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

Atkinson, Ross G.; Schröder, Roswitha; Hallett, Ian C.; Cohen, Daniel; MacRae, Elspeth

doi:10.1104/pp.010986

Cited by 157 publications

(123 citation statements)

References 55 publications

(10 reference statements)

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“…In a recent study, stomata in leaves of transgenic apple trees overexpressing EPG showed impaired responses to darkness and ABA (21). However, these effects were the result of severe malformation of epidermal and guard cells rather than specific alterations in guard cell wall composition.…”

Section: Discussionmentioning

confidence: 99%

Cell wall arabinan is essential for guard cell function

Jones

Milne²,

Ashford³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

283

228

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Stomatal guard cells play a key role in the ability of plants to survive on dry land, because their movements regulate the exchange of gases and water vapor between the external environment and the interior of the plant. The walls of these cells are exceptionally strong and must undergo large and reversible deformation during stomatal opening and closing. The molecular basis of the unique strength and flexibility of guard cell walls is unknown. We show that degradation of cell wall arabinan prevents either stomatal opening or closing. This locking of guard cell wall movements can be reversed if homogalacturonan is subsequently removed from the wall. We suggest that arabinans maintain flexibility in the cell wall by preventing homogalacturonan polymers from forming tight associations.

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Section: Discussionmentioning

confidence: 99%

Cell wall arabinan is essential for guard cell function

Jones

Milne²,

Ashford³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

283

228

View full text Add to dashboard Cite

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“…7E) can profoundly affect the mechanical strength of the cell wall and associated signaling phenomena. An unexpected perspective on the role of pectin in plant development was recently highlighted in transgenic apple (Malus domestica) trees overexpressing an endoPG (Atkinson et al, 2002). The expression of a fungal endoPG in plant tissues reported in this work provides a means to investigate such alterations.…”

Section: Discussionmentioning

confidence: 99%

Elicitor Activity of a Fungal Endopolygalacturonase in Tobacco Requires a Functional Catalytic Site and Cell Wall Localization

et al. 2003

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of Colletotrichum lindemuthianum, was transferred to tobacco (Nicotiana tabacum) leaves by using the Agrobacterium tumefaciens transient delivery system. The following four constructs were prepared: CLPG1, with or without its signal peptide (SP; PG1, PG1⌬SP); CLPG1 with the tobacco expansin1 SP instead of its own SP (Exp::PG1⌬SP); and a mutated version of the latter on two amino acids potentially involved in the catalytic site of CLPG1 (D202N/D203N). Chlorotic and necrotic lesions appeared 5 to 7 d postinfiltration, exclusively in response to CLPG1 fused to the expansin SP. The lesions were correlated to the production of an active enzyme. Necrosis-inducing activity, as well as endoPG activity, were completely abolished by site-directed mutagenesis. Ultrastructural immunocytolocalization experiments indicated that the expansin SP addressed CLPG1 to the cell wall. Staining of parenchyma cells revealed the progressive degradation of pectic material in junction zones and middle lamella as a function of time after infiltration, ultimately leading to cell separation. A 30% decrease in the GalUA content of the cell walls was simultaneously recorded, thereby confirming the hydrolytic effect of CLPG1 on pectic polysaccharides, in planta. The elicitor activity of CLPG1 was further illustrated by the induction of defense responses comprising active oxygen species and ␤-1,3-glucanase activity, before leaf necrosis. Altogether, the data demonstrate that an appropriate SP and a functional catalytic site are required for the proper expression and elicitor activity of the fungal endoPG CLPG1 in tobacco.Endopolygalacturonases (endoPGs) are a class of pectinases that participate in the degradation of plant cell walls by catalyzing the hydrolysis of the homogalacturonan domain of pectic polysaccharides, a linear chain of ␣-1,4-linked galacturonosyl residues. Depending on the source of enzyme, the degradation proceeds either by a strict endo-mode or by an endo-/exo-mode of cleavage (Cook et al., 1999). The released pectic fragments are mostly composed of linear oligogalacturonides (OGAs). The extent of degradation varies according to the level of methylesterification of the ␣-d,1-4-linked GalUA residues that compose the linear homogalacturonan chain because endoPGs only cleave unesterified rows of GalUA. Degradation can also be controlled by the presence of polygalacturonase-inhibiting proteins (PGIPs), a class of Leu-rich repeat proteins found in the cell walls of many plants.The OGAs released by cleavage of homogalacturonan were the first oligosaccharins, that is biologically active oligosaccharides (Darvill et al., 1992), that were isolated from commercial pectin and plant cell walls. OGA-induced responses have been reviewed extensively (Côté and Hahn, 1994; Ridley et al., 2001). The likelihood that such fragments elicit defense mechanisms when produced in planta is based on their effects when they are externally supplied to plant cells and tissues. Thus, early responses such as plasma membrane depolarization, ion fluxes, and c...

