Manipulation of cellular energy reveals the relationship between ultraweak luminescence and cellular energy during senescence of strawberry ( Fragaria × ananassa ) fruits

The goal of this study was to investigate the ultraweak luminescence (UWL) of strawberry fruits in relation to mitochondrial functions and energy production during strawberry senescence. Fully ripe strawberry fruits and mitochondria isolated from those fruits were treated with either adenosine triphosphate (ATP) or the respiratory chain uncoupler 2,4-dinitrophenol (DNP). The activities of H+-ATPase and Ca2+-ATPase, the content of ATP, the free radical O2− as well as the UWL intensity were measured. Our results showed that activities of H+-ATPase and Ca2+-ATPase as well as the ATP content gradually decreased during fruit senescence in all three groups. Compared with the control, DNP treatment exacerbated, while ATP treatment reduced the decrease of H+-ATPase and Ca2+-ATPase activity, the energy charge and UWL intensity. UWL intensity was positively correlated with mitochondrial function and ATP content. Our results strongly suggest that mitochondria are a major source of UWL of strawberry fruits, and that the cellular energy ATP plays important roles in senescence of strawberry fruits, and in UWL formation. Our study provides convincing evidence of the interrelationship between cellular energy and UWL, which helps researchers to better understand the process of senescence in strawberry fruits.