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David M Rizzo - One of the best experts on this subject based on the ideXlab platform.
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Five years of monitoring infection and mortality in redwood tanoak forests
2020Co-Authors: Richard C. Cobb, Shannon C. Lynch, Ross K. Meentemeyer, David M RizzoAbstract:Rates of disease incidence and tree mortality in redwood-tanoak forests were determined by repeated sampling across a system of 120 plots at five long-term research sites from 2001 through 2006. Plots were located within the known geographic area of Phytophthora ramorum in California, ranging from Monterey to Sonoma counties. All overstory species were monitored, but analysis was restricted to three important host species: California bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens). Infection in bay laurel and tanoak varied among years and plots suggesting weather patterns and abundance of susceptible species are important determinants of disease dynamics. Disease incidence was greatest in bay laurel followed by tanoak and redwood. Tanoak stems greater than 10 cm diameter at breast height were killed more frequently than smaller trees. Further analysis will use statistical modeling and validation to evaluate the role of vegetation structure and climate variation on rates of infection and mortality of tanoak. By proving baseline rates of infection and mortality across structurally heterogeneous stands, this effort will help in the design of stand-level management strategies and identification of local areas where control strategies will be most effective.
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Phytophthora ramorum and Sudden Oak Death in California: II. Transmission and Survival 1
2020Co-Authors: Jennifer M Davidson, Matteo Garbelotto, David M Rizzo, S. A. Tjosvold, Garey SlaughterAbstract:The newly discovered Phytophthora ramorum canker disease of oak (Sudden Oak Death Syndrome) threatens millions of acres of California woodlands where coast live oak (Quercus agrifolia), tanoak (Lithocarpus densiflorus), or black oak (Quercus kelloggii) are dominant species. An important step in controlling this disease involves understanding how it is spread. The presence of diseased oaks at all elevations on hillsides and the above-ground nature of the disease suggest wind-blown rain or rain splash as a common mechanism for movement of spores. Although viable spores have yet to be found on infected oak tissue, other hosts may serve as sources of rain-dispersed inoculum. In the laboratory, abundant sporangia form on moistened leaves of infected bay (Umbellularia californica) and Rhododendron spp. within 72 hours. These sporangia break off and easily disperse in water. Chlamydospores were also observed on the surface of moistened bay leaves. Consistent with these results, P. ramorum has been recovered from rain, soil, litter, and stream water from woodlands with infected oak and bay trees. Spores of P. ramorum do not survive drying, but in moist conditions can survive for at least one month.
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Effects of environmental variables on the survival of Phytophthora ramorum in bay laurel leaves
2020Co-Authors: M. V. Dileo, Richard M Bostock, David M RizzoAbstract:Bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) is the primary reservoir host of Phytophthora ramorum Werres, De Cock & Man n?t Veld in coastal California woodlands. Non-lethal foliar lesions on bay laurel trees support the majority of pathogen sporulation during the winter et season and appear to provide the primary means of surviving through California?s arid Mediterranean summers. Previous experiments have shown that the proportion of symptomatic bay leaves from which P. ramorum can be successfully isolated decreases during the summer. In addition, isolation of P. ramorum from bay laurel leaves was less at the end of the dry season within mixed evergreen forests when compared to redwoodtanoak forests. These experiments also suggested a positive correlation between bay laurel stem water potential and summer isolation frequency from leaves. A more thorough understanding of the environmental and physiological constraints on the summer survival of P. ramorum will assist in the development of SOD risk assessments.
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Summer survival of Phytophthora ramorum in California bay laurel leaves
2020Co-Authors: E. J. Fichtner, David M Rizzo, Jennifer M Davidson, Shannon C. Lynch, Gerri R. Buckles, Jennifer ParkerAbstract:Sudden oak death manifests as non-lethal foliar lesions on bay laurel (Umbellularia californica), which support sporulation and survival of Phytophthora ramorum in forest ecosystems. Infected bay laurel leaves are more likely to abscise than uninfected leaves, resulting in an accumulation of inoculum at the forest floor. The pathogen survives the dry summers in a proportion of attached bay leaves, but the histology of colonization during the survival phase and the propagules responsible for survival are unknown. This study focuses on summer pathogen survival associated with bay laurel in redwood-tanoak and mixed evergreen forests with specific objectives including: i) detection of P. ramorum in leaf litter and soils throughout summer, ii) quantification of chlamydospores on and within attached symptomatic leaves, and in fresh and aged litter, iii) determination f chlamydospore germination, and, iv) assessment of pathogen survival within litter and canopy leaves, addressing the location of viable inoculum within foliar tissues.
