Hello students. In this presentation, we will learn about RNA silencing / interference. Before understanding RNA silencing, let’s discuss about Central Dogma in brief. According to this concept, genetic information is stored in DNA. When DNA undergoes transcription, we get three types of RNA. But in this discussion, we will focus on mRNA only. This mRNA is transported to cytoplasm where it undergoes translation to form proteins. We get some specific proteins. It means that expression of genes occur through proteins. Because most of these proteins are some kind of enzymes which catalyze some specific reactions. As a result some specific products are formed in the cell. Recall lac operon, lactose metabolism is initiated when lac operon is switched on. Now we will discuss RNA silencing. If we block mRNA in a gene expression mechanism then it will not undergo translation. And if translation stops the protein synthesis will also stop. It means gene will not be able to express itself. Now we will understand mechanism of RNA interference. Usually one of the two DNA strands undergoes transcription. As a result we get single stranded RNA. But if in some mechanism, both the strands of RNA undergo transcription then we will get two transcripts of mRNA. And these transcripts will undergo base pairing due to complementary bases and we will get double stranded RNA. Bases are not exposed in this double stranded RNA. As a result such double stranded RNA will not be able to undergo translation and will stay in cytoplasm as it is. Now question rises that why we made such double stranded RNA which does not undergoes translation. Understanding the role of double stranded RNA will provide us answer to this question. When a single stranded RNA corresponding to this double stranded RNA comes in the cytoplasm then First we must tell the meaning of ssRNA ssRNA transcript is complementary to one strand to dsRNA If such ssRNA enters the cytoplasm then an enzyme named Dicer becomes active. And this enzyme will cleave dsRNA into small fragments. Some more enzymes will act on these small fragments of dsRNA and will cleave their base pairing. As a result, we will get small fragments of ssRNA These small fragments of dsRNA somewhere show complimentarity with this corresponding ssRNA These small fragments will bind to ssRNA at the multiple sites where complimentary bases are present. As a result, codons on ssRNA will be masked and such ssRNA with masked codons will not be able express itself in the cytoplasm Now question rises that why we did so think a while, if this ssRNA is of some harmful pathogen It means that we have prevented the gene expression by masking the harmful mRNA and controlled the pathogen. By now you must have understood the importance of RNA interference That we control many plant pathogens using this technique. Now we will discuss, how we control infestation of the pathogen Meliodegyne incognita Meliodegyne incognita is a nematode parasite. I must tell you that all genes of a parasite are not harmful Only some of the genes are harmful which are when expressed, harmful effects are manifested in in host organism. We target such harmful disease causing genes and recognize and extract from the body of Meliodegyne incognita. We will now manipulate this extracted gene in such a way that both the strands of this gene undergo transcription in the host body Now we introduce such manipulated gene into the body of host using Agrobacterium. This gene will express itself in host body to form dsRNA this dsRNA will exist in host body as it is Whenever this parasite attacks the plant and initiates expression of disease causing genes by producing mRNA then dsRNA will initiate the mechanism of RNA silencing. As a result this parasite will not be able survive in the host body. Students, please check your understanding by answering this question.