Abstract
We investigated the existence of the transgenerational memory of iron (Fe) deficiency stress, in Arabidopsis thaliana. Plants were grown under Fe deficiency/sufficiency, and so were their offspring. The frequency of somatic homologous recombination (SHR) events, of DNA strand breaks as well as the expression of the transcription elongation factor TFIIS-like gene increase when plants are grown under Fe deficiency. However, SHR frequency, DNA strand break events, and TFIIS-like gene expression do not increase further when plants are grown for more than one generation under the same stress, and furthermore, they decrease back to control values within two succeeding generations grown under control conditions, regardless of the Fe deficiency stress history of the mother plants. Seedlings produced from plants grown under Fe deficiency evolve more oxygen than control seedlings, when grown under Fe sufficiency: however, this trait is not associated with any change in the protein profile of the photosynthetic apparatus and is not transmitted to more than one generation. Lastly, plants grown for multiple generations under Fe deficiency produce seeds with greater longevity: however, this trait is not inherited in offspring generations unexposed to stress. These findings suggest the existence of multiple-step control of mechanisms to prevent a genuine and stable transgenerational transmission of Fe deficiency stress memory, with the tightest control on DNA integrity.
Highlights
Transgenerational iron deficiency stress memory the first exposure to stress (Conrath et al, 2006) and long-lasting responses may be mediated by chromatin remodeling, such as histone modifications and DNA methylation (Jaskiewicz et al, 2011; Paszkowski and Grossniklaus, 2011; Pastor et al, 2013a; Vriet et al, 2015)
O2 evolution in pH 7.7 s1 pH 7.7 s2 is no longer statistically significant (Figure 6A). These results show that O2 evolution was higher in seedlings grown in control conditions and with parental plants which had experienced Fe deficiency, in agreement with what was observed for chlorophyll content; this trait was lost within two generations unexposed to stress
For the first time, whether a genuine transgenerational memory of Fe deficiency stress occurs in the model plant A. thaliana; we demonstrated that Fe deficiency alters DNA damage and repair and we analyzed such traits in unstressed offspring (Vriet et al, 2015); we analyzed physiological effects of Fe deficiency occurring in unstressed offspring (Verhoeven and van Gurp, 2012), such as the status of the photosynthetic apparatus and seed longevity; all these traits are agronomically and economically relevant
Summary
Transgenerational iron deficiency stress memory the first exposure to stress (Conrath et al, 2006) and long-lasting responses may be mediated by chromatin remodeling, such as histone modifications and DNA methylation (Jaskiewicz et al, 2011; Paszkowski and Grossniklaus, 2011; Pastor et al, 2013a; Vriet et al, 2015). A screen for Arabidopsis mutants impaired in the erasure of epigenetic stress memory, identified the nucleosome remodeller Morpheus’ Molecule 1 MOM1 as a chromatin regulator acting in the restoration of the Arabidopsis epigenome to a pre-stress condition, together with another chromatin regulator Decrease in DNA Methylation 1 DDM1 (Iwasaki and Paszkowski, 2014). The analysis of loci activated by heat stress and still transgenerationally active in ddm1mom double mutants progeny plants identified 340 genes, out of around a total 3000 genes activated by same stress conditions (Tittel-Elmer et al, 2010), suggesting that DDM1 and MOM1 control only a fraction of the erasure of the transgenerational stress memory (Iwasaki and Paszkowski, 2014)
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