Umbellularia Research Articles

Methanol-free biosynthesis of fatty acid methyl ester (FAME) in Synechocystis sp. PCC 6803

To meet the increasing global demand of biodiesel over the next decades, alternative methods for producing one of the key constituents of biodiesel (e.g. fatty acid methyl esters (FAMEs)) are needed. Algal biodiesel has been a long-term target compromised by excessive costs for harvesting and processing. In this work, we engineered cyanobacteria to convert carbon dioxide into excreted FAME, without requiring methanol as a methyl donor. To produce FAME, acyl-ACP, a product of the fatty acid biosynthesis pathway, was first converted into free fatty acid (FFA) by a thioesterase, namely ’UcFatB1 from Umbellularia californica. Next, by employing a juvenile hormone acid O-methyltransferase (DmJHAMT) from Drosophila melanogaster and S-adenosylmethionine (SAM) as a methyl donor, FFAs were converted into corresponding FAMEs. The esters were naturally secreted extracellularly, allowing simple product separation by solvent overlay as opposed to conventional algae biodiesel production where the algae biomass must first be harvested and processed for transesterification of extracted triacylglycerols (TAGs). By optimizing both the promoter and RBS elements, up to 120 mg/L of FAMEs were produced in 10 days. Quantification of key proteins and metabolites, together with constructs over-expressing SAM synthetase (MetK), indicated that ’UcFatB1, MetK, and DmJHAMT were the main factors limiting pathway flux. In order to solve the latter limitation, two reconstructed ancestral sequences of DmJHAMT were also tried, resulting in strains showing a broader methyl ester chain-length profile in comparison to the native DmJHAMT. Altogether, this work demonstrates a promising pathway for direct sunlight-driven conversion of CO2 into excreted FAME.

Management Strategies for Conservation of Tanoak in California Forests Threatened by Sudden Oak Death: A Disease-Community Feedback Modelling Approach

We use a new modelling approach to predict the cumulative impact of Phytophthora ramorum on the dynamic distribution of tanoak (Notholithocarpus densiflorus) and other tree species in coastal-Californian forest-communities. We explore the effectiveness of disease-management strategies for the conservation of tanoak at stand level. Forest resources are increasingly threatened by emerging pathogens such as P. ramorum, a generalist that kills hosts and has altered ecosystems in the USA and Europe. In coastal California, P. ramorum has the greatest impact on tanoak through leaf sporulation and lethal bole infections, but also sporulates on the common overstory-tree bay laurel (Umbellularia californica) without significant health impact. Such epidemiological differences impede host-species coexistence and challenge pathogen management. For most disease-impacted natural systems, however, empirical evidence is still insufficient to identify effective and affordable pathogen-control measures for retaining at-risk host populations. Yet, landscape-scale tree mortality requires swift actions to mitigate ecological impacts and loss of biodiversity. We apply a mathematical model of the feedback between disease and forest-community dynamics to assess the impacts of P. ramorum invasion on tanoak under stand-scale disease-management strategies by landowners aiming to retain tanoak and slow disease progression: (1) removal of inoculum through reduction of bay laurel abundance; (2) prevention of tanoak infection through chemical protection (acting epidemiologically like a vaccine); and (3) a combination strategy. The model results indicate that: (1) both bay laurel removal and tanoak protection are required to help maintain tanoak populations; (2) treatment effectiveness depends on forest composition and on threshold criteria; (3) sustainable tanoak conservation would require long-term follow-up of preventive treatments; (4) arresting basal sprouting upon tree removal may help to reduce inoculum. These findings suggest potential treatments for specific forest conditions that could be tested and implemented to reduce P. ramorum inoculum and disease and to conserve tanoak at stand level.

