Biology subjects

Camilleri, V.

Publications and source records attributed to Camilleri, V..

3 recordsLinked to original sources

bioRxiv2023

Two distinct mechanisms lead to either oocyte or spermatocyte decrease in C. elegans after whole developmental exposure to gamma-rays

Wildlife is subject to various sources of pollution, including ionizing radiation. Adverse effects can impact organisms survival, growth, or reproduction, later affecting population dynamics. In invertebrates, reproduction, which directly impacts population dynamics, has been found to be the most radiosensitive endpoint. Understanding the underlying molecular pathways inducing this reproduction decrease can help to comprehend species-specific differences in radiosensitivity. In line with previous studies, we used a life stage dependent approach to better understand the molecular determinants of reproduction decrease, especially of gamete decrease, in the hermaphrodite roundworm Caenorhabditis elegans. Worms were chronically exposed to 50 mGy{middle dot}h-1 external gamma ionizing radiations throughout different developmental periods (namely embryogenesis, gametogenesis, and full development). Conserved molecular pathways across invertebrates and vertebrates involved in reproduction processes and stress response were analyzed: apoptosis and MAP kinase Ras/ERK (MPK-1). Our results showed that these pathways are life-stage dependant, resulting from an accumulation of damages upon chronic exposure to IR throughout the whole development. The Ras/ERK pathway was found to be activated in our conditions in the pachytene region of the gonad where it induces the apoptotic pathway, but not in the ovulation zone, showing no incidence on oocyte maturation and ovulation. Additionally, no effect on germ cell proliferation was found, meaning that Ras/ERK pathway is probably not involved in this process in our conditions. Finally, a functional analysis of apoptosis revealed that the decrease of ovulation rate is due to DNA-damaged induced apoptosis which does not occur in spermatocytes. Thus, sperm decrease seem to be mediated via another mechanism, probably a decrease in germ cells proliferation speed that needs further investigation to better characterize sex-specific responses to IR exposure.

pharmacology and toxicology↗

bioRxiv2020

Unusual evolution of tree frog populations in the Chernobyl exclusion zone

Despite the ubiquity of pollutants in the environment, their long-term ecological consequences are not always clear and still poorly studied. This is the case concerning the radioactive contamination of the environment following the major nuclear accident at the Chernobyl nuclear power plant. Notwithstanding the implications of evolutionary processes on the population status, few studies concern the evolution of organisms chronically exposed to ionizing radiation in the Chernobyl exclusion zone. Here, we examined genetic markers for 19 populations of Eastern tree frog (Hyla orientalis) sampled in the Chernobyl region about thirty years after the nuclear power plant accident to investigate microevolutionary processes ongoing in local populations. Genetic diversity estimated from nuclear and mitochondrial markers showed an absence of genetic erosion and higher mitochondrial diversity in tree frogs from the Chernobyl exclusion zone compared to other European populations. Moreover, the study of haplotype network permitted us to decipher the presence of an independent recent evolutionary history of Chernobyl exclusion zones Eastern tree frogs caused by an elevated mutation rate compared to other European populations. By fitting to our data a model of haplotype network evolution, we suspected that Eastern tree frog populations in the Chernobyl exclusion zone have a high mitochondrial mutation rate and small effective population sizes. These data suggest that Eastern tree frogs populations might offset the impact of deleterious mutations because of their large clutch size, but also question the long term impact of ionizing radiation on the status of other species living in the Chernobyl exclusion zone.

ecology↗

bioRxiv2020

Disruption of AtHAK/KT/KUP9 enhances plant cesium accumulation under low potassium supply

Understanding molecular mechanisms which underlie transport of cesium (Cs+) in plants is important to limit entry of its radioisotopes from contaminated area to the food chain. The potentially toxic element Cs+, which is not involved in any biological process, is chemically closed to the macronutrient potassium (K+). Among the multiple K+ carriers, the high-affinity K+ transporters family HAK/KT/KUP is thought to be relevant in mediating opportunistic Cs+ transport. On the 13 KUP identified in Arabidopsis thaliana, only HAK5, the major contributor to root K+ acquisition under low K+ supply, has been functionally demonstrated to be involved in Cs+ uptake in planta. In the present study, we showed that accumulation of Cs+ increased by up to 30% in two A. thaliana mutant lines lacking KUP9 and grown under low K+ supply. Since further experiments revealed that Cs+ release from contaminated plants to the external medium is proportionally lower in the two kup9 mutants, we proposed that KUP9 disruption could impair Cs+ efflux. By contrast, we did not measure significant impairment of K+ status in kup9 mutants suggesting that KUP9 disruption does not alter substantially K+ transport in experimental conditions used here. Putative primary role of KUP9 in plants is further discussed.

plant biology↗