Tomato fruit ripening is characterized by a decrease in chlorophyll content and an increase in lycopene synthesis. We are interested in the role of chlorophyll metabolism as it relates to tomato fruit ripening. 5-Aminolevulinic acid dehydratase (ALAD) is the first committed enzyme in the chlorophyll biosynthetic pathway, and it catalyzes the conversion of two 5-aminolevulinic acid molecules into porphobilinogen. We have isolated a full-length tomato ALAD cDNA clone from a tomato fruit library. Sequence analysis showed that this tomato ALAD was highly homologous to ALAD found in spinach and pea, and the analysis predicted a protein of 46.8 kDa. Southern analysis indicated that 1 to 3 copies of the ALAD gene are present in the tomato genome. Northern analysis suggested that the gene is expressed constitutively throughout tomato fruit development. Currently, we are subcloning the fragment into an E. coli expression vector in order to obtain protein for antibody production for Western analysis.