Featured Research

from universities, journals, and other organizations

Photosynthesis Analysis Shows Work Of Ancient Genetic Engineering

November 22, 2002
Arizona State University
The development of the biochemical process of photosynthesis is one of nature's most important events, but how did it actually happen? This is a question that molecular biology has first posed, and now perhaps answered.

The development of the biochemical process of photosynthesis is one of nature's most important events, but how did it actually happen? This is a question that molecular biology has first posed, and now perhaps answered.

Related Articles

"The process of photosynthesis is a very complex set of interdependent metabolic pathways," said Robert Blankenship, professor of biochemistry at Arizona State University. "How it could have evolved is a bit mysterious."

Photosynthesis is one of the most important chemical processes ever developed by life -- a chemical process that transforms sunlight into chemical energy, ultimately powering virtually all the living things and allowing them to dominate the earth. The evolution of aerobic photosynthesis in bacteria is also the most likely reason for the development of an oxygen-rich atmosphere that transformed the chemistry of the Earth billions of years ago, further triggering the evolution of complex life.

After decades of research, biochemists now understand that this critical biological process depends on some very elaborate and rapid chemistry involving a series of enormously large and complex molecules – a set of complex molecular systems all working together.

"We know that the process evolved in bacteria, probably before 2.5 billion years ago, but the history of photosynthesis's development is very hard to trace," said Blankenship. "There's a bewildering diversity of photosynthetic microorganisms out there that use clearly related, but somewhat different processes. They have some common threads tying them together, but it has never been clear how they relate to each other and how the process of photosynthesis started, how it developed, and how we actually wind up with two photosystems working together in more complex photosynthetic organisms."

In a paper forthcoming in the November 22 issue of the journal Science, Blankenship and colleagues partially unravel this mystery through an analysis of the genomes of five bacteria representing the basic groups of photosynthetic bacteria and the complete range of known photosynthetic processes. The paper is co-authored by ASU doctoral student Jason Raymond, Olga Zhazybayeva and J. Peter Gogarten of the University of Connecticut at Storrs, and Sveta Y. Gerdes of Integrated Genomics in Chicago, Illinois.

The analysis revealed clear evidence that photosynthesis did not evolve through a linear path of steady change and growing complexity but through a merging of evolutionary lines that brought together independently evolving chemical systems -- the swapping of blocks of genetic material among bacterial species known as horizontal gene transfer.

"We found that the photosynthesis-related genes in these organisms have not had all the same pathway of evolution. It's clear evidence for horizontal gene transfer," said Blankenship.

The team examined the genes of five already sequenced photosynthetic bacterial genomes – a cyanobacterium known as Synechocystis sp. PCC 6803; Chloroflexus aurantiacus, a green filamentous bacteria; Chlorobium tepidum, a green sulfur bacteria; Rhodobacter capsulatus, a proteobacteria; and Heliobacillus mobilis, a heliobacteria. They found a set of 188 genes that appeared to be related (orthologous) between these organisms. The five species belong to very separate classifications, but since they share, to varying degrees, the same photosynthetic chemical systems, the team deduced that the photosynthesis-related genes must be among the shared genes.

Blankenship and his colleagues then performed a mathematical analysis of the set of shared genes to determine possible evolutionary relationships between them, but they arrived at different results depending on which genes were tested.

"We did a kind of tree analysis of all 188 genes to determine what the best evolutionary tree was. We found that a fraction of the genes supported each of the different possible arrangements of the tree. It's clear that the genes themselves have different evolutionary histories," Blankenship said.

Blankenship argues that this explains the how the complex biochemical machinery of photosynthesis could have developed: Different pieces of the system evolved separately in different organisms, perhaps to serve purposes different from their current function in the photosynthesis. Brought together either by fusion of two different bacteria or by the "recruitment" of blocks of genes, the new combination of genes resulted in a new combined system. Further evolution of the system and further re-combination probably occurred many times in different organisms.

