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Seeds inherit memories from their mom. According to a new study, the experiences of a mother seed influence the dormant states of offspring.
When environmental conditions aren't ideal, seeds temporarily block germination and remain in a dormant state. Groups of "interfering" RNA, which carry the imprinted memories, put a hold on the germination process by blocking key genes.
In addition to delivering memories of the mother's dormant state to the next generation of seeds, the interfering RNA also share memories of the temperatures during the offspring's development. The memories help the seed properly time its germination.
Dormancy not only ensures seeds are treated to ideal growing conditions, they also prevent seeds from all germinating at the same time and in the same location, which would put extra pressure on local resources.
"Subspecies of the same plant can have different levels of dormancy depending on the latitudes at which they are produced, and we wanted to understand why," Luis Lopez-Molina, researcher at the University of Geneva, said in a news release.
New seeds receive two of each gene, one from each parent. The inherited alleles feature different levels of expression, however.
During the lab tests, researchers determined the gene expression levels of the dormancy regulating gene called allantoinase, or ALN, in thale cress, Arabidopsis thaliana, seeds were the same in mother and offspring. Research showed the father's ALN is silenced by biochemical modifications called methylations.
The scientists published their findings this week in the journal eLife.
"These methylations are themselves the result of a process in which different enzymatic and factor complexes are involved, as well as small fragments of so-called interfering RNA," said Geneva researcher Mayumi Iwasaki. "This is a unique example of genomic imprinting, because it is made in the absence of the enzyme usually responsible for methylation."
When the imprinted memories remind a newborn seed of the recent cold spell, the seeds remain in their holding pattern for longer. Once the seed germinates, the ALN is reactivated in the embryo and the memories are erased.
Scientists want to better understand the timing of dormancy and germination so to protect seeds from climate change.
"Studying how maternal and environmental factors cause dormant seeds to awaken is of crucial importance for agriculture, especially to prevent early germination in an environment subject to climate change," said Iwasaki.
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