Navigation Links
Amoeba may offer key clue to photosynthetic evolution
Date:2/27/2012

Stanford, CA -- The major difference between plant and animal cells is the photosynthetic process, which converts light energy into chemical energy. When light isn't available, energy is generated by breaking down carbohydrates and sugars, just as it is in animal and some bacterial cells. Two cellular organelles are responsible for these two processes: the chloroplasts for photosynthesis and the mitochondria for sugar breakdown. New research from Carnegie's Eva Nowack and Arthur Grossman has opened a window into the early stages of chloroplast evolution. Their work is published online by the Proceedings of the National Academy of Sciences in the week of February 27-March 2.

It is widely accepted that chloroplasts originated from photosynthetic, single-celled bacteria called cyanobacteria, which were engulfed by a more complex, non-photosynthetic cell more than 1.5 billion years ago. While the relationship between the two organisms was originally symbiotic, over evolutionary time the cyanobacterium transferred most of its genetic information to the nucleus of the host organism, transforming the original cyanobacterium into a chloroplast that is no longer able to survive without its host.

A similar process resulted in the creation of mitochondria.

To sustain the function of the organelle, proteins encoded by the transferred genes are synthesized in the cytoplasm, or cell's interior, and then imported back into the organelle. In most systems that have been studied, the transport of proteins into the chloroplast occurs through a multi-protein import complex that enables the proteins to pass through the envelope membranes that surround the chloroplast.

Clearly the events that gave rise to chloroplasts and mitochondria changed the world forever. But it is difficult to research the process by which this happened because it took place so long ago. One strategy used to elucidate the way in which this process evolved has relied on identifying organisms for which the events that resulted in the conversion of a bacterium into a host-dependent organelle occurred more recently.

Nowack and Grossman focused their research on a type of amoeba called Paulinella chromatophora, which contains two photosynthetic compartments that also originated from an endosymbiotic cyanobacterium, but that represent an earlier stage in the formation of a fully evolved organelle.

These compartments, called chromatophores, transferred more than 30 of the original cyanobacterial genes to the nucleus of the host organism. While gene transfer has been observed for other bacterial endosymbionts, the function of the transferred genes has been unclear, since it does not appear that the endosymbionts (in contrast to organelles) are equipped to recapture those proteins, because they do not have appropriate protein import machineries.

The Carnegie team honed in on three of the P. chromatophora transferred genes, which encode proteins involved in photosynthesis, a process localized to the chromatophore. They set out to determine whether these proteins are synthesized in the cytoplasm of the amoeba and whether the mature proteins became localized to the chromatophore.

Using an advanced array of research techniques, they were able to determine that these three proteins are synthesized in the cytoplasm and then transported into chromatophores, where they assemble together with other, internally encoded proteins into working protein complexes that are part of the photosynthetic process.

Interestingly, the process by which these proteins are transported into chromatophores may also be novel and involve transit through an organelle called the Golgi apparatus, prior to becoming localized to the chromatophore. This suggests the occurrence of an initial, rudimentary process for proteins to cross the envelope membrane of the nascent chloroplast. This process ultimately evolved into one that is potentially more sophisticated and that uses specific protein complexes for efficient transport.

"This work demonstrates that P. chromatophora is a potentially powerful model for studying evolutionary processes by which organelles developed," Nowack said. "Obtaining a comprehensive list of proteins imported into chromatophores, including their functions and origins, as well as understanding the pathway by which these proteins are imported, could provide insight into the mechanism that eukaryotic cells use to 'enslave' bacteria and turn them into organelles such as chloroplasts and mitochondria."


'/>"/>
Contact: Eva Nowack
enowack@stanford.edu
650-739-4238
Carnegie Institution
Source:Eurekalert

Related biology news :

1. Human cells exhibit foraging behavior like amoebae and bacteria
2. Indigenous peoples at forefront of climate change offer lessons on plant biodiversity
3. Superbugs from space offer new source of power
4. Stem cell study in mice offers hope for treating heart attack patients
5. Padded headgear, boxing gloves may offer some protection for fighters
6. A bugs (sex) life: Diving beetles offer unexpected clues about sexual selection
7. Test and Treat model offers new strategy for eliminating malaria
8. Lungs clothed in fresh cells offer new hope for transplant patients
9. Maker of VSL#3 probiotic offers assistance program for ulcerative colitis and ileal pouch patients
10. Metadynamics technique offers insight into mineral growth and dissolution
11. SpringerLink now offers more than 50,000 eBooks
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/21/2016)... India , January 21, 2016 ... According to a new market research report "Emotion Detection ... and Others), Software Tools (Facial Expression, Voice Recognition ... Regions - Global forecast to 2020", published by ... is expected to reach USD 22.65 Billion by ...
(Date:1/18/2016)... , Jan. 18, 2016  Extenua Inc., a ... simplifies the use and access of ubiquitous on-premise ... partnership with American Cyber.  ... experience leading transformational C4ISR and Cyber initiatives in ... the latest proven technology solutions," said Steve ...
(Date:1/11/2016)... Jan. 11, 2016 Synaptics Incorporated (NASDAQ: ... today announced that its ClearPad ® TouchView ™ ... won two separate categories in the 8 th ... Best Technology Breakthrough. The Synaptics ® TDDI solution ... supply chain, thinner devices, brighter displays and borderless designs. ...
Breaking Biology News(10 mins):
(Date:2/4/2016)... 4, 2016 - New FDA action date of ... New FDA action date of July 22, 2016   ... 22, 2016   - Lifitegrast ... decade indicated for the treatment of signs and symptoms of dry ... the potential to be the only product approved in the U.S. in the past decade ...
(Date:2/4/2016)... , Feb. 4, 2016  CytoSorbents Corporation (NASDAQ: ... commercializing its flagship CytoSorb® blood filter to treat ... around the world, announced that CEO Dr. ... the Source Capital Group,s 2016 Disruptive Growth & ... the company.  Conference Presentation Details: ...
(Date:2/4/2016)... Sinovac Biotech Ltd. ("Sinovac" or the "Company") (NASDAQ: ... China , today announced that the ... February 4, 2016 a preliminary non-binding proposal letter, dated ... V-Ming ( Shanghai ) Investment Holdings Co., ... Shenzhen ) Fund Management Co., Ltd., Beijing ...
(Date:2/3/2016)... , Feb. 3, 2016  Discovery Laboratories, Inc. ... on developing aerosolized KL4 surfactant therapies for respiratory ... has approved an inducement award as a component ... its newly appointed President and Chief Executive Officer.  ... Committee on February 1, 2016 and granted as ...
Breaking Biology Technology: