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Difficulty: HardPlant Science and Agricultural Technology

With reference to RNA interference (RNAi) technology and its applications in crop protection and plant biotechnology, which of the following statements are correct?

  1. In-planta expression of long double-stranded RNA (dsRNA) triggers the host or pest Dicer enzyme to generate small interfering RNAs (siRNAs) that target matching messenger RNA (mRNA) for degradation.Answer
  2. B
    RNAi-mediated crop protection operates by permanently inserting foreign DNA sequences into the chromosomal loci of targeted pest genomes.
  3. Host-Delivered RNAi (HDRNi) enables transgenic crops to synthesize specific double-stranded RNA molecules that induce lethal gene knockdown when ingested by targeted herbivorous insects.Answer
  4. D
    RNAi gene silencing in plant biotechnology acts exclusively by directly blocking RNA Polymerase II binding during transcription initiation.

Answer

The correct statements are that double-stranded RNA (dsRNA) is processed by Dicer enzymes into small interfering RNAs (siRNAs) to target mRNA for degradation, and Host-Delivered RNAi (HDRNi) allows transgenic crops to synthesize target dsRNA that causes lethal gene knockdown upon ingestion by pests.
The correct statements accurately describe RNA interference as a post-transcriptional gene silencing mechanism. Double-stranded precursor RNA is cleaved by Dicer into functional siRNAs that bind to the RNA-induced silencing complex (RISC) to degrade complementary messenger RNA. Furthermore, Host-Delivered RNAi (HDRNi) leverages this by enabling crop plants to express specific dsRNAs that, upon ingestion by target insect pests, disrupt vital pest physiological pathways.

Step-by-Step Solution

1
Analyze the biochemical mechanism of RNA interference in plants.
RNAi is a natural post-transcriptional gene silencing pathway wherein long double-stranded RNA (dsRNA) is recognized and cleaved by the Dicer ribonuclease enzyme into short 21-24 nucleotide duplexes called small interfering RNAs (siRNAs).
Understanding the fundamental pathway confirms the role of Dicer and siRNAs in degrading target complementary mRNA.
2
Evaluate the mechanism of Host-Delivered RNAi (HDRNi) in agricultural pest control.
Crops engineered with transgenic constructs produce insect-specific dsRNA. When pests ingest plant tissues, the dsRNA enters insect cells and triggers sequence-specific mRNA destruction of essential survival genes.
This confirms that crop protection via HDRNi is a functional biotechnology application.
3
Differentiate RNAi post-transcriptional silencing from genomic DNA alteration and transcriptional initiation blockade.
RNAi targets existing transcript molecules (mRNA) in the cytoplasm and does not insert foreign DNA into target pest chromosomes or act primarily by blocking promoter binding during transcription.
This identifies the conceptual flaws in statements asserting chromosomal gene insertion or exclusive transcriptional promoter blockage.

Key Concept

RNA Interference (RNAi) and Post-Transcriptional Gene Silencing in Agriculture
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Topics

Plant Science and Agricultural Technology

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