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Open Access Publications from the University of California

Scholarly Works (12 results)

  • Article
  • Peer Reviewed
The Proceedings of the International Plant Nutrition Colloquium XVI (2009)

Potassium (K) fertilizer is important for the reduction of many plant diseases, e.g., stalk rot of maize (Zea mays L.). However, the mechanism by which potassium promotes resistance to pathogens is not completely understood. Fusarium graminearum, which is the main pathogen causing stalk rot in maize, was selected to study the effect of potassium on phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), peroxidase (POD; EC 1.11.1.7) and polyphenol oxidase (PPO; EC 1.14.18.1), at both the physiological and molecular level. Gene expression was quantified by real-time reverse transcription PCR (Q-RT-PCR) technology. The incidence of maize stalk rot was significantly reduced by K application. After inoculation with F. graminearum, the potassium concentration increased in susceptible organs. Potassium induced the expression of and sustained elevated activities of PAL, POD, and PPO when maize was inoculated with the pathogen. The expression of the corresponding genes was also stimulated by potassium. This study demonstrated that potassium addition enhanced maize resistance to stalk rot by activating the expression and activity of defense-related enzymes involved in phenol metabolism.

    Cover page: Potassium influenced phenylalanine ammonia-lyase, peroxidases and polyphenol oxidases in Fusarium graminearum infected maize (Zea mays L.)
    • Article
    • Peer Reviewed
    The Proceedings of the International Plant Nutrition Colloquium XVI (2009)

    Over-application of nitrogen (N) and phosphorus (P), and insufficient supply of potassium (K), have been considered as reasons for restriction of yield increases in North China Plain. Field experiments were conducted to evaluate the effects of nutrient management on yield, nutrient uptake and utilization in Shanxi, Hebei, Shandong and Henan provinces, where the typical winter wheat–summer maize rotation system in North Central China is practiced. The results indicated that improved nutrient management by balanced fertilization based on soil testing and target yield (the optimum treatment, OPT) optimized grain yield, nutrient uptake and nutrient use efficiency compared with those for farmer’s practice (FP). By adoption of our improved nutrient management strategy, yield increased by 0.8–13.7% for wheat and 5.8–18.5% for maize separately and, moreover, N and P input declined by 13% (266 kg N ha–1) and 45% (430 kg P2O5 ha–1), and K input increased by 43% (265 kg K2O ha–1) at the four sites over the FP. The OPT increased partial factor productivity of nitrogen (PFPN) and agronomic efficiency of nitrogen (AEN) at all sites with the exception of Shandong where N rates were generally higher than elsewhere, and improved nitrogen recovery efficiency (REN) across all four sites in this study. The results from this study demonstrated that there is still need and great potential to improve PFPN, AEN and REN further in this intensive winter wheat–summer maize rotation system.

      Cover page: Nutrient uptake and utilization of nutrient management for wheat and maize rotation system in North Central China
      • Article
      • Peer Reviewed
      The Proceedings of the International Plant Nutrition Colloquium XVI (2009)

      From 2001 to 2008 a total of 16 field experiments were conducted in Jilin province, the so called “maize belt” of China, to study the rate of potassium fertilizer required for high yield maize production and maximum economic return under different soil available K levels. Results indicated that application of K2O at rates from 53.4 kg/ha to 155.4 kg/ha at different field sites with different soil available K levels produced maximum maize yield of 6203 kg/ha to 13668 kg/ha in the region. For maximum economic return the proper rate of K2O ranged from 37.6 kg/ha to 115.5 kg/ha, resulting in maximum economic yield from 6187 kg/ha to 13660 kg/ha. The net benefit ranged from 264 Yuan/ha (38.8 US$/ha) to 1977 Yuan/ha (290.7US$/ha), and the value and cost ratio (VCR) ranged from 1.5 to 8.0. As expected, the result indicate that soils with relatively low soil available K level received a high K2O recommended rate, while soils with relatively high soil available K level received a lower recommended rate of K2O. The use of soil testing provided a better distribution of limited fertilizer K resources and supported an overall improved net benefit to farmers.

        Cover page: Potassium Fertilization Rates for Maximum Economic Return for Maize Production under Different Soil Available K Levels in Jilin Province of China
        • Article
        • Peer Reviewed
        UC San Francisco Previously Published Works (2012)

        Objective

        To determine the variation of IFN-γ and IL-17 responses to M. tuberculosis antigens in healthy TST+ humans.