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Suppression of Phytophthora ramorum infestations through silvicultural treatment in California's north coast
2020Co-Authors: Yana Valachovic, David M Rizzo, Brendan D. Twieg, Richard Cobb, Radoslaw GlebockiAbstract:In 2006, three forested sites infested with Phytophthora ramorum in Humboldt County, California were subjected to different combinations of treatments designed to reduce inoculum and control spread. One treatment, consisting of removal of all California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) trees, was applied at all three sites, and other treatments were applied as case studies at single sites. The sites were monitored for 6 years. Results to date suggest that the treatments that involved the cutting of California bay laurel and tanoak substantially reduced P. ramorum inoculum levels. However, in treatment areas where scattered California bay laurel trees were inadvertently missed because of a restricted time window for operations, a relatively minor component of residual California bay laurel trees may have become infected following treatment and/or harbored prior cryptic infections and subsequently spread P. ramorum to regenerating California bay laurel and tanoak. The data suggest that pathogen reestablishment in these sites was driven by both incomplete treatment application and spread from adjacent, untreated stands.
Maelor H Davies - One of the best experts on this subject based on the ideXlab platform.
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developmental induction purification and further characterization of 12 0 acp thioesterase from immature cotyledons of Umbellularia californica
Archives of Biochemistry and Biophysics, 1991Co-Authors: Maelor H Davies, Lana Anderson, Deborah J HawkinsAbstract:Abstract The fatty acyl content of developing cotyledons of Umbellularia californica (California Bay) changes from a long-chain composition to a predominance of 10:0 and 12:0 in just 4–5 days at the beginning of an approximately 100-day period of medium-chain deposition. This striking change occurs at the earliest appearance of 12: 0-acyl-carrier protein (ACP) thioesterase activity. The coincidence of these rapid events is consistent with the hypothesis that the enzyme plays a major role in mediumchain biosynthesis. The 12:0-ACP thioesterase has been substantially purified; enzyme activity consistently comigrates in chromatographic and electrophoretic systems with a protein or pair of proteins having an apparent molecular weight of approximately 34 kDa. A native molecular weight of approximately 42 kDa has been estimated by gel filtration chromatography, suggesting that the enzyme is a monomer. Affinity chromatography on immobilized ACP is a critical step in the purification procedure, and resolves the 12:0-ACP and 18:1-ACP thioesterases sufficiently to confirm that the mediumchain enzyme has negligible action on 18:1-ACP.
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a specific acyl acp thioesterase implicated in medium chain fatty acid production in immature cotyledons of Umbellularia californica
Archives of Biochemistry and Biophysics, 1991Co-Authors: Michael R Pollard, Deborah J Hawkins, Lana Anderson, Maelor H DaviesAbstract:Abstract Umbellularia californica (California Bay) seeds accumulate 10:0 and 12:0 as principal reserve fatty acyl groups. An in vitro fatty acid synthesis system from the developing cotyledons produces chiefly 10:0 and 12:0, in approximately the same proportions as the intact tissue. The kinetics of acyl thioester and free fatty acid formation in this system suggest that a medium-chain specific acyl-acyl-carrier protein (ACP) hydrolysis mechanism is responsible for the preponderance of medium-chain products. A crude extract of the developing cotyledons exhibits hydrolytic activity toward acyl-ACPs, with marked preference for 12:0-ACP and 18:1-ACP in the test series 6:0, 8:0, 10:0, 11:0, 12:0, 14:0, 16:0, and 18:1-ACPs. Partial purification of the 12:0-ACP hydrolytic activity has resulted in its separation from the 18:1-ACP hydrolase(s) and the 12:0-coenzyme A hydrolase(s) that are also present, thereby demonstrating its specificity for the 12-carbon acyl chain length and the ACP derivative. During cotyledon development, as the proportion of medium-chain to other fatty acyl groups increases, the extractable yield of this activity also increases substantially. Collectively these results suggest a role for this 12-ACP thioesterase in mediumchain production in vivo .
