Xyloglucan Endotransglycosylase Activity in Pea Internodes [Effects of Applied Gibberellic Acid]

Potter, Ian D.; Fry, Stephen C.

doi:10.1104/pp.103.1.235

Cited by 81 publications

(40 citation statements)

References 28 publications

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“…Diverse factors regulate the expression of XETs and XETrelated (XTR) proteins, including auxin (Xu et al, 1995(Xu et al, , 1996Catalá et al, 1997), abscisic acid (Wu et al, 1994), gibberellin (Potter and Fry, 1993;Smith et al, 1996), ethylene (Redgwell and Fry, 1993), and brassinosteroids (Zurek and Clouse, 1994). Upregulation is also triggered by various environmental stimuli, including touch, darkness, temperature shock (Xu et al, 1995(Xu et al, , 1996, wind (Antosiewicz et al, 1997), and flooding (Saab and Sachs, 1995).…”

Section: Introductionmentioning

confidence: 99%

In Vivo Colocalization of Xyloglucan Endotransglycosylase Activity and Its Donor Substrate in the Elongation Zone of Arabidopsis Roots

et al. 2000

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We have developed a method for the colocalization of xyloglucan endotransglycosylase (XET) activity and the donor substrates to which it has access in situ and in vivo. Sulforhodamine conjugates of xyloglucan oligosaccharides (XGOSRs), infiltrated into the tissue, act as acceptor substrate for the enzyme; endogenous xyloglucan acts as donor substrate. Incorporation of the XGO-SRs into polymeric products in the cell wall yields an orange fluorescence indicative of the simultaneous colocalization, in the same compartment, of active XET and donor xyloglucan chains. The method is specific for XET, as shown by competition experiments with nonfluorescent acceptor oligosaccharides, by negligible reaction with cello-oligosaccharide-SR conjugates that are not XET acceptor substrates, by heat lability, and by pH optimum. Thin-layer chromatographic analysis of remaining unincorporated XGO-SRs showed that these substrates are not extensively hydrolyzed during the assays. A characteristic distribution pattern was found in Arabidopsis and tobacco roots: in both species, fluorescence was most prominent in the cell elongation zone of the root. Proposed roles of XET that include cell wall loosening and integration of newly synthesized xyloglucans could thus be supported. INTRODUCTIONThe primary cell walls of flowering plants consist fundamentally of a framework of cellulose microfibrils embedded in a matrix of hemicellulose, pectins, and structural proteins (Carpita and Gibeaut, 1993; Brett and Waldron, 1996). Xyloglucan, the major hemicellulosic polysaccharide in the primary cell wall matrix of dicots, consists of a backbone of ␤ -(1 → 4)-linked D -glucose residues, the majority of which are ␣ -D -xylosylated at O-6. Some xylose residues are further substituted by galactosyl and fucosyl-galactosyl groups. Other, minor carbohydrate side chains and O-acetyl groups are also present (Fry, 1989a; Hayashi, 1989). Because xyloglucans can form tight hydrogen bonds with cellulose microfibrils (Valent and Albersheim, 1974; Hayashi et al., 1987 Hayashi et al., , 1994a Hayashi et al., , 1994b Hayashi, 1989), they may thereby tether adjacent microfibrils (Fry, 1989b). A proportion of the xyloglucan molecules are covalently attached to acidic pectins (Thompson and Fry, 2000). Xyloglucans also serve as storage polysaccharides in some seeds (Edwards et al., 1985).For plant cells to expand, cellulose microfibrils in parallel alignment need to move apart or past one another, and this movement may create the possibility for newly synthesized xyloglucan molecules to become hydrogen-bonded (Fry, 1989b). Because xyloglucan tethers are thought to be the principal tension-bearing molecules in the cell wall, breaking of the tethers has been proposed as a mechanism for achieving reversible cell wall loosening in elongating tissue without compromising strength (Fry, 1989b; Hayashi, 1989; Hoson et al., 1991). Although the cell wall contains numerous enzymes that can modify polysaccharides (Fry, 1995), xyloglucan endotransglycosylases (XETs) seem well...

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Section: Introductionmentioning

confidence: 99%

In Vivo Colocalization of Xyloglucan Endotransglycosylase Activity and Its Donor Substrate in the Elongation Zone of Arabidopsis Roots

et al. 2000

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“…It was therefore of interest to investigate whether xyloglucan chains undergo transglycosylation in the walls of living plant cells. Xyloglucan endotransglycosylases (XETs) are widespread in land plants [13][14][15][16][17][18][19], and numerous correlations between XET activity and wall loosening have been noted [5,7,[20][21][22][23][24]. XET cuts a xyloglucan chain (donor substrate)…”

Section: Introductionmentioning

confidence: 99%

“…In itro, the acceptor can be a high-M r xyloglucan or a short xyloglucan oligomer as small as a pentasaccharide [25]. Transglycosylation between xyloglucan chains in the cell wall could play a role in wall construction [8,26,27] and\or wall loosening [8,14,16,21,22,25,28]. Progress in testing these ideas has been hampered by our inability to say whether XET catalyses interpolymeric transglycosylation in i o. XETs are known to catalyse polymer-to-oligomer transglycosylation in itro [15][16][17]25], interpolymeric transglycosylation in itro [17,29,30] and polymer-to-oligomer transglycosylation in i o (although not necessarily involving wall-bound polymer) [13,14].…”

