sunlight on urediniospore germination, germ tube elongation, lesion development and sporulation of the two fungal pathogens on detached leaves and whole plants. Exposure of dry or hydrated urediniospores of P. hemerocallidis to cool white fluorescent light (600 mmol s 21 m 22 ) or to sunlight (950-1910 mmol s 21 m 22 ) for 2 h or 4 h significantly reduced germination and germ tube elongation on detached Daylily leaves. Germination but not germ tube elongation of hydrated urediniospores of P. pelargonii-zonalis on detached geranium leaves was significantly reduced when exposed to fluorescent light for 2 h or 4 h. A 4 h exposure to either light source significantly reduced lesion development of P. hemerocallidis on detached Daylily leaves with fewer lesions developing from hydrated compared to dry urediniospores. Sunlight exposures of 1 h and 2 h of hydrated and dry urediniospores respectively signifi- cantly reduced lesion development by either fungus on whole plants. Increasing exposure to fluorescent light negatively affected sporulation of P. hemerocalli- dis and P. pelargonii-zonalis. Complete suppression of sporulation was not observed for either fungus with up to a 24 h exposure to fluorescent light. Light exposure negatively affected disease development by P. hemerocallidis and P. pelargonii-zonalis. Exposure to high light intensities may affect spread of rust diseases on ornamental plants.
Bernard Rubinstein - One of the best experts on this subject based on the ideXlab platform.
-
activities of nucleases in senescing Daylily petals
Plant Physiology and Biochemistry, 2000Co-Authors: Tadas Panavas, Rebbecca Levangie, John Mistler, Philip D Reid, Bernard RubinsteinAbstract:Abstract The activity of nucleases during organ death was investigated using Daylily petals (Hemerocallis hybrid cv. Stella d’Oro), in which the processes associated with senescence are rapid and clearly ordered. The number of nuclei with fragmented DNA as well as activities of various nucleases increase before certain other events that are related to senescence. Furthermore, DNA breakage and activities of nucleases occur earlier when senescence is accelerated by abscisic acid and occur later when senescence is retarded by cycloheximide. These results suggest that the activities of nucleases contribute to the senescence of Daylily petals. Therefore, studying the regulation of nuclease gene expression may be useful for understanding components of the signal transduction system that leads to the death of these organs.
-
Identification of senescence-associated genes from Daylily petals
Plant Molecular Biology, 1999Co-Authors: Tadas Panavas, Bernard Rubinstein, Philip D Reid, Agata Pikula, Elsbeth L. WalkerAbstract:The petals of Daylily (Hemerocallis hybrid) have a genetically based program that leads to senescence and cell death ca. 24 h after the flower opens. In order to determine the components of this program, six cDNAs, whose levels increase during petal senescence, were isolated and sequenced and designated DSA3, 4, 5, 6, 12 and 15. All six DSAs are members of gene families and all but DSA5 and DSA6 have one to three other very similar genes. GenBank database homology searches indicate that DSA3 is most similar at the amino acid level to an in-chain fatty acid hydroxylase which is bound to cytochrome P450, DSA4 may be an aspartic proteinase, DSA5 is as yet unidentified, DSA6 is a putative S1-type nuclease, DSA12 is very similar to a cytochrome P450-containing allene oxide synthase, and DSA15 may be a fatty acid elongase. Except for DSA12, the genes are expressed at low levels in Daylily roots. Levels of the DSA mRNAs in leaves are less than 4% of the maximum detected in petals, and there are no clear differences between younger and older leaves. With the exception of DSA4, accumulation of the DSA mRNAs is increased 3.2 to 43 times by a concentration of abscisic acid that causes premature senescence of the petals. The relationship of the putative DSA gene products to senescence and cell death of Daylily petals is discussed.
