RNA interference (RNAi) is a biological process that regulates gene expression by silencing specific genes. It involves the introduction of small RNA molecules into a host organism, which then target and degrade complementary RNA molecules, resulting in the suppression of gene expression.

In RNAi, the DNA is introduced into a host plant in such a way that it produces both sense and antisense RNA molecules. Let's understand this in detail:

1. Introduction of DNA: To initiate RNAi, a specific DNA sequence corresponding to the target gene is introduced into the host plant. This DNA sequence is designed in such a way that it can produce the desired RNA molecules.

2. Sense RNA: The introduced DNA sequence is transcribed by the host plant's cellular machinery, resulting in the production of sense RNA. Sense RNA is an RNA molecule that has the same sequence as the target gene's mRNA. It is called "sense" because its sequence can be translated into a functional protein.

3. Antisense RNA: In addition to the sense RNA, the introduced DNA sequence is also transcribed in the opposite direction, resulting in the production of antisense RNA. Antisense RNA is an RNA molecule that has a complementary sequence to the target gene's mRNA. It is called "antisense" because it can bind to the target gene's mRNA and prevent its translation into protein.

4. Formation of double-stranded RNA: When the sense and antisense RNA molecules are present in the same cellular environment, they can anneal to each other due to their complementary sequences. This leads to the formation of double-stranded RNA (dsRNA), which is a key intermediate in the RNAi process.

5. RNA-induced silencing complex (RISC) formation: The dsRNA is recognized and processed by an enzyme called Dicer. Dicer cleaves the dsRNA into smaller fragments called small interfering RNAs (siRNAs). These siRNAs then associate with a protein complex called the RNA-induced silencing complex (RISC).

6. Target mRNA degradation: The siRNA-loaded RISC complex binds to the complementary mRNA molecule, leading to the degradation of the target mRNA by a process called mRNA cleavage. As a result, the target gene's expression is silenced, and the corresponding protein is no longer produced.

By introducing DNA into a host plant in such a way that it produces both sense and antisense RNA molecules, RNAi can be effectively triggered. The sense RNA provides a template for the synthesis of complementary antisense RNA, which then facilitates the degradation of the target mRNA through the RNAi pathway. This mechanism allows researchers to selectively silence specific genes in plants, providing a powerful tool for studying gene function and developing genetically modified crops with desirable traits.