Isolation and preliminary characterization of tomato petal- and stamen-specific cDNAs from a subtracted and equilibrated cDNA library

In order to study genes involved in late stages of flower development, we were interested in isolating petal- or stamen-specific genes, particularly ones expressed at a low level, as they may include regulatory genes. To this end, a subtracted and equalized cDNA library of tomato petals and stamens was constructed. Approximately 650 clones of this library were found to represent 84 different genes. Northern analyses performed on 43 clones demonstrated that 19 of them are specific to stamens, five are almost exclusively expressed in petals, 17 clones are specifically expressed in both petals and stamens, two are restricted to petals and young fruit, and only two are non-specific. Five of the organ-specific clones, and one of the two non-specific clones showed similarity to various regulatory proteins. Seventeen of the unique flower-expressed sequences were not present in either EST or GenBank databases, indicating substantial enrichment of rare transcripts. Taken together, it was demonstrated that following careful design of subtracted and equalized cDNA library it is feasible, at reasonable time and cost, to isolate a significant number of novel petal- and/or stamen-specific cDNA clones, even in tomato, a species on which a comprehensive EST project is currently being performed.