Final Exam questions
Deane Falcone
1. Below is a portion of the pathway that leads to the synthesis of lignols or lignin monomers.
Describe how a mutation at each of the indicated steps (arrows, mutation 1 & 2) may affect the
lignin composition in the wall of plant cells that accumulate lignin. Describe in chemical detail
the possible outcomes for each mutation separately as to how the lignin polymer could be
affected. (9 points)
COOH
O C O S CoA
4CL
OH
OH
Coumaric acid
Coumaryl -CoA
C3H
COOH
OH
OH
Mutation 1
caf fei c aci d
OMT
COOH
4CL
f eruloy l-C oA
OCH 3
OH
Mutation 2
f erul ic acid
F5H
CO OH
4CL
5-hydroxy-f eruloyl-CoA
HO
OCH 3
OH
5-hydroxy-f erul ic acid
COO H
OMT
4CL
Sinapoy l-C oA
S inapi c aci d
H 3CO
OCH3
OH
2. A mutation in maize termed Bronze-2 (bz-2) is known to affect anthocyanin accumulation and
results in a bronze pigmentation of cells. Specifically, the anthocyanin precursor cyanidin-3glucoside is improperly localized in the cell. Recently, the gene encoding bz-2 was identified as a
glutathione-S-transferase (GST), that catalyzes the formation of anthocyanin-glutathione (GSH)
conjugates. Explain how such an enzymatic deficiency can affect the accumulation in cells and
therefore pigmentation. (6 points)