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Zorluk: ZorPlant Science and Agricultural Technology

In agricultural crop physiology, cold treatment applied to germinating seeds or young seedlings to accelerate the transition from vegetative to reproductive growth is known as vernalization. Which of the following biochemical mechanisms best explains how vernalization induces flowering in winter crop varieties?

  1. It induces epigenetic silencing of flowering repressor genes, such as Flowering Locus C (FLCFLC), thereby enabling the activation of floral pathway integrator genes.Cevap
  2. B
    It causes rapid degradation of endogenous gibberellins in apical buds, prompting stress-induced ethylene accumulation.
  3. C
    It directly activates the RuBisCO enzyme within bundle sheath cells, leading to localized sucrose accumulation.
  4. D
    It completely inhibits polar auxin transport from shoot tips, causing premature lateral shoot branching.

Cevap

Vernalization induces flowering by epigenetically silencing flowering repressor genes, such as Flowering Locus C (FLCFLC), which permits the expression of downstream floral pathway integrator genes.
The correct answer identifies epigenetic silencing of repressor genes as the key mechanism. In winter annuals, the gene Flowering Locus C (FLCFLC) encodes a transcription factor that blocks flowering. Prolonged cold exposure during winter induces chromatin modifications—specifically methylation of histone H3 at lysine 27—which stably silences FLCFLC. Once the repressor is turned off, floral pathway integrators such as FTFT (Flowering Locus T) are synthesized and transported to the shoot apex to initiate flower formation when favorable spring temperatures return.

Adım Adım Çözüm

1
Identify the primary molecular repressor of flowering in unvernalized winter crops.
In plants requiring vernalization (such as winter wheat and Arabidopsis), the gene Flowering Locus C (FLCFLC) acts as a potent repressor of flowering during the vegetative phase.
High levels of FLCFLC protein actively inhibit floral integrator genes like FTFT (Flowering Locus T) and SOC1SOC1.
2
Analyze the biochemical effect of prolonged cold exposure (vernalization).
Exposure to cold temperature triggers chromatin remodeling, specifically histone methylation (H3K27me3) at the FLCFLC gene locus.
Chromatin remodeling stably represses FLCFLC transcription in a process mediated by proteins such as VRN1VRN1 and VRN2VRN2.
3
Determine the downstream physiological consequence of repressor silencing.
With FLCFLC silenced, floral integrator genes (FTFT) are expressed, transported to the shoot apical meristem, and trigger the transition to floral buds.
This epigenetic memory of cold ensures that plants flower only after passing through winter, preventing premature flowering during autumn.

Anahtar Kavram

Epigenetic Regulation of Vernalization and Floral Induction in Plant Science
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Konular

Plant Science and Agricultural Technology

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