Research Summary

We would like to understand how cells construct chloroplasts. The chloroplast is an ordered assemblage of multi-subunit complexes, including photosynthetic reaction centers and ribosomes, etc. We are exploiting the unique genetic properties of the unicellular green alga Chlamydomonas to determine if the balancing of subunit synthesis involves active genetic control. Numerous mutants have been selected in the chloroplast enzyme ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO). RuBisCo has only two types of subunits; one encoded in the chloroplast and the other in the nucleus, and thus, is a simple example of a complex requiring balanced activity of both genomes. One interesting nuclear mutation specifically destabilizes the mRNA for the chloroplast-encoded subunit. We are using transformation methodology to identify the target within the message responsible for its susceptibility to stability control and to clone the mutant gene that causes degradation. Many of the mutants have proven to be valuable for investigating the fundamental chemical mechanisms of the photosynthetic reaction centers. Chloroplast transformation can now be used to generate directed mutations of individual genes. We hope to learn how the reaction center proteins control the chemical reactions at the heart of photosynthetic energy conversion.

Selected Publications

Qu, X., Wu, D., Mets, L. and Scherer, N. F. (2004). "Nanometer-localized multiple single-molecule fluorescence microscopy." Proc Natl Acad Sci U S A 101: 11298-303. (PubMed)

Lee, J. W., Mets, L. and Greenbau, E. (2002). "Improvement of photosynthetic CO2 fixation at high light intensity through reduction of chlorophyll antenna size." Appl Biochem Biotechnol 98-100: 37-48. (PubMed)

Shu, G., Pontieri, V., Dengler, N. G. and Mets, L. J. (1999). "Light induction of cell type differentiation and cell-type-specific gene expression in cotyledons of a C(4) plant, Flaveria trinervia." Plant Physiol 121: 731-41. (PubMed)

Mets, L. and J.-D. Rochaix. (1998) "Perspectives" in J.-D. Rochaix, M. Goldschmidt-Clermont and S. Merchant (eds): The Molecular Biology of Chloroplasts and Mitochondria in Chlamydomonas, pp. 685-703. Kluwer Academic.

Greenbaum, E., J.W. Lee, C.V. Tevault, S.L. Blankenship, T.G. Owens and L.J. Mets. (1997) "Photosystem I measurements in mutants B4 and F8 of Chlamydomonas." Science 277:167-168. (Science Citation)

DiMagno, L., C-K. Chan, Y. Jia, M.J. Lang, J.R. Newman, L. Mets, G.R. Fleming, and R. Haselkorn. (1995) "Energy transfer and trapping in photosystem I reaction centers from cyanobacteria." Proc. Natl. Acad. Sci. USA 92:2715-271. (PubMed)