-
possible involvement of abscisic acid in senescence of Daylily petals
Journal of Experimental Botany, 1998Co-Authors: Tadas Panavas, Elsbeth L. Walker, Bernard RubinsteinAbstract:Daylily flowers (Hemerocallis hybrid, cv. Stella d'Oro) senesce and die autonomously over a 24 h period after opening. Investigations were performed to determine some of the mechanisms that lead to death of the petals. The flowers are insensitive to ethylene, but exogenous ABA prematurely upregulates events that occur during natural senescence, such as loss of differential membrane permeability, increases in lipid peroxidation and the induction of proteinase and RNase activities. Furthermore, the same patterns of proteinase and RNase activities appearing on activity gels during natural senescence are induced prematurely by ABA. The mRNA profile from ABA-treated, prematurely senescing petals visualized by differential display shows a high degree of similarity to the mRNA profile of naturally senescing petals 18 h later. In addition, endogenous ABA increases before flower opening and continues to increase during petal senescence. An osmotic stress by sorbitol increases endogenous levels of ABA and upregulates the same parameters of senescence as those occurring during natural senescence and after application of ABA. The mRNA profile from sorbitol-treated, prematurely senescing petals shows a high degree of similarity to mRNA from naturally senescing petals, but somewhat less similarity to mRNA from ABA-treated petals. The possibility is discussed that ABA is a constituent of the signal transduction chain leading to programmed cell death of Daylily petals.
-
Characterization of proteolytic activity during senescence in daylilies
Physiologia Plantarum, 1998Co-Authors: Paul Stephenson, Bernard RubinsteinAbstract:From 12 to 24 h after the opening of Daylily flowers (Hemerocallis hybrid cv. Stella d'Oro), the petals begin to degrade and the protein levels of soluble, microsomal- and plastid-enriched fractions decrease by 50%, on a per petal basis. To help determine some of the components for the cell death program in Daylily petals, we studied the mechanisms that regulate this loss of protein. Enzyme activities capable of digesting native Daylily protein, gelatin, and azocasein markedly increase after flower opening, and their appearance is inhibited by the translation inhibitor, cycloheximide. Protein hydrolysis in vitro is prevented by inhibitors of cysteine, serine and metalloproteinases. Immunoblots using antibodies to ubiquitin pathway enzymes indicate that the ubiquitin system is not senescence specific. However, ion leakage is delayed by two inhibitors of the 26S proteasome. We propose that programmed cell death in Daylily petals may involve the increase in activity of at least three classes of proteinases, and discuss the possibility that these proteinases may operate in concert with the ubiquitin pathway.
-
programmed cell death of Daylily petals activities of wall based enzymes and effects of heat shock
Plant Physiology and Biochemistry, 1998Co-Authors: Tadas Panavas, Philip D Reid, Bernard RubinsteinAbstract:Abstract Flowers of the Daylily ( Hememcallis hybrid cv Stella d'Oro) provide an excellent system for the study of events related to cell death. The petals exhibit a highly predictable programme of senescence that occurs over a 24 h period after the flowers open. As petal cells age, they undergo large alterations in size, shape and cell-to-cell attachment. Specific activities of cellulase (EC 3.2.1.4) and pectin methylesterase (EC3.1.1.11) are highest before flower opening, and specific activities of polygalacturonase (EC 3.2.1.15) and β-galactosidase (EC3.2.1.23) increase after flower opening. Addition of an enzyme preparation that hydrolyzes wall materials accelerates senescence, as indicated by increases in peroxidized lipid and the onset of ion leakage. A 3 h heat shock administered 9 h before the flowers open induces two different classes of heat shock proteins and delays events that occur during senescence, such as increases in fresh weight, total protein, reducing sugars, protease activity, lipid peroxidation and ion leakage. Heat shock accelerates the decrease in cellulase activity and retards the increase in polygalacturonase activity. Possible roles for wall-based enzyme activity in ageing of Daylily petals are presented.
Warren E. Copes - One of the best experts on this subject based on the ideXlab platform.
