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Open Access Publications from the University of California

Open Access Policy Deposits

This series is automatically populated with publications deposited by UC Davis Department of Plant Pathology researchers in accordance with the University of California’s open access policies. For more information see Open Access Policy Deposits and the UC Publication Management System.

Cover page of Model training periods impact estimation of COVID-19 incidence from wastewater viral loads.

Model training periods impact estimation of COVID-19 incidence from wastewater viral loads.

(2023)

Wastewater-based epidemiology (WBE) has been deployed broadly as an early warning tool for emerging COVID-19 outbreaks. WBE can inform targeted interventions and identify communities with high transmission, enabling quick and effective responses. As the wastewater (WW) becomes an increasingly important indicator for COVID-19 transmission, more robust methods and metrics are needed to guide public health decision-making. This research aimed to develop and implement a mathematical framework to infer incident cases of COVID-19 from SARS-CoV-2 levels measured in WW. We propose a classification scheme to assess the adequacy of model training periods based on clinical testing rates and assess the sensitivity of model predictions to training periods. A testing period is classified as adequate when the rate of change in testing is greater than the rate of change in cases. We present a Bayesian deconvolution and linear regression model to estimate COVID-19 cases from WW data. The effective reproductive number is estimated from reconstructed cases using WW. The proposed modeling framework was applied to three Northern California communities served by distinct WW treatment plants. The results showed that training periods with adequate testing are essential to provide accurate projections of COVID-19 incidence.

Cover page of Monitoring for a new <i>I3</i> resistance gene-breaking race of <i>F. oxysporum</i> f. sp. <i>lycopersici</i> (Fusarium wilt) in California processing tomatoes following recent widespread adoption of resistant (F3) cultivars: Challenges with race 3 and 4 differentiation methods.

Monitoring for a new I3 resistance gene-breaking race of F. oxysporum f. sp. lycopersici (Fusarium wilt) in California processing tomatoes following recent widespread adoption of resistant (F3) cultivars: Challenges with race 3 and 4 differentiation methods.

(2023)

Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici (Fol), causes losses in tomato production worldwide, with major impacts on Californian tomato processing. Single-gene resistance is the primary management tool, but its efficacy has been compromised following the emergence of two successive resistance-breaking races, which, in California, emerged within 12 years of resistance deployment. Fol race 3-resistant (F3) processing tomato cultivars (containing the I3 resistance gene) were deployed in the state starting in approximately 2009. The emergence of a new resistance-breaking race (which would be called race 4) is imminent, and early detection will be critical to delay the spread while new resistance is sought. The detection of Fol race 4 is challenged by the lack of validated, rapid, and accurate diagnostic tools. In evaluating in planta phenotyping methods, this study found that rapid seedling phenotyping is not reliable and generates false positives for nonpathogens. Longer (10 weeks) mature plant assays are the most reliable, but may not be sufficiently timely. As an additional challenge, based on field and greenhouse studies, Fol race 3 can cause symptoms in resistant F3 cultivars at frequencies greater (30%) than expected for off-types (<2%). We developed a three-F3 cultivar in planta assay to overcome the challenges this posed to differentiating Fol race 3 and Fol race 4. Using the assay, we determined that all putative resistance-breaking cases were Fol race 3; Fol race 4 was not detected in these early survey efforts. These results highlight the need for developing rapid Fol race 4 detection tools and a better understanding of the factors underlying inconsistent I3 gene expression in Fol race 3.

Cover page of Engineering sorghum for higher 4-hydroxybenzoic acid content.

Engineering sorghum for higher 4-hydroxybenzoic acid content.

(2022)

Engineering bioenergy crops to accumulate coproducts in planta can increase the value of lignocellulosic biomass and enable a sustainable bioeconomy. In this study, we engineered sorghum with a bacterial gene encoding a chorismate pyruvate-lyase (ubiC) to reroute the plastidial pool of chorismate from the shikimate pathway into the valuable compound 4-hydroxybenzoic acid (4-HBA). A gene encoding a feedback-resistant version of 3-deoxy-d-arabino-heptulonate-7-phosphate synthase (aroG) was also introduced in an attempt to increase the carbon flux through the shikimate pathway. At the full maturity and senesced stage, two independent lines that co-express ubiC and aroG produced 1.5 and 1.7 dw% of 4-HBA in biomass, which represents 36- and 40-fold increases compared to the titer measured in wildtype. The two transgenic lines showed no obvious phenotypes, growth defects, nor alteration of cell wall polysaccharide content when cultivated under controlled conditions. In the field, when harvested before grain maturity, transgenic lines contained 0.8 and 1.2 dw% of 4-HBA, which represent economically relevant titers based on recent technoeconomic analysis. Only a slight reduction (11-15%) in biomass yield was observed in transgenics grown under natural environment. This work provides the first metabolic engineering steps toward 4-HBA overproduction in the bioenergy crop sorghum to improve the economics of biorefineries by accumulating a value-added coproduct that can be recovered from biomass and provide an additional revenue stream.

