improve C4 ps

Question 1

Number of points were the C4 p/way can be improved. list the 5 main points

Answer 1

1. Enhancing Co2 delivery
2. Rubisco function
3. Substrate regeneration in C4 and C3 cycles
4. metabolite+ CO2/O2 exchange
5. chloroplast election transport

Question 2

improving C4:

1. enhance Co2 delivery
   how?

Answer 2

• overexpress aquaporins
• overexpress CA
• overexpress PEPC + lower Km - higher affinity for substrate

Question 3

2. Improve rubisco function.

How does Rubisco currently compare to C3

Answer 3

lower rubisco compared to C3 but emzyme more effecient.
C4 higher Km - less affinity for substrate (28-63uM)
C3 lower km - greater affinity for sub (8-26uM)

Kcat (molCo2/mol Rubisco)

Kcat C4 = 60
Kcat C3 = 29

Question 4

3. optimising substrate regeneration between C3 and C4 cycles
   what needs regenerating?
   when is this limiting?
   potentially increase whST

Answer 4

• PEP + RuBP + e- transport
• slow regenerating can be limiting t high light /CO2 conc

if u increase substarte regerantion in BSC have to match it with regenertaion in MC

increase SBPase in calvin cycle.

Question 5

4.metabolite + Co2/O2 exchange.
can transport and diffusion be optimised?
increase what protein?

Answer 5

increase plasmodesmata between MC and BSC
have to COMPRIMISE between more malate in and CO2 leaking out

suberin (substance which lines BSC) increase expression may prevent leakiness to CO2.

Question 6

improve the electron transport within C4 plants by

Answer 6

targeting nuclear encoded proteins in the cytochrome (Cyt) b6/f complex