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Open Access Publications from the University of California

Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2018)

This dissertation aims to understand the mechanisms and consequences of the low frequency “unforced” component of variability in the climate system using interannual and decadal variability as a platform to investigate phenomena thought to be sensitive to greenhouse gas emissions. To combat the lack of temporally extended instrumental observations, this dissertation relies on coral geochemistry and Earth System Models to identify the historical range of Pacific climate variability.

Chapter 2 describes the analysis of a roughly 200 year-long coral record from Clarion Island, in the Revillagigedos Archipelago, Mexico. This record expresses substantial decadal variability in the oxygen isotopes, strongly coherent with other paleoproxies in the central equatorial Pacific and in Southern California, indicative of a coordinated system of ocean-atmospheric interaction. To best resolve the key processes involved, “forward models” are employed to interpret the decadal variability in the coral record.

The third chapter complements the first by addressing a mechanism responsible for the modulation of decadal variability in the North Pacific; the Pacific Meridional Mode (PMM). The Community Earth System Model-Last Millennium Ensemble (CESM-LME) is used to estimate the historical range of PMM variability, highlighting the considerable power of natural variability within the system. I investigate the physical processes associated with adjustments in PMM variance, emphasizing that relatively small anomalies in the background state have a significant influence on PMM variability.

Chapter 4 examines the roles of physical and biologically mediated processes on coral calcification from within an equatorial Pacific coral reef. Motivated by the biogeochemical implications of the previous sections, this work examines the manifestation of pH tracers in coral skeletal tissue across a network of diverse, monitored reef sites at Palmyra Atoll. Corals were analyzed for δ11B, trace metal, δ18O, and δ13C composition. Despite a narrow range in the pH of seawater, high variance in δ11B were observed between sites, and within single sites, suggesting that individual coral colonies have differential capacities to regulate pH variability and other environmental stressors.

    Cover page: Pacific climate variability: insights from coral records, Earth System Models, and novel geochemical tracers
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2020)
    The formation of the fungal mycelial network is facilitated by somatic cell fusion of germinating asexual spores (or germlings). Neurospora crassa germlings in close proximity display chemotropic growth that is dependent upon an intracellular network of mitogen-activated protein kinase (MAPK) signaling cascades. Approximately 80 genes involved in intercellular communication and fusion have been identified, including three mutants with similar morphological phenotypes: Δwhi-2, Δcsp-6, and Δamph-1. Here we show that WHI-2 localizes to the cell periphery and regulates endocytosis, mitochondrial organization, sporulation, and cell fusion. WHI-2 was required to transduce signals through a conserved MAPK pathway (NRC-1/MEK-2/MAK-2) and target transcription factors (PP-1/ADV-1). The amph-1 locus encodes a Bin/Amphiphysin/Rvs domain-containing protein and mis-expression of whi-2 compensated for the cell fusion and endocytosis deficiencies of a Δamph-1 mutant. The csp-6 locus encodes a haloacid dehalogenase phosphatase whose activity was essential for cell fusion. Although fusion-deficient with themselves, cells that lacked whi-2, csp-6, or amph-1 showed a low frequency of chemotropic interactions with wild type cells. We hypothesize that WHI-2 could be important for signal perception during chemotropic interactions via a role in endocytosis.
      Cover page: WHI-2 Regulates Intercellular Communication via a MAP Kinase Signaling Complex
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2013)

      Aims

      Tobacco-related cancers and, in particular, lung cancer still represents a substantial public health epidemic across Europe as a result of high rates of smoking prevalence. Countries in Europe have proposed and implemented tobacco control policies to reduce smoking prevalence, with some countries being more progressive than others. The aim of this study was to examine factors that influenced women's attitudes across five European countries relative to comprehensive smokefree laws in their countries.

      Methods

      A cross-sectional landline telephone survey on attitudes towards tobacco control laws was conducted in five European countries: France, Ireland, Italy, the Czech Republic, and Sweden. Attitudinal scores were determined for each respondent relative to questions about smokefree laws. Logistic regression models were used to obtain odds ratios with 95% confidence intervals.

      Results

      A total of 5000 women were interviewed (1000 women from each country). The majority of women, regardless of smoking history, objected to smoking in public buses, enclosed shopping centers, hospitals, and other indoor work places. More women who had quit smoking believed that new tobacco control laws would prompt cessation - as compared with women who still smoked.

      Conclusions

      In general, there is very high support for national smokefree laws that cover bars, restaurants, and public transport systems. As such laws are implemented, attitudes do change, as demonstrated by the differences between countries such as Ireland and the Czech Republic. Implementing comprehensive smokefree laws will gain high approval and will be associated with prompting people to quit.
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2019)

        Background

        Aspergillus spp. comprises a very diverse group of lower eukaryotes with a high relevance for industrial applications and clinical implications. These multinucleate species are often cultured for many generations in the laboratory, which can unknowingly propagate hidden genetic mutations. To assess the likelihood of such events, we studied the genome stability of aspergilli by using a combination of mutation accumulation (MA) lines and whole genome sequencing.

        Results

        We sequenced the whole genomes of 30 asexual and 10 sexual MA lines of three Aspergillus species (A. flavus, A. fumigatus and A. nidulans) and estimated that each MA line accumulated mutations for over 4000 mitoses during asexual cycles. We estimated mutation rates of 4.2 × 10-11 (A. flavus), 1.1 × 10-11 (A. fumigatus) and 4.1 × 10-11 (A. nidulans) per site per mitosis, suggesting that the genomes are very robust. Unexpectedly, we found a very high rate of GC → TA transversions only in A. flavus. In parallel, 30 asexual lines of the non-homologous end-joining (NHEJ) mutants of the three species were also allowed to accumulate mutations for the same number of mitoses. Sequencing of these NHEJ MA lines gave an estimated mutation rate of 5.1 × 10-11 (A. flavus), 2.2 × 10-11 (A. fumigatus) and 4.5 × 10-11 (A. nidulans) per base per mitosis, which is slightly higher than in the wild-type strains and some ~ 5-6 times lower than in the yeasts. Additionally, in A. nidulans, we found a NHEJ-dependent interference of the sexual cycle that is independent of the accumulation of mutations.

        Conclusions

        We present for the first time direct counts of the mutation rate of filamentous fungal species and find that Aspergillus genomes are very robust. Deletion of the NHEJ machinery results in a slight increase in the mutation rate, but at a rate we suggest is still safe to use for biotechnology purposes. Unexpectedly, we found GC→TA transversions predominated only in the species A. flavus, which could be generated by the hepatocarcinogen secondary metabolite aflatoxin. Lastly, a strong effect of the NHEJ mutation in self-crossing was observed and an increase in the mutations of the asexual lines was quantified.
          Cover page: Genome sequencing of evolved aspergilli populations reveals robust genomes, transversions in A. flavus, and sexual aberrancy in non-homologous end-joining mutants
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