        Methods

        We isolated peripheral blood mononuclear cells from 21 TST+ healthy adults, stimulated them with phytohemagglutinin (PHA), PPD, Ag85B, ESAT-6, and live M. bovis BCG, and assayed IFN-γ and IL-17 secretion by ELISA in supernatants after 24 or 72 hours of incubation respectively.

        Results

        As in other studies, we found a wide range of IFN-γ responses to M. tuberculosis antigens; the variation significantly exceeded that observed in the same donors to the polyclonal T cell stimulus, phytohemagglutinin (PHA). In addition, we assayed IL-17 secretion in response to the same stimuli, and found less subject-to-subject variation. Analysis of the ratio of IFN-γ to IL-17 secretion on a subject-to-subject basis also revealed a wide range, with the majority of results distributed in a narrow range, and a minority with extreme results all of which were greater than that in the majority of subjects. The data suggest that study of exceptional responses to M. tuberculosis antigens may reveal immunologic correlates with specific outcomes of M. tuberculosis infection.

        Conclusion

        Variation of IFNγ and IFN-γ/IL-17 responses to mycobacterial antigens exceeds that of responses to the polyclonal stimulus, PHA, in TST positive healthy humans. This indicates a quantitative spectrum of human immune responses to infection with M. tuberculosis. Since the outcome of human infection with M. tuberculosis varies greatly, systematic study of multiple immune responses to multiple antigens is likely to reveal correlations between selected immune responses and the outcomes of infection.
          Cover page: Variation of Mycobacterium tuberculosis Antigen-Specific IFN-γ and IL-17 Responses in Healthy Tuberculin Skin Test (TST)-Positive Human SubjectsCreative Commons 'BY' version 4.0 license
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2024)
          Two-dimensional metal-organic frameworks (MOFs) have a wide variety of applications in molecular separation and other emerging technologies, including atomically thin electronics. However, due to the inherent fragility and strong interlayer interactions, high-quality MOF crystals of atomic thickness, especially isolated MOF crystal monolayers, have not been easy to prepare. Here, we report the self-condensation-assisted chemical vapour deposition growth of atomically thin MOF single-crystals, yielding monolayer single-crystals of poly[Fe(benzimidazole)2] up to 62 μm in grain sizes. By using transmission electron microscopy and high-resolution atomic force microscopy, high crystallinity and atomic-scale single-crystal structure are verified in the atomically MOF flakes. Moreover, integrating such MOFs with MoS2 to construct ultrathin van der Waals heterostructures is achieved by direct growth of atomically MOF single-crystals onto monolayer MoS2, and enables a highly selective ammonia sensing. These demonstrations signify the great potential of the method in facilitating the development of the fabrication and application of atomically thin MOF crystals.
            Cover page: Self-condensation-assisted chemical vapour deposition growth of atomically two-dimensional MOF single-crystals.
            • Article
            • Peer Reviewed
            UC Davis Previously Published Works (2016)
            Protein poly(ADP-ribosyl)ation (PARylation) primarily catalyzed by poly(ADP-ribose) polymerases (PARPs) plays a crucial role in controlling various cellular responses. However, PARylation targets and their functions remain largely elusive. Here, we deployed an Arabidopsis protein microarray coupled with in vitro PARylation assays to globally identify PARylation targets in plants. Consistent with the essential role of PARylation in plant immunity, the forkhead-associated (FHA) domain protein DAWDLE (DDL), one of PARP2 targets, positively regulates plant defense to both adapted and non-adapted pathogens. Arabidopsis PARP2 interacts with and PARylates DDL, which was enhanced upon treatment of bacterial flagellin. Mass spectrometry and mutagenesis analysis identified multiple PARylation sites of DDL by PARP2. Genetic complementation assays indicate that DDL PARylation is required for its function in plant immunity. In contrast, DDL PARylation appears to be dispensable for its previously reported function in plant development partially mediated by the regulation of microRNA biogenesis. Our study uncovers many previously unknown PARylation targets and points to the distinct functions of DDL in plant immunity and development mediated by protein PARylation and small RNA biogenesis, respectively.
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2024)
              Graphene aerogels hold huge promise for the development of high-performance pressure sensors for future human-machine interfaces due to their ordered microstructure and conductive network. However, their application is hindered by the limited strain sensing range caused by the intrinsic stiffness of the porous microstructure. Herein, an anisotropic cross-linked chitosan and reduced graphene oxide (CCS-rGO) aerogel metamaterial is realized by reconfiguring the microstructure from a honeycomb to a buckling structure at the dedicated cross-section plane. The reconfigured CCS-rGO aerogel shows directional hyperelasticity with extraordinary durability (no obvious structural damage after 20 000 cycles at a directional compressive strain of ≤0.7). The CCS-rGO aerogel pressure sensor exhibits an ultrahigh sensitivity of 121.45 kPa-1, an unprecedented sensing range, and robust mechanical and electrical performance. The aerogel sensors are demonstrated to monitor human motions, control robotic hands, and even integrate into a flexible keyboard to play music, which opens a wide application potential in future human-machine interfaces.
                Cover page: Microstructure-Reconfigured Graphene Oxide Aerogel Metamaterials for Ultrarobust Directional Sensing at Human-Machine Interfaces.
                • Article
                • Peer Reviewed
                UC Davis Previously Published Works (2024)
                Candidatus Liberibacter spp. are insect-vectored, fastidious, and vascular-limited phytopathogens. They are the presumptive causal agents of potato zebra chip, tomato vein clearing, and the devastating citrus greening disease worldwide. There is an urgent need to develop new strategies to control them. In this study, we characterized a dual-specificity serine/tyrosine phosphatase (STP) that is well conserved among thirty-three geographically diverse Candidatus Liberibacter spp. and strains that infect multiple Solanaceaea and citrus spp. The STP is expressed in infected plant tissues, localized at the plant cytosol and plasma membrane, and interferes with plant cell death responses. We employed an in silico target-based molecular modeling and ligand screen to identify two small molecules with high binding affinity to STP. Efficacy studies demonstrated that the two molecules can inhibit Candidatus Liberibacter spp. but not unrelated pathogens and confer plant disease tolerance. The inhibitors and strategies are promising means to control Candidatus Liberibacter spp.
                  Cover page: Inhibition of a conserved bacterial dual-specificity phosphatase confers plant tolerance to Candidatus Liberibacter spp.Creative Commons 'BY-NC-ND' version 4.0 license
                  • Article
                  • Peer Reviewed
                  UC Davis Previously Published Works (2018)
                  Plants employ cell-surface pattern recognition receptors (PRRs) to detect pathogens. Although phytohormones produced during PRR signaling play an essential role in innate immunity, a direct link between PRR activation and hormone regulation is unknown. EFR is a PRR that recognizes bacterial EF-Tu and activates immune signaling. Here we report that EFR regulates the phytohormone jasmonic acid (JA) through direct phosphorylation of a receptor-like cytoplasmic kinase, BIK1. The BIK1 structure revealed that the EFR-phosphorylated sites reside on a uniquely extended loop away from the BIK1 kinase core domain. Phosphomimetic mutations of these sites resulted in increased phytohormones and enhanced resistance to bacterial infections. In addition to its documented plasma membrane localization, BIK1 also localizes to the nucleus and interacts directly with WRKY transcription factors involved in the JA and salicylic acid (SA) regulation. These findings demonstrate the mechanistic basis of signal transduction from PRR to phytohormones, mediated through a PRR-BIK1-WRKY axis.
                    Cover page: The Receptor-like Cytoplasmic Kinase BIK1 Localizes to the Nucleus and Regulates Defense Hormone Expression during Plant Innate Immunity
                    • Article
                    • Peer Reviewed
                    UC San Francisco Previously Published Works (2014)

