Photosynthesis-Activating Protein Likely Predates Oxygen On Earth

redOrbit Staff & Wire Reports – Your Universe Online

Thioredoxin, a protein essential to the process of photosynthesis in plants, likely developed on Earth long before oxygen ever became available, according to a study published in last week’s early online edition of the Proceedings of the National Academy of Sciences.

In the study, an international team of researchers analyzing methane-producing microbes found that thioredoxin, which activates photosynthesis, most likely developed 2.5 billion years ago. The authors claim that their findings could provide new insights into microbiology and evolutionary biology, as well as natural gas production, climate change, agriculture, and human health.

“By looking at this one mechanism that was not previously studied, we will be able to develop new basic information that potentially has broad impact on contemporary issues ranging from climate change to obesity,” said senior author Biswarup Mukhopadhyay, an associate professor of biochemistry at the Virginia Tech College of Agriculture and Life Sciences.

The research, which was co-led by Mukhopadhyay and University of California, Berkeley plant and microbial biology professor Bob B. Buchanan, focused on a methane-forming type of microbe known as archaea. Archaea are a type of single-celled microorganism belonging to a methane-producing group of microbes known as methanogens, which live in regions where there is no oxygen.

According to the investigators, methanogens are an essential part of the carbon cycling process. When plants die, a portion of their biomass becomes trapped in locations that do not contain oxygen. These microbes help convert this biological material to methane, which is then converted to CO2 by other organisms and ultimately used by plants.

“This natural process for producing methane forms the basis for treating municipal and industrial wastes, helps reduce pollution, and provides methane for fuel,” Virginia Tech explained in a statement. “The same process allows natural gas production from agricultural residues, a renewable resource.”

“Methanogens also play an important role in agriculture and human health. They live in the digestive systems of cattle and sheep where they facilitate the digestion of feed consumed in the diet,” it added. “Efforts to control methanogens in specific ways may improve feed utilization and enhance the production of meat and milk, researchers say.”

These microbes are also important to human nutrition, as they live in a person’s large intestine and help the food-digestion process. In fact, some experts have said that attempting to restrict this behavior of methanogens could help men and women control their weight and combat obesity.

“The team investigated an ancient type of methanogen, Methanocaldococcus jannaschii, which lives in deep-sea hydrothermal vents or volcanoes where environmental conditions mimic those that existed on the early Earth,” the university said. “They found that the protein thioredoxin, which plays a major role in contemporary photosynthesis, could repair many of the organism’s proteins damaged by oxygen.”

Since these methanogens came into being before oxygen first appeared on Earth, it is possible that thioredoxin-based metabolic regulation could have helped manage anaerobic life prior to the existence of the element.

“It is rewarding to see that our decades of research on thioredoxin and photosynthesis are contributing to understanding the ancient process of methane formation,” said Buchanan. “It is an excellent illustration of how a process that proved successful early in evolution has been retained in the development of highly complex forms of life.”