Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

Learning goals:Students will understand that 1) consistency in the reactions of photosynthesis across the tree of life is explained by inheritance from a common ancestor, and 2) C4 and CAM photosynthesis have evolved convergently many times.

For the instructor:This short slide set explains uniformity and variation in the process of photosynthesis across all life using evolutionary theory. To integrate it best, use these slides immediately after you’ve discussed C4 and CAM carbon fixation. Alternatively, you could incorporate your lecture material on the processes of C4 and CAM fixation into this slide set. This slide set could be shortened, if you wish, by cutting slides 8, 10, and 11.

Each of the following slides comes with a sample script for the instructor.  To review this script, download the PowerPoint file and view the Notes associated with each slide.

Evolution Connection slideshows are provided by Understanding Evolution (understandingevolution.org) and are copyright 2011 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California. Feel free to use and modify this presentation for educational purposes.

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

“That’s a lot of reactions. How many sets of these chemical reactions do we need to memorize?”

Not many. All plants use the same set of reactions (or slight variations on these) to photosynthesize.

Why is that?

Pterosperma photo by David Patterson and Bob Andersen and licensed via Creative Commons.Pediastrum photo by Luis Fernandez Garcia and licensed via Creative Commons. Moss photo by Charles Webber © California Academy of Sciences. Fern photo by Gerald and Buff Corsi © California Academy of Sciences. Douglas Fir photo © Br. Alfred Brousseau, Saint Mary's College. Dogwood flower photo by Sherry Ballard © California Academy of Sciences. Spirogyra photo by Micrographia.

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

… because of common ancestry

Photosynthesis begins to evolve

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

… and endosymbiosis

Photosynthesis begins to evolve

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

… followed by diversification

Plants

Photosynthesis begins to evolve

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

Because of common ancestry, the reactions of photosynthesis are largely consistent across all plants. But there are a few variations on the theme …

Cyanobacterium engulfedby common ancestor ofgreen plants

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

C4 photosynthesis

CO2

PEP carboxylase fixescarbon efficiently

RUBISCO completesphotosynthesis

C4

high O2concentration

low O2concentration

Corn photo by Doug Wilson/USDA

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

C4 photosynthesis involves specific adaptations

Cellular photo provided by Paul Schulte. PEP carboxylase image from Three-dimensional structure of phosphoenolpyruvate carboxylase: A proposed mechanism for allosteric inhibition PNAS 1999 96 (3) 823-828; doi:10.1073/pnas.96.3.823

anatomical chemical

bundle-sheathcells

mesophyllcells

PEP carboxylase

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

C4 photosynthesis among the angiosperms

Phylogeny based on Sage, R. F. (2004). The evolution of C4 photosynthesis. New Phytologist. 161: 341-370.

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

C4 photosynthesis leaf morphologies

Illustration adapted from Kadereit, G., Borsch, T., Weising, K., and Freitag, H. (2003). Phylogeny of Amaranthaceae and Chenopodiaceae and the evolution of C4 photosynthesis. International Journal of Plant Sciences. 164: 959-986.

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

PEP carboxylase for C4 photosynthesis

before duplication after duplication

serves ancestral function

serves ancestral function

free to evolve a new function—like C4 photosynthesis

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

CAM photosynthesis also evolved convergently

Pineapple photo by Enid Leff © California Academy of Sciences; aloe photo by Zoya Akulova and licensed via Creative Commons; yucca photo by Robert Sivinski and licensed via Creative Commons; cactus photo by Gary Monroe and licensed via Creative Commons.

Evolution connection: Photosynthesis IIEvolution connection: Photosynthesis II

Björn, L. O., and Govindjee. (2009). The evolution of photosynthesis and chloroplasts. Current Science. 96: 1466-1474.

Kadereit, G., Borsch, T., Weising, K., and Freitag, H. (2003). Phylogeny of Amaranthaceae and Chenopodiaceae and the evolution of C4 photosynthesis. International Journal of Plant Sciences. 164: 959-986.

Sage, R. F. (2004). The evolution of C4 photosynthesis. New Phytologist. 161: 341-370.

Svensson, P., Bläsing, O. E., and Westhoff, P. (2003). Evolution of C4 phosphoenolpyruvate carboxylase. Archives of Biochemistry and Biophysics. 414: 180-188.