Transgenerational phenotypic and epigenetic changes in response to heat stress inArabidopsis thaliana

Abstract

Abbreviations: ChiP, chromatin immunoprecipitation; DCL, Dicer-like; Dpg, days post germination; gDNA, genomic DNA; "C 1 ," progeny of control plants; "C 1 -", progeny of control plants grown under normal conditions; "C 1 +," progeny of control plants grown under stress conditions; "S 1 ," progeny of stress plants; "S 1 -," progeny of stressed plants grown under normal conditions; "S 1 +," progeny of stressed plants grown under stress conditions; qPCR, quantitative PCR; RdDM, RNA-directed DNA methylation; SAR, systemic acquired resistance; sRNAs, small RNAs; TE, transposable elements exposure to heat stress causes physiological and epigenetic changes in plants, which may also be altered in the progeny. We compared the progeny of stressed and control Arabidopsis thaliana wild type and Dicer-like mutant dcl2, dcl3, and dcl4 plants for variations in physiology and molecular profile, including global genome methylation, mRNa levels, and histone modifications in the subset of differentially expressed genes at normal conditions and in response to heat stress. We found that the immediate progeny of heat-stressed plants had fewer, but larger leaves, and tended to bolt earlier. Transposon expression was elevated in the progeny of heat-stressed plants, and heat stress in the same generation tended to decrease global genome methylation. Progeny of stressed plants had increased expression of HSFA2, and reduction in MSH2, ROS1, and several SUVH genes. Gene expression positively correlated with permissive histone marks and negatively correlated with repressive marks. Overall, the progeny of heat stressed plants varied in both their physiology and epigenome and dcl2 and dcl3 mutants were partially deficient for these changes.

Transgenerational changes in plant physiology and in transposon expression in response to UV-C stress in Arabidopsis thaliana

“…Our observations of responses to heat stress showed different results-the expression of ONSEN and TSI transposons increased in the progeny of wt and mutant plants exposed to heat for 2 consecutive generations. 11 Finally, in most cases, exposure of S 2 plants to UV stress did not significantly change TE expression in comparison to plants grown under normal conditions. There were a few fluctuations in the expression that generally led to a decrease in TE expression under stress.…”

“…Curiously, in our previous report, we have shown that ONSEN expression was only slightly higher in non-exposed dcl3 plants as compared to wild type plants. 11 It is hard to explain the discrepancy in ONSEN expression in dcl3 in these 2 reports. It is possible that some minute changes in growth conditions or plant handling could have resulted in the observed changes in dcl3 mutants.…”

“…29 ONSEN expression was also shown to be induced by stress; exposure of Arabidopsis plants to heat resulted in an increase in ONSEN expression in both the stressed tissues 30 and their progeny. 11 In the work of Ito et al (2011), no retrotransposition events were found in wt plants, as far as the progeny of stressed plants was concerned. In contrast, the progeny of stressed dcl mutants showed the evidences of new retrotransposition events.…”

“…It is interesting to note that in response to heat stress, in both the stressed plants and in their progeny, bolting occurred earlier, suggesting that responses to heat and UV-C may be different as far as transgenerational responses are concerned. 11 An impact of stress on transposon expression in the progeny of stressed and control plants…”

Epigenetic responses to heat stress at different time scales and the involvement of small RNAs

“…15 Several groups have reported transgenerational effects of stress exposure at the morphological and epigenetic level (most recently in Ref. 16,17 ). However, the significance and extent of transgenerational stress memory is still far from resolved.…”