Biology subjects

Tremblay, R.

Publications and source records attributed to Tremblay, R..

5 recordsLinked to original sources

bioRxiv2026

Positive effects of larval quality on early barnacle recruitment through adaptive substrate selection

Variation in larval supply alone often fails to explain recruitment dynamics in marine benthic populations, suggesting that larval traits may influence settlement success. We tested whether larval quality influences habitat selection and recruitment in the intertidal barnacle Chthamalus bisinuatus. Over a 26-day field sampling, we found no correlation between larval supply and settlement rates on experimental arenas featuring varying microtopographies. Instead, recruitment dynamics tracked changes in larval quality. Early settlement was primarily driven by low-quality larvae, consistent with the "desperate larva hypothesis", whereas later recruitment was characterized by high-quality larvae. Cyprids generally preferred rugose over smooth surfaces, but substrate selectivity depended on larval condition and disappeared after biofilm development. Early benthic performance indicated adaptive habitat selection, with higher survival and larger recruits on rugose surfaces. These findings identify larval quality as a key driver of settlement, shaping recruitment patterns and should be incorporated into ecological models of marine population connectivity.

ecology↗

bioRxiv2022

Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers (Mytilus sp.): a limit to poleward range shifts

Ongoing climate change has caused rapidly increasing temperatures, and an unprecedented decline in seawater pH, known as ocean acidification. Increasing temperatures are redistributing species towards higher and cooler latitudes which are most affected by ocean acidification. Whilst the persistence of intertidal species in cold environments is related to their capacity to resist sub-zero air temperatures, studies have never considered the interacting impacts of ocean acidification and freeze stress on species survival and distribution. A full-factorial experiment was used to study whether ocean acidification increases mortality in Mytilus spp. following sub-zero air temperature exposure. We examined physiological processes behind variation in freeze tolerance using 1H NMR metabolomics, analyses of fatty acids, and amino acid composition. We show that low pH conditions (pH = 7.5) significantly decrease freeze tolerance in both intertidal and subtidal populations of Mytilus spp. Under current day pH conditions (pH = 7.9), intertidal M. trossulus were more freeze tolerant than subtidal M. trossulus and M. galloprovincialis. Opposite, under low pH conditions, subtidal M. trossulus was more freeze tolerant than the other groups. We observed a marked shift from negative to positive metabolite-metabolite correlations across species under low pH conditions, but there was no evidence that the concentration of individual metabolites or amino acids affected freeze tolerance. Finally, pH-induced changes in the composition of cell membrane phospholipid fatty acids had no effect on survival. These results suggest that ocean acidification can offset the poleward expanding facilitated by warming, and that reduced freeze tolerance could result in a niche squeeze if temperatures become lethal at the equatorward edge.

ecology↗

bioRxiv2022

Persistent acetylation of newly synthesized histones inhibits DNA replication origin activity

In Saccharomyces cerevisiae, newly synthesized histone H3 are acetylated on lysine 56 (H3 K56ac) by the Rtt109 acetyltransferase prior to their deposition on nascent DNA behind replication forks. Two deacetylases of the sirtuin family, Hst3 and Hst4, remove H3 K56ac from chromatin following S phase. hst3{Delta} hst4{Delta} cells present constitutive H3 K56ac, which sensitizes cells to replicative stress via mechanisms that remain unclear. We performed a screen to identify genes that influence cell fitness upon nicotinamide (NAM)-induced inhibition of sirtuins. The screen revealed that DBF4 heterozygosity causes NAM sensitivity. DBF4 and CDC7 encode subunits of the Dbf4-dependent kinase, which activates origins of DNA replication. We show that i) cells harboring the dbf4-1 or cdc7-4 hypomorphic alleles are sensitive to NAM, ii) Rif1, an inhibitor of Cdc7-dependent activation of origins, causes DNA damage and replication defects in NAM-treated cells and hst3{Delta} hst4{Delta} mutants, and iii) cdc7-4 hst3{Delta} hst4{Delta} cells display synthetic temperature sensitivity associated with delayed initiation of DNA replication. Such replication defects are not due to activation of the intra-S phase checkpoint but require Rtt109-dependent H3 K56ac. Overall, these results suggest that persistent H3 K56ac sensitizes cells to replicative stress in part by negatively influencing replication origin activity.

molecular biology↗

bioRxiv2020

Cellular birthdate predicts laminar and regional cholinergic projection topography in the forebrain

The basal forebrain cholinergic system projects broadly throughout the cortex and constitutes a critical source of neuromodulation for arousal and attention. Traditionally, this system was thought to function diffusely. However, recent studies have revealed a high degree of spatiotemporal specificity in cholinergic signaling. How the organization of cholinergic afferents confers this level of precision remains unknown. Here, using intersectional genetic fate mapping, we demonstrate that cholinergic fibers within the cortex exhibit remarkable laminar and regional specificity and that this is organized in accordance with cellular birthdate. Strikingly, birthdated cholinergic projections within the cortex follow an inside-out pattern of innervation. While early born cholinergic populations target deep layers, late born ones innervate superficial laminae. We also find that birthdate predicts cholinergic innervation patterns within the amygdala, hippocampus, and prefrontal cortex. Our work reveals previously unappreciated specificity within the cholinergic system and the developmental logic by which these circuits are assembled.

developmental biology↗

bioRxiv2018

Heterosynaptic Plasticity Normalizes Cortical Excitatory-Inhibitory Balance

Excitation in neural circuits must be carefully controlled by inhibition to regulate information processing and network excitability. During development, cortical inhibitory and excitatory inputs are initially mismatched but become co-tuned or balanced with experience. However, little is known about how excitatory-inhibitory balance is defined at most synapses, or the mechanisms for establishing or maintaining this balance at specific set-points. Here we show how coordinated long-term plasticity calibrates populations of excitatory/inhibitory inputs onto mouse auditory cortical pyramidal neurons. Pairing pre- and postsynaptic activity induced plasticity at paired inputs and different forms of heterosynaptic plasticity at the strongest unpaired synapses, which required minutes of activity and dendritic Ca2+ signaling to be computed. Theoretical analyses demonstrated how the relative rate of heterosynaptic plasticity could normalize and stabilize synaptic strengths to achieve any possible excitatory-inhibitory correlation. Thus excitatory-inhibitory balance is dynamic and cell-specific, determined by distinct plasticity rules across multiple excitatory and inhibitory synapses.

neuroscience↗