c4 evolution

Question 1

C4 origin was when?

Answer 1

C4 probs first evolved 30mya

Question 2

diversification of C4 when

Answer 2

5-7mya in late Meiocene in responce to reduction in CO2 atmos levels

Question 3

C4 evolved how often ?

Answer 3

C$ evolved independently 66 times in >20 families

Question 4

C4 is a complecation pathway it is unlikely to have evolved in one giant step, C3-C4 intermediates have been discovered these may?

Answer 4

• provide one of the stepping stones in the evolution of C4 from anestral C3 species
• be an evolutionary dead end

Question 5

C3-C4 intermediates what are they? 3 tpes

Answer 5

C4-like types
c3/c4 types
hybrids

Question 6

What was the first dicov C3-C4 inte?

Answer 6

Mollugo verticillata (1974)

Question 7

CO2 compensation point is what in C3-C4 int?

Answer 7

light dependent
also changes with oxygen con –> PR still occurs
(not in C4)

Question 8

C3-C4 have what anatomy?

Answer 8

most C4 like anatomy:

• intermediate not Kranz
• close association bt mt and chlorplasts

Question 9

C3-4 int reduce photorespitation how?

Answer 9

not by removing the oxygenase reaction all together but ensuring the re-fixation of CO2 lost from PR
- therefore close association bt mt and chloroplasts

Question 10

c3-4 int of Moricandia show differential expression of what?

allows for what to be recaptured?

is only expressed where? why?

Answer 10

Glycine decarboxylase
(2 glycine –> NH3 + Serine + CO2) in PR

70-90% recapture of respiratory CO2

Glycine decarboxylase only expressed in BSC, CO2 released in BSC can either be 1. fixed by rubisco in BSC or 2. escapes into MC

Question 11

C3-C4 intermediates of ……… also exhibit C4 like biochemistry.
why?

Answer 11

have a high concentration of C4 pathway enzymes

Question 12

…… species span developmental progress between c3 and c4, these species can be X or X

Answer 12

Cleome

C3 or C4

Question 13

C4 evolution form C3 requires:

Answer 13

• increased veination
• larger BSC
• increase in number of chloroplast and mt in BS
• devision of PR metabolism between C3 and C4
• intervental distance bt MC and BSC decreases

Question 14

Did novel C4 genes appear? What is likely to have happened

Answer 14

NO (genes already present in C3 plant)
genome duplication of preexisting genes - some changed to C4?
modification of regulatory sequences, C3 genes with C4 expression?

Question 15

What is PEPC used for in C3 plants?

Answer 15

N assimilation

Question 16

WHat changes are needed in PEPC genes to go from C3 to C4?

How are these changes thought to have arose?

Answer 16

1. higher level of leaf-specific expression
2. activity restricted to MC (not BSC)
3. light inducibility

through changes in the promoter region of PEPC

Question 17

….. contains what in its promoter region for PEPC?

Answer 17

Maize

novel cis acting element in PEPC promoter

Question 18

Recent “….” for C4 genes in C3 plants as same ……. and similar ………. … to those in C$ plants. are we……..

Answer 18

conserved functional latency
same cis elements and promoter regions to those in C4 plants.
are we missing the transcription factor to turn it on?

Question 19

How is differential expression of rubisco bt MC and BSC achieved?

Answer 19

repression loop in MC prevents the transciption of fully functioning small subunits in MC. loop activated by MC factors.

Trancription is enhanced in BSC due to presences of cis regulatory element with light inducible expression enhancer. Allow the transcription of rubisco in Bsc.

Question 20

c4 ps was first reported?

Answer 20

40 years ago by Hatch and Slack