Hui Wu - One of the best experts on this subject based on the ideXlab platform.
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Engineering Escherichia coli for odd straight medium chain free fatty acid production
Applied Microbiology and Biotechnology, 2014Co-Authors: Hui WuAbstract:Microbial biosynthesis of free fatty acids (FFAs) can be achieved by introducing an acyl–acyl carrier protein thioesterase gene into Escherichia coli . The engineered E. coli usually produced even chain FFAs. In this study, propionyl-CoA synthetase ( prpE ) from Salmonella enterica was overexpressed in two efficient even chain FFAs producers, ML103 (pXZM12) carrying the acyl-ACP thioesterase gene from Umbellularia californica and ML103 (pXZ18) carrying the acyl-ACP thioesterase gene from Ricinus communis combined with supplement of extracellular propionate. With these metabolically engineered E. coli , the odd straight chain FFAs, undecanoic acid (C11:0), tridecanoic acid (C13:0), and pentadecanoic acid (C15:0) were produced from glucose and propionate. The highest total odd straight chain FFAs produced by ML103 (pXZM12, pBAD- prpE ) reached 276 mg/l with a ratio of 23.43 % of the total FFAs. In ML103 (pXZ18, pBAD- prpE ), the highest total odd straight chain FFAs accumulated to 297 mg/l, and the ratio reached 17.68 % of the total FFAs. Due to the different substrate specificity of the acyl-ACP thioesterases, the major odd straight chain FFA components of ML103 (pXZM12, pBAD- prpE ) were undecanoic acid and tridecanoic acid, while the ML103 (pXZ18, pBAD- prpE ) preferred pentadecanoic acid.
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Efficient Odd Straight Medium Chain Free Fatty Acid Production by Metabolically Engineered Escherichia Coli
Biotechnology and Bioengineering, 2014Co-Authors: Hui WuAbstract:Free fatty acids (FFAs) can be used as precursors for the production of biofuels or chemicals. Different composition of FFAs will be useful for further modification of the biofuel/biochemical quality. Microbial biosynthesis of even chain FFAs can be achieved by introducing an acyl-acyl carrier protein thioesterase gene into E. coli. In this study, odd straight medium chain FFAs production was investigated by using metabolic engineered E. coli carrying acyl-ACP thioesterase (TE, Ricinus communis), propionyl-CoA synthase (Salmonella enterica), and b-ketoacyl-acyl carrier protein synthase III (four different sources) with supplement of extracellular propionate. By using these metabolically engi- neered E. coli, significant quantity of C13 and C15 odd straight-chain FFAs could be produced from glucose and propionate. The highest concentration of total odd straight chain FFAs attained was 1205mg/L by the strain HWK201 (pXZ18,pBHE2),and85%oftheoddstraightchainFFAswas C15. However, the highest percentage of odd straight chain FFAswas achievedby thestrainHWK201 (pXZ18, pBHE3) of 83.2% at 48h. This strategy was also applied successfully in strains carrying different TE, such as the medium length acyl- ACP thioesterase gene from Umbellularia californica. C11 and C13 became the major odd straight-chain FFAs. Biotechnol. Bioeng. 2014;9999: 1-11. 2014 Wiley Periodicals, Inc.
Deborah J Hawkins - One of the best experts on this subject based on the ideXlab platform.
