regulation of the chlorophyll
antenna size
of the photosystems

In oxygenic photosynthesis of plants light is harvested and then converted to chemical energy by specific pigment-protein complexes that are located in the thylakoid membrane. The "light-reactions" of photosynthesis take place in two different photosystems, photosystem II (PSII) and photosystem I (PSI). Both are associated with specific light-harvesting complex proteins termed LHCII for photosystem II and LHCI for photosystem I. LHC proteins are encoded for in the nucleus and belong to a multi-gene family. LHCII are distinguished according to their location and macromolecular organization within the thylakoid membrane into major LHCII and minor LHCII. The major LHCII form trimers and belong to the outer, mobile antenna of PSII. A major LHCII protein binds approximately seven Chl a molecules, six Chl b molecules, two lutein molecules, and one neoxanthin molecule. Assembly of the minor LHCII, also termed CP29, CP26 and CP24 requires fewer Chl molecules and two lutein and/or violaxanthin molecules. Only CP24 does not require neoxanthin (N) for proper assembly. LHCI bind approximately 9 Chl molecules, but the total number and composition of carotenoids associated with one LHCI appears to be variable.

The chlorophyll antenna size of PSII can contain as many as 500 Chl a+b molecules and PSI can contain up to 250 Chl a+b molecules. However, the chlorophyll antenna size of the photosystems is not constant, because plants have to adjust the chlorophyll antenna sizes of the photosystems to their light environment. This laboratory is interested in the components that participate in the regulation of the chlorophyll antenna size of PSII and PSI.

LHC Regulation

publications

1. Polle JEW, Niyogi KK and Melis A, (2001) Absence of lutein, violaxanthin and neoxanthin affects the functional chlorophyll antenna size of photosystem-II but not that of photosystem-I in the green alga Chlamydomonas reinhardtii. Plant Cell Physiol 42 (5): 482-491

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2. Masuda T, Polle JEW, and Melis A (2002) Biosynthesis and Distribution of Chl among the photosystems during recovery of the green alga Dunaliella salina from irradiance stress. Plant Physiol, 128: 603-614

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3. Polle JEW, Kanakagiri S, Jin ES, Masuda T, and Melis A (2002) Truncated chlorophyll antenna size of the photosystems - A practical method to improve microalgal productivity and hydrogen production in mass culture. International Journal of Hydrogen Energy, 27:1257-1264

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4. Polle JEW, Kanakagiri S, and Melis A (2003) TLA1, a Chlamydomonas reinhardtii nuclear gene regulates the chlorophyll antenna size of photosynthesis. Planta, 217: 49-59

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5. Lokstein H, Tian L, Polle JEW, and DellaPenna D (2002) Xanthophyll Biosynthetic Mutants of Arabidopsis thaliana: Altered Nonphotochemical Quenching of Chlorophll Fluorescence is due to Changes in Photosystem II Antenna Size and Stability. Biochim Biophys Acta, 1533: 309-319

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collaboration

Professor Anastasios Melis
Department of Plant and Microbial Biology
411 Koshland Hall
Berkeley, CA 94720-3102
USA

email: melis@nature.berkeley.edu
http://plantbio.berkeley.edu/faculty/faculty_pages/Melis.html

A small experimental raceway pond operated at SeaAg, Inc.

Dr. Joseph Weissman
SeaAg, Inc.
705 27th Ave. S.W., Suite 5
Vero Beach, FL 329684327
USA

phone: (772) 234-9544
FAX: (722) 234-9544
email: weissm_j@bellsouth.net

Together with the company SeaAg, Inc. the laboratory works on microalgal strain improvement. Truncated light-harvesting antenna should in theory improve solar energy conversion efficiency of the algae and in consequence increase biomass production (Nakajima et al. 2001; Polle et al. 2001).