Changes in Polygalacturonase Activity and Solubility of Polyuronides during Ethylene-stimulated Leaf Abscission in<i>Sambucus nigra</i>

Taylor, Jane; Webb, Simon Tj; Coupe, Simon A.; Tucker, Gregory A.; Roberts, Jeremy A.

doi:10.1093/jxb/44.1.93

Cited by 50 publications

(30 citation statements)

References 22 publications

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“…Taylor et al (1993) correlated increases in PG activity only with the onset of abscission. Experiments with transgenics contributed to the theory that PG action was not one of the prime determinants of abscission in leaves.…”

Section: The Role Of Pg In Leaf Abscissionmentioning

confidence: 96%

Overexpression of Polygalacturonase in Transgenic Apple Trees Leads to a Range of Novel Phenotypes Involving Changes in Cell Adhesion

et al. 2002

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Polygalacturonases (PGs) cleave runs of unesterified GalUA that form homogalacturonan regions along the backbone of pectin. Homogalacturonan-rich pectin is commonly found in the middle lamella region of the wall where two adjacent cells abut and its integrity is important for cell adhesion. Transgenic apple (Malus domestica Borkh. cv Royal Gala) trees were produced that contained additional copies of a fruit-specific apple PG gene under a constitutive promoter. In contrast to previous studies in transgenic tobacco (Nicotiana tabacum) where PG overexpression had no effect on the plant (K.W. Osteryoung, K. Toenjes, B. Hall, V. Winkler, A.B. Bennett [1990] Plant Cell 2: 1239-1248), PG overexpression in transgenic apple led to a range of novel phenotypes. These phenotypes included silvery colored leaves and premature leaf shedding due to reduced cell adhesion in leaf abscission zones. Mature leaves had malformed and malfunctioning stomata that perturbed water relations and contributed to a brittle leaf phenotype. Chemical and ultrastructural analyses were used to relate the phenotypic changes to pectin changes in the leaf cell walls. The modification of apple trees by a single PG gene has offered a new and unexpected perspective on the role of pectin and cell wall adhesion in leaf morphology and stomatal development.Polygalacturonases (PGs) are expressed in a wide range of tissues and developmental stages in plants and are encoded by relatively large gene families (e.g. approximately 52 genes in Arabidopsis; The Arabidopsis Genome Initiative, 2000). PGs are associated with fruit ripening, cell separation processes such as leaf and flower abscission, pod and anther dehiscence, pollen grain maturation, pathogen defense, plant-host interactions, and processes of cell expansion, growth, and xylogenesis (for review, see Hadfield and Bennett, 1998; Bergey et al., 1999;Sitrit et al., 1999; Torki et al., 1999; Wang et al., 2000). Endo-PGs cleave runs of unesterified GalUA that form homogalacturonan regions along the backbone of pectin. Homogalacturonan-rich pectin is commonly found in the middle lamella region of the wall where two adjacent cells abut (for example, see Knox et al., 1990;Steele et al., 1997). The best characterized (fungal) endo-PG enzyme requires four to five consecutive runs of unesterified GalUA residues for cleavage; however, little is known about the enzyme activities and specificities of most cloned PGs from plants.Transgenic plants have been used to study the role of endo-PGs in vivo. In tomato (Lycopersicon esculentum), down-regulation of the fruit-specific PG gene pTOM6 under the control of the constitutive cauliflower mosaic virus 35S promoter showed reduced depolymerization of pectin polymers in fruit . Overexpression of PG in the ripeninginhibited mutant rin background restored PG activity and pectin degradation in fruit (Giovannoni et al., 1989). In both cases, only the fruit was affected by the transgene expression; therefore, the gene product isolated from tomato fruit appeared to have frui...

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Section: The Role Of Pg In Leaf Abscissionmentioning

confidence: 96%

Overexpression of Polygalacturonase in Transgenic Apple Trees Leads to a Range of Novel Phenotypes Involving Changes in Cell Adhesion

et al. 2002

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“…Antisense suppression of one EGase isoform resulted in a partial reduction in flower abscission (Lashbrook et al, 1998). PG activity also increases during abscission of both tomato flower and Sambucus nigra leaf explants (Tucker et al, 1984;Taylor et al, 1993). In contrast to EGase activity, which is distributed throughout the abscission zone, PG activity is restricted to the distal portion of the zone tissue (Roberts et al, 1989).…”

Section: Pg In Cell-separation Zonesmentioning

confidence: 98%

Polygalacturonases: Many Genes in Search of a Function1

1998

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“…Once the DZ is correctly specified and established, other essential processes include secondary wall formation at the valve margins (Mitsuda and Ohme-Takagi, 2008) and degradation of cell walls, including the middle lamella, in the separation layer. This is thought to occur by the action of proteins involved in cell wall loosening, including polygalacturonases (PGs), b-1,4-glucanase, and expansin (Bonghi et al, 1993;Taylor et al, 1993Taylor et al, , 1994Lashbrook et al, 1994;del Campillo and Bennett, 1996;Cho and Cosgrove, 2000), although this hypothesis is supported by only limited direct evidence.…”

Section: Introductionmentioning

confidence: 99%

“…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).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2009

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Cell separation is thought to involve degradation of pectin by several hydrolytic enzymes, particularly polygalacturonase (PG). Here, we characterize an activation tagging line with reduced growth and male sterility caused by increased expression of a PG encoded by QUARTET2 (QRT2). QRT2 is essential for pollen grain separation and is part of a small family of three closely related endo-PGs in the Arabidopsis thaliana proteome, including ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE1 (ADPG1) and ADPG2. Functional assays and complementation experiments confirm that ADPG1, ADPG2, and QRT2 are PGs. Genetic analysis demonstrates that ADPG1 and ADPG2 are essential for silique dehiscence. In addition, ADPG2 and QRT2 contribute to floral organ abscission, while all three genes contribute to anther dehiscence. Expression analysis is consistent with the observed mutant phenotypes. INDEHISCENT (IND) encodes a putative basic helix-loop-helix required for silique dehiscence, and we demonstrate that the closely related HECATE3 (HEC3) gene is required for normal seed abscission and show that IND and HEC3 are required for normal expression of ADPG1 in the silique dehiscence zone and seed abscission zone, respectively. We also show that jasmonic acid and ethylene act together with abscisic acid to regulate floral organ abscission, in part by promoting QRT2 expression. These results demonstrate that multiple cell separation events, including both abscission and dehiscence, require closely related PG genes.

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Changes in Polygalacturonase Activity and Solubility of Polyuronides during Ethylene-stimulated Leaf Abscission inSambucus nigra

Cited by 50 publications

References 22 publications

Overexpression of Polygalacturonase in Transgenic Apple Trees Leads to a Range of Novel Phenotypes Involving Changes in Cell Adhesion

Overexpression of Polygalacturonase in Transgenic Apple Trees Leads to a Range of Novel Phenotypes Involving Changes in Cell Adhesion

Polygalacturonases: Many Genes in Search of a Function1

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

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