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developmental induction purification and further characterization of 12 0 acp thioesterase from immature cotyledons of Umbellularia californica
Archives of Biochemistry and Biophysics, 1991Co-Authors: Maelor H Davies, Lana Anderson, Deborah J HawkinsAbstract:Abstract The fatty acyl content of developing cotyledons of Umbellularia californica (California Bay) changes from a long-chain composition to a predominance of 10:0 and 12:0 in just 4–5 days at the beginning of an approximately 100-day period of medium-chain deposition. This striking change occurs at the earliest appearance of 12: 0-acyl-carrier protein (ACP) thioesterase activity. The coincidence of these rapid events is consistent with the hypothesis that the enzyme plays a major role in mediumchain biosynthesis. The 12:0-ACP thioesterase has been substantially purified; enzyme activity consistently comigrates in chromatographic and electrophoretic systems with a protein or pair of proteins having an apparent molecular weight of approximately 34 kDa. A native molecular weight of approximately 42 kDa has been estimated by gel filtration chromatography, suggesting that the enzyme is a monomer. Affinity chromatography on immobilized ACP is a critical step in the purification procedure, and resolves the 12:0-ACP and 18:1-ACP thioesterases sufficiently to confirm that the mediumchain enzyme has negligible action on 18:1-ACP.
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a specific acyl acp thioesterase implicated in medium chain fatty acid production in immature cotyledons of Umbellularia californica
Archives of Biochemistry and Biophysics, 1991Co-Authors: Michael R Pollard, Deborah J Hawkins, Lana Anderson, Maelor H DaviesAbstract:Abstract Umbellularia californica (California Bay) seeds accumulate 10:0 and 12:0 as principal reserve fatty acyl groups. An in vitro fatty acid synthesis system from the developing cotyledons produces chiefly 10:0 and 12:0, in approximately the same proportions as the intact tissue. The kinetics of acyl thioester and free fatty acid formation in this system suggest that a medium-chain specific acyl-acyl-carrier protein (ACP) hydrolysis mechanism is responsible for the preponderance of medium-chain products. A crude extract of the developing cotyledons exhibits hydrolytic activity toward acyl-ACPs, with marked preference for 12:0-ACP and 18:1-ACP in the test series 6:0, 8:0, 10:0, 11:0, 12:0, 14:0, 16:0, and 18:1-ACPs. Partial purification of the 12:0-ACP hydrolytic activity has resulted in its separation from the 18:1-ACP hydrolase(s) and the 12:0-coenzyme A hydrolase(s) that are also present, thereby demonstrating its specificity for the 12-carbon acyl chain length and the ACP derivative. During cotyledon development, as the proportion of medium-chain to other fatty acyl groups increases, the extractable yield of this activity also increases substantially. Collectively these results suggest a role for this 12-ACP thioesterase in mediumchain production in vivo .
John B. Ohlrogge - One of the best experts on this subject based on the ideXlab platform.
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Medium-chain fatty acid biosynthesis and utilization in Brassica napus plants expressing lauroyl-acyl carrier protein thioesterase
Planta, 1996Co-Authors: Victoria S. Eccleston, Toni A. Voelker, Ann M. Cranmer, John B. OhlroggeAbstract:We have examined production of mediumchain fatty acids by Brassica napus L. plants transformed with a California bay ( Umbellularia californica ) medium-chain acyl-acyl carrier protein (ACP) thioesterase ( UcFatB1 ) cDNA under the control of the constitutive cauliflower mosaic virus 35S promoter. These plants were found to accumulate medium-chain fatty acids in seeds but not in leaves or roots. Assay of thioesterase activity in extracts of leaves indicated that lauroyl-ACP thioesterase activity is comparable to oleoyl-ACP thioesterase (EC 3.1.2.14) activity in transformant leaves. Furthermore, leaf lauroyl-ACP thioesterase activity was in excess of that which produced a significant increase in the amount of laurate (12:0) in seed. Studies in which isolated chloroplasts were ^14C-labelled were used to evaluate whether medium-chain fatty acids were produced in transformed leaves. Up to 34% of the fatty acids synthesized in vitro by isolated chloroplasts were 12:0. These results demonstrate that the normally seed-localized lauroyl-ACP thioesterase can be expressed in active form in leaves, imported into chloroplasts and can access acyl-ACP intermediates of leaf de-novo fatty acid synthesis. The most likely explanation for the lack of accumulation of 12:0 in transformed leaves is its rapid degradation by β-oxidation. In support of this hypothesis, isocitrate lyase (EC 4.1.3.1) activity was found to be significantly increased in plants transformed with 35S- UcFatB1 .