skip to main content


Search for: All records

Creators/Authors contains: "Mack, James"

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Yucca moths ( Tegeticula and Parategeticula) are specialized pollinators of yucca plants, possessing unique, tentacle-like mouthparts used to actively collect pollen and deposit it onto the flowers of their hosts. The moths' larvae feed on the developing seeds and fruit tissue. First described in 1873, the yucca–yucca moth pollination system is now considered the archetypical example of a coevolved intimate mutualism. Research conducted over the past three decades has transformed our understanding of yucca moth diversity and host plant interactions. We summarize the current understanding of the diversity, ecology, and evolution of this group, review evidence for coevolution of the insects and their hosts, and describe how the nature of the interaction varies across evolutionary time and ecological contexts. Finally, we identify unresolved questions and areas for future research.

     
    more » « less
    Free, publicly-accessible full text available January 25, 2025
  2. Free, publicly-accessible full text available October 16, 2024
  3. Free, publicly-accessible full text available September 15, 2024
  4. Over the last several years, chemists and engineers have identified the utility of using twin-screw extruders for performing large-scale organic chemistry mechanochemically. This equipment is convenient as it is familiar to several relevant industries for its use in formulation, and it is also well-equipped for temperature control and intense grinding of materials. However, the research and development scale of mechanochemistry is just like that of conventional synthesis: milligrams. These milligram-scale reactions are performed in batch-type reactors, often a ball mill. Commercially available ball mills do not have strict temperature control, limiting the information that can be obtained to inform the scale-up process reliably. This work uses an in-house modified, temperature-controlled, ball mill to bridge the knowledge gap regarding predictable, well-informed, economical, and reliable mechanochemical scale-ups. Included in this work is the first extrusion example of a nucleophilic aromatic substitution. 
    more » « less
  5. Green plants play a fundamental role in ecosystems, human health, and agriculture. As de novo genomes are being generated for all known eukaryotic species as advocated by the Earth BioGenome Project, increasing genomic information on green land plants is essential. However, setting standards for the generation and storage of the complex set of genomes that characterize the green lineage of life is a major challenge for plant scientists. Such standards will need to accommodate the immense variation in green plant genome size, transposable element content, and structural complexity while enabling research into the molecular and evolutionary processes that have resulted in this enormous genomic variation. Here we provide an overview and assessment of the current state of knowledge of green plant genomes. To date fewer than 300 complete chromosome-scale genome assemblies representing fewer than 900 species have been generated across the estimated 450,000 to 500,000 species in the green plant clade. These genomes range in size from 12 Mb to 27.6 Gb and are biased toward agricultural crops with large branches of the green tree of life untouched by genomic-scale sequencing. Locating suitable tissue samples of most species of plants, especially those taxa from extreme environments, remains one of the biggest hurdles to increasing our genomic inventory. Furthermore, the annotation of plant genomes is at present undergoing intensive improvement. It is our hope that this fresh overview will help in the development of genomic quality standards for a cohesive and meaningful synthesis of green plant genomes as we scale up for the future. 
    more » « less
  6. Solvent-free mechanochemical conditions have been developed to investigate the significance of ion pairing and the use of weak bases for driving forward nucleophilic substitution reactions. This approach takes advantage of the lack of solvent shells to incorporate weaker and safer bases to drive reactions to completion through specific ion pairing pathways. The most efficient reactions contained larger and more polarizable cation and anion pairs. 
    more » « less
  7. Summary

    The adaptation of weeds to herbicide is both a significant problem in agriculture and a model of rapid adaptation. However, significant gaps remain in our knowledge of resistance controlled by many loci and the evolutionary factors that influence the maintenance of resistance.

    Here, using herbicide‐resistant populations of the common morning glory (Ipomoea purpurea), we perform a multilevel analysis of the genome and transcriptome to uncover putative loci involved in nontarget‐site herbicide resistance (NTSR) and to examine evolutionary forces underlying the maintenance of resistance in natural populations.

    We found loci involved in herbicide detoxification and stress sensing to be under selection and confirmed that detoxification is responsible for glyphosate (RoundUp) resistance using a functional assay. We identified interchromosomal linkage disequilibrium (ILD) among loci under selection reflecting either historical processes or additive effects leading to the resistance phenotype. We further identified potential fitness cost loci that were strongly linked to resistance alleles, indicating the role of genetic hitchhiking in maintaining the cost.

    Overall, our work suggests that NTSR glyphosate resistance inI. purpureais conferred by multiple genes which are potentially maintained through generationsviaILD, and that the fitness cost associated with resistance in this species is likely a by‐product of genetic hitchhiking.

     
    more » « less
  8. Abstract

    Mechanochemistry through high‐speed ball milling has become an increasingly popular method for performing organic transformations. This newfound interest in high‐speed ball milling is in part driven by the benefit of performing reactions in the absence of solvent. Mechanochemical reactions are often conducted in stainless‐steel vials with stainless‐steel balls. Since stainless steel is made of several readily oxidizable metals (Fe, Cr, and Ni), reduction reactions using water as a hydrogen source were explored using a temperature‐controlled mixer mill. Mechanistic studies suggest that the reduction proceeds via a single electron transfer (SET) pathway, with iron and nickel being essential components for the reaction.

     
    more » « less