Gene expression indicates plants are adapting to increased CO2 levels

The research from the University of Southampton, UK, published recently in the journal ‘Global Change Biology’, shows that as plants are exposed to elevated CO2 emissions, gene expression is altered, indicating that changes in gene regulation could be a prominent mechanism underpinning adaption to elevated CO2.

Short-term benefits of rising CO2

With increasing levels of atmospheric CO2 (emissions grew faster in the 2000s than the 1990s and the concentration of CO2 reached 400 ppm for the first time in 2013), the short-term impact on plants can be described as relatively positive, as this drives up photosynthesis and plant growth, including crop growth and food production. Recent decades have actually seen the Earth become greener as vegetation growth has been stimulated by CO2 rises.

However, the long-term impact of higher levels of atmospheric CO2 on plant life is still a matter of scientific debate. ‘Until now, few reports had given us any insight into the long-term impacts of rising CO2 over multiple generations and none have been undertaken on the molecular signature underpinning such adaption,’ commented lead study author Professor Gail Taylor of the University of Southampton. ‘One reason for this is that it’s a difficult problem crack – to find plants that have been exposed to conditions of the future but are available today.’

To investigate this further, the research team used a unique resource – naturally high CO2 springs where plants have been subjected to more CO2 over many hundreds of years and multiple plant generations. Taking plantago lanceolata plants from a ‘spring’ site in Bossoleto, Italy, and comparing the molecular signature with the same plants from a nearby ‘control’ site (at today’s CO2) showed striking differences in the total gene expression (the process by which specific genes are activated to produce a required protein).

‘The study shows that when we take plants from these two places that represent the atmosphere of today with that of the future (out to 2100), and place them together in the same environment, the plants from spring sites were bigger and had a better rate of photosynthesis,’ said Prof. Taylor. ‘Most importantly, plants from the spring sites had differences in the expression of hundreds of genes.’

Prof. Taylor and her team predict that from their gene expression data that planetary greening will continue. ‘It won’t switch off or become acclimated as CO2 continues to rise, but some of the extra carbon in future plants is likely to go into secondary chemicals for plant defence. This is associated with more gene expression underpinning plant respiration.’

Impact on stomatal pores

One of the most interesting findings from the research was that stomatal pores on the surface of the leaf (small holes that control the uptake of CO2 for photosynthesis and the loss of water vapour) increase in number after multi-generation exposure to future CO2. The team had predicted that pore number would decline, in line with past research over geological timescales using fossil plants.

Prof. Taylor added: ‘This is a counter-intuitive finding but strongly suggests that stomatal pore numbers increase, since we have identified several key regulators of stomatal number that are sensitive to future high levels of CO2. One of those is SCREAM (SCRM2), which is a member of the basic helix-loop-helix (bHLH) protein family that acts to regulate plant developmental transitions.’

She admits that the full consequences of this developmental change is not yet fully understood but shows that plants will adapt in unpredictable ways to future levels of CO2 over multiple generations. This is an important question to address, as it is imperative to know how food crops may evolve over future generations as a result of the changing climate, as well as whether planetary greening will continue and the impacts of this for global nature preservation.

As well as being part-funded through the FP7 EXPEER (Distributed Infrastructure for EXPErimentation in Ecosystem Research) project, which concluded in May 2015, the research also received support from the British Council and the UK’s National Environment Resource Council (NERC).

For more information, please see:
EXPEER project website