Biology subjects

Jamet, J.-L.

Publications and source records attributed to Jamet, J.-L..

4 recordsLinked to original sources

bioRxiv2023

Complete zooplankton size spectra re-constructed from in situ imaging and Multinet data in the global ocean

Plankton size spectra are important indicators of the ecosystem state, as they illustrate the quantity of organisms available for higher marine food web and reflect multiple size-dependent processes. Yet, such measurements are typically biased by the available sampling methods, either disrupting fragile organisms or lacking good resolution (in size and/or time and space). In this study, we combined two of the most common approaches to measure zooplankton Normalized Biomass/Biovolume Size Spectra (NBSS) to calculate a complete zooplankton distribution for organisms larger than 1 mm. The reconstructed NBSS slopes appeared steeper and closer to those measured by the UVP5 (+7.6%) and flatter than those of the Multinet (- 20%) particularly in tropics and temperate latitudes. The overall gain in polar biomass was relatively small for reconstructed biomass compared to bulk estimates from Multinet (+0.24 mgC/m3 or +4.25%) and high from the UVP5 (+2.0 mgC/m3 or +53%). In contrast, in the tropical and temperate ecosystems, the gain in biomass was small for UVP5 (+0.67 mgC/m3 or +30.44% and +0.74 mgC/m3 or +19.59% respectively) and high for Multinet (+1.66 mgC/m3 or +136% and +3.4 mgC/m3 or +309% respectively). Given these differences, we suggest here to combine in situ imaging sensors and net data in any comprehensive study exploring key living players in the ocean ecosystem and their contributions to the biological pump.

ecology↗

bioRxiv2021

Male differentiation in the marine copepod Oithona nana reveals the development of a new nervous ganglion linked to Lin12-Notch-Repeat protein-associated proteolysis

BackgroundCopepods are among the most numerous animals, and play an essential role in the marine trophic web and biogeochemical cycles. The genus Oithona is described as having the highest density of copepods, and as being the most cosmopolite copepods. The Oithona male paradox describes the activity states of males, which are obliged to alternate between immobile and mobile phases for ambush feeding and mate searching, respectively, while the female is typically less mobile and often feeding. To characterize the molecular basis of this sexual dimorphism, we combined immunofluorescence, genomics, transcriptomics, and protein-protein interaction approaches. ResultsImmunofluorescence of {beta}3- and -tubulin revealed two male-specific nervous ganglia in the lateral first segment of the Oithona nana males prosome. In parallel, transcriptomic analysis showed male-specific enrichment for nervous system development-related transcripts. Twenty-seven Lin12-Notch Repeat domain-containing protein coding genes (LDPGs) of the 75 LDPGs identified in the genome were specifically expressed only in males. Furthermore, most of the LDPGs (27%) coded for proteins having predicted proteolytic activity, and non-LDPG proteolysis-associated transcripts showed a male-specific enrichment. Using yeast double-hybrid assays, we constructed a protein-protein interaction network involving two LDPs with proteases, extracellular matrix proteins, and neurogenesis-related proteins. ConclusionsFor the first time, our study describes the lateral nervous ganglia of O. nana males, unique to copepods. We also demonstrated a role of LDPGs and their associated proteolysis in male-specific physiology, and we hypothesize a role of the LDPGs in the development of the lateral ganglia through directed lysis of the extracellular matrix for the growth of neurites and genesis of synapses.

molecular biology↗

bioRxiv2019

Proteolysis and neurogenesis modulated by LNR domain proteins explosion support male differentiation and sacrificial behaviour in the iteroparous crustacean Oithona nana.

Copepods are the most numerous animals and play an essential role in the marine trophic web and biogeochemical cycles. The genus Oithona is described as having the highest numerical density, as the most cosmopolite copepod and iteroparous. The Oithona male paradox obliges it to alternate feeding (immobile) and mating (mobile) phases. As the molecular basis of this trade-off is unknown, we investigated this sexual dimorphism at the molecular level by integrating genomic, transcriptomic and protein-protein interaction analyses.\n\nWhile a ZW sex-determination system was predicted in O. nana, a fifteen-year time-series in the Toulon Little Bay showed a biased sex ratio toward females (male / female ratio < 0.15{+/-}0.11) highlighting a higher mortality in male. Here, the transcriptomic analysis of the five different developmental stages showed enrichment of Lin12-Notch Repeat (LNR) domains-containing proteins coding genes (LDPGs) in male transcripts. The male also showed enrichment in transcripts involved in proteolysis, nervous system development, synapse assembly and functioning and also amino acid conversion to glutamate. Moreover, several male down-regulated genes were involved in the increase of food uptake and digestion. The formation of LDP complexes was detected by yeast two-hybrid, with interactions involving proteases, extracellular matrix proteins and neurogenesis related proteins.\n\nTogether, these results suggest that the O. nana male hypermotility is sustained by LDP-modulated proteolysis allowing the releases and conversions of amino acid into the excitatory neurotransmitter glutamate. This process could permit new axons and dendrites formation suggesting a sexual nervous system dimorphism. This could support the hypothesis of a sacrificial behaviour in males at the metabolic level.

molecular biology↗

bioRxiv2019

Linking Allele-Specific Expression And Natural Selection In Wild Populations

Allele-specific expression (ASE) is a widely studied molecular mechanism at cell, tissue and organism levels. Here, we extrapolated the concept of ASE to the population-scale (psASE), aggregating ASEs detected at smaller scales. We developed a novel approach to detect psASE based on metagenomic and metatranscriptomic data of environmental samples containing communities of organisms. This approach which measures the deviation between the frequency and the relative expression of biallelic loci, was applied on samples collected during the Tara Oceans expedition (2009-2013), in combination to new Oithona similis transcriptomes, a widespread marine copepod. Among a total of 25,768 single nucleotide variants (SNVs) of O. similis, 587 (2.3%) were targeted by psASE in at least one population. The distribution of SNVs targeted by psASE in different populations is significantly shaped by population genomic differentiation (p-value = 9.3x10-9), supporting a partial genetic control of psASE. To investigate the link between evolution and psASE, loci under selection were compared to loci under psASE. A significant amount of SNVs (0.6%) were targeted by both selection and psASE (p-values < 9.89x10-3), supporting the hypothesis that natural selection and ASE may lead to the same phenotype. Population-scale ASE offers new insights into the gene regulation control in populations and its link with natural selection.

genomics↗