Abiotic Stress Response Leads Directly to Trans-Generational Adaptation in Barley

In “trans-generational adaptation”, adaptive epigenetic reprogramming induced in a parent in response to stress or environmental change is transmitted to progeny. However, in comparison with the large volume of research addressing “intra-generational” response to biotic or abiotic stress in plants or animals, there have been relatively few studies of “inter-“ or trans-generational adaptation. Consider the numerous studies addressing plant response to phosphorus limitation: there are no published studies of trans-generational adaptation to P limitation in Arabidopsis or any crop species. In studies reported here, progeny of barley (Hordeum vulgare L.) parents grown under macronutrient (N, P, K) limitation performed dramatically better when grown under a similar but more moderate stress, as compared with progeny of non-stressed parents: a doubling of tiller number, grain yield and grain P per plant. Further, RNAseq indicates that more than 50% of genes previously well documented to be intra-generationally induced in response to macronutrient stress also display either trans-generational induction, defined as increased expression in progeny of stressed parents as compared with progeny of non-stressed parents when both progenies are grown under an identical stress, or trans-generational “training”, defined as increased expression in stressed progeny as compared with that observed in their own stressed parents. Thus it appears that a common attribute of genes important to intra-generational abiotic stress response is that they are also a vehicle for trans-generational adaptation. These results also illustrate numerous cases of a causal relationship between epigenetic change in a gene’s expression and trans-generational adaptation at the whole plant level.