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

Redgwell, Robert J.; Fry, Stephen C.

doi:10.1104/pp.103.4.1399

Cited by 133 publications

(90 citation statements)

References 17 publications

(21 reference statements)

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“…However, it is possible that they act at the cellulose/xyloglucan interface at the onset of fruit softening, disrupting a crucial structural component of the wall. A consequence of this activity might also be to increase the extent of wall swelling, allowing increased access of other cell wall-degradative enzymes to their substrates and reducing the degree of physical entanglement of cell wall polymers, as has been suggested to occur in ripening kiwifruit (Redgwell et al, 1992;Redgwell and Fry, 1993).…”

Section: Discussionmentioning

confidence: 99%

Temporal Sequence of Cell Wall Disassembly in Rapidly Ripening Melon Fruit1

Rose¹,

Hadfield²,

et al. 1998

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The Charentais variety of melon (Cucumis melo cv Reticulatus F1 Alpha) was observed to undergo very rapid ripening, with the transition from the preripe to overripe stage occurring within 24 to 48 h. During this time, the flesh first softened and then exhibited substantial disintegration, suggesting that Charentais may represent a useful model system to examine the temporal sequence of changes in cell wall composition that typically take place in softening fruit. The total amount of pectin in the cell wall showed little reduction during ripening but its solubility changed substantially. Initial changes in pectin solubility coincided with a loss of galactose from tightly bound pectins, but preceded the expression of polygalacturonase (PG) mRNAs, suggesting early, PG-independent modification of pectin structure. Depolymerization of polyuronides occurred predominantly in the later ripening stages, and after the appearance of PG mRNAs, suggesting the existence of PG-dependent pectin degradation in later stages. Depolymerization of hemicelluloses was observed throughout ripening, and degradation of a tightly bound xyloglucan fraction was detected at the early onset of softening. Thus, metabolism of xyloglucan that may be closely associated with cellulose microfibrils may contribute to the initial stages of fruit softening. A model is presented of the temporal sequence of cell wall changes during cell wall disassembly in ripening Charentais melon.Ripening in many fruits is associated with textural changes that are believed to result from disassembly of the primary cell wall. This includes modifications of the structure and composition of the constituent polysaccharides that have been correlated with the expression of a range of hydrolases and transglycosylases (Fischer and Bennett, 1991; Lashbrook et al., 1997) and the potential alteration of covalent and noncovalent interactions between polysaccharide classes. A recent model of the plant primary cell wall described a network of cellulose microfibrils that surrounds the cell and is enmeshed in coextensive matrices of pectic and hemicellulosic polymers, with additional minor components such as structural proteins (Carpita and Gibeaut, 1993). During fruit softening, pectins (Brady, 1987; Fischer and Bennett, 1991) and hemicelluloses (Lashbrook et al., 1997) typically undergo solubilization and depolymerization that are thought to contribute to wall loosening and disintegration, although the relative extent and timing vary between species.

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Section: Discussionmentioning

confidence: 99%

Temporal Sequence of Cell Wall Disassembly in Rapidly Ripening Melon Fruit1

Rose¹,

Hadfield²,

et al. 1998

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“…A wealth of evidence has been documented that high XTH enzyme activity and its mRNA level were closely correlated with the elongation zone of stems and roots and in ripening fruits in various plant species [23,26,27,[33][34][35][36][37][38]. Analysis of tobacco plants transformed with an antisense construction of NtXET-1 suggested that the reduction in Nt-XET-1 expression might be coupled with strengthening of cell walls [28].…”

Section: Discussionmentioning

confidence: 99%

Constitutive expression of abiotic stress‐inducible hot pepper CaXTH3, which encodes a xyloglucan endotransglucosylase/hydrolase homolog, improves drought and salt tolerance in transgenic Arabidopsis plants

et al. 2006

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Xyloglucan endotransglucosylase/hydrolase (XTH) has been recognized as a cell wall-modifying enzyme, participating in the diverse physiological roles. From water-stressed hot pepper plants, we isolated three different cDNA clones (pCaXTH1, pCaXTH2, and pCaXTH3) that encode XTH homologs. RT-PCR analysis showed that three CaXTH mRNAs were concomitantly induced by a broad spectrum of abiotic stresses, including drought, high salinity and cold temperature, and in response to stress hormone ethylene, suggesting their role in the early events in the abiotic-related defense response. Transgenic Arabidopsis plants that constitutively expressed the CaXTH3 gene under the control of the CaMV 35S promoter exhibited abnormal leaf morphology; the transgenic leaves showed variable degrees of twisting and bending along the edges, resulting in a severely wrinkled leaf shape. Microscopic analysis showed that 35S-CaXTH3 leaves had increased numbers of small-sized cells, resulting in disordered, highly populated mesophyll cells in each dorsoventral layer, and appeared to contain a limited amount of starch. In addition, the 35S-CaXTH3 transgenic plants displayed markedly improved tolerance to severe water deficit, and to lesser extent to high salinity in comparison with the wild-type plants. These results indicate that CaXTH3 is functional in heterologous Arabidopsis cells, thereby effectively altering cell growth and also the response to abiotic stresses. Although the physiological function of CaXTHs is not yet clear, there are several possibilities for their involvement in a subset of physiological responses to counteract dehydration and high salinity stresses in transgenic Arabidopsis plants.

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“…It is becoming increasingly clear that related enzymes are associated with xyloglucan metabolism in primary cell walls. XETs are involved in developmentally regulated xyloglucan metabolism (Nishitani and Tominaga, 1992;Potter and Fry, 1994;Redgwell and Fry, 1993;Schroder et al, 1998;de Silva et al, 1994), and a xyloglucan oligosaccharide-specific α-xylosidase is associated with xyloglucan turnover in elongation growth (Koyama et al, 1983;O'Neil et al, 1989).…”

Section: Introductionmentioning

confidence: 99%