title: Cloning of a tomato polygalacturonase expressed in abscission.
abstract: Abscission, organ separation, is accompanied by cell wall breakdown in separation layer cells. In tomato (Lycopersicon esculentum), ethylene-induced abscission is correlated with an increase in polygalacturonase (PG) and endo-beta-1,4-D-glucanase (cellulase) activity. We have identified a putative, abscission-specific cDNA clone for PG, pTAPG1. The TAPG1 cDNA has 43% identity at the amino acid level with the tomato fruit PG. Genomic blot analysis suggests that the gene for TAPG1 is a member of a small subfamily of PG genes that is distinct from the tomato fruit PG. The TAPG1 cDNA hybridizes to mRNA expressed during the course of ethylene-induced leaf and flower abscission. A high level of PG transcript accumulation coincides with the occurrence of abscission. Auxin, an abscission inhibitor, and silver thiosulfate, an ethylene action inhibitor, suppressed accumulation of mRNA in leaf abscission zones complementary to the TAPG1 cDNA. Expression of TAPG1 transcripts is several-fold higher in flower abscission zones than in leaf abscission zones. The identification of cDNAs that encode abscission-specific PG provide and additional tool to study the regulation of abscission and cell wall dissolution in separation layer cells.
authors.affiliation: Plant Molecular Biology Lab, USDA/ARS, BARC-West, Beltsville, MD 20705, USA.
authors.forename: P
authors.initials: P
authors.lastname: Kalaitzis
authors.forename: S M
authors.initials: SM
authors.lastname: Koehler
authors.forename: M L
authors.initials: ML
authors.lastname: Tucker
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D018076:DNA, Complementary / Q000235:genetics; D015723:Gene Library; D007210:Indoleacetic Acids / Q000494:pharmacology; D018551:Solanum lycopersicum / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology*; D011096:Polygalacturonase / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D013885:Thiosulfates / Q000494:pharmacology*; D014018:Tissue Distribution
chemical_list: D018076:DNA, Complementary; D007210:Indoleacetic Acids; D012333:RNA, Messenger; D013885:Thiosulfates; C095213:silver thiosulfate; D011096:Polygalacturonase