SUBJECT

Title

Photosynthesis and its Evolution

Type of instruction

lecture

Level

master

Faculty

Faculty of Science

Part of degree program

Biology MSc

Credits

Recommended in

Semesters 1-4

Typically offered in

Autumn/Spring semester

Course description

1. Introduction. Principle and basic processes of photosynthesis (a survey). Photosynthetic organisms. Oldest records of photosynthesis (geological and chemical evidences, fossils).

2. Photosynthetic pigments: Types, spectral properties, functions in photosynthesis. Evolutionary development of biosynthetic pathways. Light independent and light dependent pathways, their molecular biological ground and significance.

3. Evolution of photosynthetic pigments. Gradual recruitment of porphyrin ring in parallel to the appearance of the visible absorption bands. Development of molecular properties and reaction centers: loss of charge, appearance of apolar structures, ability to insert into membranes. Significance of the geometry of antennae and reaction centers.

4. Structure and function of Q-type centers in higher plants. Crystal structure of photosystem II. New results concerning water splitting (H-abstraction model), reaction center (active tetramer), quinone reduction (lipids and proton wire), and light protection (function of cytochrome b559, cyclic electron transport around photosystem II).

5. Structure and function of Q-type centers in bacterial photosynthetic organisms. Structure and function of the Q-type centers in Chloroflexus and purple bacteria, comparison with photosystem II. Q-type centers containing Zn-chlorophyll.

6. Structure and function of FeS-type centers. Crystal structure of photosystem I. Structure and function of FeS-type centers of Chlorobium and Heliobacteria, comparison with photosystem I. FeS-type centers containing chlorophyll d. Photosynthesis in Halobacteria.

7. Evolution of photosynthetic reaction centers. Comparison of proteins (amino acid sequence, helix structure, connectivity), cofactors, and inner antennae in different centers. Hypotheses about the evolution of reaction centers and their evidences (Olson, Blankenship, Vermaas models, „export model”, „redox switch” hypothesis, apoprotein early model). Evolution of the water splitting system.

8. Photosynthetic antennae in higher plants. Chlorophyll-proteins of LHCI and LHCII. Energy transfer inside and between chlorophyll-proteins. Other LHC-like antennae (PsbS, ELIP, etc.). Their function in light regulation and protection (LHC-phosphorylation, non-photochemical quenching, violaxanthine cycle).

9. Antenna complexes in algae and photosynthetic bacteria. Chlorophyll a/b, chlorophyll a/c and peridinin-chlorophyll antennae in algae. Phycobilisomes in cyanobacteria and red algae. Pcb and phycobilin antennae in Prochlorophyta. Membrane (LHI és LHII) and membrane attached antennae (FMO, chlorosomes) in bacteria.

10. Hypotheses on the evolution of photosynthetic antennae. Common origin of chlorophyll a, chlorophyll a/b, chlorophyll a/c, and peridinin-chlorophyll antennae (hydrophobic cluster analysis). Evolution of phycobilins and phycobilisomes. Reaction center origin of bacterial antennae.

11. New results on the structure and function of citb6/f and ATP synthase. Comparison with mitochondrial and chloroplast complexes. Their evolutionary relationships. Regulatory mechanisms of photosynthetic light reactions.

12. Ancestral procaryotic processes of CO2 fixation (reductive tricarboxylic acid cycle, 3-hydroxi-propionate cycle). C3 route of CO2 fixation. Evolutionary origin and mechanism of Calvin cycle. Structure and enzymatic properties of RUBISCO. Types, appearance and functional characteristics of RUBISCO. Regulation of RUBISCO, role of Rubisco activase and its regulation. Conditions of carboxylation and oxigenation of RUBISCO. Oxigenation –photorespiration. Role of climatic conditions on the stimulation of photorespiration. Evolutionary trials for elimination of photorespiration, changes of enzymatic feature of RUBISCO. Experiments to change RUBISCO function.

13. Carbon dioxid concentrating mechanisms (CCM). C4 route of CO2 fixation. Anatomical and functional characteristics of C4 adaptation. Structure, function and regulation of PEP carboxylase. Relationship between C4 mechanism and photorespiration. Anatomical and functional characteristics of CAM adaptation. Evolutionary origin, appearance and distribution of C4 and CAM CCM in autotrophic organisms. Carbonic anhydrase (CA) as a CCM. Structure, function and distribution of CAs.

14. Plastid evolution. Characterization of plastids of different type. Endosymbiotic origin of plastids. Primary, secondary and tercier endosymbioses, reduced plastids, cleptochloroplasts. Monophyletic origin of plastids: plastid, mitochondrial, and nuclear genes are related in the plastid bearing organisms. Origin of plastids in secondary and terciary endosymbioses.

15. Postendosymbiotic history of plastids. Reduction of the genom. Ways of gene loss. Transfer of genes into the nucleus. Protein import into the different type plastids. Sorting inside the plastid. Evolution of the protein import apparatus. Signal transduction and redox regulation of gene expression.

Readings

Malkin R, Niyogi K (2000) Photosynthesis. In: Biochemistry & Molecular Biology of Plants (B Buchanan, W Gruissem & R Jones, eds.), 2000, ISBN 0-943088-39-9, John Wiley & Sons Ltd, Bognar Regis, UK, pp. 568-628.
Recent reviews