California Bay Watershed Education and Training Program (DOC)

California Bay Watershed Education and Training Program (DOC)

Michael Milken: The Junk Dealer

We take a closer look at the life and legacy of Micheal Milken. We discuss why Michael Milken, also know as the Junk Bond King, was not just any other King or run-of-the-mill Junk Dealer, but "The Junk Dealer". We find parallels between the three parts to any magic act and what Micheal Milken did, showing that his accomplishments were nothing short of a miracle. His compensation at that time captures to a certain extent the magnitude of the changes he brought about, the eco-system he created for businesses to flourish, the impact he had on the wider economy and also on the future growth and development of American Industry. We emphasize two of his contributions to the financial industry that have grown in importance over the years. One was the impetus given to the Private Equity industry and the use of LBOs. The second was the realization that thorough research was the key to success, financial and otherwise. Perhaps an unintended consequence of the growth in junk bonds and tailored financing was the growth of Silicon valley and technology powerhouses in the California bay area. Investors witnessed that there was a possibility for significant returns and that financial success could be had due to the risk mitigation that Milken demonstrated by investing in portfolios of so called high risk and low profile companies. We point out the current trend in many regions of the world, which is the birth of financial and technology firms and we suggest that finding innovative ways of financing could be the key to the sustained growth of these eco-systems.

Depositional model of early Cretaceous lacustrine carbonate reservoirs of the Coqueiros formation - Northern Campos Basin, southeastern Brazil

Abstract Recent discoveries of giant hydrocarbon accumulations in coquinas and other lacustrine carbonate rocks of Rift and Post-rift (pre-salt) super-sequences of the Campos and Santos Basins have motivated a series of studies focused on understanding the genesis of these unique reservoirs. An integrated petrologic-sedimentologic-stratigraphic-seismic study of the Coqueiros Formation delineated the depositional model and evolution of reworked bioclastic rocks and other associated rocks deposited on the external high in the northern Campos Basin during the transition between late-rift and sag stages. Bioclastic rudstones and grainstones with moderate to high shell reworking represent 65% of the samples described. The following pieces of evidence point to a predominantly shallow lacustrine depositional environment, dominated by storm currents: (i) presence of high-angle (>14°) longshore cross-bedded rudstones; (ii) limited occurrence of muddy sediments interbedded with thick packages of amalgamated bioclastic rudstones; (iii) great lateral continuity of rudstone deposits devoid of matrix on the structural high, consistent with processes of storm action on large expanses of shallow lakes; (iv) deposits of massive rudstones, with disorganized shells, similar to the modern coastal bioclastic deposits of California and Shark Bay. Three sets of facies association are proposed: (i) high-energy facies, composed of bioclastic rudstones and grainstones devoid of matrix deposited above the fair weather wave base (FWB); (ii) low energy facies, composed of hybrid rocks with muddy or peloidal matrix and other fine grained rocks deposited below the FWB or in protected shallow environments; (iii) an alkaline set, composed of mainly magnesian clay ooids deposited in a more alkaline composition of lake water. The evolution of the facies associations over time demonstrates an overall fall of the relative lake level. High proportion of low energy facies associated with a deeper lacustrine environment occurs at the Coqueiros Fm. base, while at the top predominate high energy facies associated with a shallow lacustrine environment, in addition to magnesian clay-rich facies associated to restricted and alkaline water bodies. Paleocurrents suggest the activity of two main wind direction (northwest and southeast) over the external high that result in clean bioclastic facies with good reservoir potential on both flanks. The knowledge of wind directions during the late Barremian and early Aptian in the northern Campos Basin is extremely important for targeting the best depositional facies for hydrocarbon accumulation in the Coqueiros Formation.

Phytophthora ramorum and Phytophthora gonapodyides Differently Colonize and Contribute to the Decomposition of Green and Senesced Umbellularia californica Leaves in a Simulated Stream Environment

Plant pathogenic as well as saprotrophic Phytophthora species are now known to inhabit forest streams and other surface waters. How they survive and function in aquatic ecosystems, however, remains largely uninvestigated. Phytophthora ramorum, an invasive pathogen in California forests, regularly occurs in forest streams, where it can colonize green leaves shed in the stream but is quickly and largely succeeded by saprotrophically competent clade 6 Phytophthora species, such as Phytophthora gonapodyides. We investigated, using controlled environment experiments, whether leaf litter quality, based on senescence, affects how P. ramorum and P. gonapodyides compete in leaf colonization and to what extent each species can contribute to leaf decomposition. We found that both Phytophthora species effectively colonized and persisted on green or yellow (senescing) bay leaves, but only P. gonapodyides could also colonize and persist on brown (fully senesced and dried) leaves. Both Phytophthora species similarly accelerated the decomposition of green leaves and yellow leaves compared with non-inoculated controls, but colonization of brown leaves by P. gonapodyides did not affect their decomposition rate.

