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.

ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE1 (ADPG1), ADPG2, and QUARTET2 Are Polygalacturonases Required for Cell Separation during Reproductive Development inArabidopsis

“…Endopolygalacturonases (endo-PGs) catalyze random hydrolysis of a-1,4-glycosidic linkages in polygalacturonic acid (GalUA), a polymer that constitutes the main chain of the homogalacturonan region of pectin (Biely et al, 1996). Although there is only limited direct genetic evidence for the physiological importance of individual PGs, correlations have been reported between increasing PG activity and cell separation in fruit ripening and in the shedding of leaves, flowers, and fruit (Taylor et al, 1993;Kalaitzis et al, 1995;Brown, 1997;Kalaitzis et al, 1997). More recently, silencing of tomato (Solanum lycopersicum) abscission-related PGs was shown to increase the break strength of the leaf abscission zone and delay abscission in explants treated with ethylene (Jiang et al, 2008), and a putative Arabidopsis PG has been shown to promote floral organ abscission (Gonzá lezCarranza et al, 2007).…”

Immunodetection and Characterization of Tomato Endo-β-1,4-Glucanase Cel1 Protein in Flower Abscission Zones

“…In many plants, organ abscission is associated with an increase in ethylene production and involves ethylenerelated changes in gene expression (Sexton and Roberts, 1982;Reid, 1985). Ethylene induces cell wall hydrolases and, in particular, EGase (Horton and Osborne, 1967;Lewis and Varner 1970;Tucker et al, 1988) and polygalacturonase (Tucker et al, 1984;Taylor et al, 1990;Kalaitzis et al, …”

Senescence of Eustoma Flowers as Affected by Pollinated Area of the Stigmatic Surface

“…In Eustoma, pollen tube growth was correlated with ethylene production induced by pollination. Ethylene is known to induce pectinase and other wall hydrolase activity in a variety of tissues including the abscission zone in leaf stalks and flowers (Kalaitzis et al, 1995;Tucker et al, 1984) and in the pericarp of climacteric fruit (Giovannoni, 2001). In tobacco styles, the vacuolation, disorganization, and modification of the transmitting tissue cells coincided with the physical penetration of this tissue by pollen tubes; STS treatment inhibited the modification of the transmitting tissue cells (Wang et al, 1996).…”