-
(44) Microscopic and Macroscopic Studies on the Development of Puccinia hemerocallidis in Resistant and Susceptible Daylily Cultivars
HortScience, 2020Co-Authors: Yonghao Li, Mark T. Windham, Robert N. Trigiano, Donna C. Fare, James M. Spiers, Warren E. CopesAbstract:Infection process of Puccinia hemerocallidis, the causal agent of Daylily rust, and resistance responses in eight Daylily cultivars, were studied macroscopically and microscopically. After germination of urediniospores, appressoria were formed at the tip of germ tubes and penetrated through stomatal openings. Intercellular hyphae aggregated and formed uredia under the infection sites, and released urediniospores after rupturing the epidermis. In highly resistant cultivars `Prairie Blue Eyes' and `Bertie Ferris', intercellular hyphal growth was restricted and uredia were not formed. No macroscopic symptoms of the disease were present on the leaf surface, although a few collapsed cells were observed microscopically. Both resistant and moderately resistant reactions were characterized by necrotic lesions with many collapsed cells under infection sites. The difference between these two reactions was that uredia and urediniospores were observed on the moderately resistant cultivar `Chicago Apache', but not on resistant cultivars, `Buttered Popcorn' and `Stella De Oro'. Sporulation was observed on both moderately susceptible and susceptible cultivars, but latent periods were delayed and the amount of urediniospore production was reduced on moderately susceptible cultivars, `Mary Todd' and `Chorus Line', compared to the susceptible cultivar `Pardon Me'. The results indicate that the hypersensitive cell death is one of the resistance responses to Daylily rust, but necrotic lesions on leaf surfaces are associated with the amount of collapsed host cells. The delayed latent periods and reduced sporulation that resulted from restricted intercellular hyphal growth could represent another resistance mechanism in the Daylily rust pathosystem.
-
Microscopic and Macroscopic Studies of the Development of Puccinia hemerocallidis in Resistant and Susceptible Daylily Cultivars.
Plant disease, 2020Co-Authors: Y H Li, Mark T. Windham, Robert N. Trigiano, Donna C. Fare, James M. Spiers, Warren E. CopesAbstract:Infection and colonization of eight Daylily cultivars, which varied in resistance to Daylily rust, by Puccinia hemerocallidis was studied macroscopically and microscopically. After germination of urediniospores, appressoria formed at the tip of germ tubes and the fungus penetrated the host through stomatal openings 2 days after inoculation (DAI). Under the infection sites, intercellular hyphae aggregated and formed uredia, which released urediniospores 8 DAI. Resistant cultivars, characterized by the development of rapid death of host cells, were separated into three qualitative categories based on absence and presence of necrotic lesions without or with sporulation. In highly resistant cvs. Prairie Blue Eyes and Bertie Ferris, no macroscopic disease symptoms were observed on leaf surfaces although a few collapsed cells were detected microscopically. Both resistant and moderately resistant reactions were characterized by necrotic lesions with many collapsed cells under infection sites. The difference between these two reactions was that uredia and urediniospores were observed in the moderately resistant cv. Chicago Apache, but not in resistant cvs. Buttered Popcorn and Stella De Oro. Susceptible cultivars, characterized by the absence of a hypersensitive response, were separated into two qualitative categories based on restriction of intercellular hyphal growth that delayed development of uredia and formation of urediniospores. Compared to the susceptible cv. Pardon Me, moderately susceptible cvs. Mary Todd and Chorus Line had a delayed latent period and reduced amount of sporulation. The results indicate that hypersensitive cell death is one of the resistance responses to Daylily rust. Necrotic lesions on leaf surfaces are associated with the number of collapsed host cells. Delayed latent period and reduced sporulation that resulted from restriction of intercellular hyphal growth could represent another type of resistance response in the Daylily-rust pathosystem.
