(N/A) Pest-resistant plants are developed to reduce the reliance on chemical pesticides. $A$ notable example is the protection of tobacco plants against the nematode $Meloidogyne$ $incognita$,which infects roots and reduces yield.
$RNA$ interference $(RNAi)$ is a method of cellular defense that occurs in all eukaryotic organisms. It involves the silencing of a specific $mRNA$ due to a complementary $dsRNA$ molecule that binds to and prevents the translation of the $mRNA$.
Mechanism of $RNAi$:
$1$. Using $Agrobacterium$ vectors,nematode-specific genes are introduced into the host plant.
$2$. The introduced $DNA$ is designed to produce both sense and antisense $RNA$ in the host cells.
$3$. These two $RNA$ strands are complementary to each other and form a double-stranded $RNA$ $(dsRNA)$.
$4$. This $dsRNA$ initiates the $RNAi$ process,which silences the specific $mRNA$ of the nematode.
$5$. Consequently,the parasite cannot survive in the transgenic host,and the plant is protected from the infestation.