April+6

Bob Blankenship Paper: Ito and Tanaka PNAS 2011. Evolution of a divinyl chlorophyll-based photosystem in Prochlorococcus

Student Discussion Leader: Jeremy King

Questions for Discussion
 * 1) Explain why //Prochlorococcus// species that contain divinyl chlorophylls have an advantage over related species that contain normal chlorophylls in the environment in which they are found.
 * 2) How does the biosynthesis of divinyl chlorophyll differ from that of normal chlorophyll?
 * 3) How were the M205 and C282 positions identified and their mutants constructed in //Synechocystis// PCC 6803? Why were the reverse mutants V205 and G282 not made in //Prochlorococcus?//
 * 4) What are cyanophages and why do they contain genes for the Photosystem II reaction center protein D1?
 * 5) There are two evolutionarily distinct genes that code for the vinyl reductase enzyme. (Ito et al. //JBC// **283**: 9002-9011 (2008)). The distribution of these genes among phototrophic taxa is very scattered. What are the evolutionary implications of this?
 * 6) What is it about the structure of divinyl chlorophyll that makes organisms that contain it sensitive to high light? Can you explain this photosensitivity and the role of the 205 and 282 residues using the Photosystem II reaction center structure shown in figure S5?
 * 7) What are the implications of this paper for efforts to add new types of chlorophylls to photosynthetic organisms to increase the spectral coverage and improve the efficiency of photosynthesis?