Direct and indirect effects of forest microclimate on pathogen spillover.

Disease dynamics are governed by variation of individuals, species, and environmental conditions across space and time. In some cases, an alternate reservoir host amplifies pathogen loads and drives disease transmission to less competent hosts in a process called pathogen spillover. Spillover is frequently associated with multi-host disease systems where a single species is more tolerant of infection and more competent in pathogen transmission compared to other hosts. Pathogen spillover must be driven by biotic factors, including host and community characteristics, yet biotic factors interact with the abiotic environment (e.g., temperature) to create disease. Despite its fundamental role in disease dynamics, the influence of the abiotic environment on pathogen spillover has seldom been examined. Improving our understanding of disease processes such as pathogen spillover hinges on disentangling the effects of interrelated biotic and abiotic factors over space and time. We applied 10yr of fine-scale microclimate, disease, and tree community data in a path analysis to investigate the relative influence of biotic and abiotic factors on pathogen spillover for the emerging infectious forest disease sudden oak death (SOD). Disease transmission in SOD is primarily driven by the reservoir host California bay laurel, which supports high foliar pathogen loads that spillover onto neighboring oak trees and create lethal canker infections. The foliar pathogen load and susceptibility of oaks is expected to be sensitive to forest microclimate conditions. We found that biotic factors of pathogen load and tree diversity had relatively stronger effects on pathogen spillover compared to abiotic microclimate factors, with pathogen load increasing oak infection and tree diversity reducing oak infection. Abiotic factors still had significant effects, with greater heat exposure during summer months reducing pathogen loads and optimal pathogen conditions during the wet season increasing oak infection. Our results offer clues to possible disease dynamics under future climate change where hotter and drier or warmer and wetter conditions could have opposing effects on pathogen spillover in the SOD system. Disentangling direct and indirect effects of biotic and abiotic factors affecting disease processes can provide key insights into disease dynamics including potential avenues for reducing disease spread and predicting future epidemics.

Michael Milken: The Junk Dealer

We take a closer look at the life and legacy of Micheal Milken. We discuss why Michael Milken, also know as the Junk Bond King, was not just any other King or run-of-the-mill Junk Dealer, but ”The Junk Dealer”. We find parallels between the three parts to any magic act and what Micheal Milken did, showing that his accomplishments were nothing short of a miracle. His compensation at that time captures to a certain extent the magnitude of the changes he brought about, the eco-system he created for businesses to flourish, the impact he had on the wider economy and also on the future growth and development of American Industry. We emphasize two of his contributions to the financial industry that have grown in importance over the years. One was the impetus given to the Private Equity industry and the use of LBOs. The second was the realization that thorough research was the key to success, financial and otherwise. Perhaps an unintended consequence of the growth in junk bonds and tailored financing was the growth of Silicon valley and technology powerhouses in the California bay area. Investors witnessed that there was a possibility for significant returns and that financial success could be had due to the risk mitigation that Milken demonstrated by investing in portfolios of so called high risk and low profile companies. We point out the current trend in many regions of the world, which is the birth of financial and technology firms and we suggest that finding innovative ways of financing could be the key to the sustained growth of these eco-systems.

Double Entendre Got Bodied

I explore how two Latinx young men made use of rapping within a creative and healing afterschool hip hop space at a California Bay Area High School. I argue that they performed a calculated, strategic ambivalence. That is, just as they composed raps that made use of wordplay with double or more meanings, they constructed personhoods that quite literally embodied double or more meanings. They became the embodiment of double entendre, strategically performing, rapping and narrativizing personas that allowed them to synchronously survive the classroom and the 'hood, subverting the "White gaze" and the gaze of the streets.

