Research Scientist Donald Danforth Plant Science Center St Louis, Missouri
With the increasing challenges of climate change, it is essential to understand plant growth response under rising carbon dioxide (CO2) levels. The plant growth response to high CO2 levels has been well studied and is typically limited to plants grown for a single generation in a high CO2 environment. The transgenerational impact of high CO2 environment beyond the initial exposure is relatively less understood. Quantifying whole plant area grown under ambient and elevated CO2 conditions confirmed previous reports that plants grow faster and larger under elevated CO2 conditions. Seeds were collected from these plants and grown at ambient CO2 levels in the next generation to understand the transgenerational impact of exposure to high CO2. We used the model organism Arabidopsis thaliana and the seedless nonvascular plant Physcomitrium patens to demonstrate that plants continue to display accelerated growth rates in the progeny of plants exposed to high CO2. We aimed to specifically uncover the underlying mechanism of this heritability of plant growth response. Over the last decade many studies have elucidated an epigenetic response to various abiotic stresses such as temperature and salinity. We aimed to identify if there is an epigenetic response to high CO2 and if this response is heritable akin to plant growth response. By linking plant growth and form to known epigenetic marks such as cytosine DNA methylation, our goal was to uncover the key mechanisms that dictate a persistent response to elevated CO2 across generations. We found that DNA methylation pathways are necessary for heritability of the plant growth response. More specifically the pathways of RNA-directed DNA methylation are required to initiate methylation and the proteins CMT2 and CMT2 are needed for the transgenerational propagation of this DNA methylation to the progeny plants. Together these two DNA methylation pathways establish and then maintain a cellular memory to high CO2 exposure.