Crown gall properties — Once induced by Agrobacterium, what are the in vitro characteristics of crown gall tissue?
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AIt can be cultivated in vitro in the absence of bacteria
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BIt retains tumorous properties when cultivated (hormone-autotrophic growth and opine production)
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CBoth (a) and (b)
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DIt shows tumorous properties only in the presence of the bacteria
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EIt rapidly reverts to normal without T-DNA
Answer
Correct Answer: Both (a) and (b)
Explanation
Introduction / Context:Crown gall results from stable integration of T-DNA into the plant genome. After transformation, the tissue becomes autonomous: it can grow without Agrobacterium and often without exogenous hormones, reflecting the expression of T-DNA oncogenes and opine synthesis genes.
Given Data / Assumptions:
- T-DNA integration is stable and heritable in cultured cells.
- Opine synthesis and auxin/cytokinin biosynthesis genes alter metabolism and growth control.
- Eliminating the bacteria does not remove the integrated T-DNA.
Concept / Approach:Because the tumor phenotype is encoded by plant-integrated T-DNA, crown gall tissue remains tumorous in culture without the bacterium. This autonomy is a cornerstone of Agrobacterium-mediated transformation evidence.
Step-by-Step Solution:
Induction: Agrobacterium transfers T-DNA → integration.Post-induction culture: remove bacteria; tissue still grows aberrantly.Conclusion: both independence from bacteria and retention of tumor traits occur.Verification / Alternative check:Opine assays and hormone-free growth of tumor lines confirm persistent T-DNA function.
Why Other Options Are Wrong:
d) Incorrect; tumor properties do not require persistent bacteria.e) Reversion requires loss/silencing of T-DNA, which is not the default.Common Pitfalls:Assuming antibiotic curing of bacteria will cure the tumor; integrated T-DNA remains.
Final Answer:Both (a) and (b).