Citation:
Katherine Cools, Gemma A. Chope, John P. Hammond, Andrew J. Thompson and Leon A. Terry. Ethylene and 1-methylcyclopropene differentially regulate gene expression during
onion sprout suppression. Plant Physiology, July 2011, vol 156, no 3, pp1639-1652
Abstract:
Onion (Allium cepa) is regarded as a nonclimacteric vegetable. In onions,
however, ethylene can suppress sprouting while the ethylene-binding inhibitor 1-
methylcyclopropene (1-MCP) can also suppress sprout growth; yet, it is unknown
how ethylene and 1-MCP elicit the same response. In this study, onions 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 (6 weeks) at 20°C or 28°C
and then stored at 1°C. Following curing, a subset of these same onions was
stored separately under continuous air or ethylene (10 μL L(-1)) at 1°C. Onions
treated with ethylene and 1-MCP in combination after curing for 24 h had reduced
sprout growth as compared with the control 25 weeks after harvest. Sprout growth
following storage beyond 25 weeks was only reduced through continuous ethylene
treatment. This observation was supported by a higher proportion of down-
regulated genes characterized as being involved in photosynthesis, measured
using a newly developed onion microarray. Physiological and biochemical data
suggested that ethylene was being perceived in the presence of 1-MCP, since
sprout growth was reduced in onions treated with 1-MCP and ethylene applied in
combination but not when applied individually. A cluster of probes representing
transcripts up-regulated by 1-MCP alone but down-regulated by ethylene alone or
in the presence of 1-MCP support this suggestion. Ethylene and 1-MCP both down-
regulated a probe tentatively annotated as an ethylene receptor as well as
ethylene-insensitive 3, suggesting that both treatments down-regulate the
perception and signaling events of e
