Ethylene-induced water soaking in Dendrobium floral buds, accompanied by increased lipoxygenase and phospholipase D (PLD) activity and expression of a PLD gene

After a short exposure to exogenous ethylene, the tepals of floral buds on Dendrobium cv. juree Red inflorescences exhibited water-soaking, preceded by an increased in electrolyte leakage. Phospholipase D (PLO; EC 3.1.4.4) and lipoxygenase (LOX; EC 1.13.11.12) activities in the tepals showed a large increase after ethylene exposure, prior to the increase in electrolyte leakage. Ethylene also increased expression of a DenPLD gene in tepals. However, this was too late to account for the early rise in PLO activity. 1-Methylcyclopropene (1-MCP, which is an antagonist of ethylene perception) reduced the increase in DenPLD expression. The expression of a DenLOX gene was down-regulated by ethylene and up-regulated by 1-MCP, thus did not account for the increase in LOX activity. It was previously found that exposure to 5 degrees C resulted in water soaking and PLD activation, for which endogenous ethylene was required. The present data strongly suggest that these chilling effects are caused by endogenous ethylene. Chilling-induced ethylene apparently resulted in plasma membrane damage, possibly due to PLD and LOX activity. (C) 2015 Elsevier B.V. All rights reserved.