Michael Kuchka, Ph.D. Associate Professor Molecular Biology 111 Research Drive, B220 Bethlehem, PA 18015 610-758-3687 E-mail me

About my research...

Our lab studies the regulation of expression of organellar genes. We are particularly interested in the chloroplast of eukaryotic plant cells, and the ways in which genes located in this organelle are transcribed and the protein products of these transcripts synthesized. Of special interest is the interaction between the organellar genetic compartment and the nucleo-cytoplasm. It is known that nuclear genes of eukaryotic algae and higher plants encode products which are sent into the chloroplast where they are involved in the expression of chloroplast genes. Similarly, there is evidence that the chloroplast sends signals to the nucleus to regulate gene expression there. We are interested in these interactions and in the communication between these spatially distinct genetic compartments. We seek to define the molecular mechanisms by which products of nuclear genes influence gene expression in the chloroplast and vice versa. 

Our experimental organism is the unicellular green alga Chlamydomonas reinhardtii (Chlamydomonas website). Chlamydomonas cells have a single chloroplast which carries out photosynthesis in a manner identical to higher plants. The organism is amenable to genetic analysis - a large collection of mutant strains is available, standard crosses can be done to define genetic loci, and genes can be cloned by complementation. We study an important protein, encoded by a chloroplast gene, which is essential for photosynthesis. This protein, called D2, is involved in electron transfer reactions through the photosystem II complex. The synthesis of the D2 protein is blocked by mutations in several different nuclear genes. Molecular characterization of these mutant strains has determined that the product of one nuclear gene is necessary for the stabilization of the mRNA which codes for D2, and the products of two different chloroplast genes are required for the translation of this mRNA. We are currently in the process of cloning these nuclear genes to understand how their products are involved in mRNA stabilization and translation. One gene, AC115, has recently been cloned. The product of this gene is a small, novel polypeptide with a hydrophobic stretch of amino acids at its carboxy terminus which is long enough to be a membrane spanning domain. Our working hypothesis is that the AC115 gene product is a single- pass trans-thylakoid membrane protein which functions to stabilize the nascent D2 polypeptide as it is being synthesized. 

Ultimately, with a combination of genetic and molecular techniques, our ambition is to clone additional nuclear genes and define how the products of these genes are involved in the synthesis of individual gene products within the chloroplast. This experimentation will help define basic aspects of the mechanics of RNA stabilization and the regulation of translation.

Publications

Godfried Sie, C., Hesler, S., Maas, S., and Kuchka, M. (2012) IGFBP7's susceptibility to proteolysis is altered by A-to-I RNA editing of its transcript. FEBS Letters, 586: 2313 - 2317.

Godfried Sie, C. P. and Kuchka, M. (2011) RNA Editing Adds Flavor to Complexity.  Biochemistry (Mosc), 76: 869 - 881. 

Rattanachaikunsopon, P., C. Rosch, and M. R. Kuchka (1999). Cloning and characterization of the nuclear AC115 gene of Chlamydomonas reinhardtii. Plant Molecular Biology,39: 1-10.

Yohn, C., A. Cohen, C. Rosch, M. R. Kuchka, and S. P. Mayfield.(1998).Translation of the chloroplast psbA mRNA requires the nuclear-encoded poly(A)-binding protein, RB47.  Journal of Cell Biology, 142: 435-442.

Wu, H. and M. R. Kuchka (1995). A nuclear suppressor overcomes defects in the synthesis of the chloroplast psbD gene product caused by mutations in two distinct nuclear genes of Chlamydomonas.  Current Genetics, 27: 263-269.

Rochaix, J.-D., M. Goldschmidt-Clermont, Y. Choquet, M. Kuchka, and J. Girard-Bascou (1991). Nuclear and chloroplast genes involved in the expression of specific chloroplast genes of Chlamydomonas reinhardtii, in Plant Molecular Biology (ed. R. G. Herman) Plenum Press, New York, NY.

Kuchka, M. R., M. Goldschmidt-Clermont, J. vanDillewijn, and J.-D. Rochaix (1989). Mutation at the nuclear NAC2 locus of C. reinhardtii afects the stability of the chloroplast psbD transcript encoding polypeptide D2 of photosystem II.  Cell, 58: 869-876.

Rochaix, J.-D., M. Kuchka, S. Mayfield, M. Schirmer-Rahire, J. Girard-Bascou, and P. Bennoun (1989). Nuclear mutations affect the synthesis or stability of the chloroplast psbC gene product in Chlamydomonas reinhardtii.  EMBO Journal, 8: 1013-1021.

Day, A., M. Schirmer-Rahire, M. R. Kuchka, S. P. Mayfield, and J.-D. Rochaix (1988). A transposon with an unusual arrangement of long terminal repeats in the green alga Chlamydomonas reinhardtii. EMBO Journal, 7: 1917-1927.

Kuchka, M.R. and Jarvik, J.W. (1987). Short-Flagella Mutants of Chlamydomonas reinhardtii. Genetics 115: 685-691.

Kuchka, M. R., S. P. Mayfield, and J.-D. Rochaix (1987). Nuclear mutations specifically affect the synthesis and/or degradation of the chloroplast-encoded D2 polypeptide of photosystem II in Chlamydomonas reinhardtii. EMBO Journal, 7: 319-324.

Kuchka, M.R. and Jarvik, J.W. (1982). Analysis of Flagellar Size Control Using a Mutant of Chlamydomonas reinhardtii with a Variable Number of Flagella. The Journal of Cell Biology, 92: 170-175.

top