1
Given below are two statements
Statement (I) : Phaseolotoxin produced by Pseudomonas syringae py. phaseolicola disrupts apical dominance
Statement (II) : Phaseolotoxin also increases the accumulation of amino acid ornithine
In light of the above statements, choose the most appropriate answer from the options given below.
EXPLANATION
Pathogenesis Mechanisms, Enzymes, Toxins & Vi
- Mode of Action of Phaseolotoxin: Phaseolotoxin is a non-host-specific chlorosis-inducing phytotoxin produced by Pseudomonas syringae pv. phaseolicola (halo blight of bean):
- Inhibition of OCTase: Inside plant tissues, phaseolotoxin is cleaved into octicidin (phosphosulfamylornithine), which irreversibly inhibits the urea cycle enzyme ornithine carbamoyltransferase (OCTase).
- Accumulation of Ornithine: Blocking OCTase prevents the conversion of ornithine and carbamoyl phosphate into citrulline, resulting in a dramatic buildup of the amino acid ornithine and an arginine deficiency (Statement II is true).
- Disruption of Apical Dominance: The systemic physiological shock and hormonal imbalance cause chlorotic halos, stunted bushy growth, and loss of apical dominance in affected bean shoots (Statement I is true).
- Conclusion: Both Statement (I) and Statement (II) are true (Option 1).
Correct option: (1) Both Statement (I) and Statement (II) are true.
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