-
concentration and intervals of hydrogen dioxide applications to control puccinia hemerocallidis on Daylily
Crop Protection, 2009Co-Authors: Warren E. CopesAbstract:Abstract Hydrogen dioxide (H 2 O 2 ) is a disinfestant used to kill fungal spores, such as urediniospores of Puccinia hemerocallidis , on plant and production surfaces. Excised sections of Daylily leaves with sporulating rust pustules were sprayed with concentrations between 19 and 270 g active ingredient (a.i.) H 2 O 2 l −1 . Treated spores were rubbed onto the surface of PDA, and germination of >100 spores per replication per treatment was determined 24 h later. An exponential decay model was fitted to the data and a lethal dose (LD) of 57 and 114 g a.i. H 2 O 2 l −1 solution was predicted to cause 90 and 99% urediniospore mortality, respectively. In an irrigation pad study, one label concentration (2.7 g a.i. H 2 O 2 l −1 ) and approximate LD 90 and LD 99 concentrations (54 and 108 g a.i. H 2 O 2 l −1 ) were sprayed 1 or 2 times per week on healthy Daylily plants exposed to naturally dispersing inoculum. Disease incidence and severity decreased with increasing concentration and number of applications of H 2 O 2 per week. H 2 O 2 , at 108 g a.i. l −1 applied once per week, provided control equal to a fungicide treatment (azoxystrobin and chlorothalonil plus thiophanate-methyl rotation), but was also significantly phytotoxic. In a greenhouse study, two concentrations (2.0 and 2.7 g a.i. H 2 O 2 l −1 ) registered for application on plants and one concentration (3.4 g a.i. H 2 O 2 l −1 ) registered for application on production surfaces were sprayed 2, 3, and 5 times per week on healthy Daylily plants exposed to naturally dispersed inoculum. In greenhouse experiment I where the maximum mean incidence was 59%, 2.7 and 3.4 g a.i. H 2 O 2 l −1 applied 2–5 times per week provided control equal to the fungicide treatment. In greenhouse experiment II where the maximum mean incidence was 89%, 5 applications of H 2 O 2 at 2.0–3.4 g a.i. H 2 O 2 l −1 provided control that was better than the water treatment but not as good as the fungicide treatment. Higher label concentrations (2.7 g a.i. H 2 O 2 l −1 ) and multiple applications per week (≥5) can provide disease control equal to a fungicide when disease pressure is low, but may not be effective when disease pressure is high.
-
microscopic and macroscopic studies of the development of puccinia hemerocallidis in resistant and susceptible Daylily cultivars
Plant Disease, 2007Co-Authors: Yonghao Li, Mark T. Windham, Robert N. Trigiano, Donna C. Fare, James M. Spiers, Warren E. CopesAbstract:ABSTRACT Infection and colonization of eight Daylily cultivars, which varied in resistance to Daylily rust, by Puccinia hemerocallidis was studied macroscopically and microscopically. After germination of urediniospores, appressoria formed at the tip of germ tubes and the fungus penetrated the host through stomatal openings 2 days after inoculation (DAI). Under the infection sites, intercellular hyphae aggregated and formed uredia, which released urediniospores 8 DAI. Resistant cultivars, characterized by the development of rapid death of host cells, were separated into three qualitative categories based on absence and presence of necrotic lesions without or with sporulation. In highly resistant cvs. Prairie Blue Eyes and Bertie Ferris, no macroscopic disease symptoms were observed on leaf surfaces although a few collapsed cells were detected microscopically. Both resistant and moderately resistant reactions were characterized by necrotic lesions with many collapsed cells under infection sites. The differ...
-
44) Microscopic and Macroscopic Studies on the Development of Puccinia hemerocallidis in Resistant and Susceptible Daylily Cultivars
Hortscience, 2007Co-Authors: Yonghao Li, Mark T. Windham, Robert N. Trigiano, Donna C. Fare, James M. Spiers, Warren E. CopesAbstract:ABSTRACT Infection and colonization of eight Daylily cultivars, which varied in resistance to Daylily rust, by Puccinia hemerocallidis was studied macroscopically and microscopically. After germination of urediniospores, appressoria formed at the tip of germ tubes and the fungus penetrated the host through stomatal openings 2 days after inoculation (DAI). Under the infection sites, intercellular hyphae aggregated and formed uredia, which released urediniospores 8 DAI. Resistant cultivars, characterized by the development of rapid death of host cells, were separated into three qualitative categories based on absence and presence of necrotic lesions without or with sporulation. In highly resistant cvs. Prairie Blue Eyes and Bertie Ferris, no macroscopic disease symptoms were observed on leaf surfaces although a few collapsed cells were detected microscopically. Both resistant and moderately resistant reactions were characterized by necrotic lesions with many collapsed cells under infection sites. The differ...
