A Stress-Activated Transposon in Arabidopsis Induces Transgenerational Abscisic Acid Insensitivity

Abstract

Transposable elements (TEs), or transposons, play an important role in adaptation. TE insertion can affect host gene function and provides a mechanism for rapid increases in genetic diversity, particularly because many TEs respond to environmental stress. In the current study, we show that the transposition of a heat-activated retrotransposon, ONSEN, generated a mutation in an abscisic acid (ABA) responsive gene, resulting in an ABA-insensitive phenotype in Arabidopsis, suggesting stress tolerance. Our results provide direct evidence that a transposon activated by environmental stress could alter the genome in a potentially positive manner. Furthermore, the ABA-insensitive phenotype was inherited when the transcription was disrupted by an ONSEN insertion, whereas ABA sensitivity was recovered when the effects of ONSEN were masked by IBM2. These results suggest that epigenetic mechanisms in host plants typically buffered the effect of a new insertion, but could selectively “turn on” TEs when stressed.

The Arabidopsis DNA Methylome Is Stable under Transgenerational Drought Stress

“…This is unsurprising, given the expected relationship between DNA methylation and TEs. TE movement is considered to be a driving force in the appearance of epialleles (facilitated or obligatory epi-alleles; Richards, 2006), and, indeed, documented environmentally induced epigenetic changes correlate with, although are not always necessary for, TE activity (Ito et al, 2011(Ito et al, , 2016Eichten et al, 2013;Ong-Abdullah et al, 2015;Stuart et al, 2016). Future studies should take into consideration the impact of TE regulation, under conditions of abiotic stress particularly in species with greater TE content, which possibly underpins at least a subset of the stochastic or spontaneous epi-alleles observed in this study.…”

The “Polyploid Hop”: Shifting Challenges and Opportunities Over the Evolutionary Lifespan of Genome Duplications

“…The best example of this adaptive potential can be found in the classic case of industrial melanism in the peppered moth, where a young TE insertion that appeared and rapidly rose to fixation during the industrial revolution (∼200 years ago) has been proposed as responsible for the dark morph providing camouflage from predators ( Van't Hof et al, 2016). The variation produced by TE activity can thus become a fruitful target of natural selection, providing adaptive solutions to the very stresses that initiated their reactivation (Ito et al, 2016). Thus, a global transposition burst triggered by genomic shock could immediately provide nascent polyploids with a pool of high-effect mutations to test against new challenges.…”

Transcriptome-wide Identification and Expression Analysis of Brachypodium distachyon Transposons in Response to Viral Infection

“…Since the discovery of transposable elements (TEs) by Barbara McClintock in maize (McClintock, 1950) the origins, roles, and regulation of TEs have been subject to tremendous interest. They have long been assumed as "silent, "junk" or "selfish" DNA; however, recent studies have revealed that most of these repetitive sequences have potential roles in affecting host gene regulation and genomic rearrangements (Lisch, 2013;Ito et al, 2016). In addition several studies have shown that under abiotic or biotic stress TEs are activated or transcribed (Negi et al, 2016).…”