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Cell wall structures leading to cultivar differences in softening rates develop early during apple (Malus x domestica) fruit growth.

Ng JK, Schröder R, Sutherland PW, Hallett IC, Hall MI, Prakash R, Smith BG, Melton LD, Johnston JW - BMC Plant Biol. (2013)

Bottom Line: Stronger cell adhesion in ripe 'Scifresh' resulted in tissue fracture by cell rupture rather than by cell-to-cell-separation as seen in 'Royal Gala'.CDTA-soluble pectin differed in both cultivars during development, implicating its involvement in cell adhesion.Low pectin methylesterase activity during early stages of fruit development coupled with the lack of immuno-detectable PG was associated with increased cell adhesion in 'Scifresh'.

View Article: PubMed Central - HTML - PubMed

Affiliation: Food Science, School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand. jovyn.ng@plantandfood.co.nz.

ABSTRACT

Background: There is a paucity of information regarding development of fruit tissue microstructure and changes in the cell walls during fruit growth, and how these developmental processes differ between cultivars with contrasting softening behaviour. In this study we compare two apple cultivars that show different softening rates during fruit development and ripening. We investigate whether these different softening behaviours manifest themselves late during ethylene-induced softening in the ripening phase, or early during fruit expansion and maturation.

Results: 'Scifresh' (slow softening) and 'Royal Gala' (rapid softening) apples show differences in cortical microstructure and cell adhesion as early as the cell expansion phase. 'Scifresh' apples showed reduced loss of firmness and greater dry matter accumulation compared with 'Royal Gala' during early fruit development, suggesting differences in resource allocation that influence tissue structural properties. Tricellular junctions in 'Scifresh' were rich in highly-esterified pectin, contributing to stronger cell adhesion and an increased resistance to the development of large airspaces during cell expansion. Consequently, mature fruit of 'Scifresh' showed larger, more angular shaped cells than 'Royal Gala', with less airspaces and denser tissue. Stronger cell adhesion in ripe 'Scifresh' resulted in tissue fracture by cell rupture rather than by cell-to-cell-separation as seen in 'Royal Gala'. CDTA-soluble pectin differed in both cultivars during development, implicating its involvement in cell adhesion. Low pectin methylesterase activity during early stages of fruit development coupled with the lack of immuno-detectable PG was associated with increased cell adhesion in 'Scifresh'.

Conclusions: Our results indicate that cell wall structures leading to differences in softening rates of apple fruit develop early during fruit growth and well before the induction of the ripening process.

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Related in: MedlinePlus

Fracture pattern and tensile strength of cortical tissue of ‘Royal Gala’ and ‘Scifresh’ fruit during ripening. Scanning electron micrographs of ripe ‘Royal Gala’ (A, C) and ‘Scifresh’ fruit (B, D) (20 weeks at 0.5°C), showing a different fracture pattern between cells with the appearance of more intact cells in ‘Royal Gala’ and more broken open cells in ‘Scifresh’. (E) Tensile tests to quantify the force required to pull cortex tissue apart (expanding fruit 100 DAFB, mature and ripe fruit). Bars A, B = 500 μm; bars C, D = 100 μm. Values in (E) are the mean of 15 measurements ± SE.
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Figure 4: Fracture pattern and tensile strength of cortical tissue of ‘Royal Gala’ and ‘Scifresh’ fruit during ripening. Scanning electron micrographs of ripe ‘Royal Gala’ (A, C) and ‘Scifresh’ fruit (B, D) (20 weeks at 0.5°C), showing a different fracture pattern between cells with the appearance of more intact cells in ‘Royal Gala’ and more broken open cells in ‘Scifresh’. (E) Tensile tests to quantify the force required to pull cortex tissue apart (expanding fruit 100 DAFB, mature and ripe fruit). Bars A, B = 500 μm; bars C, D = 100 μm. Values in (E) are the mean of 15 measurements ± SE.

Mentions: Using conventional scanning electron microscopy, distinct differences in the fracture pattern were observed in ripe tissue (Figure 4A–D). ‘Royal Gala’ tissue primarily fractured between cells resulting in minimal cell rupture (Figure 4A, C), while fracturing of ‘Scifresh’ tissue occurred more by cell rupture with minimal evidence of cell separation between adjacent cells (Figure 4B, D). Tensile tests were used to quantify the force required to pull cortex tissue apart. At earlier stages of development (100 DAFB and mature) the tensile properties of the two cultivars were similar, with both having loss of tensile strength during the final stages of fruit growth (100 DAFB to maturity). Once ripe, ‘Royal Gala’ required 50% less force than ‘Scifresh’ to fracture the tissue (Figure 4E). These tensile properties support the fracture surface images (Figure 4A–D) by showing that cell separation is associated with weak adhesion forces between adjacent cells in ‘Royal Gala’.


