The elucidation of stress memory inheritance in Brassica rapa plants

Abstract

Plants are able to maintain the memory of stress exposure throughout their ontogenesis and faithfully propagate it into the next generation. Recent evidence argues for the epigenetic nature of this phenomenon. Small RNAs (smRNAs) are one of the vital epigenetic factors because they can both affect gene expression at the place of their generation and maintain non-cell-autonomous gene regulation. Here, we have made an attempt to decipher the contribution of smRNAs to the heat-shock-induced transgenerational inheritance in Brassica rapa plants using sequencing technology. To do this, we have generated comprehensive profiles of a transcriptome and a small RNAome (smRNAome) from somatic and reproductive tissues of stressed plants and their untreated progeny. We have demonstrated that the highest tissue-specific alterations in the transcriptome and smRNAome profile are detected in tissues that were not directly exposed to stress, namely, in the endosperm and pollen. Importantly, we have revealed that the progeny of stressed plants exhibit the highest fluctuations at the smRNAome level but not at the transcriptome level. Additionally, we have uncovered the existence of heat-inducible and transgenerationally transmitted tRNA-derived small RNA fragments in plants. Finally, we suggest that miR168 and braAGO1 are involved in the stress-induced transgenerational inheritance in plants.

Integration of decoy domains derived from protein targets of pathogen effectors into plant immune receptors is widespread

“…Integrated domains are unlikely to act in downstream signaling triggered by NLR‐mediated effector recognition, which is thought to be rather conserved between NLRs and between species. An activity of the integrated domains in other pathways and in the absence of the Avr effector cannot be completely excluded until it is experimentally demonstrated not to occur, but seems, in particular in the cases where partial or nonfunctional domains are integrated, rather improbable (Wu et al ., 2015b). …”

“…Accordingly, effector targets are involved in a broad range of cellular pathways and have many different molecular functions, such as protein kinases, transcription factors and proteases (Martin & Kamoun, 2011; Deslandes & Rivas, 2012; Presti et al ., 2015). A third intermediate mode of effector recognition relies on the integration of decoy domains mimicking effector target proteins into NLRs (Césari et al ., 2014; Nishimura et al ., 2015; Wu et al ., 2015b). Integration of decoy domains was first suspected in poplar (Populus trichocarpa) , where 32 NLR proteins were found to carry the same additional domain (Germain & Séguin, 2011).…”

Epigenetic inheritance in apomictic dandelions : stress-induced and heritable modifications in DNA methylation and small RNA

“…Thus, in plants interaction between sRNAs and DNA methylation takes place in transmitting information between generations (Mirouze & Paszkowski 2011). Stress-induced sRNA inheritance has also been detected in some studies: Bilichak et al (2015) observed sRNAs that migrated from soma cells in stressed tissues to germ cells and the same sRNAs were found back in leaf tissue of the developed offspring. Rasmann et al (2012) showed epigenetic inheritance of induced defense and enhanced resistance against herbivory guided by transmitted sRNAs.…”

“…For example a previous study on an apomictic dandelion lineage revealed stress-induced (most notably chemical induction of herbivore and pathogen defenses) DNA methylation changes that were transmitted to the subsequent generation (Verhoeven et al 2010b). And in Brassica rapa a heat-stress induced effect on the small RNAs of the stressed plant and their unstressed progeny was observed (Bilichak et al 2015). In my thesis I investigated stress-induced epigenetic changes (DNA methylations and small RNAs) in several apomictic dandelion lineages by applying drought stress and salicylic acid, which mimics pathogen attack.…”

“…In few plant studies indications for epigenetic and transgenerational responses to stress were found, for instance in the form of heritable sRNA signals (Bilichak et al 2015) or as heritable DNA methylation changes (Verhoeven et al 2010b;Luna et al 2012). However, also stochastic epimutations can have important influences: a modeling study based on empirically observed epimutation rates in the Arabidopsis mutation accumulation lines suggests that they arise fast enough to uncouple epigenetic variation from genetic variation but revert slow enough to sustain long-term selection responses (van der Graaf et al 2015).…”