ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Ethylene feedback mechanisms in tomato and strawberry fruit tissues in relation to fruit ripening and climacteric patterns

Mordy A. Atta-Aly, Jeffrey K. Brecht and Donald J. Huber

Postharvest Biology and Technology Vol: 20 Issue: 2 Pages: 151-162.

2000

บทคัดย่อ

Exposing pericarp tissue excised from immature tomato fruit to 4.5 mol l^-1 C₂H₄ revealed a negative C₂H₄ feedback mechanism in relation to its biosynthesis since ACC concentration and C₂H₄ production by the tissue were reduced. An opposite trend (positive C₂H₄ feedback mechanism) was observed in pericarp tissue excised from fruit at the pink stage. At the mature-green stage however, tissue showed a transition from negative to positive C₂H₄ feedback mechanism with the onset of tissue ripening. In strawberry tissues excised from green, white and half-coloured fruits however, C₂H₄ application caused a short-term increase in C₂H₄ production followed by a sharp reduction to the control level along with a marked reduction in ACC levels. In both tomato and strawberry fruit tissues, C₂H₄ application significantly induced ACC oxidase (ACO) activity at all ripening stages, as measured by in vivo ACC conversion to C₂H₄. This strongly suggests that ACC synthesis is the limiting step in C₂H₄ autocatalysis and the only limiting step in C₂H₄ autoinhibition. In tomato pericarp tissues, C₂H₄ autoinhibition and autocatalysis caused by C₂H₄ application in immature and pink fruits, respectively, were eliminated when tissues were transferred to air and re-occurred when tissues were returned back to C₂H₄. These responses did not occur in all strawberry tissues due to the sharp reduction in C₂H₄ production with the time course of C₂H₄ application. Inhibiting C₂H₄ action with STS pretreatment inhibited both negative and positive C₂H₄ feedback mechanisms in both tomato and strawberry tissues indicating that C₂H₄ feedback mechanism is one sort of C₂H₄ action. In addition, only tomato fruit tissue showed significant increases in CO₂ production with C₂H₄ application. In contrast to the nonclimacteric behaviour of strawberry fruit which exhibits only a negative C₂H₄ feedback mechanism, these data strongly suggest that the transition of the C₂H₄ feedback mechanism from negative to positive, which occurs in tomato fruit only with ripening initiation and progress, may be the reason behind the climacteric behaviour of tomato fruit.