Plant tumor metabolism — In crown gall disease, what are opines and where are they typically found?

Introduction / Context:
Agrobacterium tumefaciens induces crown gall tumors by transferring T-DNA into plant cells. The transformed cells synthesize unusual metabolites called opines, which reveal a fascinating plant–microbe metabolic relationship and serve as diagnostic markers of transformation.

Given Data / Assumptions:

• T-DNA encodes enzymes that redirect plant metabolism.
• Opines are typically condensation products of amino acids with keto acids or sugars.
• Different Ti plasmids specify different opine types (e.g., nopaline, octopine, agropine).

Concept / Approach:
Opines are synthesized in tumor tissues (not in healthy tissues) and can be catabolized by the infecting Agrobacterium as exclusive carbon/nitrogen sources. This creates a selective ecological niche benefiting the bacterium that initiated the tumor.

Step-by-Step Solution:

Verification / Alternative check:
Paper chromatography and enzymatic assays historically differentiated opine types and correlated them with Ti plasmid classes.

Why Other Options Are Wrong:

• Normal tissues do not synthesize opines in the absence of T-DNA genes.
• “Both normal and tumor tissues” contradicts the hallmark of transformation.
• “Simple sugars in healthy leaves” mischaracterizes opines.

Common Pitfalls:
Assuming opines are general plant metabolites; they are transformation-specific markers.

Final Answer:
amino acid derivatives found in tumor tissues