Ethylene and 1-MCP differentially regulate gene expression during onion (Allium cepa L.) sprout suppression

Onion is regarded as non-climacteric. In onion, ethylene can suppress sprouting however, the ethylene binding inhibitor, 1-MCP can also suppress sprout growth although it is unknown how ethylene and 1-MCP elicit the same response. In this study, onion bulbs were treated with 10 μL L-1 ethylene or 1 μL L-1 1-MCP individually or in combination for 24 h at 20°C before or after curing (six weeks) at 20 or 28°C then stored at 1°C. Following curing, a subset of these same onion bulbs was stored separately under continuous air or ethylene (10 μL L-1) at 1°C Six treatments were chosen for microarray analysis; four samples were taken before curing immediately after treatment with ethylene or 1-MCP or ethylene and 1-MCP in combination for 24 h at 20°C. The other two samples and two were taken at the end of storage following 6 weeks curing at 28°C and after 29 weeks cold storage (1°C) in continuous air or continuous ethylene totalling 35 weeks storage. The four pre-curing samples used were untreated (control) or treated with EB, MB or EMB and the two samples after storage were control bulbs stored in continuous ethylene or air at 1°C. There were three biological replicates of each of the six treatments making 18 samples in total.