scholarly journals The PIWI/piRNA response is relaxed in a rodent that lacks mobilizing transposable elements

2019 ◽  
Author(s):  
Michael W. Vandewege ◽  
Roy N. Patt ◽  
Dana K. Merriman ◽  
David A. Ray ◽  
Federico G. Hoffmann
Keyword(s):  
Transposable Elements ◽  
Ground Squirrel ◽  
Small Rnas ◽  
Oryctolagus Cuniculus ◽  
Genome Integrity ◽  
European Rabbit ◽  
Present Evidence ◽  
Major Threat ◽  
Crucial Difference ◽  
Mammalian Genomes

AbstractTransposable elements (TEs) have the capability to propagate throughout genomes. Mammalian genomes are typically dominated by LINE retrotransposons and their associated SINEs, and their mobilization in the germline is a challenge to genome integrity. There are genomic defenses against TE proliferation and the PIWI/piRNAs defense is among the most well understood. However, the PIWI/piRNA system has been investigated largely in animals with abundant and actively mobilizing TEs and it is unclear how the PIWI/piRNA system functions in the absence of mobilizing TEs. The thirteen-lined ground squirrel provides an excellent opportunity to examine PIWI/piRNA and TE dynamics within the context of minimal, and possibly nonexistent, TE accumulation. We sequenced RNA and small RNAs pools from the testis of juvenile and adult squirrels and compared results to TE and PIWI/piRNA dynamics in the European rabbit (Oryctolagus cuniculus) and house mouse (Mus musculus). Interestingly in squirrels, despite a lack of young insertions, TEs were still actively transcribed in comparable levels to mouse and rabbit. All three PIWI proteins were either not expressed, or only minimally expressed, prior to P8 in squirrel testis, moreover we also discovered that PIWIL4 is expressed all the way into adulthood in the squirrel. This is a crucial difference as PIWIL4 is understood to facilitate TE methylation. We present evidence the PIWI/piRNA system reduced TE expression in rabbit and mouse, but the squirrel PIWIs largely did not affect TE expression. These observations indicate that L1s do not represent a major threat to genome integrity in the squirrel genome, and therefore repression mechanisms have relaxed.

scholarly journals Nurse cell-derived small RNAs define paternal epigenetic inheritance in Arabidopsis

2021 ◽  
Author(s):  
Jincheng Long ◽  
James Walker ◽  
Wenjing She ◽  
Billy Aldridge ◽  
Hongbo Gao ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Small Rnas ◽  
Nurse Cell ◽  
De Novo ◽  
Epigenetic Inheritance ◽  
Genome Integrity ◽  
Nurse Cells ◽  
Male Germline ◽  
Methylation Patterns

AbstractThe plant male germline undergoes DNA methylation reprogramming, which methylates genes de novo and thereby alters gene expression and facilitates meiosis. Why reprogramming is limited to the germline and how specific genes are chosen is unknown. Here, we demonstrate that genic methylation in the male germline, from meiocytes to sperm, is established by germline-specific siRNAs transcribed from transposons with imperfect sequence homology. These siRNAs are synthesized by meiocyte nurse cells (tapetum) via activity of the tapetum-specific chromatin remodeler CLASSY3. Remarkably, tapetal siRNAs govern germline methylation throughout the genome, including the inherited methylation patterns in sperm. Finally, we demonstrate that these nurse cell-derived siRNAs (niRNAs) silence germline transposons, thereby safeguarding genome integrity. Our results reveal that tapetal niRNAs are sufficient to reconstitute germline methylation patterns and drive extensive, functional methylation reprogramming analogous to piRNA-mediated reprogramming in animal germlines.

scholarly journals Hypomethylated poplars show higher tolerance to water deficit and highlight a dual role for DNA methylation in shoot meristem: regulation of stress response and genome integrity

2020 ◽  
Author(s):  
M.D. Sow ◽  
A-L. Le Gac ◽  
R. Fichot ◽  
S. Lanciano ◽  
A. Delaunay ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Stress Response ◽  
Transposable Elements ◽  
Water Deficit ◽  
Shoot Apical Meristem ◽  
Apical Meristem ◽  
Shoot Meristem ◽  
Genome Integrity ◽  
Dependent Manner ◽  
Altered Expression

AbstractAs fixed and long living organisms subjected to repeated environmental stresses, trees have developed mechanisms such as phenotypic plasticity that help them to cope with fluctuating environmental conditions. Here, we tested the role DNA methylation as a hub of integration, linking plasticity and physiological response to water deficit in the shoot apical meristem of the model tree poplar (Populus). Using a reverse genetic approach, we compared hypomethylated RNAi-ddm1 lines to wild-type trees for drought tolerance. An integrative analysis was realized with phytohormone balance, methylomes, transcriptomes and mobilomes.Hypomethylated lines were more tolerant when subjected to moderate water deficit and were intrinsically more tolerant to drought-induced cavitation. The alteration of the DDM1 machinery induced variation in DNA methylation in a cytosine context dependent manner, both in genes and transposable elements. Hypomethylated lines subjected to water deficit showed altered expression of genes involved in phytohormone pathways, such as salicylic acid and modified hormonal balance. Several transposable elements showed stress- and/or line-specific patterns of reactivation, and we could detect copy number variations for two of them in stressed ddm1 lines.Overall, our data highlight two major roles for DNA methylation in the shoot apical meristem: control of stress response and plasticity through transduction of hormone signaling and maintenance of genome integrity through the control of transposable elements.

Mother-Young and Within-Litter Relations in the European Rabbit Oryctolagus cuniculus

2008 ◽  
pp. 211-223 ◽  
Author(s):  
Amando Bautista ◽  
Margarita Martínez-Gómez ◽  
Robyn Hudson
Keyword(s):  
Oryctolagus Cuniculus ◽  
European Rabbit
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