Uzoma E. Ihemere, Diana I. Arias-Garzon and Richard T. Sayre

Departments of Horticulture and Crop Science, and Plant Biology, The Ohio State University, Columbus, OH 43210.

Attempts are made to transform tomato via Agrobacterium-mediated transformation with two vectors pCAT (CAB1/TP glgC) and pCA (CAB1/glgC). The two vectors contain modified AGPase gene driven by heterologous CAB1 promoter. By contrast, pCAT contains a transit peptide while pCA does not. We are investigating the impact of over-expressing a mutated glgC gene from E. coli driven by CAB1 promoter on increasing tomato fruit starch content. This effort will also determine the location of AGPase activity (chloroplast or cytosol) in tomato. Tomato fruits are used in making source and paste for the cuisinary industry, but, unfortunately, it comprises about 80% water, whereas the desirable ingredient in making source and paste is starch. This makes it cumbersome to transport from the farms to the processing centers. Also, during ripening, most of the starch is hydrolysed and transported out of the fruit as hexoses by glucose transporters. Our objective is to increase the starch content of the fruit and later on, block the transport of starch through its breakdown products, by antisense expression of glucose transporter. This way, we will produce tomato fruits with increase in starch content. At the moment, hypocotyl and cotyledon explants were used in transformation of the tomato cultivar Roma VF with pCA and pCAT constructs. Plantlets have been regenerated in both hypocotyl and cotyledon explants on a regenerating medium supplemented with 75 mg/I kanamycin. Putative transformants have been confirmed through fluorescence quenching which determines whether or not plants under selection are under stress or growing normally. Biochemical and molecular analysis will be carried out when plantlets produce enough materials for analysis.