Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

Table 8.3 Transgenic genetics to determine role cell wall–modifying enzymes
Enzyme/protein
glycanases Transgene Fruit Phenotype References
Polygalacturonase (PG)
PG Overexpression Tomato No effect
Increased pectin solubilization Giovannoni et al. (1989)
Antisense Tomato Slightly firmer Langley et al. (1994)
Increased juice viscosity Schuch et al. (1991)
Reduced pectin solubilization Kramer et al. (1992)
Brummell and Labavitch (1997)
PG-β-subunit Antisense Tomato Increases fruit softening Watson et al. (1994)
Deceased middle lamella cohesion Chun and Huber (2000)
Reduced tissue integrity
Pectin methylesterase (PME)
PME Antisense Tomato No effect on softening Tieman et al. (1992)
Reduced tissue integrity at late-ripening stages Hall et al. (1993)
Increased degree of methylesterification Tieman and Handa (1994)
Reduced pectin degradation Thakur et al. (1996a, b)
Increased soluble solids
Increased juice and paste viscosity
Increased serum viscosity
Pectate lyase Antisense Strawberry Increased fruit firmness Jiménez-Bermúdez et al. (2002)
Cellulase
Endo-1,4-β-glucanase Antisense Pepper No reduction xyloglucan depolymerization Harpster et al. (2002a)
Overexpression Pepper No increase in xyloglucan depolymerization Harpster et al. (2002b)
β-Galactosidase
β-Galactosidase 1 Antisense Tomato No effect on cell wall galactose Carey et al. (2001)
No effect on fruit softening
β-Galactosidase 3 Antisense Tomato Reduction in TBG1 and TBG4 transcripts de Silva and Verhoeyen (1998)
Higher GalA in cell wall
Reduced fruit deterioration
β-Galactosidase 4 Antisense Tomato Reduced fruit softening Smith et al. (2002)
Higher GalA in cell wall
Expensin Antisense Tomato Increased firmness Brummell et al. (1999)
Reduced polymer
Expansin and PG Both antisense Tomato Increased fruit firmness
Modify juice rheology Kalamaki et al. (2003)
PG and PME Both antisense Tomato Modify juice rheology Errington et al. (1998)
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