Homeostatic systems that rely on genetic regulatory networks are intrinsically limited by the transcriptional response time, which may restrict a cell's ability to adapt to unanticipated environmental challenges. To bypass this limitation, cells have evolved mechanisms whereby exposure to mild stress increases their resistance to subsequent threats. However, the mechanisms responsible for such adaptive homeostasis remain largely unknown. Here, we used live-cell imaging and microfluidics to investigate the adaptive response of budding yeast to temporally controlled H 2 O 2 stress patterns. We demonstrate that acquisition of tolerance is a systems-level property resulting from nonlinearity of H 2 O 2 scavenging by peroxiredoxins and our study reveals that this regulatory scheme induces a striking hormetic effect of extracellular H 2 O 2 stress on replicative longevity. Our study thus provides a novel quantitative framework bridging the molecular architecture of a cellular homeostatic system to the emergence of nonintuitive adaptive properties.
RESUME Les activités humaines ont favorisé l'émergence de guildes particulières de micromammifères. La diffusion et la radiation adaptative de la guilde des souris en Europe sont analysées d'un point de vue archéozoologique et écologique. Plus généralement, depuis le Plio-Pléistocène les faunes de mammifères subissent les conséquences des activités humaines. Celles- ci entraînent donc, outre des changements dans la composition des faunes, des modifications radicales dans la structure des communautés. Ces bouleversements fauniques s'apparentent à ceux observés lors des grandes crises écoclimatiques. L'anthropisation de la biosphère apparaît ainsi comme le fait générateur d'une crise écologique majeure.
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