Improving our Food

Question 1

How much dietary protein is provided from plants?

Answer 1

Plants supply 65% of human dietary protein. Mostly from cereal and legumes.
Essential amino acids come from dietary protein

Question 2

What proteins do legumes and cereals lack?

Answer 2

Legumes lack cytosine and methionine
Cereals lack lysine

Question 3

How can amino acid composition be improved?

Answer 3

Possible routes include:
- Altering the sequence of the endogenous gene
- Designing a synthetic gene, rich in specific amino acids, but synthetic genes are unstable
It is better to express lysine/methionine rich proteins from other plants (e.g. Brazil nut, but potential risk with allergens)

Question 4

What are potatoes low in?

Answer 4

Low in cytosine, lysine and methionine.
-> Expressed Amaranth albumin gene in potato, increased lysine and sulphur containing amino acids

Question 5

What are carotenoids and how have they been manipulated in rice?

Answer 5

• Carotenoids are precursors of vitamin A
• Genetically manipulated rice so that endosperm produced pro-vitamin A (Vitamin A is toxic, so converts precursor Pro-vit A to active form in the body)

Question 6

What are the transgenes in Golden Rice?

Answer 6

PSY and CRTI transgenes affecting Beta carotenoid expression

Question 7

What is Golden Rice 2?

Answer 7

Tested PSY from different sources
Maize gene gave the highest activity (20x more B carotene)
Freely available to small scale farmers
2024: Philippines ordered an end to commercial growing

Question 8

What are some of the objections to Golden Rice?

Answer 8

• ‘Deficiency can be solved by food supplements’
• ’ GR will contaminate non-GM rice and effect export market
• Could be unknown health consequences
• ‘Forcing product on a community that doesn’t want it’

Question 9

What does polygalacturonase do?

Answer 9

Cleaves pectins and breaks down the middle lamella, allows cells to slide over each other, producing cracks
Overripening of fruit

Question 10

How was polygalacturonase modified for combatting overripeness?

Answer 10

• Using antisense PG gene in CaMV 35S promoter, caused <1% PG activity
• Antisense strand would bind to coding strand, preventing translation
• Delayed overripening, improved shelf life
• First GM food licensed for human consumption

Question 11

When were GM tomatoes on the market in the US and the UK?

Answer 11

US fresh market: 1994-97 (production issue)
UK processed market: 1995-99 (anti-GM debate halted sales)

Question 12

What is the Sanatech 2021 tomato?

Answer 12

• Japan
• Higher levels of GABA by deleting autoinhibitory domain of the glutamate decarboxylase gene
• Claims to lower blood pressure, relieve stress, improve sleep, maintain skin elasticity

Question 13

How can delayed ripening be engineered?

Answer 13

Genetic modification to reduce ethylene levels
Developed and approved, but not on the market yet

Question 14

How is bruising and browning reduced in potatos?

Answer 14

• RNA interference to silence polyphenol oxidase genes (which usually produce dark pigments when cells are damaged)
• Also potatoes designed for reduced acrylamide formation during baking (toxic)