Living Fossils Under Threat – The oldest living land plants are in danger due to climate change

Wild inhabitants of Takakia on the Tibetan Plateau. Credit: Xuedong Li / Capital Normal University Beijing

rare moss classify takakia It evolved over millions of years to thrive in high altitude environments. A collaborative research effort headed by Prof. Dr. Ralf Riske of the University of Freiburg and Prof. Dr. Yiqun He of Capital Normal University in China recently revealed how they evolved the ability to survive life-threatening frost and high UVB. .

Published in a reputable journal cellThe study identifies the genetic characteristics that arm the algae against harsh environmental factors. Researchers have also reported how rapid climate change has dramatically affected the natural habitats of this highly specialized species in just a few years.

sex takakia It contains only two types. Together, these creatures are found only on the Tibetan Plateau, the “roof of the world,” a biodiversity hotspot. There, Prof. Dr. Xuedong Li, one of the first authors of the study, discovered clusters of this type takakia lepidozoides at an altitude of more than four thousand meters in 2005. Since then, the team has been studying takakia In the mountains and in the lab for more than a decade.

For example, the study’s other first author, Dr. Ruyang He, was on the site more than twenty times during the study period. “It’s hard to work at that altitude. It shows me that altitude sickness is a problem and sometimes our instruments fail.” I still love working in this environment. “There you really realize how important it is to preserve and protect the environment,” Hu says.

A view of the area where the researchers studied algal populations

A view of the area where the researchers studied algae populations. East Gowalong Glacier on the left. Credit: Ruyang Hu / Capital Normal University Beijing

on the tibetan plateau, takakia It is buried under snow for eight months of the year and is exposed to high levels of ultraviolet radiation. To survive there, organisms need special adaptations. to takakiaThese organisms have evolved over the past 65 million years: only since then has this region of land been lifted by continental drift, making the algae’s habitat increasingly extreme.

“These geological time records help us track the gradual adaptation of life to high altitudes in the world takakia “The genome,” explains Riski, who conducts research at the University of Freiburg and its CIBSS group of excellence. In the current study, his team investigated the biological signaling pathways that protect algae cells from freezing and mutagenic ultraviolet light, among other things.

takakia It is the oldest living land plant

The moss, which is only a few millimeters in size, is of particular interest to researchers because its systematic affiliation was not clear for a long time, as it combines features of green algae, liverworts, and mosses. “Now we’ve been able to prove it takakia It is a moss that separated from other algae 390 million years ago, shortly after the first land plants appeared. We were surprised to find that takakia “It contains the largest number of rapidly evolving genes known under positive selection,” says He.

living fossil

The other surprise was that special shape of the takakia It can already be found in 165-million-year-old fossils from Inner Mongolia. The fossils thus provide biologists with another valuable time reference because they show that genetic changes that affect shape evolved more than 165 million years ago under very different environmental conditions.

Among these distinguishing features is a mode of action, unusual for plants, of the signaling molecule auxin, which controls growth and development in plants. “although takakia The genome is evolving very quickly, and its shape has not changed significantly for more than 165 million years. This makes takakia A real living fossil. Riski describes this apparent discrepancy between an unchanged form and a rapidly changing genome as a scientific challenge for evolutionary biologists.

Changing metabolic processes protects against UV rays

On the other hand, the genetic traits that affect the processing of stress signals and the regulation of some metabolic processes are younger, according to the current study, and did not appear until after the uplift of the Tibetan plateau. The researchers were able to reconstruct their gradual emergence over the past 50 million years and show how algal cells protected them from harmful environmental influences.

“For example, takakia It regulates metabolism accumulating molecules such as flavonoids and unsaturated fatty acids that protect against harmful UV rays and free radicals. “We see in the genome that it’s signaling molecules that are regulating DNA with peace, Photosynthesis Mechanisms against oxidative stress are subject to particularly strong positive selection and have changed dramatically over the past few million years.

Climate change may put an end to takakia Evolution after 390 million years

while takakia It had millions of years to adapt to lower temperatures and increased radiation intensity, but now its habitat is changing within decades: since measurements began in 2010, researchers have found an average temperature rise of about half a degree. Celsius annually there.

Meanwhile, glaciers near the sampling sites have been retreating by about 50 meters per year. Highly specialized moss copes less well with such an increase in temperature than other species. takakia Their numbers became much lower over the study period, while other plant species benefited from global warming. Researchers fear this trend will continue.

“Our study shows how important it is takakia It is in tracing the evolution of wild plants. “The population decline we found is frightening,” he says. “Fortunately, knowing that the plant is endangered also gives us an opportunity to protect it, for example by growing it in a laboratory,” Hu points out. “takakia He has seen dinosaurs come and go. She saw us humans coming. “Now we can learn something about resilience and extinction from this little algae,” Riski concludes.

Reference: “Adaptive Evolution of Mysterious Takakia Now Facing Climate Change in Tibet” By Ruoyang Hu, Xuedong Li, Yong Hu, Runjie Zhang, Qiang Lv, Min Zhang, Xianyong Sheng, Feng Zhao, Zhijia Chen, Yuhan Ding, Huan Yuan, Xiaofeng Wu, Shuang Xing, Xiaoyu Yan, Fang Pao, Peng Wan, Lihong Xiao, Xiao Chen Wang, Wei Xiao, Eva L. Decker and Yokoon Hee, Aug. 9, 2023, Available here. cell.
doi: 10.1016/j.cell.2023.07.003

The study was funded by the National Natural Science Foundation of China, the Department of Science and Technology of the Tibet Autonomous Region, the Interdisciplinary New Building for Bioinformatics and Statistics of Capital Normal University, Shenzhen Key Laboratory for Southern Subtropical Plant Diversity, the German Research Foundation DFG as well as by the Freiburg Institute. FRIAS for Advanced Studies and USIAS Institute for Advanced Studies of the University of Strasbourg (METABEVO).

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