Rising Tides: Assessing Habitat Vulnerability for an Endangered Salt Marsh-Dependent Species with Sea-Level Rise

Salt marsh-dependent species are vulnerable to impacts of sea-level rise (SLR). Site-specific differences in ecogeomorphic processes result in different SLR vulnerabilities. SLR impacts to Ridgway’s rail (Rallus obsoletus) of Southern California (SC) and San Francisco Bay (SF), U.S.A. could foreshadow SLR effects on other coastal endemic species. Salt marsh vulnerabilities to SLR were forecasted across 14 study sites using the Wetland Accretion Rate Model of Ecosystem Resilience, which accounts for changes in above and belowground marsh processes. Changes in suitable habitat for rail were projected with MaxEnt. Under a high (166 cm/100 yr) SLR scenario, current extent of suitable habitat is projected to increase by 34% across the combined area of 14 sites by 2050, but by 2100, total habitat suitability is projected to decrease by 83%, with six salt marshes losing over 95% of suitable habitat. Under a high SLR scenario, SF’s suitable habitat is predicted to increase by 35% at mid-century, and SC’s current suitable habitat extent will increase by 24%. However, by 2100, SF is forecasted to lose 84% of suitable habitat and SC to lose 80% of its current habitat extent. If accretion rates cannot keep pace with SLR, salt marsh obligate species are in danger of being extirpated from their habitat.

Biomass and fossil fuel combustion contributions to elemental carbon across the San Francisco Bay Area

Ambient black carbon (BC) has detrimental effects on both human health and near-term global warming. To mitigate these negative effects, there have been significant efforts to reduce emissions of BC from anthropogenic and biomass burning sources in California's Bay Area since the 1960s. Recent reductions in BC have mainly been from fossil fuel combustion sources such as diesel but additional reductions may be needed for contemporary carbon sources like biomass burning and meat cooking. In this study, PM10 (particulate matter with aerodynamic diameter of less than or equal to 10 μm) samples were collected at seven sites across the San Francisco Bay Area from November 2011 to October 2012 to create winter and non-winter composites for each site. Radiocarbon (14C) abundance and chemical mass balance (CMB) modeling were used for source apportionment of ambient elemental carbon (EC, a proxy for BC). The 14C abundance in the EC fraction was used to quantify the relative contributions of fossil carbon and contemporary carbon sources. The average biomass burning contributions are 48 ± 8% and 41 ± 5% for winter and non-winter seasons, respectively, across the Bay Area. Ambient concentrations of EC are approximately two to three times higher during the winter compared to the non-winter season, except for Cupertino. A CMB model, using bulk aerosol composition and select inorganic compounds, was used to understand the contributions of natural gas combustion, gasoline exhaust, and diesel exhaust to fossil carbon as well as the contribution of biomass burning and meat cooking to contemporary carbon. The different apportionment methods for EC (14C and CMB analysis) agree within 16 ± 12% for fraction fossil and biomass burning for both winter and non-winter seasons. The contemporary contribution to EC is much higher than estimated by current emission inventories, suggesting that the inventories may overestimate the contribution from fossil fuels, particularly diesel exhaust. The results from this study are compared to literature values from other 14C-EC or BC studies from across the world.

Transcendence Via Active Imagination: Ritual, Culture and Choreographic Offerings

This paper concentrates on the presentation of a California Bay Area Jungian focused study group for the 50 Anniversary of the American Dance Therapy Association Annual Conference. Examining the evolution of Jung’s basic psychoanalytic perceptions over the years, this panel of presenters offered an in-depth study of related topics via lecture in the morning and its amplification via authentic movement in the service of dance/movement therapy in the afternoon. The latter included embodying and transforming remnants of participants’ morning reflections, channeled via authentic movement (AM). Panelist took turns leading an AM experience related to her morning’s topic and concluding by pairing or grouping participants to demonstrate and relate his/her personal journey. The final presenter initiated a process of transcendence in which the parts are amplified into choreography. Our panelists demonstrated a clinical approach to healing in which authentic movement stokes active imagination, elevating unconscious problematic issues to conscious awareness. Overtly expressed in choreographic form, such revelations can enable integrated therapeutic closure to group dance/movement therapy sessions.

