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The SEPALLATA (SEP) MADS-box genes are required in Arabidopsis for:

  • A Root system development through specific control over the formation of lateral root primordia along the main root structure
  • B Formation of any floral organs (in sep1 sep2 sep3 triple mutants, all organs become leaf-like despite functional ABC genes)
  • C Pollen tube guidance alone, specifically directing tube growth toward the micropyle opening of the developing ovule
  • D Seed dormancy mechanisms that are regulated largely independently of any floral organ identity gene activity present

Correct answer: B. Formation of any floral organs (in sep1 sep2 sep3 triple mutants, all organs become leaf-like despite functional ABC genes)

Explanation: SEP genes (SEP1-4): essential cofactors for floral homeotic MADS proteins. Without SEP, ABC proteins cannot form active tetrameric complexes. All organs revert to leaf-like structures in sep triple mutants.

Concept context

Flower structure, pollination, double fertilization, and seed/fruit development — the highest-scoring Class 12 biology chapter in NEET.

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