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Title: EFFECTS OF ETHYLENE AND 1-MCP ON GENE EXPRESSION IN GRAPEFRUIT FLAVEDO

Author
item McCollum, Thomas
item Maul, Dora

Submitted to: International Society of Citriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/27/2004
Publication Date: 2/1/2004
Citation: Mccollum,T.G.,Maul,D.P.2004.Effects of ethylene and 1-mcp on gene expression in grapefruit flavedo.International Society of Citriculture Proceedings.

Interpretive Summary: The gaseous plant hormone ethylene is used in commerce to remove green color from citrus fruit; however, treatment with ethylene can lead to increased decay. We are interested in the role of ethylene on citrus fruit physiology with the goal of reducing losses following harvest. We have conducted a study to determine the effects of ethylene on gene expression in grapefruit. We compared the effects of ethylene with those of 1-methylcyclopropene (1-MCP), a potent inhibitor of ethylene action. We found that loss of green color was promoted by ethylene, but suppressed by 1-MCP. In addition, expression of the gene coding for chlorophyllase, the enzyme that degrades chlorophyll was promoted by ethylene, but inhibited by 1-MCP. Ethylene treatment stimulated ethylene production by the fruit, but much less than treatment with 1-MCP. Expression of ACC synthase and ACC oxidase, the two enzymes responsible for ethylene production, was much greater in 1-MCP treated fruit than in ethylene treated fruit. These results provide evidence that the effects of ethylene are mediated through changes in gene expression in citrus fruit.

Technical Abstract: In an effort to obtain a better understanding of the role of ethylene in citrus fruit development and physiology, we have determined the effects of ethylene and 1-MCP, a specific inhibitor of ethylene action, on gene expression in grapefruit flavedo. 'Marsh' grapefruit were treated with either ethylene or 1-MCP continuously for 72 hours. Ethylene treated fruit had a rapid loss of green color and an increase the abundance of chlorophyllase mRNA whereas control and 1-MCP-treated fruit remained green and chlorophyllase mRNA diminished. Ethylene evolution was slightly, but significantly increased in ethylene-treated fruit compared to control fruit, but was dramatically stimulated in response to 1-MCP. Abundance of ACC synthase and ACC oxidase mRNA was also increased in response to ethylene and to a greater extent by 1-MCP. Our results lend further support to the role of ethylene in citrus fruit physiology and show that ethylene functions to regulate gene expression both positively and negatively in citrus.