Academic Staff - Dr Min Chen

Career Profile

• B. Sc., M. Sc, North-east Normal University, China (1984, 1987)
• Ph. D, University of Sydney (USyd), 2003
• Postdoctoral Fellow, ANU, 2003
• Australian Research Council (ARC) Postdoctoral Fellow, USyd, 2004 - 2006
• Research Fellow, USyd, 2007
• ARC QEII Fellow, USyd, 2008 - present

Areas of Interest

My research interests are primarily concerned with elucidating the molecular and biochemical mechanisms of the energy-storing reactions and photo-regulatory processes in photosynthetic organisms, especially the function of red-shifted chlorophylls in oxygenic photosynthetic organisms (cyanobacteria and algae). My research “platform” lies in the broad field of biochemistry of photosynthesis, including biochemical, biophysical and molecular biological studies on isolated pigments and protein-pigment complexes. The experimental techniques that we use include comparison of genomic sequence information, gene expression analysis/meta-transcription analysis, proteomic analysis and spectroscopic analysis. My current projects also include elements of microbial ecology, microbiology/marine microbiology (mainly phototrophic organisms, cyanobacteria and algae), chromatic responses and photo-regulation.

Red-Shifted Chlorophylls, Chlorophylls d and f

The photosynthetic reactions take place within the membrane-bound pigment-protein complexes, light-harvesting systems and reaction centre systems. Chlorophylls are the essential pigments for photosynthesis. There are 5 forms of chlorophylls that have been discovered to date, chlorophyll a, b, c, d and f. Chlorophyll a plays a vital role in plant and algal photosynthesis. Chlorophylls b and c can only serve as accessory photosynthetic pigments in antenna complexes.

The red-shifted chlorophylls (Chl d and Chl f) allow the photosynthetic organisms the critical advantage of using longer wavelength photons (690-760 nm) that are not absorbed by organisms containing chlorophyll a, b, c. Chlorophyll d is the only chlorophyll known to date to replace all of the functions of chlorophyll a in oxygenic photosynthesis. The newly found chlorophyll f (absorption maximum at 706 nm in vitro), suggests that oxygenic photosynthesis can be extended even further into the infrared region, which may open up associated bioenergy applications. The function of Chl f in photosynthetic reactions is uncertain and the ecological distribution of chlorophyll f remains unknown.

The studies on photophysiological and biochemical properties of red-shifted chlorophylls will advance our understanding of its ecological and evolutionary significance. Discovery of those red-shifted chlorophyll synthases can be applied for increasing photosynthetic ability to absorb and utilize additional regions of the solar spectrum. This could lead to significant improvements in agricultural efficiency or bioenergy storage. It may also be useful for remote sensing and detection of plants that contain this pigment.

Photoregulation and pigment composition

In addition to chlorophylls, there are two types of pigments found in phototrophs, the polyene pigments known as carotenoids and open chain tetrapyrroles known as bilins. Carotenoids function as light-harvesting photopigments in photosynthesis, also have an essential function in light protection against damage from excess excitation energy or reactive oxygen species. Bilins are important pigments for light-harvesting function in phycobiliproteins and phycobilisomes and photoregulation/chromatic changes in phytochromes and related proteins. The latter functions are also performed in non-photosynthetic organisms or tissues. We are interested to understand the biochemical mechanisms, such as the types and function of phytochromes and their relationship with photosynthetic reactions, as well as changes in carotenoids and their physiological functions.

Evolutionary transition from anaerobic to aerobic metabolism

How life on Earth survived the revolutionary changes when cyanobacteria first released oxygen into the atmosphere is not well understood. The process by which the transition from the anoxic (oxygen-free) to the oxic (oxygen-rich) worlds occurred is still largely a mystery. The comparative genomic study will be performed at the molecular level with ecological interpretation. the co-evolution of oxygen use and oxygen detoxification will allow us to understand life cycles, adaptation and evolution in the biosphere. The ocean provides multi-layers of microenvironments, with changing gradients of chemicals, light and available oxygen. These environments shape the biosphere and its essential cycles.

Some cyanobacteria have the ability to perform two seemingly incompatible metabolisms stimutaneously, such as oxygen production (oxygenic photosynthesis) and a strictly anaerobic process (nitrogen fixation). The gradient of available oxygen concentration may play an important regulatory role for such metabolic reaction shifts.

