Identification and Characterization of Spontaneous Auxotrophic Mutants in &lt;em&gt;Fusarium langsethiae&lt;/em&gt;

Toker

et al. 2019

Preprint

In C. elegans nematodes, components of liquid-like germ granules were shown to be required for transgenerational small RNA inheritance. Surprisingly, we show here that mutants with defective germ granules (pptr-1, meg-3/4, pgl-1) can nevertheless inherit potent small RNA-based silencing responses, but some of the mutants lose this ability after many generations of homozygosity. Animals mutated in pptr-1, which is required for stabilization of P granules in the early embryo, display extremely strong heritable RNAi responses, which last for tens of generations, long after the responses in wild type animals peter out. The phenotype of mutants defective in the core germ granules proteins MEG-3 and MEG-4, depends on the genotype of the ancestors: Mutants that derive from maternal lineages that had functional MEG-3 and MEG-4 proteins exhibit enhanced RNAi inheritance for multiple generations. While functional ancestral meg-3/4 alleles correct, and even potentiates the ability of mutant descendants to inherit RNAi, defects in germ granules functions can be memorized as well; Wild type descendants that derive from lineages of mutants show impaired RNAi inheritance for many (>16) generations, although their germ granules are intact. Importantly, while P granules are maternally deposited, wild type progeny derived from meg-3/4 male mutants also show reduced RNAi inheritance. Unlike germ granules, small RNAs are inherited also from the sperm.Moreover, we find that the transgenerational effects that depend on the ancestral germ granules require the argonaute protein HRDE-1, which carries heritable small RNAs in the germline. Indeed, small RNA sequencing reveals imbalanced levels of many endogenous small RNAs in germ granules mutants. Strikingly, we find that hrde-1;meg-3/4 triple mutants inherit RNAi, although hrde-1 was previously thought to be essential for heritable silencing. We propose that germ granules sort and shape the RNA pool, and that small RNA inheritance memorizes this activity for multiple generations.

“…RNAi inheritance experiments 5,7,14,35 . Surprisingly, when we tested pptr-1 and meg-3/4 mutants, we found that both strains exhibit enhanced RNAi inheritance.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Germ Granules Functions are Memorized by Transgenerationally Inherited Small RNAs

Toker

et al. 2019

Preprint

“…Previously, histone-H3-lysine-9 (H3K9) methylations were implicated in trans-generational inheritance of small RNAs [47][48][49][50]. H3K9 mono-and di-methylations are deposited by the MET-2 methyltransferase [51], while H3K9me3 is deposited by the SET-25 and SET-32 methyltransferases [51,52].…”

Section: (A) Progeny Of Liquid-grown Worms Are Longermentioning

confidence: 99%

Inter-generational consequences for growing Caenorhabditis elegans in liquid

Bril

Liu

et al. 2019

Phil. Trans. R. Soc. B

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’.

“…H3K9 mono and di-methylations are deposited by the MET-2 methyltransferase [51], while H3K9me3 is deposited by the SET-25 and SET-32 methyltransferases [51,52]. We found that met-2, set-25 and set-32 mutants also inherit the elongated morphology from their liquid-grown parents (Figure 4).…”

Section: Progeny Of Liquid-grown Worms Are Longer Even In Mutants Defmentioning

confidence: 76%

Inter-generational Consequences for Growing C.elegans in Liquid

Bril

Liu

et al. 2018

Preprint

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. In contrast, in the lab, 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 media-grown worms were longer than control worms, and the heritable effects were apparent already 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 intergenerational effects are canceled. 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 1-2 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.