Chapter 8, Problem 58P

Canavanine is an amino acid similar to arginine (see accompanying figure) that is normally synthesized by some plants. Usually, in plants or animals that don’t make canavanine, arginine aminoacyl-tRNA synthetase cannot distinguish between canavanine and arginine, and tRNA can be charged with canavanine. Incorporation of canavanine in proteins in place of arginine can cause misfolding and destroys protein structure and function.

a.	Can you think of a reason why a plant might have evolved the ability to make canavanine?
b.	How do you suppose plants that make canavanine escape its toxicity?
c.	A particular vining legume called Dioclea megacarpa makes canavanine and yet still has a single insect predator, a beetle, Caryedes brasiliensis. The beetle lays its eggs on the ripe fruit of the vine, and after hatching, the beetle larvae live in the fruit until they mature into adults. How do you suppose that the beetle evades canavanine toxicity?