Molecular characterization of a tomato polygalacturonase gene abundantly expressed in the upper third of pistils from opened and unopened flowers.

A polygalacturonase (PG) gene, TPG7 (Lyces;Pga1;8), has been cloned from tomato (Lycopersicon esculentum Mill., cv. Rutgers). RNA blot analysis reveals that TPG7 is highly expressed in pistils (ovary removed) from unopened and fully open flowers. Dissection of mature pistils demonstrated that TPG7 expression is limited to the top third (stigmatic region) of the pistils. This is contrasted with another tomato PG, TAPG4, which is also expressed in the same region of the pistil but only in mature pistils from fully open flowers. Hybridization of the TPG7 probe to anther RNA was nil to none and was barely detectable in RNA from leaf and flower abscission zones. The TPG7 polypeptide shares 39% sequence identity with the tomato fruit PG and between 63% and 73% sequence identities with six other tomato PGs.