RNA interference (RNAi) is heritable in Caenorhabditis elegans; the progeny of C. elegans exposed to dsRNA inherit the ability to silence genes that were targeted by RNAi in the previous generation. ...Here we investigate the mechanism of RNAi inheritance in C. elegans. We show that exposure of animals to dsRNA results in the heritable expression of siRNAs and the heritable deposition of histone 3 lysine 9 methylation (H3K9me) marks in progeny. siRNAs are detectable before the appearance of H3K9me marks, suggesting that chromatin marks are not directly inherited but, rather, reestablished in inheriting progeny. Interestingly, H3K9me marks appear more prominently in inheriting progeny than in animals directly exposed to dsRNA, suggesting that germ-line transmission of silencing signals may enhance the efficiency of siRNA-directed H3K9me. Finally, we show that the nuclear RNAi (Nrde) pathway maintains heritable RNAi silencing in C. elegans. The Argonaute (Ago) NRDE-3 associates with heritable siRNAs and, acting in conjunction with the nuclear RNAi factors NRDE-1, NRDE-2, and NRDE-4, promotes siRNA expression in inheriting progeny. These results demonstrate that siRNA expression is heritable in C. elegans and define an RNAi pathway that promotes the maintenance of RNAi silencing and siRNA expression in the progeny of animals exposed to dsRNA.
In the fight to resist environmental toxins, Caenorhabditis elegans might have co-opted cysteine-synthase-related enzymes that were likely acquired from algae and then integrated them into a ...hypoxia-signaling pathway to adapt to cyanide.
Alzheimer's, Parkinson's and Huntington's diseases can be caused by mutations that enhance protein aggregation, but we still do not know enough about the molecular players of these pathways to ...develop treatments for these devastating diseases. Here, we screen for mutations that might enhance aggregation in Caenorhabditis elegans, to investigate the mechanisms that protect against dysregulated homeostasis. We report that the stomatin homologue UNC‐1 activates neurohormonal signalling from the sulfotransferase SSU‐1 in ASJ sensory/endocrine neurons. A putative hormone, produced in ASJ, targets the nuclear receptor NHR‐1, which acts cell autonomously in the muscles to modulate polyglutamine repeat (polyQ) aggregation. A second nuclear receptor, DAF‐12, functions oppositely to NHR‐1 to maintain protein homeostasis. Transcriptomics analyses of unc‐1 mutants revealed changes in the expression of genes involved in fat metabolism, suggesting that fat metabolism changes, controlled by neurohormonal signalling, contribute to protein homeostasis. Furthermore, the enzymes involved in the identified signalling pathway are potential targets for treating neurodegenerative diseases caused by disrupted protein homeostasis.
Synopsis
A neurohormonal signal emanating from Caenorhabditis elegans ASJ neurons modulates protein homeostasis in the body wall muscles. The signal depends on the stomatin homologue UNC‐1 in neurons and the nuclear receptor NHR‐1 in muscles.
Electrical synapse disruption modulates protein homeostasis in a non‐cell autonomous manner in C. elegans.
PolyQ aggregation in muscles is modulated by a neurohormonal signal involving the sulfotransferase SSU‐1 and sulfatases SUL‐2 and SUL‐3.
The nuclear receptor NHR‐1 is a transcription factor that regulates lipid gene expression to modulate proteostasis in the muscle.
A neurohormonal signal emanating from Caenorhabditis elegans ASJ neurons modulates protein homeostasis in the body wall muscles. The signal depends on the stomatin homologue UNC‐1 in neurons and the nuclear receptor NHR‐1 in muscles.
Comprehensive major-, trace-element and rhenium–osmium (Re–Os) isotope data are presented for abyssal peridotites from Ocean Drilling Program (ODP) Leg 209, in the North Atlantic. The samples are ...from a single core (Site 1274A) located on the western wall of the axial rift valley of the Mid-Atlantic ridge, and their study allows elemental and isotope information to be precisely related to spatial variations in primary lithology, serpentinisation and seafloor weathering. The harzburgites and dunites at this site are highly serpentinised (with the degree of serpentinisation increasing with depth below the sea floor). Petrographic observations and variations of fluid mobile elements (such as Ba, Sr, U, and Re) are consistent with seawater interaction in the upper part of the core. Nevertheless, major and trace element indicators of the extent of melt depletion indicate extreme melt loss, and suggest that these are amongst the most depleted abyssal peridotites recovered thus far. Despite the evidence for extensive serpentinisation and sea floor weathering all of the samples possess
187Os/
188Os isotope compositions that are less radiogenic than estimates for the primitive upper mantle (PUM), lower than any yet reported for abyssal peridotites, and consistent with melt loss over, at least, the past 1.5
Ga. Single sulphide Re–Os data show evidence for recent recrystallisation or diffusional modification either due to partial melting or seawater alteration. However, some grains are extremely unradiogenic (
187Os/
188Os
=
0.114) providing unequivocal evidence for at least some degree of melt depletion at ca. 2
Ga. Taken with recently published data these results suggest that ancient melt depletion may be a widespread feature of the oceanic upper lithosphere, even though evidence for this depleted reservoir has not yet been observed in the Re–Os chemistry of mid-ocean ridge basalts.
The evolution of eusociality Tarnita, Corina E; Wilson, Edward O; Nowak, Martin A
Nature (London),
08/2010, Letnik:
466, Številka:
7310
Journal Article
Recenzirano
Odprti dostop
Eusociality, in which some individuals reduce their own lifetime reproductive potential to raise the offspring of others, underlies the most advanced forms of social organization and the ecologically ...dominant role of social insects and humans. For the past four decades kin selection theory, based on the concept of inclusive fitness, has been the major theoretical attempt to explain the evolution of eusociality. Here we show the limitations of this approach. We argue that standard natural selection theory in the context of precise models of population structure represents a simpler and superior approach, allows the evaluation of multiple competing hypotheses, and provides an exact framework for interpreting empirical observations.
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