The team also compared the set of shared photosynthetic bacteria genes with known genomes from other bacteria and found that very few of the shared genes are actually unique to photosynthetic organisms. While a number of the widely shared genes are probably "housekeeping genes" that are basic to most bacteria, Blankenship thinks that many of the shared genes involve metabolic pathways in non-photosynthetic bacteria that have been recruited to be part of photosynthesis systems.

"This kind of evolution in bacteria is kind of like what happens at a junk dealer," said Blankenship. "Bits and pieces of whatever there is out in the yard get hauled back and welded together and made into this new thing. All these metabolic pathways get borrowed and bent a bit and changed."

Blankenship points out that nature's way of creating useful and complicated chemical systems through horizontal gene transfer also points to how human-directed biodesign might co-opt the process.

"This work gives us some insights into how complex metabolic pathways originated and evolved, so this might give some ideas about how to engineer new pathways into microorganisms," he said. "These organisms could be designed to carry out new types of chemistry that may benefit mankind, such as multi-step synthesis of drugs."

The research applies as well to collaborative efforts going on at ASU between the university's Center for the Study of Early Events in Photosynthesis and its membership in the NASA Astrobiology Institute.

"A major focus of the astrobiology program is to try to figure out what path life might have taken on some other world besides Earth," he said "There are people that make the argument that it would be likely to have taken a similar trajectory. You have to have some kind of energetic source for organisms to live on and certainly sunlight is one of the most likely options, since it's a high quality flow of energy. Now we have a picture of how life has developed that source on our planet."

Story Source:

The above story is based on materials provided by Arizona State University. Note: Materials may be edited for content and length.

Cite This Page:

Arizona State University. "Photosynthesis Analysis Shows Work Of Ancient Genetic Engineering." ScienceDaily. ScienceDaily, 22 November 2002. <www.sciencedaily.com/releases/2002/11/021122074236.htm>.
Arizona State University. (2002, November 22). Photosynthesis Analysis Shows Work Of Ancient Genetic Engineering. ScienceDaily. Retrieved January 26, 2015 from www.sciencedaily.com/releases/2002/11/021122074236.htm
Arizona State University. "Photosynthesis Analysis Shows Work Of Ancient Genetic Engineering." ScienceDaily. www.sciencedaily.com/releases/2002/11/021122074236.htm (accessed January 26, 2015).

Share This

More From ScienceDaily

More Plants & Animals News

Monday, January 26, 2015

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Florida Might Legalize Black Bear Hunting

Florida Might Legalize Black Bear Hunting

Newsy (Jan. 24, 2015) A string of black bear attacks has Florida officials considering lifting the ban on hunting the animals to control their population. Video provided by Newsy
Powered by NewsLook.com
Ebola Killing Large Portion Of Ape Population

Ebola Killing Large Portion Of Ape Population

Newsy (Jan. 23, 2015) Experts estimate Ebola has wiped out one-third of the world&apos;s gorillas and chimpanzees. Video provided by Newsy
Powered by NewsLook.com
Controversy Shrouds Captive Killer Whale in Miami

Controversy Shrouds Captive Killer Whale in Miami

Reuters - Light News Video Online (Jan. 23, 2015) Activists hope the National Oceanic and Atmospheric Agency (NOAA) will label killer whales endangered, allowing lawyers to sue a Miami aquarium to release an orca into the wild after 44 years. Jillian Kitchener reports. Video provided by Reuters
Powered by NewsLook.com
‘Healthy’ Foods That Surprisingly Pack on Pounds

‘Healthy’ Foods That Surprisingly Pack on Pounds

Buzz60 (Jan. 23, 2015) Some &apos;healthy&apos; foods are actually fattening. Fitness and nutrition expert John Basedow (@JohnBasedow) shines a light on the sneaky foods like nuts, seeds, granola, trail mix, avocados, guacamole, olive oil, peanut butter, fruit juices and salads that are good for you...but not so much for your waistline. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins