 The first thing that comes to our minds when we say genes is probably DNA and DNA is always accompanied by RNA. Now the thing about RNAs is that not all of them are good. Some of them are straight up villains. But every organism has this super specific defense mechanism called RNA interference which kind of takes care of all of these troublemakers of all of these really bad like the viral RNAs or even the cancer inducing micro RNAs. Now when we found out that how precise and specific this RNA interference process is, we decided to use it for a bunch of other different things. These days we use RNA interference to understand gene function by knocking them down and studying its consequences. Then we also use it to control pests especially nematodes and even cure diseases by silencing the genes that can produce harmful proteins in us. In this video however, we will be focusing on the pest control part. We will explore how RNA interference has been revolutionary for controlling nematode or roundworm infestations in several crops around the world. One of the most nightmarish infestations that have farmers worried all around the world is this one nematode or a roundworm called melloidogine incognita. Now this took me a really long time which I rather not say to understand or to pronounce this name. So we'll just go with m-cognita. I feel like that's an easier way to address this roundworm. Now this pesky little roundworm what it does it's going to go ahead and infect the root cells of plants like tomatoes and tobaccos and when it does so it kind of reduces the plant's ability to take up nutrients and water from the soil. Now in this problem in this scenario how exactly is RNA interference going to do anything about it? Like how is it going to be of any use here? Now using genetic engineering what scientists decided is that they came up with this genetically modified tobacco or tomato plant that had the double stranded RNA for a nematode specific target gene. Now none of that really made any sense so let's break this down a little bit more. Like every living organism that we know even roundworms or this specific roundworm to be exact also has a set of essential proteins that it needs to survive. What we can do is that we can use RNA interference to shut down these essential proteins and that would eventually lead to the death of these roundworms. But how exactly do we do that? Now before we go there let's take a quick look at how the RNA or RNA interference process really works. Now if we take a look at the process over here then we know that whenever there is a double stranded RNA present inside the cell that is when the RNA interference mechanism will kick in. So this yellow color double helix structure this is the double stranded RNA and whenever it's there inside the cell an enzyme called Dyser will show up and literally dice it into really small pieces of RNA which are called the small interfering RNAs. Now these small pieces of RNAs will be picked up by another enzyme complex called RISC and it will use one of the strands of these small pieces of RNA as a guide and find the mRNA corresponding to that small piece of RNA which is that is the complementary mRNA to this SI RNA. So this purple colored strand this is the mRNA and once it finds this mRNA the enzyme complex will slice it therefore preventing any kind of translation of proteins that would have happened from this mRNA strand. Now how are we going to use this process in in order to control pests? In order to use this RNA interference process against the roundworm scientists first needed to target an essential roundworm gene you know a gene which if we mess with will cause major damage to the roundworm. So this blue colored DNA that you see over here this is the essential gene and what scientists did is that when once they figured out which gene they were going to use they decided to clone a part or a portion of this gene and then transfer that cloned gene into the host plant with the help of this bacterium called agro bacterium. So this yellow colored bacteria that bacterium that you see over here this is agro bacterium. So it's an agro bacterium vector and essentially a vector is something that kind of acts as a ship of some sort which transfers your cargo from one place to another. So for our situation over here this bacteria or this bacterium it has a plasmid and that plasmid is the ship it is what carries the cloned DNA from the cloned DNA that we have and then integrate into the plant's genome. So this red colored DNA this is our cloned DNA and let's just write that here as well so that I don't forget. So this cloned DNA it gets in it gets integrated with the agro bacterium's plasmid which is then used as a vector and inserted into the plant or the host plant where it gets integrated into the plant's genome. Now this cloned gene has double stranded DNA inside the host plant what will happen is that each of these strands will undergo transcription and give rise to a new strand of mRNA and since both of these new RNA strands are complementary to one another they will end up forming a double stranded RNA. So you see this yellow colored double stranded thingy this is the double stranded RNA. Now over here two things can happen one this double stranded RNA can stay as it is or it will get broken down into small pieces of RNA by the plant's RNA interference machinery. Now in both of these cases if our pesky little roundworm decides to feed on this transgenic plant it will end up ingesting either the small interfering RNAs or the double stranded RNA and it will enter into its system which will kind of kick in the worms RNA interference machinery. So it will try to find the mRNA which is complementary to these small interfering RNAs or to this double stranded RNA aka the mRNA which is corresponding to the original target gene. Now once it finds that mRNA what the machinery will do the RNAi mechanism or the RNA interference mechanism it will go ahead and slice that mRNA and because of that the targeted essential protein will not be translated at all and because of that and you know what will happen if that protein is not getting translated it's an essential protein so the nematode our little roundworm over here will not survive because no that essential protein won't be translated anymore won't be produced anymore and that's how this entire process of RNA interference can kind of shut down an essential protein inside the inside the roundworm and eventually kill them. Now while I was looking this entire process up as to how you can use RNA interference for controlling pests and stuff I had this one major question which you probably might have had too. Now notice now let's go back to our host plant and remember that the plant's machinery had kicked in the plant's RNA interference machinery had kicked in and this double stranded RNA was broken down into small interfering RNA small pieces of RNAs and then it just stopped there I mean it could have it could have just gotten ahead and completed the whole process but it didn't do that now why is that why did it stop at the small interfering RNAs only. Now the answer to that question is is that all of this so the mRNA which is complementary to this small interfering RNA or this really small piece of RNA won't be found in the host plant it is not present in the host plant it is present inside this nematode right here. So what will happen is that in order to complete that entire process right we need the mRNA which will eventually be sliced and blah blah blah but if you cannot find that mRNA in the plant itself then that machinery won't complete itself that mechanism will just stop right there the process won't be finished and that is exactly what is happening over here remember we started off with a round worm gene so the mRNA which will be complementary to this target gene will be present in the nematode and not in the host plant because the mRNA which is complementary to these small interfering RNAs or to this double stranded RNA is found inside the nematode and not the host plant which is why the plant's RNAi machinery or any interference machinery will shut down at the small interfering RNAs or it will stop not shut down it will stop and then when they are picked up by the round worm over here then the round worms RNA interference machinery will kick in and that's when the process will be completed absolutely and that is how because of all of this that is happening that is how RNAi or RNA interference eventually became a huge deal became so revolutionary in tackling this extremely major problem so this is how RNAi or RNA interference became such a revolutionary thing in the world of agriculture where you can now control you can not just study genes or cure diseases but you can also control pests in this very in this exact same way so this is how you can say that RNA interference can help in controlling pests