Tadas Panavas - One of the best experts on this subject based on the ideXlab platform.
-
activities of nucleases in senescing Daylily petals
Plant Physiology and Biochemistry, 2000Co-Authors: Tadas Panavas, Rebbecca Levangie, John Mistler, Philip D Reid, Bernard RubinsteinAbstract:Abstract The activity of nucleases during organ death was investigated using Daylily petals (Hemerocallis hybrid cv. Stella d’Oro), in which the processes associated with senescence are rapid and clearly ordered. The number of nuclei with fragmented DNA as well as activities of various nucleases increase before certain other events that are related to senescence. Furthermore, DNA breakage and activities of nucleases occur earlier when senescence is accelerated by abscisic acid and occur later when senescence is retarded by cycloheximide. These results suggest that the activities of nucleases contribute to the senescence of Daylily petals. Therefore, studying the regulation of nuclease gene expression may be useful for understanding components of the signal transduction system that leads to the death of these organs.
-
Identification of senescence-associated genes from Daylily petals
Plant Molecular Biology, 1999Co-Authors: Tadas Panavas, Bernard Rubinstein, Philip D Reid, Agata Pikula, Elsbeth L. WalkerAbstract:The petals of Daylily (Hemerocallis hybrid) have a genetically based program that leads to senescence and cell death ca. 24 h after the flower opens. In order to determine the components of this program, six cDNAs, whose levels increase during petal senescence, were isolated and sequenced and designated DSA3, 4, 5, 6, 12 and 15. All six DSAs are members of gene families and all but DSA5 and DSA6 have one to three other very similar genes. GenBank database homology searches indicate that DSA3 is most similar at the amino acid level to an in-chain fatty acid hydroxylase which is bound to cytochrome P450, DSA4 may be an aspartic proteinase, DSA5 is as yet unidentified, DSA6 is a putative S1-type nuclease, DSA12 is very similar to a cytochrome P450-containing allene oxide synthase, and DSA15 may be a fatty acid elongase. Except for DSA12, the genes are expressed at low levels in Daylily roots. Levels of the DSA mRNAs in leaves are less than 4% of the maximum detected in petals, and there are no clear differences between younger and older leaves. With the exception of DSA4, accumulation of the DSA mRNAs is increased 3.2 to 43 times by a concentration of abscisic acid that causes premature senescence of the petals. The relationship of the putative DSA gene products to senescence and cell death of Daylily petals is discussed.
-
possible involvement of abscisic acid in senescence of Daylily petals
Journal of Experimental Botany, 1998Co-Authors: Tadas Panavas, Elsbeth L. Walker, Bernard RubinsteinAbstract:Daylily flowers (Hemerocallis hybrid, cv. Stella d'Oro) senesce and die autonomously over a 24 h period after opening. Investigations were performed to determine some of the mechanisms that lead to death of the petals. The flowers are insensitive to ethylene, but exogenous ABA prematurely upregulates events that occur during natural senescence, such as loss of differential membrane permeability, increases in lipid peroxidation and the induction of proteinase and RNase activities. Furthermore, the same patterns of proteinase and RNase activities appearing on activity gels during natural senescence are induced prematurely by ABA. The mRNA profile from ABA-treated, prematurely senescing petals visualized by differential display shows a high degree of similarity to the mRNA profile of naturally senescing petals 18 h later. In addition, endogenous ABA increases before flower opening and continues to increase during petal senescence. An osmotic stress by sorbitol increases endogenous levels of ABA and upregulates the same parameters of senescence as those occurring during natural senescence and after application of ABA. The mRNA profile from sorbitol-treated, prematurely senescing petals shows a high degree of similarity to mRNA from naturally senescing petals, but somewhat less similarity to mRNA from ABA-treated petals. The possibility is discussed that ABA is a constituent of the signal transduction chain leading to programmed cell death of Daylily petals.
