Time dynamics of stress legacy in clonal transgenerational effects: a
case study on Trifolium repens
Abstract
Stress can be remembered by plants in a form of stress legacy that can
alter future phenotypes of previously stressed plants and even
phenotypes of their offspring. DNA methylation belongs among the
mechanisms mediating the stress legacy. It is however not known for how
long the stress legacy is carried by plants. If the legacy is long
lasting, it can become maladaptive in situations when parental-offspring
environments do not match. We investigated for how long after the last
exposure of a parental plant to drought can the phenotype of its clonal
offspring be altered. We grew parental plants of three genotypes of
Trifolium repens for five months either in control conditions or in
control conditions that were interrupted with intense drought periods
applied for two months in four different time-slots. We also treated
half of the parental plants with a demethylating agent (5-azaC) to test
for the potential role of DNA methylation in the stress legacy. Then, we
transplanted parental cuttings (ramets) individually to control
environment and allowed them to produce offspring ramets for two months.
The drought stress experienced by parents affected phenotypes of
offspring ramets. The stress legacy resulted in enhanced number of
offspring ramets originating from parents that experienced drought
stress even 8 weeks before their transplantation to the control
environment. 5-azaC altered transgenerational effects on offspring
ramets. We confirmed that drought stress can trigger transgenerational
effect in T. repens that is very likely mediated by DNA methylation.
Most importantly, the stress legacy in parental plants persisted for at
least 8 weeks suggesting that the stress legacy can persist in a clonal
plant Trifolium repens for relatively long period. We suggest that the
stress legacy should be considered in future ecological studies on
clonal plants.