Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 1998
Publication Date: N/A
Interpretive Summary: Abscission (organ separation) reduces the yield of agriculturally important crops. Our goal is to genetically engineer plants with economically beneficial abscission characteristics. Cellulases and polygalacturonase (PG) are enzymes that are important in breaking down the cell wall surrounding plant cells allowing the cells to separate from each other. We have cloned a polygalacturonase gene, TPG7, (plant genetic material) from tomato. The TPG7 gene is closely related to four other polygalacturonase genes that we previously demonstrated to be expressed in abscission. We examined several different tissues for expression of the TPG7 gene. The TPG7 gene is expressed in pistils of fully open flowers but not abscission zones, fruit, meristems, roots or root initials. The purpose of this study is to define and characterize genetic material that scientists and biotechnologists can use to genetically engineer plants with beneficial abscission properties (i.e., increased yield and quality).
Technical Abstract: Polygalacturonases (PG) hydrolyze pectin in the middle lamella and primary cell wall. Currently, the public databases include sequences for seven tomato PG genes: TOM6 (expressed in ripening fruit), TAPG1, TAPG2, TAPG4 and TAPG5 (predominantly expressed in abscission), and TPG3 and TPG6 (expression unknown). We report here an eighth PG gene, TPG7, from tomato (Lycopersicon esculentum Mill., cv. Rutgers). RNA blot analysis reveals that TPG7 is abundantly expressed in mature pistils (ovaries removed). A very faint hybridization signal was detected in leaf and flower abscission zones but no hybridization in fruit pericarp, flower and fruit calyx, meristems, root initials and roots. The TPG7 gene encodes a polypeptide of 397 amino acids that includes a predicted signal peptide. The TPG7 polypeptide shares only 39% sequence identity with the tomato fruit PG and from 63% to 73% sequence identity with the other six tomato PGs.