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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

Immunofluorescence labelling for calcium-associated HG regions with antibody 2F4 in mature and ripe apple fruit. ‘Royal Gala’ (A, B) and ‘Scifresh’ (C, D) apple cortex tissue of mature fruit and ripe fruit. 2F4-labelling (green) was concentrated at tricellular junctions as indicated by the arrows. No labelling was detected in ripe ‘Royal Gala’ (B). Bar in (A) = 10 μm for all micrographs.
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Figure 7: Immunofluorescence labelling for calcium-associated HG regions with antibody 2F4 in mature and ripe apple fruit. ‘Royal Gala’ (A, B) and ‘Scifresh’ (C, D) apple cortex tissue of mature fruit and ripe fruit. 2F4-labelling (green) was concentrated at tricellular junctions as indicated by the arrows. No labelling was detected in ripe ‘Royal Gala’ (B). Bar in (A) = 10 μm for all micrographs.

Mentions: HG regions with sufficiently low degree of methyl-esterification (<40%) and with at least nine consecutive non-esterified galacturonic acid residues can interact with divalent cations like calcium[28]. The monoclonal antibody 2F4 is specific to these calcium cross-linked HG epitopes. Labelling of cell walls with 2F4 was detected in mature fruit of both cultivars, but disappeared during softening in ‘Royal Gala’ and remained in ‘Scifresh’ (Figure 7). In both cultivars labelling was restricted to junction zones, particularly tricellular junctions. No labelling was found throughout the cell walls and very little was detected in the middle lamella, confirming that calcium cross-linked HG epitopes are restricted to the middle lamellae at cell corners and pit fields[29]. No labelling was detected in fruitlets of both cultivars (not shown), while expanding fruit were not examined.


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)

Immunofluorescence labelling for calcium-associated HG regions with antibody 2F4 in mature and ripe apple fruit. ‘Royal Gala’ (A, B) and ‘Scifresh’ (C, D) apple cortex tissue of mature fruit and ripe fruit. 2F4-labelling (green) was concentrated at tricellular junctions as indicated by the arrows. No labelling was detected in ripe ‘Royal Gala’ (B). Bar in (A) = 10 μm for all micrographs.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Immunofluorescence labelling for calcium-associated HG regions with antibody 2F4 in mature and ripe apple fruit. ‘Royal Gala’ (A, B) and ‘Scifresh’ (C, D) apple cortex tissue of mature fruit and ripe fruit. 2F4-labelling (green) was concentrated at tricellular junctions as indicated by the arrows. No labelling was detected in ripe ‘Royal Gala’ (B). Bar in (A) = 10 μm for all micrographs.
Mentions: HG regions with sufficiently low degree of methyl-esterification (<40%) and with at least nine consecutive non-esterified galacturonic acid residues can interact with divalent cations like calcium[28]. The monoclonal antibody 2F4 is specific to these calcium cross-linked HG epitopes. Labelling of cell walls with 2F4 was detected in mature fruit of both cultivars, but disappeared during softening in ‘Royal Gala’ and remained in ‘Scifresh’ (Figure 7). In both cultivars labelling was restricted to junction zones, particularly tricellular junctions. No labelling was found throughout the cell walls and very little was detected in the middle lamella, confirming that calcium cross-linked HG epitopes are restricted to the middle lamellae at cell corners and pit fields[29]. No labelling was detected in fruitlets of both cultivars (not shown), while expanding fruit were not examined.

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