Regulation of ethylene biosynthesis in climacteric apple fruit by elevated CO2 and reduced O2 atmospheres
James R. Gorny and Adel A. Kader
Postharvest Biology and Technology Vol: 9 Issue: 3 Pages: 311-323.
1996
บทคัดย่อ
Autocatalytic (System II) C2H4 biosynthesis in climacteric `Golden Delicious' apples (Malus domestica Borkh) was effectively inhibited at 20°C by atmospheres of 20% CO2-enriched air (17% O2 + 63% N2) or 0.25% O2 (balance N2). In vitro 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACC-S) activity of apples held in atmospheres of air + 20% CO2 or 0.25% O2 was significantly inhibited when compared to apples kept in air, and correlated well with fruit C2H4 production rates. In vivo and in vitro ACC oxidase (ACC-O) activity of fruit held in atmospheres of air, air + 20% CO2 or 0.25% O2 were similar when the assays were performed under standard assay conditions (i.e., in vivo assay performed in air, in vitro assay performed in air + 6% CO2). However, if the in vivo or in vitro ACC-O enzyme activity assays were performed in an atmosphere of 0.25% O2, ACC-O catalytic competency and activity were significantly reduced. When the in vivo or in vitro ACC-O enzyme activity assays were performed in an atmosphere of air + 20% CO2, ACC-O enzyme activity was actually stimulated. These data indicate that elevated levels of CO2 do not inhibit ACC-O catalytic competency. Western blot analysis revealed that ACC-O protein abundance was not significantly affected by any of the treatments tested, and only the 0.25% O2 atmosphere significantly inhibited ACC-O activity. ACC-S activity was significantly reduced by atmospheres of air + 20% CO2 or 0.25% O2 but not via direct inhibition of ACC-S catalytic competency.