TLS Online TPP Program

#Id: 7105

#Unit 6. System Physiology – Plant

Inhibitors of ethylene synthesis

IN CASE OF TOMATOES:

pTOM5 encodes for phytoene synthase which promote  lycopene synthesis that gives red coloration

pTOM6 gene encodes for polygalacturonase. This enzyme  degrades the cell wall, resulting in fruit softening.

pTOM gene encodes for ACC oxidase. This enzyme  catalyzes the ethylene formation that triggers the fruit ripening.

Calgene introduced a gene in plant which synthesize a  complementary mRNA to PG gene and inhibiting the  synthesis of PG enzyme.

On May 21, 1994, the genetically engineered Flavr Savr tomato was introduced.

TLS Online TPP Program

#Id: 7106

#Unit 6. System Physiology – Plant

Inhibitors of ethylene action

Most of the effects of ethylene can be antagonized by specific ethylene inhibitors. Silver ions (Ag+) applied as silver nitrate (AgNO3) or as silver thiosulfate (Ag(S2O3)2 3–) are potent inhibitors of ethylene action. Silver is very specific; the inhibition it causes cannot be induced by any other metal ion.

TLS Online TPP Program

#Id: 7107

#Unit 6. System Physiology – Plant

The volatile compound trans-cyclooctene is a strong competitive inhibitor of ethylene binding; trans-cyclooctene is thought to act by competing with ethylene for binding to the receptor. A novel inhibitor, 1-methylcyclopropene (MCP), was recently found that binds almost irreversibly to the ethylene receptor

TLS Online TPP Program

#Id: 7108

#Unit 6. System Physiology – Plant

FLAVR SAVR TOMATO GENES INVOLVED

TLS Online TPP Program

#Id: 7109

#Unit 6. System Physiology – Plant

All fruits that ripen in response to ethylene exhibit a characteristic respiratory rise before the ripening phase called a climacteric.

TLS Online TPP Program

#Id: 7110

#Unit 6. System Physiology – Plant

In banana, ripening is characterized by a climacteric rise in

respiration rate, as evidenced by the increased CO2 production.

A climacteric rise in ethylene production precedes the increase in CO2 production, suggesting that ethylene is the hormone that triggers the ripening process.