In this video we will be discussing about plant pathogen interaction where we will see how pathogen interacts with the plant cell. Before getting into the interaction pathway, first of all we will see what are the proteins and factors involved in the process of interaction. In plant cell we see it has got PRR on its surface that's Patern Recognition Receptors. and in pathogen we see it has got PAMP or MAMP pathogen associated molecular pattern or microbe associated molecular pattern and it's this PAMP molecule which recognizes PRR of the plant cell then we see plant cell has got R gene which expresses R protein termed as resistance protein and in pathogens they have got effector molecules called pathogen effectors and these are detected by R protein in the plant cell Now in plant immunity we come across with two types of immunity. One is ETI that's effector triggered immunity and other being the PTI that's pattern or PAMP triggered immunity.
So the pathogen effectors evokes the ETI while as PAMP or MAMP evokes the PTI. Now let's get into the detail of plant pathogen interaction. We see in this diagram we have a plant cell which is getting encountered by a pathogen. On the pathogen it has got small molecules what we called as PAMP or MAMP.
While as on plant cell it has got PRR molecules as shown in the diagram. And these PRR molecules will bind to the PAMP molecules of pathogen. After PRR recognizes and receives the PAMP molecule the signal is mediated.
And this signal mediates or we can say triggers the PTI that's pattern or PAMP triggered immunity. and furthermore this pti will initiate the mapk cascade which will eventually activate the expression of defense genes in plant cell this is one type of immunity and it's basic one but there is another way how plant cell combats the pathogen we see in the meantime pathogen also secretes some molecules called effector molecules or pathogen effectors and when these molecules are injected into the cell by pathogen in order to hijack the plant cellular system These pathogen effectors are detected by NBLRR proteins. That's nucleotide binding leucine rich. Repeat. This NBLRR acts as a sensor protein.
And this protein is a class of R protein. Remember it. That's resistance protein. So upon detection of pathogen effectors, the R genes are activated, which causes ion flux. Where there is efflux of hydroxide and potassium ions and influx of calcium and hydrogen ions.
and this ultimately causes HR that's hypersensitive response. The HR in turn causes oxidative burst by producing ROS with which the cell gets distracted. And it must be noted that ROS also triggers the deposition of lignin and callos to the walls of surrounding cells with which infection is not dispersed to the other cells.
So in this way pathogen infection is contained and nearby cells are not getting infected. This is short term response by plant. But not only this is a way to stop the infection. But there are other ways also.
The hypersensitive response also triggers other types of ATI with which HR induces SAR, that's systemic aqueous resistance. It's a more advanced immunity in the plants. In systemic aqueous resistance, hypersensitive response activates the transcription of certain proteins like phytoalexins and chitinases. Both these compounds degrades the cell wall of fungi and even affects the exoskeleton of some orthopods. So now the question is how these defensive proteins are getting produced within the plant cell.
When hypersensitive response fails to eradicate the infection, it activates the hormonal signaling pathway and different pathogens activate different pathways because we have two types of pathogens. One is necrotrophic pathogen which completely destroy the plant cell and other is the biotropic pathogen which does not instantly cause much destruction of the plant tissue. So we see here this biotropic pathogen induces the SA pathway that's salicylic acid pathway while a neurotrophic pathogen induces the JA pathway that's jasmonic pathway.
So both these different types of pathogens initiate different types of hormonal pathways and furthermore these pathways activates the transcription of PR gene. pathogenesis related gene which are defense genes in plant so finally pr gene will express pr protein like chitinases which will combat the pathogen infection in several ways so this is how plant immune system works when they encounter the pathogen i hope you like the video if you like it give it a thumbs up and make sure to subscribe this channel thanks