A New Class of Acetyl‐TAG Present in Seed Oils of Polygala Species

A New Class of Acetyl‐TAG Present in Seed Oils of <i>Polygala</i> Species

The alternative vote: Do changes in single-member voting systems affect descriptive representation of women and minorities?

There exist two, conflicting, conventional wisdoms in the United States about which electoral systems best provide for descriptive representation. On the one hand, single-member districts are understood to be the best way to ensure representation for ethnic and racial minority groups, at least when populations are geographically concentrated. On the other hand, it is well-established that a greater proportion of women are elected in multi-member districts in the United States, especially in state legislatures. At the intersection, minority women are not well served by single-member districts, at least using plurality or majority runoff election, but it is far from clear that multi-member districts are much better. This paper takes a fine-grained approach to electoral systems reform and descriptive representation, exploring the impacts of the reform of the electoral formula in single-member systems in the context of the adoption of the alternative vote (AV) in several California Bay Area cities. Using similar cities in the area that did not adopt AV as controls and a difference-in-differences research design, we show that reform of single-member electoral formulae can have a significant positive effect on descriptive representation.

Characterization of phenotypic variation and genome aberrations observed among Phytophthora ramorum isolates from diverse hosts

BackgroundAccumulating evidence suggests that genome plasticity allows filamentous plant pathogens to adapt to changing environments. Recently, the generalist plant pathogen Phytophthora ramorum has been documented to undergo irreversible phenotypic alterations accompanied by chromosomal aberrations when infecting trunks of mature oak trees (genus Quercus). In contrast, genomes and phenotypes of the pathogen derived from the foliage of California bay (Umbellularia californica) are usually stable. We define this phenomenon as host-induced phenotypic diversification (HIPD). P. ramorum also causes a severe foliar blight in some ornamental plants such as Rhododendron spp. and Viburnum spp., and isolates from these hosts occasionally show phenotypes resembling those from oak trunks that carry chromosomal aberrations. The aim of this study was to investigate variations in phenotypes and genomes of P. ramorum isolates from non-oak hosts and substrates to determine whether HIPD changes may be equivalent to those among isolates from oaks.ResultsWe analyzed genomes of diverse non-oak isolates including those taken from foliage of Rhododendron and other ornamental plants, as well as from natural host species, soil, and water. Isolates recovered from artificially inoculated oak logs were also examined. We identified diverse chromosomal aberrations including copy neutral loss of heterozygosity (cnLOH) and aneuploidy in isolates from non-oak hosts. Most identified aberrations in non-oak hosts were also common among oak isolates; however, trisomy, a frequent type of chromosomal aberration in oak isolates was not observed in isolates from Rhododendron.ConclusionThis work cross-examined phenotypic variation and chromosomal aberrations in P. ramorum isolates from oak and non-oak hosts and substrates. The results suggest that HIPD comparable to that occurring in oak hosts occurs in non-oak environments such as in Rhododendron leaves. Rhododendron leaves are more easily available than mature oak stems and thus can potentially serve as a model host for the investigation of HIPD, the newly described plant-pathogen interaction.