-
programmed cell death of Daylily petals activities of wall based enzymes and effects of heat shock
Plant Physiology and Biochemistry, 1998Co-Authors: Tadas Panavas, Philip D Reid, Bernard RubinsteinAbstract:Abstract Flowers of the Daylily ( Hememcallis hybrid cv Stella d'Oro) provide an excellent system for the study of events related to cell death. The petals exhibit a highly predictable programme of senescence that occurs over a 24 h period after the flowers open. As petal cells age, they undergo large alterations in size, shape and cell-to-cell attachment. Specific activities of cellulase (EC 3.2.1.4) and pectin methylesterase (EC3.1.1.11) are highest before flower opening, and specific activities of polygalacturonase (EC 3.2.1.15) and β-galactosidase (EC3.2.1.23) increase after flower opening. Addition of an enzyme preparation that hydrolyzes wall materials accelerates senescence, as indicated by increases in peroxidized lipid and the onset of ion leakage. A 3 h heat shock administered 9 h before the flowers open induces two different classes of heat shock proteins and delays events that occur during senescence, such as increases in fresh weight, total protein, reducing sugars, protease activity, lipid peroxidation and ion leakage. Heat shock accelerates the decrease in cellulase activity and retards the increase in polygalacturonase activity. Possible roles for wall-based enzyme activity in ageing of Daylily petals are presented.
-
oxidative events during programmed cell death of Daylily hemerocallis hybrid petals
Plant Science, 1998Co-Authors: Tadas Panavas, Bernard RubinsteinAbstract:Abstract Petals of the Daylily, Hemerocallis hybrid cv Stella d'Oro, show visible signs of degradation just 24 h after flower opening. This is preceded by increases in ion leakage. Since losses of membrane differential permeability have been linked to reactive oxygen species (ROS), we are asking if Daylily senescence is controlled in part by reactions associated with ROS. Ion leakage is prevented by hypoxic conditions, and peroxidized lipid, lipoxygenase activity and H 2 O 2 increase even before flower opening. Treatments that stimulate cell death also prematurely increase levels of H 2 O 2 . The specific activity of protective enzymes such as catalase and ascorbate peroxidase decreases during flower senescence as do levels of ascorbic acid. Superoxide dismutase and peroxidase specific activities increase. We suggest that membrane changes leading to cell death may be induced in part by lipoxygenase activity and by ROS that are increasing because of reduced effectiveness of certain protective enzymes.
Anthony D Stead - One of the best experts on this subject based on the ideXlab platform.
-
changes in protein ubiquitination and the expression of ubiquitin encoding transcripts in Daylily petals during floral development and senescence
Physiologia Plantarum, 1994Co-Authors: S E Courtney, C C Rider, Anthony D SteadAbstract:The occurrence of ubiquitin-protein conjugates and the expression of ubiquitin genes during floral development and senescence of Hemerocallis fulva (Daylily) is reported. Daylily petal proteins were extracted at various stages of floral development and the abundance of ubiquitinated proteins determined by western blotting with affinity purified antibody to ubiquitin. Up to 100 ubiquitin conjugates in the molecular mass range 22–220 kDa were detected within the petals during bud development through to flower opening. The intensity of several of the ubiquitinated protein bands changed markedly during flower opening and/or senescence. Ubiquitinated proteins of apparent molecular masses 160, 105 and 29 kDa were intense in the Daylily bud, but rapidly disappeared after flower opening, whereas ubiquitinated proteins of apparent molecular masses 26 and 15.5 kDa increased in intensity as the flowers senesced. Treatment of Daylily buds with a 1-h pulse of cycloheximide as the flowers commenced opening prevented these changes; this treatment also delayed the onset of visual signs of senescence by 5–6 days. Analysis by northern blotting demonstrated differential expression of ubiquitin transcripts by the multi-ubiquitin gene family during floral development and senescence. Inhibition of petal senescence by treatment with cycloheximide resulted in the accumulation of several ubiquitin-encoding transcripts and the down-regulation of a 3.4 kb transcript. Overall, these studies suggest that ubiquitin is involved in the degradation of many petal proteins during floral development and senescence and that, during senescence, this selective degradation is occurring against a background of net proteolysis.
