Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Y10: Evolution of Cellular ComplexityInvited Live
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Sponsoring Units: DBIO Chair: Srividya Iyer-Biswas, Purdue University; Wallace Marshall |
Friday, March 19, 2021 11:30AM - 12:06PM Live |
Y10.00001: Lessons from molecular evolution: from origin of life to phage-based nanomaterials Invited Speaker: Irene Chen An experimental model for the origin of life is based on the 'RNA World', in which catalytic RNA (ribozymes) performed the functions of a primitive cell. We study evolution of an RNA world systematically by mapping fitness landscapes (the sequence-activity relationship) for ribozymes, using in vitro selection and a massively parallel kinetic assay. I will present our work examining the effect of encapsulation inside protocells and the role of chance during RNA evolution. |
Friday, March 19, 2021 12:06PM - 12:42PM Live |
Y10.00002: Our evolving view of cell motility Invited Speaker: Lillian Fritz-Laylin Various cells scattered throughout the eukaryotic tree crawl across surfaces or through three-dimensional environments in order to hunt prey, evade predators and find mates. Evidence now indicates that cell crawling is not a single behavior, but rather a collection of processes, driven by different molecular mechanisms. We seek to understanding regulation and evolution of these mechanisms by first narrowly defining mechanical modes of locomotion, and then identifying phenotypic and molecular markers of each. The best studied mode of cell migration is the adhesion-based migration of highly adherent animal cells, including fibroblasts and epithelial cells, a mode limited to cells of the animal lineage. In contrast, a mode we refer to as “alpha-motility” is widely dispersed among eukaryotic phyla and is characterized by dynamic, actin-filled pseudopods and weak adhesion to external substrates. We are currently defining gene complements required for each mode, and using the resulting data to predict crawling motility in new species. We use this approach to predict alpha-motility in the amphibian-killing chytrid fungus Batrachochytrium dendrobatidis, a prediction we have verified using microscopy and small molecule inhibitors of actin cytoskeletal components. By developing mechanistic definition of distinct modes of crawling motility, and expanding our phylogenetic analysis to many eukaryotes, we are identifying genetic markers and regulatory mechanisms to understand basic principles of this key eukaryotic behavior. |
Friday, March 19, 2021 12:42PM - 1:18PM Live |
Y10.00003: The role of large-scale gene duplication in the evolution of the eukaryotic membrane traffic system Invited Speaker: Mukund Thattai While the role of gene duplication in the evolution of individual proteins or interacting protein pairs has been well documented, less is known about the conditions under which large gene sets are duplicated. The membrane traffic system of eukaryotic cells dynamically emerges via the interaction of proteins belonging to large gene families, such as Rabs, SNAREs, and coats. Biophysical and phylogenetic analyses suggest that the evolution of organelles with new compositions requires gene family expansion. Both whole-genome duplication and inter-species hybridization are sources of such genetic novelty. What is the fate of gene duplicates arising from these distinct processes? The lager brewing yeast Saccharomyces pastorianus is an ideal model system to study this question. This allotetraploid species arose about 500 years ago via a hybridization event, closely followed by a whole-genome duplication event. We have compared the hybrid with its parents, using genome, transcriptome and functional assays. Our data show that hybridization outstrips whole-genome duplication as a source of persistent genetic novelty. Hybridization may have thus played a pivotal role in the evolution of unicellular eukaryotes. |
Friday, March 19, 2021 1:18PM - 1:54PM Live |
Y10.00004: Drift, Mutation, and the Origin of Cellular Features Invited Speaker: Mike Lynch Although natural selection may be the most powerful force in the biological world, it is not all powerful. As a consequence, many aspects of genomic evolution can only be explained by the inability of natural selection to operate. This general principle extends to numerous cellular features, e.g., genomic mutation rates; transcription error rates; the multimeric states of proteins; and the phylogenetic drift of gene-regulatory vocabulary. |
Friday, March 19, 2021 1:54PM - 2:30PM Live |
Y10.00005: The evolution of cell division: from archaea to eukaryotes Invited Speaker: Buzz Baum Living systems propagate by undergoing rounds of cell growth and division. In fact, all modern day organisms are the progeny of a single cell that divided over 3.5 billion years ago. In this talk, by looking at features of the cell division machinery that we (eukaryotes) share with our cellular relatives, the archaea, we will attempt to shed light on the origins of our cell division machinery. In addition, by studying cell division in Sulfolobus, a member of the TACK/Asgard archaea, we will ask whether it is possible to use these relatively simple organisms to reveal fundamental features of the process of cell division that are hard to discern in our cells because of their relative complexity. |
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