Cover page of Diversity in the soil virosphere: to infinity and beyond?

Diversity in the soil virosphere: to infinity and beyond?

(2022)

Viruses are key members of Earth's microbiomes, shaping microbial community composition and metabolism. Here, we describe recent advances in 'soil viromics', that is, virus-focused metagenome and metatranscriptome analyses that offer unprecedented windows into the soil virosphere. Given the emerging picture of high soil viral activity, diversity, and dynamics over short spatiotemporal scales, we then outline key eco-evolutionary processes that we hypothesize are the major diversity drivers for soil viruses. We argue that a community effort is needed to establish a 'global soil virosphere atlas' that can be used to address the roles of viruses in soil microbiomes and terrestrial biogeochemical cycles across spatiotemporal scales.

Cover page of The secretome of Verticillium dahliae in collusion with plant defence responses modulates Verticillium wilt symptoms.

The secretome of Verticillium dahliae in collusion with plant defence responses modulates Verticillium wilt symptoms.

(2022)

Verticillium dahliae is a notorious soil-borne pathogen that enters hosts through the roots and proliferates in the plant water-conducting elements to cause Verticillium wilt. Historically, Verticillium wilt symptoms have been explained by vascular occlusion, due to the accumulation of mycelia and plant biomacromolecule aggregation, and also by phytotoxicity caused by pathogen-secreted toxins. Beyond the direct cytotoxicity of some members of the secretome, this review systematically discusses the roles of the V. dahliae secretome in vascular occlusion, including the deposition of polysaccharides as an outcome of plant cell wall destruction, the accumulation of fungal mycelia, and modulation of plant defence responses. By modulating plant defences and hormone levels, the secretome manipulates the vascular environment to induce Verticillium wilt. Thus, the secretome of V. dahliae colludes with plant defence responses to modulate Verticillium wilt symptoms, and thereby bridges the historical concepts of both toxin production by the pathogen and vascular occlusion as the cause of wilting symptoms.

Cover page of Lessons from Cost-Effectiveness Analysis of Smoking Cessation Programs for Cancer Patients.

Lessons from Cost-Effectiveness Analysis of Smoking Cessation Programs for Cancer Patients.

(2022)

Background

Smoking among patients diagnosed with cancer poses important health and financial challenges including reduced effectiveness of expensive cancer therapies. This study explores the value of smoking cessation programs (SCPs) for patients already diagnosed with cancer. It also identifies conditions under which SPCs may be wise investments.

Methods

Using a simplified decision analytic model combined with insights from a literature review, we explored the cost-effectiveness of SCPs.

Results

The findings provide insights about the potential impact of cessation probabilities among cancer patients in SCPs and the potential impact of SCPs on cancer patients' lives.

Conclusion

The evidence suggests that there is good reason to believe that SCPs are an economically attractive way to improve outcomes for cancer patients when SCPs are offered in conjunction with standard cancer care.

Cover page of Rapid Review of Real-World Cost-Effectiveness Analyses of Cancer Interventions in Canada.

Rapid Review of Real-World Cost-Effectiveness Analyses of Cancer Interventions in Canada.

(2022)

Cost-effectiveness analysis (CE Analysis) provides evidence about the incremental gains in patient outcomes costs from new treatments and interventions in cancer care. The utilization of "real-world" data allows these analyses to better reflect differences in costs and effects for actual patient populations with comorbidities and a range of ages as opposed to randomized controlled trials, which use a restricted population. This rapid review was done through PubMed and Google Scholar in July 2022. Relevant articles were summarized and data extracted to summarize changes in costs (in 2022 CAD) and effectiveness in cancer care once funded by the Canadian government payer system. We conducted statistical analyses to examine the differences between means and medians of costs, effects, and incremental cost effectiveness ratios (ICERs). Twenty-two studies were selected for review. Of those, the majority performed a CE Analysis on cancer drugs. Real-world cancer drug studies had significantly higher costs and effects than non-drug therapies. Studies that utilized a model to project longer time-horizons saw significantly smaller ICER values for the treatments they examined. Further, differences in drug costs increased over time. This review highlights the importance of performing real-world CE Analysis on cancer treatments to better understand their costs and impacts on a general patient population.

Cover page of A secreted ribonuclease effector from Verticillium dahliae localizes in the plant nucleus to modulate host immunity.

A secreted ribonuclease effector from Verticillium dahliae localizes in the plant nucleus to modulate host immunity.