Selected Publications

• Chen M., Schliep, M., Willows R.D., Cai Z.-L., Neilan B.A., and Scheer, H. (2010) A red-shifted chlorophyll, Science 329: 1318–19.
• Schliep M., Crossett B., Willows R.D., and Chen M. (2010) O-labelling of chlorophyll d in acaryochloris marina reveal chlorophyll [a and molecular oxygen are precursors, J. Bio. Chem. 285: 28450–58.
• Yang D., Yang Q., and Chen M. (2010) Characterization of Chl d-binding light-harvesting protein of Acaryochloris in Synechocystis sp. PCC6803, Biochim. Biophys. Acta 1797: 204–11.
• Mohr R., Voss B., Schliep M., Kurz T., Maldener I., Adams D.G., Larkum A.W.D., Chen M, and Hess W.R. (2010) Niche adaptation in a new chlorophyll d-containing cyanobacterium from the genus Acaryochloris, ISME J 4:1456–1469..
• Chen M., Floetnmeyer M., and Bibby T.S. (2009) Supramolecular organization of phycobiliproteins in the chlorophyll d-containing cyanobacterium Acaryochloris marina, FEBS Lett. 583: 2535–39.
• Bibby T.S., Zhang Y.N., and Chen M. (2009) Biogeography of photosynthetic light-harvesting genes in marine phytoplankton, PLoS ONE 4:e4601.
• Swingley, W.D., Chen M., Cheung, P.C., et al (25 co-authors) (2008) Genome expansion in the chlorophyll d-producing cyanobacterium Acaryochloris marina, Proc. Natl. Acad. Sci. U.S.A. 105: 2005–10.
• Hoober J.K., Eggink L.L., and Chen M. (2007) Chlorophylls, ligands and assembly of light-harvesting complexes in chloroplasts, Photosyn. Res. 94:387–400.
• Chen M., and Cai, Z.-L. (2007) Theoretical study on the thermodynamic properties of chlorophyll d-peptides coordinating ligand, Biochim. Biophys. Acta 1767:603–609.
• Kühl, M., Chen M., Ralph, P., Schreiber, U., and Larkum, A.W.D. (2005) A niche for cyanobacteria containing chlorophyll d, Nature 433:820.
• Chen M., Hiller, R.G., Howe, C.J., and Larkum, A.W.D. (2005) Unique origin and lateral transfer of prokaryotic chlorophyll-b and chlorophyll d light-harvesting systems, Mol. Biol. Evol. 22:21–28.
• Chen M., Eggink, L.L., Hoober, J.K., and Larkum, A.W.D. (2005) Influence of structure on binding of chlorophylls to peptide ligands, J. Amer. Chem. Soc. 127:2052–53.
• Chen M., Telfer, A., Lin, S., Pascal, A., Larkum, A.W.D., Barber, J., and Blankenship, R.E. (2005) The nature of the Photosystem II reaction centre in the chlorophyll d containing prokaryote, Acaryochloris marina, Photochem. Photobiol. Sci. 4:1060–64.
• Chen M., Bibby, T. S., Nield, J., Larkum, A. W. D., and Barber, J. (2005) Structure of a large photosystem II supercomplex from Acaryochloris marina, FEBS Lett. 579:1306–10.
• Bibby, T. S., Nield, J., Chen M., Larkum, A. W. D., and Barber, J. (2003) Structure of a photosystem II supercomplex isolated from Prochloron didemni retaining its chlorophyll a/b light harvesting system, Proc. Natl. Acad. Sci. U.S.A. 100:9050–54.
• Chen M., Quinnell R.G., and Larkum A.W.D. (2002) The major light-harvesting pigment proteins in Acaryochloris marina, FEBS Lett. 514:149–152.

Patent

• US Provisional Patent Application Number: 61/346743
  Title: Gene Constructs Comprising Nucleic Acids That Modulate Chlorophyll
  Biosynthesis and Uses Thereof. (2010)
  Inventors: Min Chen, Robert Willows, Robert Blankenship
  Applicants: The University of Sydney (Australia), Macquarie University (Australia) and Washington University in St. Louis (U.S.A)