Cell wall structures leading to cultivar differences in softening rates develop early during apple (Malus x domestica) fruit growth.

Ng JK, Schröder R, Sutherland PW, Hallett IC, Hall MI, Prakash R, Smith BG, Melton LD, Johnston JW - BMC Plant Biol. (2013)

Fracture pattern and tensile strength of cortical tissue of ‘Royal Gala’ and ‘Scifresh’ fruit during ripening. Scanning electron micrographs of ripe ‘Royal Gala’ (A, C) and ‘Scifresh’ fruit (B, D) (20 weeks at 0.5°C), showing a different fracture pattern between cells with the appearance of more intact cells in ‘Royal Gala’ and more broken open cells in ‘Scifresh’. (E) Tensile tests to quantify the force required to pull cortex tissue apart (expanding fruit 100 DAFB, mature and ripe fruit). Bars A, B = 500 μm; bars C, D = 100 μm. Values in (E) are the mean of 15 measurements ± SE.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4225529&req=5

Figure 4: Fracture pattern and tensile strength of cortical tissue of ‘Royal Gala’ and ‘Scifresh’ fruit during ripening. Scanning electron micrographs of ripe ‘Royal Gala’ (A, C) and ‘Scifresh’ fruit (B, D) (20 weeks at 0.5°C), showing a different fracture pattern between cells with the appearance of more intact cells in ‘Royal Gala’ and more broken open cells in ‘Scifresh’. (E) Tensile tests to quantify the force required to pull cortex tissue apart (expanding fruit 100 DAFB, mature and ripe fruit). Bars A, B = 500 μm; bars C, D = 100 μm. Values in (E) are the mean of 15 measurements ± SE.
Mentions: Using conventional scanning electron microscopy, distinct differences in the fracture pattern were observed in ripe tissue (Figure 4A–D). ‘Royal Gala’ tissue primarily fractured between cells resulting in minimal cell rupture (Figure 4A, C), while fracturing of ‘Scifresh’ tissue occurred more by cell rupture with minimal evidence of cell separation between adjacent cells (Figure 4B, D). Tensile tests were used to quantify the force required to pull cortex tissue apart. At earlier stages of development (100 DAFB and mature) the tensile properties of the two cultivars were similar, with both having loss of tensile strength during the final stages of fruit growth (100 DAFB to maturity). Once ripe, ‘Royal Gala’ required 50% less force than ‘Scifresh’ to fracture the tissue (Figure 4E). These tensile properties support the fracture surface images (Figure 4A–D) by showing that cell separation is associated with weak adhesion forces between adjacent cells in ‘Royal Gala’.

Bottom Line: Stronger cell adhesion in ripe 'Scifresh' resulted in tissue fracture by cell rupture rather than by cell-to-cell-separation as seen in 'Royal Gala'.CDTA-soluble pectin differed in both cultivars during development, implicating its involvement in cell adhesion.Low pectin methylesterase activity during early stages of fruit development coupled with the lack of immuno-detectable PG was associated with increased cell adhesion in 'Scifresh'.

View Article: PubMed Central - HTML - PubMed

Affiliation: Food Science, School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand. jovyn.ng@plantandfood.co.nz.

ABSTRACT

Background: There is a paucity of information regarding development of fruit tissue microstructure and changes in the cell walls during fruit growth, and how these developmental processes differ between cultivars with contrasting softening behaviour. In this study we compare two apple cultivars that show different softening rates during fruit development and ripening. We investigate whether these different softening behaviours manifest themselves late during ethylene-induced softening in the ripening phase, or early during fruit expansion and maturation.

Results: 'Scifresh' (slow softening) and 'Royal Gala' (rapid softening) apples show differences in cortical microstructure and cell adhesion as early as the cell expansion phase. 'Scifresh' apples showed reduced loss of firmness and greater dry matter accumulation compared with 'Royal Gala' during early fruit development, suggesting differences in resource allocation that influence tissue structural properties. Tricellular junctions in 'Scifresh' were rich in highly-esterified pectin, contributing to stronger cell adhesion and an increased resistance to the development of large airspaces during cell expansion. Consequently, mature fruit of 'Scifresh' showed larger, more angular shaped cells than 'Royal Gala', with less airspaces and denser tissue. Stronger cell adhesion in ripe 'Scifresh' resulted in tissue fracture by cell rupture rather than by cell-to-cell-separation as seen in 'Royal Gala'. CDTA-soluble pectin differed in both cultivars during development, implicating its involvement in cell adhesion. Low pectin methylesterase activity during early stages of fruit development coupled with the lack of immuno-detectable PG was associated with increased cell adhesion in 'Scifresh'.

Conclusions: Our results indicate that cell wall structures leading to differences in softening rates of apple fruit develop early during fruit growth and well before the induction of the ripening process.

Show MeSH
Related in: MedlinePlus