The Role of Ethylene and Calcium in Programmed Cell Death of Cold-Stored Cucumber Fruit

Abstract

Programmed cell death (PCD) occurs during plant development and in response to various stimuli, including biotic and abiotic stresses. Characteristics of PCD were detected in cucumber fruit after 9 days of cold storage at 2C, including chromatin condensation and DNA fragmentation. PCD development was accompanied by ethylene emission and cytosolic free calcium ([Ca 2+ ]cyt) release. The role of ethylene production and [Ca 2+ ]cyt in chill-induced PCD were studied through the application of 1-methylcyclopropene (1-MCP; an ethylene perception inhibitor) and ethylene glycol bis (2-aminoethyl) tetraacetic acid (EGTA; a divalent cation chelator). Results indicated that hallmarks of PCD were identified in cucumber fruit suffering from chilling stress and diagnostic events of PCD were alleviated and/or delayed by 1-MCP or EGTA applications. Therefore, ethylene and calcium could play significant roles in the initiation and execution progress of coldinduced PCD. PRACTICAL APPLICATIONSCucumber fruit is chilling sensitive at temperatures below 10C. It has also been showed that exogenous ethylene could induce PCD features in cucumber fruits and [Ca 2+ ]cyt plays a key role in regulating apoptosis. However, information about roles of endogenous ethylene and calcium in the PCD process of cucumber under cold stress has been rarely reported. The data in this study provided a theoretical basis for understanding the mechanism of chilling injury in cucumber fruit and benefited exploration of strategies to prevent it.

Physiological, molecular and ultrastructural analyses during ripening and over‐ripening of banana (Musa spp., AAA group, Cavendish sub‐group) fruit suggest characteristics of programmed cell death

“…PCD processes have been extensively studied in flower petals and vegetative tissues . There are very limited reports on PCD events in fleshy fruits including heat‐induced PCD in tomato, ethylene induced PCD in immature cucumber, and CI‐induced PCD in cucumber . None have addressed the occurrence of PCD‐like events during ripening and over‐ripening in fleshy fruits.…”

“…[12][13][14] There are very limited reports on PCD events in fleshy fruits including heat-induced PCD in tomato, 15 ethylene induced PCD in immature cucumber, [16][17][18] and CI-induced PCD in cucumber. 19,20 None have addressed the occurrence of PCD-like events during ripening and over-ripening in fleshy fruits. Qu et al 15 made no mention of deleterious effects of the PCD responses on tomato fruit ripening.…”

Comparison of tissue deterioration of ripening banana fruit (Musa spp., AAA group, Cavendish subgroup) under chilling and non‐chilling temperatures

“…In fleshy fruits, PCD has been induced by heat treatments in tomato fruit and by exogenous ethylene exposure in immature cucumber . PCD symptoms have also been induced in immature cucumber fruit by exposure to low temperatures . In cucumber fruit, DNA degradation, chromatin condensation, and ethylene and Ca 2+ signaling were involved in the induction and progression of CI‐induced PCD .…”

“…[16][17][18] PCD symptoms have also been induced in immature cucumber fruit by exposure to low temperatures. 19,20 In cucumber fruit, DNA degradation, chromatin condensation, and ethylene and Ca 2+ signaling were involved in the induction and progression of CI-induced PCD. 20 Expression of BAX, a pro-apoptotic protein, was higher in chill-induced death at 2 ∘ C. 19,21 Gene expression of BAX and BI-1 (Bax inhibitor-1, a cell death suppressor) was synchronized with initiation of CI symptoms.…”

“…19,20 In cucumber fruit, DNA degradation, chromatin condensation, and ethylene and Ca 2+ signaling were involved in the induction and progression of CI-induced PCD. 20 Expression of BAX, a pro-apoptotic protein, was higher in chill-induced death at 2 ∘ C. 19,21 Gene expression of BAX and BI-1 (Bax inhibitor-1, a cell death suppressor) was synchronized with initiation of CI symptoms. 19 Aside from immature cucumber fruit, no other fleshy fruit has been evaluated for CI-induced PCD, especially mature fruit with full ripening capacity that would simulate commercial life.…”