-
Changes in protein ubiquitination and the expression of ubiquitin‐encoding transcripts in Daylily petals during floral development and senescence
Physiologia Plantarum, 1994Co-Authors: S E Courtney, C C Rider, Anthony D SteadAbstract:The occurrence of ubiquitin-protein conjugates and the expression of ubiquitin genes during floral development and senescence of Hemerocallis fulva (Daylily) is reported. Daylily petal proteins were extracted at various stages of floral development and the abundance of ubiquitinated proteins determined by western blotting with affinity purified antibody to ubiquitin. Up to 100 ubiquitin conjugates in the molecular mass range 22–220 kDa were detected within the petals during bud development through to flower opening. The intensity of several of the ubiquitinated protein bands changed markedly during flower opening and/or senescence. Ubiquitinated proteins of apparent molecular masses 160, 105 and 29 kDa were intense in the Daylily bud, but rapidly disappeared after flower opening, whereas ubiquitinated proteins of apparent molecular masses 26 and 15.5 kDa increased in intensity as the flowers senesced. Treatment of Daylily buds with a 1-h pulse of cycloheximide as the flowers commenced opening prevented these changes; this treatment also delayed the onset of visual signs of senescence by 5–6 days. Analysis by northern blotting demonstrated differential expression of ubiquitin transcripts by the multi-ubiquitin gene family during floral development and senescence. Inhibition of petal senescence by treatment with cycloheximide resulted in the accumulation of several ubiquitin-encoding transcripts and the down-regulation of a 3.4 kb transcript. Overall, these studies suggest that ubiquitin is involved in the degradation of many petal proteins during floral development and senescence and that, during senescence, this selective degradation is occurring against a background of net proteolysis.
-
flower senescence in Daylily hemerocallis
Physiologia Plantarum, 1992Co-Authors: Michael Layyee, Anthony D Stead, Michael S. ReidAbstract:Daylily (Hemerocallis hybrid cv. Cradle Song) flower development and senescence was categorised into seven stages, each separated by one day. As the bud developed (Stages I to III) its fresh and dry weight increased, but during flower opening (Stages III to IV) only the fresh weight increased, reaching a maximum when the flower was fully open (Stage IV). Fresh and dry weight declined as the flower senesced (Stages V to VII), and the petal tissue became water-soaked. Flower respiration was relatively constant through Stages I to III, but during opening the CO2 production increased, then declined as the flowers senesced. Ethylene production was low throughout flower development, and there was a transient increase, up to 2.5 nl flower−1 h−1, as flowers senesced. Petal protein content per gram fresh weight decreased throughout flower development and senescence either on or off the plant. One-dimensional SDS-PAGE revealed a general gradual loss of protein bands during flower senescence and loss of some specific bands (e.g. at M, 30 000 and 40 000). Flowers, detached from the plant at Stage III, placed in deionised (DI) water for 7 h and then transferred to fresh DI water or actinomycin D (25 mg l−1), showed an increase in fresh weight up to a maximum at about 12 h after transfer, followed by a rapid decline. By 48 h the flowers had completely senesced, the tissue becoming watersoaked and free moisture appearing on the tips of collapsed petals. In contrast, senescence of flowers treated during opening with cycloheximide (1 mM) was greatly delayed, with little loss of fresh weight or reduction in flower diameter, even up to 181 h after transfer. When such flowers did finally senesce, they did not show the same pattern of senescence as seen with those in water or actinomycin D. Cycloheximide-treated flowers wilted gradually and showed no water-soaking and no free moisture at the petal tips. Cycloheximide treatment retarded the decline in protein content of the petals; and the protein population, as visualised by SDS-PAGE, was maintained for up to 204 h after transfer to cycloheximide.