(2022)

The arms race between fungal pathogens and plant hosts involves recognition of fungal effectors to induce host immunity. Although various fungal effectors have been identified, the effector functions of ribonucleases are largely unknown. Herein, we identified a ribonuclease secreted by Verticillium dahliae (VdRTX1) that translocates into the plant nucleus to modulate immunity. The activity of VdRTX1 causes hypersensitive response (HR)-related cell death in Nicotiana benthamiana and cotton. VdRTX1 possesses a signal peptide but is unlikely to be an apoplastic effector because its nuclear localization in the plant is necessary for cell death induction. Knockout of VdRTX1 significantly enhanced V. dahliae virulence on tobacco while V. dahliae employs the known suppressor VdCBM1 to escape the immunity induced by VdRTX1. VdRTX1 homologs are widely distributed in fungi but transient expression of 24 homologs from other fungi did not yield cell death induction, suggesting that this function is specific to the VdRTX1 in V. dahliae. Expression of site-directed mutants of VdRTX1 in N. benthamiana leaves revealed conserved ligand-binding sites that are important for VdRTX1 function in inducing cell death. Thus, VdRTX1 functions as a unique HR-inducing effector in V. dahliae that contributes to the activation of plant immunity.

Cover page of Sulfotyrosine residues: Interaction specificity determinants for extracellular protein-protein interactions.

Sulfotyrosine residues: Interaction specificity determinants for extracellular protein-protein interactions.

(2022)

Tyrosine sulfation, a post-translational modification, can determine and often enhance protein-protein interaction specificity. Sulfotyrosyl residues (sTyrs) are formed by the enzyme tyrosyl-protein sulfotransferase during protein maturation in the Golgi apparatus and most often occur singly or as a cluster within a six-residue span. With both negative charge and aromatic character, sTyr facilitates numerous atomic contacts as visualized in binding interface structural models, thus there is no discernible binding site consensus. Found exclusively in secreted proteins, in this review, we discuss the four broad sequence contexts in which sTyr has been observed: first, a solitary sTyr has been shown to be critical for diverse high-affinity interactions, such as between peptide hormones and their receptors, in both plants and animals. Second, sTyr clusters within structurally flexible anionic segments are essential for a variety of cellular processes, including coreceptor binding to the HIV-1 envelope spike protein during virus entry, chemokine interactions with receptors, and leukocyte rolling cell adhesion. Third, a subcategory of sTyr clusters is found in conserved acidic sequences termed hirudin-like motifs that enable proteins to interact with thrombin; consequently, many proven and potential therapeutic proteins derived from blood-consuming invertebrates depend on sTyrs for their activity. Finally, several proteins that interact with collagen or similar proteins contain one or more sTyrs within an acidic residue array. Refined methods to direct sTyr incorporation in peptides synthesized both in vitro and in vivo, together with continued advances in mass spectrometry and affinity detection, promise to accelerate discoveries of sTyr occurrence and function.

Cover page of Novel Fusarium wilt resistance genes uncovered in natural and cultivated strawberry populations are found on three non-homoeologous chromosomes.

Novel Fusarium wilt resistance genes uncovered in natural and cultivated strawberry populations are found on three non-homoeologous chromosomes.

(2022)

Key message

Several Fusarium wilt resistance genes were discovered, genetically and physically mapped, and rapidly deployed via marker-assisted selection to develop cultivars resistant to Fusarium oxysporum f. sp. fragariae, a devastating soil-borne pathogen of strawberry. Fusarium wilt, a soilborne disease caused by Fusarium oxysporum f. sp. fragariae, poses a significant threat to strawberry (Fragaria [Formula: see text] ananassa) production in many parts of the world. This pathogen causes wilting, collapse, and death in susceptible genotypes. We previously identified a dominant gene (FW1) on chromosome 2B that confers resistance to race 1 of the pathogen, and hypothesized that gene-for-gene resistance to Fusarium wilt was widespread in strawberry. To explore this, a genetically diverse collection of heirloom and modern cultivars and octoploid ecotypes were screened for resistance to Fusarium wilt races 1 and 2. Here, we show that resistance to both races is widespread in natural and domesticated populations and that resistance to race 1 is conferred by partially to completely dominant alleles among loci (FW1, FW2, FW3, FW4, and FW5) found on three non-homoeologous chromosomes (1A, 2B, and 6B). The underlying genes have not yet been cloned and functionally characterized; however, plausible candidates were identified that encode pattern recognition receptors or other proteins known to confer gene-for-gene resistance in plants. High-throughput genotyping assays for SNPs in linkage disequilibrium with FW1-FW5 were developed to facilitate marker-assisted selection and accelerate the development of race 1 resistant cultivars. This study laid the foundation for identifying the genes encoded by FW1-FW5, in addition to exploring the genetics of resistance to race 2 and other races of the pathogen, as a precaution to averting a Fusarium wilt pandemic.