A Two-Step Enzymatic Pathway in Plants
Auxins are plant hormones that coordinate root growth and development. Indole-3-acetic acid (IAA) is an auxin usually synthesized from the amino acid tryptophan (Figure 1). Gene Trp-T encodes an enzyme that converts tryptophan to indole-3-pyruvic acid (I3PA), which is then converted to IAA by an enzyme encoded by the gene YUC.
(a)Identify the arrow in Figure 1 that represents transcription, and identify the molecule that would be absent if enzyme YUC is nonfunctional. [2 pts]
(b)Describe the process represented by the arrow from mRNA to enzyme, and identify the cell structure where it occurs. [2 pts]
(c)A mutant plant accumulates unusually high levels of I3PA. Predict which gene is most likely mutated and justify your prediction using Figure 1. [2 pts]
(d)Researchers grow wild-type and YUC-mutant seedlings and measure root length. Describe an appropriate control treatment and explain what result would support the claim that IAA promotes root elongation. [2 pts]