Inter-generational consequences for growing Caenorhabditis elegans in liquid

Abstract

In recent years, studies in Caenorhabditis elegans nematodes have shown that different stresses can generate multigenerational changes. Here, we show that worms that grow in liquid media, and also their plate-grown progeny, are different from worms whose ancestors were grown on plates. It has been suggested that C. elegans might encounter liquid environments in nature, although actual observations in the wild are few and far between. By contrast, in the laboratory, growing worms in liquid is commonplace, and often used as an alternative to growing worms on agar plates, to control the composition of the worms' diet, to starve (and synchronize) worms or to grow large populations for biochemical assays. We found that plate-grown descendants of M9 liquid medium-grown worms were longer than control worms, and the heritable effects were already apparent very early in development. We tested for the involvement of different known epigenetic inheritance mechanisms, but could not find a single mutant in which these inter-generational effects are cancelled. While we found that growing in liquid always leads to inter-generational changes in the worms’ size, trans-generational effects were found to be variable, and in some cases, the effects were gone after one to two generations. These results demonstrate that standard cultivation conditions in early life can dramatically change the worms' physiology in adulthood, and can also affect the next generations. This article is part of the theme issue ‘Developing differences: early-life effects and evolutionary medicine’.

A parental transcriptional response to microsporidia infection induces inherited immunity in offspring

“…Several inherited multigenerational responses that last for more than two generations are dependent on RNAi pathways 16,52 . Consistent with recent reports of responses that last only one or two generations being transmitted independent of these pathways, heritable immunity to microsporidia (which lasts a single generation) is not reliant on RNAi machinery 19,37 .…”

“…To explore this, we tested whether mutants defective in small-RNA inheritance and histone modification were able to transmit immunity phenotypes to offspring. We found that the offspring of N. parisii infected mutants still became protected against infection ( Figure S7A-D) 19,37 . In addition, we found that the master immune regulator PMK-1 was not required for the induction of immunity, consistent with this pathway not being involved in immunity to N. parisii ( Figure S7C-D) 27 .…”

“…We found that the offspring of N. parisii infected mutants still became protected against infection ( fig. S8, A to D) 19,36 . In addition, we found that the master immune regulator PMK-1 was not required for the induction of inherited immunity, consistent with this pathway not being involved in immunity to N. parisii ( fig.…”

Prohibitin depletion extends lifespan of a TORC2/SGK-1 mutant through autophagy

“…HIF-1 depletion did not increase P hsp-6 ::GFP (average FC 1.067) in our screen as when assayed on plate (Figure 3A). One possible explanation is that liquid growing conditions are energetically more demanding, metabolism is altered and the UPR mt might be differentially regulated [59]. We reasoned that transcription factors that genetically interact with sgk-1 should further reduce worm size.…”

Phenotypic Screening in C. elegans as a Tool for the Discovery of New Geroprotective Drugs

“…First, lifespan of worms grown in monoxenic liquid culture may be different from those grown on solid medium [179]. Worms grown in liquid culture are longer [245] and have a higher incidence of internal hatching [246] compared to NGM agar. Liquid culture also induces changes in gene expression [247,248].…”