The higher temperatures brought on by global warming can disrupt trees鈥� ability to track time, with potential consequences for their capacity to sequester carbon or even survive.
Climate change is already disturbing the timings of events in ecosystems by shuffling migrations, breeding, and food cycles that have historically been intricately coordinated. But like humans and other animals, plants have a genetic ability to track time that functions independently of their ecosystems.
at Argentina鈥檚 National Scientific and Technical Research Council (CONICET) and her colleagues studied saplings of Nothofagus pumilio, a southern beech that is common in the forests of Patagonia. They found that the accuracy of time-keeping genes in the species鈥� circadian clock was severely compromised when the trees were planted at temperatures warmer than their typical niche.
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The circadian clock is governed by many genes. Their expression, and the amount of proteins they encode, oscillates throughout the day. While light and temperature cues help keep the clock in sync with the environment, this ebb and flow continues even without these external signals. The circadian clock helps plants time and coordinate things like growth and dormancy.
In the study of N. pumilio, which is a frost-tolerant tree that can cope with temperatures as low as -30掳C (-22掳F), the oscillations of several clock genes were profoundly altered at higher temperatures. For example, the gene NpLHY peaked around dawn at the control temperature of 20掳C (68掳F), but at the heat stress temperature of 34掳C (93掳F), it peaked several hours earlier, and less of the protein encoded by the gene was produced at the peak.
Even when the saplings were 鈥渢rained鈥� to reset their clocks in the lab, with controlled day-night cycles of light, the warming-induced disruption was still visible in the patterns of genetic oscillation. The saplings also had lower survival rates and were smaller than those of a closely related cousin, Nothofagus听辞产濒颈辩耻补, which can cope with warmer temperatures.
Overall, the team wrote, N. pumilio鈥檚 preference for cold temperatures and higher elevations means it is a species potentially threatened by climate change.
at Ume氓 University in Sweden says the research is consistent with studies in other plants, including a type of cress, Arabidopsis thaliana, often used in lab experiments. Similar results are also seen in trees like chestnuts and aspen, where temperature cues can trigger clock gene disruption and out-of-season dormancy. But she says there are still many gaps in our understanding of how circadian clocks function in plants and which physiological processes they affect.
Much of the circadian clock research in trees is still at the foundational stage, says Eriksson, and different species may have different sensitivities to changing temperatures. Because both light and temperature can affect clock synchronisation, it will also be important in the long run to understand which genes are more sensitive to which external cues.
鈥淲e don鈥檛 know how this connects to physiological outputs,鈥� she says, 鈥渂ut it鈥檚 a clear indication that something is out of balance.鈥�
bioRxiv
