Biology subjects

Setayeshgar, S.

Publications and source records attributed to Setayeshgar, S..

3 recordsLinked to original sources

bioRxiv2025

A minimal model for the role of Rim4 in regulating meiotic exit in budding yeast

Meiosis ensures formation of haploid gametes through two rounds of chromosome segregation after one round of DNA replication. How this complex cell cycle process is restricted to two and only two divisions is poorly understood. In budding yeast, RNA-binding protein Rim4 binds various mRNAs to prevent their translation. At the onset of meiosis II, phosphorylation and degradation of Rim4, along with the concomitant release of sequestered mRNA, has an important role in ensuring meiotic exit. Building on previous work, we developed a parsimonious mathematical model of meiotic termination that elucidates the role of Rim4-mRNA release and translation of AMA1 mRNA in the fidelity of meiotic exit. Central to our model is the accumulation of Ama1 protein, a meiosis-specific activator of APC/C. Our mathematical model predicted further outcomes, which we tested experimentally. We found that either slowing Rim4 degradation or disrupting APC/CAma1 activity delayed meiosis II. In some cells, this disruption prevented meiotic exit entirely, leading them to re-enter cell cycle oscillations after meiosis II. These findings demonstrate that the timely activation of this regulatory network is crucial for ensuring irreversible meiotic exit.

cell biology↗

bioRxiv2025

Microbial cross-feeding is stabilized when a dependent mutant is segregated from its independent ancestor

Microbial gene loss is hypothesized to be beneficial when gene function is costly, and the gene product can be replaced via cross-feeding from a neighbor. However, cross-fed metabolites are often only available at low concentrations, limiting the growth rates of gene-loss mutants that are dependent on those metabolites. Here we define conditions that support a loss of function mutant in a three-member bacterial community of: (i) N2-utilizing Rhodopseudomonas palustris as an NH4+ -excreting producer, (ii) N2-utilizing Vibrio natriegens as the ancestor, and (iii) a V. natriegens N2-utilizaton mutant that is dependent on the producer for NH4+. Using experimental and simulated cocultures, we found that the ancestor outcompeted the mutant due to low NH4+ availability under uniform conditions where both V. natriegens strains have equal access to nutrients. However, spatial structuring that separated the mutant from the ancestor, while maintaining access to NH4+ from the producer, allowed the mutant to avoid extinction. Counter to predictions, mutant enrichment under spatially structured conditions did not require a growth rate advantage from gene loss and the mutant coexisted with its ancestor. Thus, cross-feeding can originate from loss-of-function mutations that are otherwise detrimental, provided that the mutant can segregate from a competitive ancestor. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/634601v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1140808org.highwire.dtl.DTLVardef@1b72e8org.highwire.dtl.DTLVardef@14f70borg.highwire.dtl.DTLVardef@6707bb_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2017

Layered structure and complex mechanochemistry of a strong bacterial adhesive

While designing adhesives that perform in aqueous environments has proven challenging for synthetic adhesives, microorganisms commonly produce bioadhesives that efficiently attach to a variety of substrates, including wet surfaces that remain a challenge for industrial adhesives. The aquatic bacterium Caulobacter crescentus uses a discrete polar polysaccharide complex, the holdfast, to strongly attach to surfaces and resist flow. The holdfast is extremely versatile and has an impressive adhesive strength. Here, we use atomic force microscopy (AFM) to unravel the complex structure of the holdfast and characterize its chemical constituents and their role in adhesion. We used purified holdfasts to dissect the intrinsic properties of this component as a biomaterial, without the effect of the bacterial cell body. Our data support a model where the holdfast is a heterogeneous material composed of two layers: a stiff nanoscopic core, covered by a sparse, flexible brush layer. These two layers contain not only N-acetyl-D-glucosamine (NAG), the only yet identified component present in the holdfast, but also peptides and DNA, which provide structure and adhesive character. Biochemical experiments suggest that, while polypeptides are the most important components for adhesive force, the presence of DNA mainly impacts the brush layer and initial adhesion, and NAG plays a primarily structural role within the core. Moreover, our results suggest that holdfast matures structurally, becoming more homogeneous over time. The unanticipated complexity of both the structure and composition of the holdfast likely underlies its distinctive strength as a wet adhesive and could inform the development of a versatile new family of adhesives.

biophysics↗