Editorial introductions

Current Opinion in Obstetrics and Gynecology was launched in 1989. It is one of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The field of obstetrics and gynecology is divided into nine sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Journal's Section Editors for this issue. SECTION EDITORS Deirdre J. LyellDeirdre J. LyellDr Lyell is a Professor of Obstetrics and Gynecology in the Division of Maternal-Fetal Medicine at Stanford University, where she serves as the Associate Division Director, Director of the Program in Placental Disorders, and Program Director of the Maternal-Fetal Medicine Fellowship. From 2013–2016 she served as an alternate P.I. to the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Unit (MFMU) Network. In 2010 she formed the Program in Placental Disorders at Stanford, a multidisciplinary patient care and research program for women with placenta accreta and cofounded a Placenta Accreta Special Interest Group that meets annually at the Society for Maternal-Fetal Medicine meeting. Dr Lyell has previously designed and executed multicenter, randomized clinical trials, including “Magnesium sulfate versus nifedipine for tocolysis of preterm labor: a randomized, controlled trial” and “Maintenance nifedipine tocolysis compared with placebo: a randomized controlled trial” which won the 2009 A.C.O.G. Roy M. Pitkin Award “for one of four most outstanding manuscripts in Obstetrics & Gynecology in the previous year.” She is a member of the Child Health Research Institute at Stanford, the March of Dimes Prematurity Research Center at Stanford, and conducts a wide range of research in clinical obstetrics. Dr Lyell earned a Bachelors of Arts and Sciences in History and Biology from Stanford University and a Medical Degree from the George Washington University School of Medicine. She completed residency training in Obstetrics and Gynecology at Harvard (Brigham and Women's and Massachusetts General Hospitals), and fellowship in Maternal-Fetal Medicine at Stanford University. She is certified by the American Board of Obstetrics + Gynecology in Obstetrics and Gynecology and Maternal-Fetal Medicine. Martha RodeMartha RodeDr Martha Rode received her bachelor degree in Biology at Harvard University before attending medical school at the University of California, Los Angeles. She then completed residency and a Maternal-Fetal Medicine fellowship at the University of Pennsylvania in Philadelphia. She has since worked in both academic and hospital-based practices on both the East coast and Northern California Bay Area. She is currently a Clinical Associate Professor at Stanford Medical School, serving as the Medical Director of the Perinatal Diagnostic Center in Santa Cruz. Her interests include perinatal diagnosis and high risk obstetrics as well as community physician outreach and continued education. Mark BoddyMark BoddyDr Mark Boddy received his bachelor degree from Georgia State University. He received his medical degree from the Medical College of Georgia prior to completing a residency in obstetrics and gynecology at Atlanta Medical Center. He subsequently completed a fellowship in Maternal Fetal Medicine at The George Washington University School of Medicine. He practiced for 17 years in a hospital based setting while also serving as a Regional Perinatal Director for the State of Georgia. Currently, Dr Boddy is an Associate Clinical Professor at Stanford University School of Medicine and the Medical Director of the Stanford Children's Healthcare Perinatal Diagnostic Center in Salinas, California. His interests include prenatal diagnosis, improving quality of care and patient safety. Jane ChuehJane ChuehDr Jane Chueh received her Bachelor Degrees in Biology and Humanities at Stanford University. She attended medical school at University of California San Diego, completed her residency at University of Washington and her fellowships in Maternal Fetal Medicine and Clinical Genetics at University of California San Francisco. She has worked in both academic and hospital-based practices in the Northern California Bay Area. Currently she is a Clinical Professor at Stanford Medical School, serving as the Director of Prenatal Diagnosis and Therapy at Stanford Children's Health. She enjoys practicing prenatal diagnosis and high risk obstetrics, collaborating in research projects related to ultrasound and simulation teaching, and mentoring Stanford undergraduates and medical students.

Application of GC/Q-ToF Combined with Advanced Data Mining and Chemometric Tools in the Characterization and Quality Control of Bay Leaves.

Correct identification of the true bay leaf (Laurus nobilis) and its substitutes is important not only for the quality control of the products, but also for the safety of the consumers. L.nobilis is often substituted or confused with other species, such as Cinnamomum tamala, Pimenta racemosa, Syzygium polyanthum, and Umbellularia californica. In the present study, the potential of gas chromatography combined with quadrupole time-of-flight mass spectrometry for the profiling of various bay leaf products was evaluated for the first time. Thirty-nine authenticated samples representing the true bay leaf and the four commonly substituted species were analyzed. An automatic feature extraction algorithm was applied for data mining and pretreatment in order to identify the most characteristic compounds representing different bay leaf groups. This set of data was employed to construct a sample class prediction model based on stepwise reduction of data dimensionality followed by principal component analysis and partial least squares discriminant analysis. The statistical model, with demonstrated excellent accuracies in recognition and prediction abilities, enabled the correct classification of commercial samples including complex mixtures and essential oils. In addition, in-house developed personal compound database and library with retention time locking offered the advantage of combining retention time matching with accurate mass matching, resulting in high confidence of compound identification for each bay leaf subgroup. At least three marker compounds were identified for each bay leaf species that could be used to discriminate among them.