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“…Either up-and down-regulation in tomato of an endogenous gene encoding an endopolygalacturonase involved in fruit softening had no apparent effect on growth and development (Giovannoni et al, 1989;Smith et al, 1990). The expression of a tomato PG in tobacco (Nicotiana tabacum) resulted in no phenotype (Osteryoung et al, 1990), whereas the overexpression of an apple (Malus domestica) fruit PG in apple resulted in novel phenotypes involving changes in cell adhesion (Atkinson et al, 2002).…”

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confidence: 99%

Targeted Modification of Homogalacturonan by Transgenic Expression of a Fungal Polygalacturonase Alters Plant Growth

et al. 2004

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Pectins are a highly complex family of cell wall polysaccharides comprised of homogalacturonan (HGA), rhamnogalacturonan I and rhamnogalacturonan II. We have specifically modified HGA in both tobacco (Nicotiana tabacum) and Arabidopsis by expressing the endopolygalacturonase II of Aspergillus niger (AnPGII). Cell walls of transgenic tobacco plants showed a 25% reduction in GalUA content as compared with the wild type and a reduced content of deesterified HGA as detected by antibody labeling. Neutral sugars remained unchanged apart from a slight increase of Rha, Ara, and Gal. Both transgenic tobacco and Arabidopsis were dwarfed, indicating that unesterified HGA is a critical factor for plant cell growth. The dwarf phenotypes were associated with AnPGII activity as demonstrated by the observation that the mutant phenotype of tobacco was completely reverted by crossing the dwarfed plants with plants expressing PGIP2, a strong inhibitor of AnPGII. The mutant phenotype in Arabidopsis did not appear when transformation was performed with a gene encoding AnPGII inactivated by site directed mutagenesis.Although biochemical events causing structural changes of cell walls are expected to influence plant growth and development (Pilling et al., 2000;Bouton et al., 2002), the degradation and remodeling of cell wall constituents during development appear to be of considerable complexity and far from being fully understood. For example, the remodeling of pectin, which is thought to impact upon processes such as adhesion between cells and plant growth, requires the action of several different enzyme classes (Ridley et al., 2001). The complex role of pectin in the dynamics of cell walls is further indicated by the presence of large families of these pectic enzymes in plant genomes. For example, more than 50 genes encoding putative polygalacturonases (PGs) have been identified in Arabidopsis (Arabidopsis Genome Initiative, 2000).Indications that the pectic polymers homogalacturonan (HGA), rhamnogalacturonan-I (RG-I), and rhamnogalacturonan-II (RG-II) play an important role in plant development have been obtained by analyzing several cell wall mutants, most of which have been obtained by mutagenesis of Arabidopsis. Among these, Arabidopsis emb30 mutants, having a mutation in a gene putatively involved in the secretory pathway, show an abnormal localization and accumulation of pectin in intercellular/interstitial spaces rather than in the corners. Cells of emb30 mutants are larger than those of the wild type and do not adhere well to each other; the seeds are impaired in the control of cell division, expansion, and polarity and do not develop as wild type (Shevell et al., 2000). The Arabidopsis quartet mutants have microspores that fail to separate during pollen development as a result of the persistence of pectin in the pollen mother cell wall (Rhee and Somerville, 1998). The Arabidopsis mur1 mutation, leading to a deficiency in fucosyl residues, affects RG-II, reducing its capacity to dimerize through the formation of boron diest...

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

Cited by 157 publications

References 55 publications

Cell wall arabinan is essential for guard cell function

Cell wall arabinan is essential for guard cell function

Elicitor Activity of a Fungal Endopolygalacturonase in Tobacco Requires a Functional Catalytic Site and Cell Wall Localization

Targeted Modification of Homogalacturonan by Transgenic Expression of a Fungal Polygalacturonase Alters Plant Growth

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