Monellin is a protein found in the fruit of an African plant that is 3000 times sweeter than sucrose. It is a dimer made of an A chain and B chain held together by weak bonds that dissociate when heated, causing it to lose sweetness during cooking. To resolve this, researchers chemically synthesized a monellin gene encoding both chains as a single peptide. This fusion gene was inserted into tomato and lettuce plants using Agrobacterium tumefaciens and specific promoters, resulting in monellin production and sweetness in ripe tomatoes and lettuce leaves but not green tomatoes. Genetically engineering sweetness could benefit many fruits and vegetables.

1. Sweetness
By,
Malathinathan

2. Sweetness:
Fruits or vegetable may have high nutritional value, humans
usually will not eat, if it is not tasty.
Monellin proteins found in the fruit of an African
plants.
Dioscoreophyllum cumminsii
3000 times sweets than sucrose

3. What is monellin?
• It is a dimer with an A chain – 45aminoacid
B chain – 50aminoacid
• Held together by weak non covalent bond
• It dissociates readily and losses its sweetness when it is
heated during cooking. This is the complication.

4. How the complication is
resolved?
1) Monellin gene that encodes both the A & B chains as a
single peptide was chemically synthesized.
2) The fusion protein was produced in transgene tomato &
lettuce plants.
3) Two different promoers
i. Tomato fruit specific promoter E8 Tomato
ii. 35s promoter from CaMV Lettuce

5. Contin..
4) Nopaline synthase gene used for transcription termination.
5) A.tumefaciens used to introduce the construct into the plant
cell.
6) Monellin was defected in ripe & partially ripe tomatoes and
in lettuce leaves not in green tomatoes.
7) Genetically sweetened foods are positive, would be
applicable to a wide range of fruits and vegetables.

6. A
B
Chemically synthesized
monellin gene
Tomato fruit specific
promotor
35S CaMV promotor

7. LB TFSPE8
Promotor
monellin
gene
tNos
RB
Ti plasmid
LB 35S CaMV promotor
Promotor
monellin
gene
tNos
RB
Ti plasmid
Inserted into the A.tumefaciens
Tomato plant cell
Sweet potato
Inserted into the A.tumefaciens
Lettuce plant cell
Sweet potato