Distinct Trophic Specializations Affect How Phytophthora ramorum and Clade 6 Phytophthora spp. Colonize and Persist on Umbellularia californica Leaves in Streams.

Phytophthora spp. are regularly recovered from streams but their ecology in aquatic environments is not well understood. Phytophthora ramorum, invasive in California forests, persists in streams at times when sporulation in the canopy is absent, suggesting that it reproduces in the water. Streams are also inhabited by resident, clade 6 Phytophthora spp., believed to be primarily saprotrophic. We conducted experiments to determine whether differences of trophic specialization exist between these two taxa, and investigated how this may affect their survival and competition on stream leaf litter. P. ramorum effectively colonized fresh (live) rhododendron leaves but not those killed by freezing or drying, whereas clade 6 species colonized all leaf types. However, both taxa were recovered from naturally occurring California bay leaf litter in streams. In stream experiments, P. ramorum colonized bay leaves rapidly at the onset; however, colonization was quickly succeeded by clade 6 species. Nevertheless, both taxa persisted in leaves over 16 weeks. Our results confirm that clade 6 Phytophthora spp. are competent saprotrophs and, though P. ramorum could not colonize dead tissue, early colonization of suitable litter allowed it to survive at a low level in decomposing leaves.

Structural Insight into Acyl-ACP Thioesterase toward Substrate Specificity Design.

Acyl-ACP thioesterase (TE) catalyzes the hydrolysis of thioester bonds during type II fatty acid synthesis and directly determines fatty acid chain length. Most TEs are responsible for recognition of 16:0 and 18:1 substrates, while specific TEs interrupt acyl-ACP elongation at C8-C14. However, the acyl selection mechanism of TE has not been thoroughly elucidated to date. In this study, the crystal structure of the C12-specific thioesterase FatB from Umbellularia californica, which consists of two independent hotdog domains, was determined. An uncanonical Asp-His-Glu catalytic network was identified on the C-terminal hotdog domain, whereas the substrate binding pocket was determined to be on the N-terminal hotdog domain. Moreover, we elucidated UcFatB's substrate selection mechanism, which is accommodated by several unconservative amino acids on the β5, β2, and β4 sheets and enclosed by T137 on the α1 helix. On this basis, the C12-specific TE was rationally redesigned toward C14 selectivity by tuning the substrate binding pocket capacity. The T137G mutant demonstrated comparative relative activity on C14 substrates compared to C12 substrates in vitro. Furthermore, the reconstructed UcFatB_T137G achieved C14 fatty acid content up to 40% in contrast to 10% C14 from the wild type in engineered E. coli cells. The unraveled substrate selection mechanism of TE provides a new strategy for tailoring fatty acid synthesis.

Interspecific interactions between the Sudden Oak Death pathogen Phytophthora ramorum and two sympatric Phytophthora species in varying ecological conditions

Abstract Even when introduced invasive pathogens lack their natural predators or competitors, they must still interact with other organisms in their introduced range. Sudden Oak Death (SOD), caused by Phytophthora ramorum (Oomycota), is an introduced disease causing large-scale tree mortality. Two additional Phytophthora species, Phytophthora nemorosa and Phytophthora pseudosyringae, cause significantly lower oak mortality, yet they also commonly colonize leaves of Umbellularia californica, the major transmissive host of SOD in California. We combined field surveys and inoculation experiments to understand disease prevalence dynamics and competitive interactions among these pathogen species. Despite the broader geographic distribution of P. nemorosa with respect to that of P. ramorum, our results suggest that P. nemorosa exhibits a narrower ecological amplitude and, in any given region, occupies fewer sites than P. ramorum. Our results additionally suggest that, perhaps due to priority effects, P. nemorosa can persist at levels comparable to those of P. ramorum in ecologically suitable plots when climate favors P. ramorum dormancy. However, P. ramorum prevalence increases to levels higher than those of the competing species when abundant rainfall triggers its sporulation. Understanding the determinants and outcomes of competition between these species has important implications for understanding the epidemiology and possible control strategies for Sudden Oak Death.