                    Purpose

                    The endoplasmic reticulum-associated degradation pathway is responsible for the translocation of misfolded proteins across the endoplasmic reticulum membrane into the cytosol for subsequent degradation by the proteasome. To define the phenotype associated with a novel inherited disorder of cytosolic endoplasmic reticulum-associated degradation pathway dysfunction, we studied a series of eight patients with deficiency of N-glycanase 1.

                    Methods

                    Whole-genome, whole-exome, or standard Sanger sequencing techniques were employed. Retrospective chart reviews were performed in order to obtain clinical data.

                    Results

                    All patients had global developmental delay, a movement disorder, and hypotonia. Other common findings included hypolacrima or alacrima (7/8), elevated liver transaminases (6/7), microcephaly (6/8), diminished reflexes (6/8), hepatocyte cytoplasmic storage material or vacuolization (5/6), and seizures (4/8). The nonsense mutation c.1201A>T (p.R401X) was the most common deleterious allele.

                    Conclusion

                    NGLY1 deficiency is a novel autosomal recessive disorder of the endoplasmic reticulum-associated degradation pathway associated with neurological dysfunction, abnormal tear production, and liver disease. The majority of patients detected to date carry a specific nonsense mutation that appears to be associated with severe disease. The phenotypic spectrum is likely to enlarge as cases with a broader range of mutations are detected.
                      Cover page: Mutations in NGLY1 cause an inherited disorder of the endoplasmic reticulum–associated degradation pathway
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