Member Institutions:

• Bowling Green State U.
• Cleveland State U.
• Kent State U.
• Medical College of Ohio
• Miami U.
• The Ohio State U.
• Ohio U.
• University of Cincinnati
• University of Toledo
• Wright State U.
• Youngstown State U.

Research Interests

There are three major research programs in our lab including; 1) molecular studies on the structure and function of the photosynthetic electron transport complexes in chloroplasts, 2) studies on the regulation of cyanogenesis and its molecular manipulation in the tropical root crop cassava, and 3) the biochemical characterization and genetic manipulation of heavy metal binding sites in algae.

The focus areas of our photosynthesis research program include the characterization of structure/function relationships and the study of energy transfer mechanisms in photosystem II reaction center complexes. Our lab uses recombinant DNA techniques to generate site-directed mutations in chloroplast genes encoding proteins the PSII complex. The mutants are characterized using a variety of biochemical and biophysical techniques. Notable accomplishments include mapping the molecular topology of PSII membrane proteins, and identification of functional residues associated with the water oxidation and light-harvesting processes. Presently, we are testing models for the structural and functional organization of chlorophylls involved in primary charge separation.

The objectives of our cyanogenesis research program in cassava are to characterize the biochemistry of cyanogenic glycoside synthesis, transport and turnover, and to develop transgenic plants which are less toxic (low cyanogenic) for human consumption. Recently, we have demonstrated that cyanogens are synthesized in all tissues and sequestered in the vacuole. In addition, we are isolating genes encoding cytochrome P450(s) involved in the first dedicated step of cyanogen synthesis by yeast complementation. We also have developed Agrobacterium Ti plasmid vectors for cassava transformation and tissue culture systems for regeneration of recalcitrant cassava cultivars. Recently, we have begun studies on the genetic manipulation of starch production in cassava.

The most recent addition to our research program focuses on the biochemistry of heavy metal binding in algae. The objectives of the program are to characterize the chemistry of heavy metal binding factors in algae and to generate transgenic algae which over-express heavy metal binding proteins. These recombinant algae will be used for the bioremediation of heavy metal contaminated waters. Initial accomplishments include the characterization of heavy metal binding sites in algae and the generation of transgenic algae expressing novel heavy metal binding proteins and genes which reduce heavy metal stress. This work also has recently lead to the identification of ABC-type, xenobiotic transporters which apparently export toxic or foreign substances out of the cell.

Selected References

Cassava

• Arias-Garcon DI and Sayre RT (1999) Genetic engineering approaches to reducing the cyanide toxicity in cassava. Euphytica (in press)

Photosynthesis

• Ruffle S, Hutchinson R and Sayre RT (1999) Mutagenesis of the photosystem II D2-H117 residue in Chlamydomonas: Implications for peripheral accessory chlorophyll function. (submitted)
• Johnston, HG, Wang J, Sayre RT and Gustafson T (1999) Fluorescence decay kinetics of wild type and D2-H117N mutant photosystem II reaction centers isolated from Chlamydomonas reinhardtii. (in press, J. Phys. Chem B).

Heavy Metals Biology

• Cai X-H, Brown C, Adhiya J, Traina S and Sayre RT (1999) Growth and heavy metal binding properties of transgenic algae (Chlamydomonas reinhardtii) expressing a foreign metallothionein gene. Int. J. Phytoremediation 1:53-65
• Adhiya J, Cai X-H, Traina S and Sayre RT (1999) Binding of aqueous cadmium by the lyophilized biomass of Chlamydomonas reinhardtii. (in press, Journal of Colloid and Interface Science).

Department of Plant Biology
Dr. Sayre's Lab
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