Antiviral Defense Mechanism in Plants [Part-1]

Plants are the most successful survival organism species of this earth. Confronted confliction by themselves made their phenotypic organization better for their survival chances. Environmental conditions variated their genome (genetic composition) which led to the amendment within the whole body of plants. The cumulative survival rate of plant species dispersed a photosynthetic civilization throughout the world. Whether it’s phytoplanktons or terrestrial plant species. There are many paradoxes which thrive upon the plants and illustrated their effect as a death of them. But in reality, plants are soo powerful than the viral species. In this era, we have a great intellect of their survival strategy as well as their growth phenomena. Today we will know about on the defense mechanism of plants against viruses. So, let's go for it.

Plant Immunity and defense mechanism stages

Generally, plants have innate immunity which helps to increase their survival chances during the pathogenic interaction. Innate immunity is categorized into the two wide branches which describe the defense mechanism of plants via different stages. The initial entity is the “extracellular viral recognition receptors” which deal with the special kind of factors that show their action of mechanism outside the cell. The second immunofacient (immunomodulatory) entity is “intracellular immune receptors” which has a great coordination with protein molecules and these proteins act as the receptor molecules to capture the chemical signature of pathogenic entry

Extracellular viral recognition: -

It deals with some plasma membrane receptors which has an important role in the antigen identification. These receptors are PRRs (Pattern recognition receptors). PRRs helps to capture the PAMP (Pathogen-associated molecular pattern) which includes the chemical signature of the presence of a pathogenic entity. PRRs acts as a primary stimulus for the activation of PTI (PAMP-Triggered Immunity). PTI is a primary immunity for the plant cell.

Some pathogenic species are much powerful so that PTI immunity never able to halt virus goals. So, their affection would be continuously going on. To prevent from such conditions, plant cells have made another kind of immunity called as ETI (Effector-triggered immunity)

Now it’s time to know about Intracellular immune receptors because, without them, ETI can’t be activated.

Intracellular immune receptors: -

These receptors are protein molecules which helps in the transduction of signals to the sensors of the cell through which cell regulate their metabolism i.e. to secrete some chemicals to remove unwanted obstacles from the signaling pathway.

Initially, cell receptors present nearer to the plasma membrane detect the presence of viral entity inside the cell and signals gets transduced towards cell sensors which leads to the secretion of chemicals that can stop the translation process by RNA silencing. As virus needs translation process to replicate and transfer itself in the form of protein molecules within the whole organism body. To prevent this RNA silencing situation, virus evolves suppressors. The suppressors are called “coevolving viral suppressors” which regulates the m-RNA translocation. Plant again raise a step against this action and releases NB-LRR (Nuclear Binding- Leucine Rich Repeater) which distort the coevolving viral suppressors. Along with this activity, it also induces the activation of Rx-protein which open the doors of ETI mechanism, the second most effective mechanism strengthened with many facultative enacts of it.

The main resistance providing protein is Rx-protein molecule, which is encoded by “N- gene”, leads to the activation of ETI mechanism.

Additional information

Some resistance providing genes against various crops affecting viruses has been found.

*Resistance providing genes against crop viruses: -

Resistant Gene	Virus
RTM-1& RTM-2	Tobacco etch virus
RCY-1	Cucumber mosaic virus
SW-5	Tomato spotted wilt virus
Rx-1 & Rx-2	Potato Virus-X

Plants defense mechanism against pathogens hasn’t been understood properly. Still, researches are going on. ETI defense mechanism has been explored in an adequate way. This isn’t the end of this concept, it’s too long and interesting as well. This elaboration would be continued in next part.

Antiviral defense mechanism in plants [Part-2] to be continued…………

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