The Temperature-Dependent Change in Methylation of theAntirrhinumTransposon Tam3 Is Controlled by the Activity of Its Transposase

Abstract

The Antirrhinum majus transposon Tam3 undergoes low temperature-dependent transposition (LTDT). Growth at 158C permits transposition, whereas growth at 258C strongly suppresses it. The degree of Tam3 DNA methylation is altered somatically and positively correlated with growth temperature, an exceptional epigenetic system in plants. Using a Tam3-inactive line, we show that methylation change depends on Tam3 activity. Random binding site selection analysis and electrophoretic mobility shift assays revealed that the Tam3 transposase (TPase) binds to the major repeat in the subterminal regions of Tam3, the site showing the biggest temperature-dependent change in methylation state. Methylcytosines in the motif impair the binding ability of the TPase. Proteins in a nuclear extract from plants grown at 158C but not 258C bind to this motif in Tam3. The decrease in Tam3 DNA methylation at low temperature also requires cell division. Thus, TPase binding to Tam3 occurs only during growth at low temperature and immediately after DNA replication, resulting in a Tam3-specific decrease in methylation of transposon DNA. Consequently, the Tam3 methylation level in LTDT is regulated by Tam3 activity, which is dependent on the ability of its TPase to bind DNA and affected by growth temperature. Thus, the methylation/demethylation of Tam3 is the consequence, not the cause, of LTDT.

TheCaenorhabditis elegans rsd-2andrsd-6Genes Are Required for Chromosome Functions During Exposure to Unfavorable Environments

“…Furthermore, as nondisjunction, transposon mobilization, and membrane functions such as secretion are intrinsically environmentally sensitive even in wild-type organisms, we hypothesize that rsd-2 and rsd-6 contribute to buffering activities that facilitate proper functioning of chromosomes as cells experience unfavorable environments. Demonstrations of environmental influences on transposon mobilization, nondisjunction, and chromosomal recombination have long been noted (Hildreth and Ulrichs 1969;Rose and Baillie 1979;Hashida et al 2006). These mechanisms can result in large-scale genetic changes that are driving forces for evolution.…”

Analysis of DNA methylation of perennial ryegrass under drought using the methylation-sensitive amplification polymorphism (MSAP) technique

“…Transposons have reportedly shown changes in methylation status during plant development and adverse stresses (Banks et al 1988;Slotkin et al 2009;Li et al 2010). The methylation/demethylation of transposons can affect programmed genome epigenetic regulation and the expressions of downstream genes in plants, which can be altered by environmental stresses (Yaish 2013;Cokus et al 2008;Hashida et al 2003Hashida et al , 2006. Transposon inactivity is necessary for the stable maintenance of the genome, but the hypomethylation of transposons can activate transcription and transposition.…”

Epigenetic control of plant stress response

“…Low temperature treatment decreases methylation and increases the excision rate of Tam3 transposon by binding its transposase to GCHCG (H 5 not G) sites immediately after DNA replication, thus preventing de novo sequence methylation [Hashida et al, 2003[Hashida et al, ,2006. Stress-mediated induction was shown for Tos17 (rice) [Hirochika et al, 1996], Tto1 (tobacco) [Takeda et al, 1999], Tnt1 (tobacco) [Beguiristain et al, 2001], and BARE-1 (barley) [Kalendar et al, 2000] retrotransposons.…”