Biology subjects

Peiser, J. M.

Publications and source records attributed to Peiser, J. M..

3 recordsLinked to original sources

bioRxiv2026

Canonical insulin receptor/DAF-2 signaling-independent patterning and role for FoxO/DAF-16 in early embryos

Forkhead box O (FoxO) transcription factors (DAF-16 in Caenorhabditis elegans) regulate aging, metabolism, and development. Canonically, FoxO/DAF-16 activity is regulated by insulin/insulin-like receptor (DAF-2) signaling, which inhibits its nuclear localization. In C. elegans, strong loss-of-function daf-16; daf-2 double mutants are embryonic lethal. However, because daf-2 null mutants are maternally rescued as embryos and then arrest as larvae, the role of DAF-2 signaling in embryogenesis is unknown. We therefore used quantitative imaging and genetics to study DAF-16 and DAF-2 in early C. elegans embryos. DAF-16 was uniformly low in all nuclei at the 2- to 4-cell stage. From the 8- to 64-cell stage, DAF-16 became enriched in 1-2 nuclei of germ lineage cells. This patterning required germ fate determinants and the lipid phosphatase PTEN/DAF-18, but not DAF-2 kinase activity, and was independent of maternal age. We also found that daf-16; daf-2 double mutant embryos failed morphogenesis, with severe mitotic defects as early as the 1-cell stage. This work identifies germ lineage-specific DAF-16 patterning and a role for DAF-16 in early embryogenesis that is independent of canonical DAF-2 signaling.

developmental biology↗

bioRxiv2024

The genetic basis of predation resistance in Pseudomonas species associated with the bactivorous soil amoeba Dictyostelium discoideum.

Predation is likely to influence the function of bacterial communities and the evolution of bacterial pathogens, because characteristics that permit escape from predators often overlap with traits used for biocontrol of plant pathogens, virulence, or even bioremediation. Soil bacteria are preyed upon by a variety of microorganisms, including the amoeba Dictyostelium discoideum, which has led some strains to evolve resistance. We identified genes required for three Pseudomonas species associated with D. discoideum to evade predation by screening more than 6,000 transposon mutants for loss of resistance. One species required a variety of genes including toxins and secondary metabolism genes, but the other two appear to have functionally redundant mechanisms of resistance, since disruption of genes with pleiotropic effects was required to render them susceptible. We determined that GacA, which positively regulates secondary metabolism, is required for resistance in all three species. Predation resistance also appears to be a social trait based on enrichment of cooperative genes in one species and rescue of mutants by wild type in another. Many genes required for resistance are conserved among both resistant and susceptible species, but several are found in few genomes and some of these have homologs in distantly related species. Gain and loss of resistance appears to be a dynamic process in which regulatory and structural genes are well conserved across species, the specific toxins they regulate may be lost in the absence of predators, and new toxins may be acquired through horizontal gene transfer.

microbiology↗

bioRxiv2023

Predation-resistant Pseudomonas bacteria engage in symbiont-like behavior with the social amoeba Dictyostelium discoideum

The soil amoeba Dictyostelium discoideum acts as both a predator and potential host for diverse bacteria. We tested fifteen Pseudomonas strains that were isolated from transiently infected wild D. discoideum for ability to escape predation and infect D. discoideum fruiting bodies. Three predation-resistant strains frequently caused extracellular infections of fruiting bodies but were not found within spores. Furthermore, infection by one of these species induces secondary infections and suppresses predation of otherwise edible bacteria. Another strain can persist inside of amoebae after being phagocytosed but is rarely ingested. We sequenced isolate genomes and discovered that predation-resistant isolates are not monophyletic. Many Pseudomonas isolates encode secretion systems and toxins known to improve resistance to phagocytosis in other species, as well as diverse secondary metabolite biosynthetic gene clusters that may contribute to predation resistance. However, the distribution of these genes alone cannot explain why some strains are edible and others are not. Each lineage may employ a unique mechanism for resistance.

microbiology↗