title: Potential role of pectate lyase and Ca(2+) in the increase in strawberry fruit firmness induced by short-term treatment with high-pressure CO2.
abstract: Postharvest treatment with high-pressure CO2 helps to control decay and increase firmness in strawberries. Increases in firmness occurred through modification of calcium binding to cell wall. However, the mechanism(s) involved in Ca(2+) migration to pectic polymers and other physiological events associated with the maintenance of increased firmness are not clearly understood. The focus of this study was to find potential mechanism(s) that are associated with calcium movement, increases in firmness, or maintenance of firmness in strawberry fruit after high-pressure CO2 treatment. An increase in firmness was induced by high-pressure CO2 treatment, but not by high-pressure N2 treatment. This indicates that CO2 stimulates a change in firmness. The increase in firmness induced by high-pressure CO2 seems to involve calcium efflux. Using membrane Ca(2+) -dependent ATPase inhibitors sodium vanadate (250 μM) and erythrosin B (100 μM) delayed both the increase in firmness and calcium binding to wall polymers. Exogenous application of CaCl2 (10 mM) enhanced the firmness increase of fruit slices only when they were exposed to high-pressure CO2 . The activity of pectate lyase was downregulated by CO2 treatment, but β-galactosidase activity was not affected. The increase in strawberry firmness induced by high-pressure CO2 treatment primarily involves the efflux of calcium ions and their binding to wall polymers. These physiological changes are not induced by an anaerobic environment. The downregulation of wall-modifying enzymes, such as pectate lyase, appeared to contribute to the maintenance of firmness that was induced by high-pressure CO2 treatment.
authors.affiliation: Dept. of Horticultural Science, College of Agriculture and Life Science, Chungnam Natl. Univ., Deajeon, 305-764, South Korea.
authors.forename: Mao Hua
authors.initials: MH
authors.lastname: Wang
authors.forename: Jin Gook
authors.initials: JG
authors.lastname: Kim
authors.forename: Sun Eun
authors.initials: SE
authors.lastname: Ahn
authors.forename: Ah Youn
authors.initials: AY
authors.lastname: Lee
authors.forename: Tae Min
authors.initials: TM
authors.lastname: Bae
authors.forename: Deu Re
authors.initials: DR
authors.lastname: Kim
authors.forename: Yong Soo
authors.initials: YS
authors.lastname: Hwang
mesh_terms: D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002122:Calcium Chloride / Q000378:metabolism / Q000494:pharmacology; D002245:Carbon Dioxide / Q000494:pharmacology*; D002473:Cell Wall / Q000378:metabolism*; D031985:Fragaria / Q000201:enzymology* / Q000378:metabolism; D005638:Fruit / Q000201:enzymology* / Q000378:metabolism; D006244:Hardness; D006801:Humans; D007477:Ions / Q000378:metabolism; D011133:Polysaccharide-Lyases / Q000378:metabolism*; D011312:Pressure
chemical_list: D007477:Ions; D002245:Carbon Dioxide; D011133:Polysaccharide-Lyases; C023911:pectate lyase; D002122:Calcium Chloride; D002118:Calcium
keywords: Fragaria × ananassa Duch; apoplast pH; calcium blockage; pectate lyase; β-galactosidase