1-Methylcyclopropene (1-MCP)-induced protein expression associated with changes in Tsai Tai (Brassica chinensis) leaves during low temperature storage

• Postharvest leaf yellowing severely affects quality of leafy vegetables.
• 1-MCP reduced leaf yellowing severity of Tsai Tai stored at 1 °C.
• 16 1-MCP-responsive proteins were detected, 12 of which were identified.
• 1-MCP regulated expression of proteins involved in photosynthesis, TAC, GAs and ROS.

Leaf yellowing is an early symptom of senescence and greatly affects the commercial value of leafy vegetable products. The ethylene action inhibitor 1-methylcyclopropene (1-MCP) has been widely studied regarding its effects on senescence, but little is known on how it influences the protein expression profile of leafy vegetables in storage. In this study, by using a proteomic approach, changes in proteomic profile induced by 1-MCP in Tsai Tai (Brassica chinensis) leaves during storage under low but non-freezing temperature were investigated. Compared with the control, 1-MCP treatment inhibited leaf etiolation and reduced weight loss of Tsai Tai stored at 1 °C, indicating that it delayed senescence. Two dimensional electrophoresis revealed 16 differentially accumulated protein spots, 12 of which were successfully identified by mass spectrometry. A comparison between the control and the 1-MCP-treated Tsai Tai showed that 1-MCP enhanced levels of four proteins involved in photosynthesis, i.e. photosystem II protein, oxygen-evolving enhancer protein 2, chloroplast ribulose 1,5-bisphosphate carboxylase/oxygenase activase and high molecular weight RuBisCO, inhibited malate dehydrogenase, a key enzyme involved in the tricarboxylic acid cycle, downregulated gibberellin 2-beta-dioxygenase expression, a key enzyme involved in biosynthesis of active gibberellins, and suppressed glutathione s-transferase, an important scavenger for reactive oxygen species. These results imply that 1-MCP could maintain leaf capacity for carbon assimilation, inhibit the tricarboxylic acid cycle, induce biosynthesis of GAs and reduce levels of reactive oxygen species, which together may have contributed to inhibition of leaf yellowing and delay of senescence.