Section: Introductionmentioning

confidence: 99%

Xyloglucan undergoes interpolymeric transglycosylation during binding to the plant cell wall in vivo: evidence from 13C/3H dual labelling and isopycnic centrifugation in caesium trifluoroacetate

Thompson

Smith

Fry

1997

Biochemical Journal

105

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Xyloglucan from the walls of Rosa cells that had been cultured on [12C]- or [13C]-glucose formed bands in caesium trifluoroacetate with mean buoyant densities of 1.575 or 1.616 g/ml respectively. Incubation of a mixture of [13C,3H]xyloglucan and [12C,1H]xyloglucan in the presence of xyloglucan endotransglycosylase (XET) activity caused the mean buoyant density of the radioactive material to decrease, indicating that interpolymeric transglycosylation could be detected in vitro. We used two 13C/3H-dual-labelling protocols to look for interpolymeric transglycosylation in vivo. In protocol A, [13C]glucose-grown Rosa cells were transferred into [12C]glucose medium 6 h after a ≈ 2 h pulse of L-[1-3H]arabinose (which radiolabels the xylose residues of xyloglucan). The mean buoyant density of the wall-bound [3H]xyloglucan decreased during the following 7 days in culture. This indicates that, during or after the wall-binding of newly synthesized [12C,1H]xyloglucan, it became covalently attached to previously wall-bound [13C,3H]xyloglucan. In protocol B, [12C]glycerol- or [12C]glucose-grown Rosa cells were transferred into [13C]glucose medium, 20 or 60 min before a ≈ 2 h pulse of [3H]arabinose. The buoyant density of the earliest wall-bound [3H]xyloglucan showed that it had a 12C/13C ratio of ~ 1:1. This indicates that, during (or, implausibly, before) wall-binding, the newly synthesized [13C,3H]xyloglucan became covalently attached to previously synthesized [12C]xyloglucan. During the following 7 days in culture, the mean buoyant density of the [3H]xyloglucan increased, showing that later-synthesized [13C,1H]xyloglucan can be covalently attached to previously wall-bound [12C,13C,3H]xyloglucan. The only known mechanism by which segments of xyloglucans could become covalently attached to each other in the cell wall is by interpolymeric transglycosylation catalysed by XET. We conclude that XET-catalysed interpolymeric transglycosylation accompanies, and probably causes, the integration of newly secreted xyloglucan into the cell-wall architecture.

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“…Vol. 103, 1993 for this idea is provided by a strong correlation between growth rates and XET activity in spinach cell cultures and pea stems (Fry et al, 1992a), especially after GA3 treatment (Potter and Fry, 1993). Nevertheless, in the presence of suitable oligosaccharides (such as could arise during partia1 lysis of matrix polysaccharides during fruit ripening), XET can catalyze polysaccharide-to-oIigosaccharide endotransglycosylation.…”

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confidence: 99%

Xyloglucan Endotransglycosylase Activity Increases during Kiwifruit (Actinidia deliciosa) Ripening (Implications for Fruit Softening)

1993

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l h e activity of xyloglucan endotransglycosylase (XET) was assayed in three tissue zones of kiwifruit (Actinidia deliciosa [A.Chev.] C.F. Liang et A.R. Ferguson var deliciosa cv Hayward) at harvest and at severa1 softening stages following a postharvest ethylene treatment. At harvest, extractable XET activity per unit fresh weight in the inner pericarp (IP) and core tissue was 4.5 and 42 times higher, respectively, than in the outer pericarp (OP).Within 24 h of ethylene treatment there was an increase in the adivity and specific activity of XET in all tissues that continued throughout softening. Activity increased most in the OP, where it showed a 12-fold rise 6 d after ethylene treatment compared with 4.5-and 2.5-fold increases in the IP and core tissues, respectively. Visible swelling of the cell wall in each tissue was observed 24 h after the first detectable rise in XET activity and was most pronounced in the OP, which showed the greatest percentage increase in XET activity. Xyloglucan, galactoglucomannan, and cell wall materials isolated and purified from kiwifruit OP were tested as donor substrates for kiwifruit XET. The enzyme showed activity against xyloglucan but was inadive against galadoglucomannan. XET was active against cell wall materials from unripe and ripe fruit, with swollen walls from the latter being the better substrate. l h e results indicate that XET may have a key role early in fruit ripening, loosening the cell wall in preparation for further modification by other cell wall-associated enzymes.

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Xyloglucan Endotransglycosylase Activity in Pea Internodes [Effects of Applied Gibberellic Acid]

Abstract: Xyloglucan endotransglycosylase (XET) activity extractable from internodes of tal1 and dwarf varieties of pea (Pisum sativum 1.) was assayed radiochemically using tamarind seed xyloglucan as

Cited by 81 publications

References 28 publications

In Vivo Colocalization of Xyloglucan Endotransglycosylase Activity and Its Donor Substrate in the Elongation Zone of Arabidopsis Roots

In Vivo Colocalization of Xyloglucan Endotransglycosylase Activity and Its Donor Substrate in the Elongation Zone of Arabidopsis Roots

Xyloglucan undergoes interpolymeric transglycosylation during binding to the plant cell wall in vivo: evidence from 13C/3H dual labelling and isopycnic centrifugation in caesium trifluoroacetate

Xyloglucan Endotransglycosylase Activity Increases during Kiwifruit (Actinidia deliciosa) Ripening (Implications for Fruit Softening)

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