Analysis of ripening hormone levels, and hormone biosynthesis and receptor gene expression, following treatment of tomato fruit with the ripening blocker 1-MCP
CALS Impact Statement
Ethylene initiates the ripening and senescence of climacteric fruit, whereas polyamines have been considered senescence inhibitors. We have analyzed the levels of ethylene and polyamines in tomato fruit following treatment with the anti-ripening compound 1-MCP ("Smartfresh"), and examined the level of enzymes and the expression of genes involved in their biosynthesis in order to determine whether the effect of 1-MCP could be via polyamines as well as through a direct effect on the ethylene receptor. 1-MCP delayed ripening for 8 days, similarly delaying ethylene production and the expression of the ethylene biosynthesis enzyme, ACC-synthase, and the ethylene receptor genes. Polyamine contents peaked during ripening, which was early in untreated fruit, but remained low while ripening was inhibited by 1-MCP, and then increased when the fruit started to ripen. The activity of the polyamine biosynthetic enzymes, and the expressions of the genes encoding these enzymes, peaked at the same time as polyamine levels in both untreated and treated fruit. Polyamines are thus not directly associated with a delay in tomato fruit ripening but may prolong the fully-ripe stage before the fruit tissues undergo senescence.
We wanted to characterize the action of 1-MCP on tomatoes at the hormonal and molecular level. We also wanted to see if the ripening delaying effects of 1-MCP could be via a change in the level of polyamines as well as blocking the ethylene receptor.
We have shown that the effect of 1-MCP is short lived in tomato fruit, and is associated with the blocking of new ethylene receptor formation, and the blocking of the the formation of more ethylene. However the inhibition of ripening by 1-MCP was not associated with an increase in polyamines. Rather polyamines increased as ripening progressed when the effect of 1-MCP declined due to the synthesis of more ethylene receptor proteins. Polyamines may thus function as ripening or over-ripening modulators but are not associated with the inhibition of ripening.
The project facilitates a basic understanding of the action of 1-MCP and the role of polyamines in ripening/over-ripening.
funding source description
Federal Formula Funds - Research (e.g., Hatch, McIntire-Stennis, Animal Health)
Fulbright Foundation (fellowship to Dr. Annalisa Tassoni)